U.S. patent application number 13/791150 was filed with the patent office on 2014-09-11 for polymethine compounds and their use as fluorescent labels.
This patent application is currently assigned to ILLUMINA CAMBRIDGE LIMITED. The applicant listed for this patent is ILLUMINA CAMBRIDGE LIMITED. Invention is credited to Xiaohai Liu, Nikolai Nikolaevich Romanov.
Application Number | 20140255917 13/791150 |
Document ID | / |
Family ID | 51301642 |
Filed Date | 2014-09-11 |
United States Patent
Application |
20140255917 |
Kind Code |
A1 |
Romanov; Nikolai Nikolaevich ;
et al. |
September 11, 2014 |
POLYMETHINE COMPOUNDS AND THEIR USE AS FLUORESCENT LABELS
Abstract
The present disclosure relates to new polymethine compounds and
their use as fluorescent labels. The compounds may be used as
fluorescent labels for nucleotides in nucleic acid sequencing
applications.
Inventors: |
Romanov; Nikolai Nikolaevich;
(Essex, GB) ; Liu; Xiaohai; (Essex, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ILLUMINA CAMBRIDGE LIMITED |
Essex |
|
GB |
|
|
Assignee: |
ILLUMINA CAMBRIDGE LIMITED
Essex
GB
|
Family ID: |
51301642 |
Appl. No.: |
13/791150 |
Filed: |
March 8, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61775092 |
Mar 8, 2013 |
|
|
|
Current U.S.
Class: |
435/6.1 ;
536/23.1; 548/455 |
Current CPC
Class: |
C09B 23/08 20130101;
C07D 209/14 20130101; C12Q 1/6869 20130101; C07H 21/04 20130101;
C07D 209/24 20130101; C07H 17/02 20130101; C07H 19/10 20130101;
C09B 23/06 20130101; C12Q 2563/107 20130101; C07D 209/60
20130101 |
Class at
Publication: |
435/6.1 ;
548/455; 536/23.1 |
International
Class: |
C12Q 1/68 20060101
C12Q001/68 |
Claims
1. A compound of formula (I) or mesomeric forms thereof:
##STR00029## wherein mCat+ or mAn- is an organic or inorganic
positively/negatively charged counterion and m is an integer 0-3;
each of Ra.sub.1 and Ra.sub.2 is independently H, SO.sub.3.sup.-,
sulfonamide, halogen, or a further ring fused to an adjacent carbon
atom; Rb is optionally substituted aryl or optionally substituted
alkyl; each of Rc.sub.1 and Rc.sub.2 is independently alkyl or
substituted alkyl; and either Rb or one of Rc.sub.1 or Rc.sub.2
contains a linking moiety for further attachment or is linked to a
further molecule; with the proviso that Rb is not unsubstituted
phenyl when the compound is not linked via said linking moiety to a
further molecule.
2. A compound according to claim 1 wherein Rb is alkyl or alkyl
substituted with a carboxy or a sulfonic group or derivatives
thereof.
3. A compound according to claim 1 wherein Rc1 or Rc2 is methyl,
ethyl, propyl or --(CH.sub.2).sub.qSO.sub.3.sup.- where q is
1-6.
4. A compound according to claim 1 wherein one of the Ra groups is
a further fused ring forming a structure of formula (II):
##STR00030## wherein Ra.sub.3 is H, SO.sub.3.sup.-, sulphonamide or
halogen; and Rc.sub.1 is alkyl or substituted alkyl.
5. A compound according to claim 1 wherein the linking moiety is
attached to Rb.
6. A compound according to claim 1 wherein the compound is attached
to a nucleotide or oligonucleotide via Rb.
7. A nucleotide or oligonucleotide labelled with a compound
according to claim 1.
8. A labelled nucleotide or oligonucleotide according to claim 7
wherein the label is attached via substituted alkyl group Rb.
9. A labelled nucleotide or oligonucleotide according to claim 7
wherein the label is attached to the C5 position of a pyrimidine
base or the C7 position of a 7-deaza purine base through a linker
moiety.
10. A labelled nucleotide or oligonucleotide according to claim 7,
further comprising a 3' OH blocking group covalently attached to
the ribose or deoxyribose sugar of the nucleotide.
11. A kit comprising two or more nucleotides wherein at least one
nucleotide is a labelled nucleotide according to claim 7.
12. A kit according to claim 11 wherein two of the labelled
nucleotides are excited using a single laser.
13. A kit according to claim 11 further comprising a second, third,
and fourth nucleotide, each labelled with a different compound,
wherein each compound has a distinct absorbance maximum and each of
the compounds is distinguishable from the other three
compounds.
14. A kit according to claim 11 wherein a first of four nucleotides
is a labelled nucleotide according to claim 7 and two of the
compounds have a distinct absorbance maximum above 600 nm.
15. A method of sequencing comprising: a) providing a nucleotide
according to claim 7; b) incorporating the nucleotide into the
complement of an immobilized target polynucleotide; and c)
detecting the nucleotide incorporated in step b).
16. The method according to claim 15, wherein said detecting is
performed on an automated sequencing instrument wherein said
automated sequencing instrument comprises two light sources
operating at different wavelengths.
17. A method of synthesising a compound according to claim 1
comprising: a) providing one or more of the following starting
material: ##STR00031## or a salt thereof wherein Ra is H,
SO.sub.3.sup.-, sulfonamide, halogen, or a further ring fused to an
adjacent carbon atom; and b) performing a synthetic reaction with
said starting material to obtain a compound according to claim 1.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 61/775,092, filed on Mar. 8, 2013, which is hereby
incorporated by reference in its entirety.
[0002] The present disclosure relates to new polymethine compounds
and their use as fluorescent markers. In particular the compounds
may be used as fluorescent labels for nucleotides in nucleic acid
sequencing applications.
BACKGROUND
[0003] Several publications and patent documents are referenced in
this application in order to more fully describe the state of the
art to which this disclosure pertains. The disclosure of each of
these publications and documents is incorporated by reference
herein.
[0004] Non-radioactive detection of nucleic acids utilizing
fluorescent labels is an important technology in molecular biology.
Many procedures employed in recombinant DNA technology previously
relied heavily on the use of nucleotides or polynucleotides
radioactively labelled with, for example .sup.32P. Radioactive
compounds permit sensitive detection of nucleic acids and other
molecules of interest. However, there are serious limitations in
the use of radioactive isotopes such as their expense, limited
shelf life and more importantly safety considerations. Eliminating
the need for radioactive labels enhances safety whilst reducing the
environmental impact and costs associated with, for example,
reagent disposal. Methods amenable to non-radioactive fluorescent
detection include by way of non-limiting example, automated DNA
sequencing, hybridization methods, real-time detection of
polymerase-chain-reaction products and immunoassays.
[0005] For many applications it is desirable to employ multiple
spectrally distinguishable fluorescent labels in order to achieve
independent detection of a plurality of spatially overlapping
analytes. In such multiplex methods the number of reaction vessels
may be reduced simplifying experimental protocols and facilitating
the production of application-specific reagent kits. In
multi-colour automated DNA sequencing for example, multiplex
fluorescent detection allows for the analysis of multiple
nucleotide bases in a single electrophoresis lane thereby
increasing throughput over single-colour methods and reducing
uncertainties associated with inter-lane electrophoretic mobility
variations.
[0006] However, multiplex fluorescent detection can be problematic
and there are a number of important factors which constrain
selection of fluorescent labels. First, it may be difficult to find
dye compounds whose emission spectra are suitably spectrally
resolved in a given application. In addition when several
fluorescent dyes are used together, to generate fluorescence
signals in distinguishable spectral regions by simultaneous
excitation may be difficult because the absorption bands of the
dyes which could be useable for this are usually widely separated,
so it is difficult to achieve more or less equal fluorescence
excitation efficiency even for two dyes. Many excitation methods
use high power light sources like lasers and therefore the dye must
have sufficient photo-stability to withstand such excitation.
[0007] A final consideration of particular importance in molecular
biology methods is the extent to which the fluorescent dyes must be
compatible with the reagent chemistries used such as for example
DNA synthesis solvents and reagents, buffers, polymerase enzymes
and ligase enzymes.
[0008] As sequencing technology advances a need has developed for
further fluorescent dye compounds, their nucleic acid conjugates
and dye sets which satisfy all of the above constraints and which
are amenable particularly to high throughput molecular methods such
as solid phase sequencing and the like.
[0009] Fluorescent dye molecules with improved fluorescence
properties such as fluorescence intensity, shape and wavelength
maximum of fluorescence band can improve the speed and accuracy of
nucleic acid sequencing. Strong fluorescence signal is especially
important when measurements are made in water-based biological
buffers and at higher temperature as the fluorescence intensity of
most dyes is significantly lower at such conditions. Moreover, the
nature of the base to which a dye is attached also affects the
fluorescence maximum, fluorescence intensity and others spectral
dye properties. The sequence specific interactions between the
nucleobases and the fluorescent dyes can be tailored by specific
design of the fluorescent dyes. Optimisation of the structure of
the fluorescent dyes can improve the efficiency of nucleotide
incorporation, reduce the level of sequencing errors and decrease
the usage of reagents in, and therefore the costs of, nucleic acid
sequencing.
[0010] Described herein are improved polymethine constructs and
their use as bio-molecule labels, particularly as labels for
nucleotides used in nucleic acid sequencing. Particular
improvements can be seen in the efficiency of labelled nucleotide
incorporation and length of sequencing read obtainable using the
new fluorescent constructs.
SUMMARY
[0011] According to a first aspect this disclosure provides
polymethine dye compounds of the formula (I) or mesomeric forms
thereof:
##STR00001##
wherein mCat+ or mAn- is an organic or inorganic
positively/negatively charged counterion and m is an integer 0-3;
each of Ra.sub.1 and Ra.sub.2 is independently H, SO.sub.2.sup.-,
sulfonamide, halogen, or a further ring fused to an adjacent carbon
atom; Rb is optionally substituted aryl or optionally substituted
alkyl; each of Rc.sub.1 and Rc.sub.2 is independently alkyl or
substituted alkyl; and either Rb or one of Rc.sub.1 or Rc.sub.2
contains a linking moiety for further attachment or is linked to a
further molecule.
[0012] In another embodiment the compounds of the present
disclosure can be conjugated with a variety of substrate moieties
such as, for example, nucleosides, nucleotides, polynucleotides,
polypeptides, carbohydrates, ligands, particles, cells, semi-solid
surfaces (e.g. gels) and solid surfaces.
[0013] According to a further aspect of the disclosure therefore,
there are provided dye compounds comprising linker groups to
enable, for example, covalent attachment to such substrate
moieties.
[0014] According to a further aspect the disclosure provides a
nucleoside or nucleotide compound defined by the formula: N-L-Dye,
wherein N is a nucleotide, L is an optional linker moiety and Dye
is a fluorescent compound according to the present disclosure.
[0015] In a further aspect the disclosure provides methods of
sequencing using the dye compounds of the present disclosure.
[0016] According to a further aspect the disclosure also provides
kits comprising dye compounds (free or in conjugate form) which may
be used in various immunological assays, oligonucleotide and
nucleic acid labelling and for DNA sequencing by synthesis. In yet
another aspect the disclosure provides kits comprising dye `sets`
particularly suited to cycles of sequencing by synthesis on an
automated instrument platform.
[0017] A further aspect of the disclosure is the chemical
preparation of compounds of the disclosure.
DETAILED DESCRIPTION
[0018] This disclosure provides novel polymethine dye compounds
particularly suitable for methods of fluorescence detection and
sequencing by synthesis.
[0019] According to a first aspect the disclosure provides
polymethine dye compounds of the formula (I) or mesomeric form
thereof:
##STR00002##
wherein mCat+ or mAn- is an organic or inorganic
positively/negatively charged counterion and m is an integer 0-3;
each of Ra.sub.1 and Ra.sub.2 is independently H, SO.sub.3.sup.-,
sulfonamide, halogen, or a further ring fused to an adjacent carbon
atom; Rb is optionally substituted aryl or optionally substituted
alkyl; each of Rc.sub.1 and Rc.sub.2 is independently alkyl or
substituted alkyl; and either Rb or one of Rc.sub.1 or Rc.sub.2
contains a linking moiety for further attachment or is linked to a
further molecule.
[0020] Each Ra.sub.1 or Ra.sub.2 can be independently H,
SO.sub.3.sup.-, sulphonamide, halogen, or a further ring fused to
an adjacent carbon atom. Ra.sub.1 or Ra.sub.2 can be H. Ra.sub.1 or
Ra.sub.2 can be SO.sub.3.sup.-. Ra.sub.1 can be different to
Ra.sub.2, for example the structure can have a single sulfonic acid
group at Ra.sub.1, and H as Ra.sub.2. Ra.sub.1 or Ra.sub.2 can be
sulphonamide. The sulphonamide can be SO.sub.2NH.sub.2 or
SO.sub.2NHR, where R is an alkyl, substituted alkyl, aryl or
substituted aryl group.
[0021] Ra.sub.1 or Ra.sub.2 can be a further aliphatic, aromatic or
heterocyclic ring fused to an adjacent carbon of the indole ring.
For example, in such cases when an aromatic ring is fused the dyes
end group can represent a structure of type
##STR00003##
[0022] Thus the dyes of the disclosure can be described by Formula
(1A), (IB) or (IC):
##STR00004##
[0023] In formula (IA), (IB) and (IC) one or both additional rings
fused to an adjacent carbon atoms of the indole ring may be
optionally substituted, for example with sulfonic acid or
sulphonamide.
[0024] The compound may be where one of the Ra groups is a further
fused ring forming a structure of formula (II):
##STR00005##
wherein Ra.sub.3 is H, SO.sub.3.sup.-, sulphonamide or halogen; and
Rc.sub.1 is alkyl or substituted alkyl.
[0025] Rb can be optionally substituted aryl or optionally
substituted alkyl. Rb can be alkyl. Rb can be methyl, ethyl,
propyl, butyl, pentyl or hexyl. The alkyl chain can be further
substituted, for example with carboxy or sulfonic groups. The Rb
can be used for further conjugation. For example if Rb contains a
COOH moiety, this can be conjugated with further molecules in order
to attach the label. In the case of biomolecule, protein, DNA
labelling and suchlike, the conjugation can be carried out via Rb.
Rb can form amide or ester derivatives once the conjugation has
occurred. The compound may be attached to a nucleotide or
oligonucleotide via Rb.
[0026] Rb can be aryl or substituted aryl. Rb can be phenyl.
[0027] Each Rc.sub.1 and Rc.sub.2 can be independently alkyl or
substituted alkyl. Rc.sub.1 and Rc.sub.2 may be methyl, ethyl,
propyl, butyl, pentyl, hexyl or (CH.sub.2).sub.qSO.sub.2H, where q
is 1-6. q may be 1-3. Rc.sub.1 and Rc.sub.2 may be a substituted
alkyl group. Rc.sub.1 and Rc.sub.2 may contain a COOH or
--SO.sub.3H moiety or their ester or amide derivatives.
[0028] Either Rb or Rc.sub.1 or Rc.sub.2 contains a linking moiety
for further attachment or is linked to a further molecule. Rb or
Rc.sub.1 or Rc.sub.2 may contain a carboxy or carboxylate (COOH or
COO.sup.-) moiety. Once conjugated has occurred, Rb or Rc.sub.1 or
Rc.sub.2 may contain an amide or ester.
[0029] Examples of compounds include:
##STR00006##
or salts thereof.
[0030] A particularly useful compound is a nucleotide or
oligonucleotide labelled with a dye as described herein. The
labelled nucleotide or oligonucleotide may have the label attached
via substituted alkyl group Rb or Rc.sub.1 or Rc.sub.2. The
labelled nucleotide or oligonucleotide may have the label attached
to the C5 position of a pyrimidine base or the C7 position of a
7-deaza purine base through a linker moiety.
[0031] The labelled nucleotide or oligonucleotide may also have a
blocking group covalently attached to the ribose or deoxyribose
sugar of the nucleotide. The blocking group may be attached at any
position on the ribose or deoxyribose sugar. In particular
embodiments, the blocking group is at the 3' OH position of the
ribose or deoxyribose sugar of the nucleotide.
[0032] Provided herein are kits including two or more nucleotides
wherein at least one nucleotide is a nucleotide labelled with a
compound of the present disclosure. The kit may include two or more
labelled nucleotides. The nucleotides may be labelled with two or
more fluorescent labels. Two or more of the labels may be excited
using a single excitation source, which may be a laser. For
example, the excitation bands for the two or more labels may be at
least partially overlapping such that excitation in the overlap
region of the spectrum causes both labels to emit fluorescence. In
particular embodiments, the emission from the two or more labels
will occur in different regions of the spectrum such that presence
of at least one of the labels can be determined by optically
distinguishing the emission.
[0033] The kit may contain four labelled nucleotides, where the
first of four nucleotides is labelled with a compound as disclosed
herein. In such a kit, the second, third, and fourth nucleotides
can each be labelled with a compound that is optionally different
from the label on the first nucleotide and optionally different
from the labels on each other. Thus, one or more of the compounds
can have a distinct absorbance maximum and/or emission maximum such
that the compound(s) is(are) distinguishable from other compounds.
For example, each compound can have a distinct absorbance maximum
and/or emission maximum such that each of the compounds is
distinguishable from the other three compounds. It will be
understood that parts of the absorbance spectrum and/or emission
spectrum other than the maxima can differ and these differences can
be exploited to distinguish the compounds. The kit may be such that
two or more of the compounds have a distinct absorbance maximum
above 600 nm.
[0034] The compounds, nucleotides or kits that are set forth herein
may be used to detect, measure or identify a biological system
(including, for example, processes or components thereof).
Exemplary techniques that can employ the compounds, nucleotides or
kits include sequencing, expression analysis, hybridisation
analysis, genetic analysis, RNA analysis, cellular assay (e.g. cell
binding or cell function analysis), or protein assay (e.g. protein
binding assay or protein activity assay). The use may be on an
automated instrument for carrying out a particular technique, such
as an automated sequencing instrument. The sequencing instrument
may contain two lasers operating at different wavelengths.
[0035] Disclosed herein is a method of synthesising compounds of
the disclosure. A compound of formula (X) and/or (X1), (X2) or a
salt thereof may be used as a starting material for the synthesis
of symmetrical or unsymmetrical polymethine dyes:
##STR00007##
wherein Ra is H, SO.sub.3.sup.-, sulphonamide, halogen, or a
further ring fused to an adjacent carbon atoms; Rb is optionally
substituted aryl or optionally substituted alkyl; and Rc is alkyl
or substituted alkyl.
[0036] As used herein, the term "alkyl" refers to C1-C20
hydrocarbon and may include C3-C10 non-aromatic carbocyclic rings.
In particular embodiments the alkyl groups are C1-C6 alkyl which
refers to saturated, straight- or branched-chain hydrocarbon
radicals containing between one and six carbon atoms, respectively.
Alkyl groups may include one or more unsaturated groups, and thus
include alkenyl and alkynyl.
[0037] The term "halogen" as used herein refers to
fluoro-(hereafter designated as F), chloro-(hereafter designated as
Cl), bromo-(hereafter designated as Br) or iodo-(hereafter
designated as I), and usually relates to substitution for a
hydrogen atom in an organic compound, this substitution is
optionally a full substitution for the hydrogen.
[0038] The term "substituted alkyl", refers to alkyl, alkenyl or
alkynyl groups as defined above where they may optionally be
further substituted with, but not limited to, halo, cyano,
SO.sub.3.sup.-, SRa, ORa, NRbRc, oxo, CONRbRc, COOH and COORb. Ra,
Rb and Rc may be each independently selected from H, alkyl,
substituted alkyl, alkenyl, substituted alkenyl, alkynyl,
substituted alkynyl, aryl and substituted aryl. Further, said
substituted alkyl, substituted alkenyl and substituted alkynyl may
optionally be interrupted by at least one hetero atom or group
selected from O, NRb, S(O).sub.t where t is 0 to 2, and the like.
Substituted alkyl also covers group such as benzyl where the alkyl
groups is comprises a further aryl or substituted aryl moiety.
[0039] Dyes according to the present disclosure may be synthesised
from a variety of different starting materials, including N-phenyl
indoles. The dyes may be made symmetrically, such that the same
indole is at both end of the trimethine chain, or unsymmetrically
such that different indoles are at either end of the chromophore.
Methods for preparing polymethine dyes are well known in the
art.
[0040] According to an aspect of the disclosure there are provided
dye compounds suitable for attachment to substrate moieties,
particularly comprising linker groups to enable attachment to
substrate moieties. Substrate moieties can be virtually any
molecule or substance to which the dyes of the disclosure can be
conjugated and, by way of non-limiting example, may include
nucleosides, nucleotides, polynucleotides, carbohydrates, ligands,
particles, solid surfaces, organic and inorganic polymers,
chromosomes, nuclei, living cells and combinations or assemblages
thereof. The dyes can be conjugated by an optional linker by a
variety of means including hydrophobic attraction, ionic attraction
and covalent attachment. Particularly the dyes are conjugated to
the substrate by covalent attachment. More particularly the
covalent attachment is by means of a linker group.
[0041] The dyes according to the present disclosure may include a
reactive linker group at one of the substituent positions for
covalent attachment of the dye to another molecule. Reactive
linking groups are moieties capable of forming a bond (e.g. a
covalent or non-covalent bond). In a particular embodiment the
linker may be a cleavable linker. Use of the term "cleavable
linker" is not meant to imply that the whole linker is required to
be removed. The cleavage site can be located at a position on the
linker that results in part of the linker remaining attached to the
dye and/or substrate moiety after cleavage. Cleavable linkers may
be, by way of non-limiting example, electrophilically cleavable
linkers, enzymatically cleavable linkers, nucleophilically
cleavable linkers, photocleavable linkers, cleavable under
reductive conditions (for example disulfide or azide containing
linkers), oxidative conditions, cleavable via use of safety-catch
linkers and cleavable by elimination mechanisms. The use of a
cleavable linker to attach the dye compound to a substrate moiety
provides the option of removing the label, for example after
detection, thereby avoiding any interfering signal in downstream
steps.
[0042] Useful linker groups may be found in PCT publication number
WO2004/018493 (herein incorporated by reference) examples of which
include linkers that, may be cleaved using water-soluble phosphines
or water-soluble transition metal catalysts formed from a
transition metal and at least partially water-soluble ligands. In
aqueous solution the latter form at least partially water-soluble
transition metal complexes. Such cleavable linkers can be used to
connect bases of nucleotides to labels such as the dyes set forth
herein.
[0043] Particular linkers may be found in PCT publication number
WO2004/018493 (herein incorporated by reference) such as those that
include moieties of the formula:
##STR00008##
(wherein X is selected from the group comprising O, S, NH and NQ
wherein Q is a C1-10 substituted or unsubstituted alkyl group, Y is
selected from the group comprising O, S, NH and N(allyl), T is
hydrogen or a C1-10 substituted or unsubstituted alkyl group and *
indicates where the moiety is connected to the remainder of the
nucleotide or nucleoside).
[0044] In particular embodiments, the length of the linker between
a fluorescent dye (fluorophore) and a guanine base can be altered,
for example, by introducing a polyethylene glycol spacer group,
thereby increasing the fluorescence intensity compared to the same
fluorophore attached to the guanine base through other linkages
known in the art. Exemplary linkers and their properties are set
forth in GB patent application number 0517097.2, published as
WO07020457, (herein incorporated by reference). The design of
linkers, and especially their increased length, can allow
improvements in the brightness of fluorophores attached to the
guanine bases of guanosine nucleotides when incorporated into
polynucleotides such as DNA. Thus, when the dye is for use in any
method of analysis which employs detection of a fluorescent dye
label attached to a guanine-containing nucleotide, it can be
advantageous to use a linker having a spacer group of formula
--((CH.sub.2).sub.2O).sub.n.sup.- wherein n is an integer between 2
and 50, for example, as described in WO07020457.
[0045] The present disclosure further provides conjugates of
nucleosides and nucleotides labelled with one or more of the dyes
set forth herein (modified nucleotides). Labelled nucleosides and
nucleotides are useful for labelling polynucleotides formed by
enzymatic synthesis, such as, by way of non-limiting example, in
PCR amplification, isothermal amplification, solid phase
amplification, polynucleotide sequencing (e.g. solid phase
sequencing), nick translation reactions and the like.
[0046] Nucleosides and nucleotides may be labelled at sites on the
sugar or nucleobase. As known in the art, a "nucleotide" consists
of a nitrogenous base, a sugar, and one or more phosphate groups.
In RNA the sugar is ribose and in DNA is a deoxyribose, i.e. a
sugar lacking a hydroxyl group that is present in ribose. The
nitrogenous base is a derivative of purine or pyrimidine. The
purines can be adenine (A) or guanine (G), and the pyrimidines can
be cytosine (C), thymine (T) or in the context of RNA, uracil (U).
The C-1 atom of deoxyribose is bonded to N-1 of a pyrimidine or N-9
of a purine. A nucleotide is also a phosphate ester of a
nucleoside, with esterification occurring on the hydroxyl group
attached to the C-3 or C-5 of the sugar. Nucleotides are usually
mono, di- or triphosphates.
[0047] A "nucleoside" is structurally similar to a nucleotide but
is missing the phosphate moieties. An example of a nucleoside
analog would be one in which the label is linked to the base and
there is no phosphate group attached to the sugar molecule.
[0048] Although the base is usually referred to as a purine or
pyrimidine, the skilled person will appreciate that derivatives and
analogues are available which do not alter the capability of the
nucleotide or nucleoside to undergo Watson-Crick base pairing.
"Derivative" or "analogue" means a compound or molecule whose core
structure is the same as, or closely resembles that of a parent
compound but which has a chemical or physical modification, such
as, for example, a different or additional side group, which allows
the derivative nucleotide or nucleoside to be linked to another
molecule. For example, the base may be a deazapurine. In particular
embodiments, the derivatives are capable of undergoing Watson-Crick
pairing. "Derivative" and "analogue" also include, for example, a
synthetic nucleotide or nucleoside derivative having modified base
moieties and/or modified sugar moieties. Such derivatives and
analogues are discussed in, for example, Scheit, Nucleotide analogs
(John Wiley & Son, 1980) and Uhlman et al., Chemical Reviews
90:543-584, 1990. Nucleotide analogues can also have modified
phosphodiester linkages including phosphorothioate,
phosphorodithioate, alkyl-phosphonate, phosphoranilidate,
phosphoramidate linkages and the like.
[0049] A dye may be attached to any position on a nucleotide base,
for example, through a linker. In particular embodiments
Watson-Crick base pairing can still be carried out for the
resulting analogue. Particular nucleobase labelling sites include
the C5 position of a pyrimidine base or the C7 position of a
7-deaza purine base. As described above a linker group may be used
to covalently attach a dye to the nucleoside or nucleotide.
[0050] In particular embodiments the labelled nucleoside or
nucleotide may be enzymatically incorporable and enzymatically
extendable. Accordingly a linker moiety may be of sufficient length
to connect the nucleotide to the compound such that the compound
does not significantly interfere with the overall binding and
recognition of the nucleotide by a nucleic acid replication enzyme.
Thus, the linker can also comprise a spacer unit. The spacer
distances, for example, the nucleotide base from a cleavage site or
label.
[0051] Nucleosides or nucleotides labelled with dyes of the
disclosure may have the formula:
##STR00009##
[0052] Where Dye is a dye compound according to the present
disclosure, B is a nucleobase, such as, for example uracil,
thymine, cytosine, adenine, guanine and the like and L is an
optional linker group which may or may not be present. R' can be H,
monophosphate, diphosphate, triphosphate, thiophosphate, a
phosphate ester analog, --O-- attached to a reactive phosphorous
containing group or --O-- protected by a blocking group. R'' can be
H, OH, a phosphoramidite or a 3'OH blocking group and R''' is H or
OH.
[0053] Where R'' is phosphoramidite, R' is an acid-cleavable
hydroxyl protecting group which allows subsequent monomer coupling
under automated synthesis conditions.
[0054] In a particular embodiment the blocking group is separate
and independent of the dye compound, i.e. not directly attached to
it. In an alternative embodiment the dye may comprise all or part
of the 3'OH blocking group. Thus R'' can be a 3'OH blocking group
which may or may not comprise a dye compound disclosed herein.
[0055] In still yet another alternative embodiment there is no
blocking group on the 3' carbon of the pentose sugar and the dye
(or dye and linker construct) attached to the base, for example,
can be of a size or structure sufficient to act as a block to the
incorporation of a further nucleotide. Thus the block can be due to
steric hindrance or can be due to a combination of size, charge and
structure, whether or not the dye is attached to the 3' position of
the sugar.
[0056] In still yet another alternative embodiment the blocking
group is present on the 2' or 4' carbon of the pentose sugar and
can be of a size or structure sufficient to act as a block to the
incorporation of a further nucleotide.
[0057] The use of a blocking group allows polymerisation to be
controlled, such as by stopping extension when a modified
nucleotide is incorporated. If the blocking effect is reversible,
for example by way of non-limiting example by changing chemical
conditions or by removal of a chemical block, extension can be
stopped at certain points and then allowed to continue.
[0058] In another particular embodiment a 3'OH blocking group will
comprise moieties disclosed in WO2004/018497 (herein incorporated
by reference). For example the blocking group may be azidomethyl
(CH.sub.2N.sub.3) or allyl.
[0059] In a particular embodiment a linker (between dye and
nucleotide) and a blocking group are both present and are separate
moieties. In particular embodiments the linker and blocking group
are both cleavable under substantially similar conditions. Thus
deprotection and deblocking processes may be more efficient since
only a single treatment will be required to remove both the dye
compound and the block. However, in some embodiments a linker and
blocking group need not be cleavable under similar conditions,
instead being individually cleavable under distinct conditions.
[0060] This disclosure also encompasses polynucleotides
incorporating dye compounds. Such polynucleotides may be DNA or RNA
comprised respectively of deoxyribonucleotides or ribonucleotides
joined in phosphodiester linkage. Polynucleotides according to the
disclosure may comprise naturally occurring nucleotides,
non-naturally occurring (or modified) nucleotides other than the
modified nucleotides of the disclosure or any combination thereof,
in combination with at least one modified nucleotide (e.g. labelled
with a dye compound) set forth herein. Polynucleotides according to
the disclosure may also include non-natural backbone linkages
and/or non-nucleotide chemical modifications. Chimeric structures
comprised of mixtures of ribonucleotides and deoxyribonucleotides
comprising at least one modified nucleotide according to the
disclosure are also contemplated.
[0061] Modified nucleotides (or nucleosides) comprising a dye
compound according to the present disclosure may be used in any
method of analysis such as methods that include detection of a
fluorescent label attached to a nucleotide or nucleoside, whether
on its own or incorporated into or associated with a larger
molecular structure or conjugate. In this context the term
"incorporated into a polynucleotide" can mean that the 5' phosphate
is joined in phosphodiester linkage to the 3' hydroxyl group of a
second (modified or unmodified) nucleotide, which may itself form
part of a longer polynucleotide chain. The 3' end of a modified
nucleotide set forth herein may or may not be joined in
phosphodiester linkage to the 5' phosphate of a further (modified
or unmodified) nucleotide. Thus, in one non-limiting embodiment the
disclosure provides a method of detecting a modified nucleotide
incorporated into a polynucleotide which comprises: (a)
incorporating at least one modified nucleotide of the disclosure
into a polynucleotide and (b) detecting the modified nucleotide(s)
incorporated into the polynucleotide by detecting the fluorescent
signal from the dye compound attached to said modified
nucleotide(s).
[0062] This method can include: a synthetic step (a) in which one
or more modified nucleotides according to the disclosure are
incorporated into a polynucleotide and a detection step (b) in
which one or more modified nucleotide(s) incorporated into the
polynucleotide are detected by detecting or quantitatively
measuring their fluorescence.
[0063] In one embodiment of the present disclosure at least one
modified nucleotide is incorporated into a polynucleotide in a
synthetic step by the action of a polymerase enzyme. However, other
methods of joining modified nucleotides to polynucleotides, such as
for example chemical oligonucleotide synthesis or ligation of
labelled oligonucleotides to unlabelled oligonucleotides can be
used. Therefore, the term "incorporating", when used in reference
to a nucleotide and polynucleotide, can encompass polynucleotide
synthesis by chemical methods as well as enzymatic methods.
[0064] In a specific embodiment a synthetic step is carried out and
may optionally comprise incubating a template polynucleotide strand
with a reaction mixture comprising fluorescently labelled modified
nucleotides of the disclosure. A polymerase can also be provided
under conditions which permit formation of a phosphodiester linkage
between a free 3' hydroxyl group on a polynucleotide strand
annealed to the template polynucleotide strand and a 5' phosphate
group on the modified nucleotide. Thus, a synthetic step can
include formation of a polynucleotide strand as directed by
complementary base-pairing of nucleotides to a template strand.
[0065] In all embodiments of the method, the detection step may be
carried out whilst the polynucleotide strand into which the
modified nucleotides are incorporated is annealed to a template
strand, or after a denaturation step in which the two strands are
separated. Further steps, for example chemical or enzymatic
reaction steps or purification steps, may be included between a
synthetic step and a detection step. In particular, the target
strand incorporating the modified nucleotide(s) may be isolated or
purified and then processed further or used in a subsequent
analysis. By way of example, target polynucleotides labelled with
modified nucleotide(s) in a synthetic step may be subsequently used
as labelled probes or primers. In other embodiments the product of
a synthetic step set forth herein may be subject to further
reaction steps and, if desired, the product of these subsequent
steps can be purified or isolated.
[0066] Suitable conditions for a synthetic step will be well known
to those familiar with standard molecular biology techniques. In
one embodiment a synthetic step may be analogous to a standard
primer extension reaction using nucleotide precursors, including
modified nucleotides set forth herein, to form an extended target
strand complementary to the template strand in the presence of a
suitable polymerase enzyme. In other embodiments a synthetic step
may itself form part of an amplification reaction producing a
labelled double stranded amplification product comprised of
annealed complementary strands derived from copying of target and
template polynucleotide strands. Other exemplary synthetic steps
include nick translation, strand displacement polymerisation,
random primed DNA labelling etc. A particularly useful polymerase
enzyme for a synthetic step is one that is capable of catalysing
the incorporation of one or more of the modified nucleotides set
forth herein. A variety of naturally occurring or modified
polymerases can be used. By way of example, a thermostable
polymerase can be used for a synthetic reaction that is carried out
using thermocycling conditions, whereas a thermostable polymerase
may not be desired for isothermal primer extension reactions.
Suitable thermostable polymerases which are capable of
incorporating the modified nucleotides according to the disclosure
include those described in WO 2005/024010 or WO06120433, each of
which is incorporated herein by reference. In synthetic reactions
which are carried out at lower temperatures such as 37.degree. C.,
polymerase enzymes need not necessarily be thermostable
polymerases, therefore the choice of polymerase will depend on a
number of factors such as reaction temperature, pH,
strand-displacing activity and the like.
[0067] In specific non-limiting embodiments the disclosure
encompasses methods of nucleic acid sequencing, re-sequencing,
whole genome sequencing, single nucleotide polymorphism scoring, or
any other application involving the detection of the modified
nucleotide or nucleoside labelled with dyes set forth herein when
incorporated into a polynucleotide. Any of a variety of other
applications benefitting from the use of polynucleotides labelled
with the modified nucleotides comprising fluorescent dyes can use
modified nucleotides or nucleosides labelled with dyes set forth
herein.
[0068] In a particular embodiment the disclosure provides use of
modified nucleotides comprising dye compounds according to the
disclosure in a polynucleotide sequencing-by-synthesis reaction.
Sequencing-by-synthesis generally involves sequential addition of
one or more nucleotides or oligonucleotides to a growing
polynucleotide chain in the 5' to 3' direction using a polymerase
or ligase in order to form an extended polynucleotide chain
complementary to the template nucleic acid to be sequenced. The
identity of the base present in one or more of the added
nucleotide(s) can be determined in a detection or "imaging" step.
The identity of the added base may be determined after each
nucleotide incorporation step. The sequence of the template may
then be inferred using conventional Watson-Crick base-pairing
rules. The use of the modified nucleotides labelled with dyes set
forth herein for determination of the identity of a single base may
be useful, for example, in the scoring of single nucleotide
polymorphisms, and such single base extension reactions are within
the scope of this disclosure.
[0069] In an embodiment of the present disclosure, the sequence of
a template polynucleotide is determined by detecting the
incorporation of one or more nucleotides into a nascent strand
complementary to the template polynucleotide to be sequenced
through the detection of fluorescent label(s) attached to the
incorporated nucleotide(s). Sequencing of the template
polynucleotide can be primed with a suitable primer (or prepared as
a hairpin construct which will contain the primer as part of the
hairpin), and the nascent chain is extended in a stepwise manner by
addition of nucleotides to the 3' end of the primer in a
polymerase-catalysed reaction.
[0070] In particular embodiments each of the different nucleotide
triphosphates (A, T, G and C) may be labelled with a unique
fluorophore and also comprises a blocking group at the 3' position
to prevent uncontrolled polymerisation. Alternatively one of the
four nucleotides may be unlabelled (dark). The polymerase enzyme
incorporates a nucleotide into the nascent chain complementary to
the template polynucleotide, and the blocking group prevents
further incorporation of nucleotides. Any unincorporated
nucleotides can be washed away and the fluorescent signal from each
incorporated nucleotide can be "read" optically by suitable means,
such as a charge-coupled device using laser excitation and suitable
emission filters. The 3'-blocking group and fluorescent dye
compounds can then be removed (deprotected), (simultaneously or
sequentially) to expose the nascent chain for further nucleotide
incorporation. Typically the identity of the incorporated
nucleotide will be determined after each incorporation step but
this is not strictly essential. Similarly, U.S. Pat. No. 5,302,509
(which is incorporated herein by reference) discloses a method to
sequence polynucleotides immobilised on a solid support.
[0071] The method, as exemplified above, utilizes the incorporation
of fluorescently labelled, 3'-blocked nucleotides A, G, C and T
into a growing strand complementary to the immobilised
polynucleotide, in the presence of DNA polymerase. The polymerase
incorporates a base complementary to the target polynucleotide, but
is prevented from further addition by the 3'-blocking group. The
label of the incorporated nucleotide can then be determined and the
blocking group removed by chemical cleavage to allow further
polymerisation to occur. The nucleic acid template to be sequenced
in a sequencing-by-synthesis reaction may be any polynucleotide
that it is desired to sequence. The nucleic acid template for a
sequencing reaction will typically comprise a double stranded
region having a free 3' hydroxyl group which serves as a primer or
initiation point for the addition of further nucleotides in the
sequencing reaction. The region of the template to be sequenced
will overhang this free 3' hydroxyl group on the complementary
strand. The overhanging region of the template to be sequenced may
be single stranded but can be double-stranded, provided that a
"nick is present" on the strand complementary to the template
strand to be sequenced to provide a free 3' OH group for initiation
of the sequencing reaction. In such embodiments sequencing may
proceed by strand displacement. In certain embodiments a primer
bearing the free 3' hydroxyl group may be added as a separate
component (e.g. a short oligonucleotide) which hybridises to a
single-stranded region of the template to be sequenced.
Alternatively, the primer and the template strand to be sequenced
may each form part of a partially self-complementary nucleic acid
strand capable of forming an intra-molecular duplex, such as for
example a hairpin loop structure. Hairpin polynucleotides and
methods by which they may be attached to solid supports are
disclosed in International application publication nos. WO0157248
and WO2005/047301, each of which is incorporated herein by
reference. Nucleotides can be added successively to a growing
primer, resulting in synthesis of a polynucleotide chain in the 5'
to 3' direction. The nature of the base which has been added may be
determined, particularly but not necessarily after each nucleotide
addition, thus providing sequence information for the nucleic acid
template. Thus, a nucleotide is incorporated into a nucleic acid
strand (or polynucleotide) by joining of the nucleotide to the free
3' hydroxyl group of the nucleic acid strand via formation of a
phosphodiester linkage with the 5' phosphate group of the
nucleotide.
[0072] The nucleic acid template to be sequenced may be DNA or RNA,
or even a hybrid molecule comprised of deoxynucleotides and
ribonucleotides. The nucleic acid template may comprise naturally
occurring and/or non-naturally occurring nucleotides and natural or
non-natural backbone linkages, provided that these do not prevent
copying of the template in the sequencing reaction.
[0073] In certain embodiments the nucleic acid template to be
sequenced may be attached to a solid support via any suitable
linkage method known in the art, for example via covalent
attachment. In certain embodiments template polynucleotides may be
attached directly to a solid support (e.g. a silica-based support).
However, in other embodiments of the disclosure the surface of the
solid support may be modified in some way so as to allow either
direct covalent attachment of template polynucleotides, or to
immobilise the template polynucleotides through a hydrogel or
polyelectrolyte multilayer, which may itself be non-covalently
attached to the solid support.
[0074] Arrays in which polynucleotides have been directly attached
to silica-based supports are those for example disclosed in
WO00006770 (incorporated herein by reference), wherein
polynucleotides are immobilised on a glass support by reaction
between a pendant epoxide group on the glass with an internal amino
group on the polynucleotide. In addition, polynucleotides can be
attached to a solid support by reaction of a sulphur-based
nucleophile with the solid support, for example, as described in
WO2005/047301 (incorporated herein by reference). A still further
example of solid-supported template polynucleotides is where the
template polynucleotides are attached to hydrogel supported upon
silica-based or other solid supports, for example, as described in
WO00/31148, WO01/01143, WO02/12566, WO03/014392, U.S. Pat. No.
6,465,178 and WO00/53812, each of which is incorporated herein by
reference.
[0075] A particular surface to which template polynucleotides may
be immobilised is a polyacrylamide hydrogel. Polyacrylamide
hydrogels are described in the references cited above and in
WO2005/065814, which is incorporated herein by reference.
[0076] DNA template molecules can be attached to beads or
microparticles, for example as described in U.S. Pat. No. 6,172,218
(which is incorporated herein by reference). Attachment to beads or
microparticles can be useful for sequencing applications. Bead
libraries can be prepared where each bead contains different DNA
sequences. Exemplary libraries and methods for their creation are
described in Nature. 437, 376-380 (2005); Science. 309, 5741,
1728-1732 (2005), each of which is incorporated herein by
reference. Sequencing of arrays of such beads using nucleotides set
forth herein is within the scope of the disclosure.
[0077] Template(s) that are to be sequenced may form part of an
"array" on a solid support, in which case the array may take any
convenient form. Thus, the method of the disclosure is applicable
to all types of high density arrays, including single-molecule
arrays, clustered arrays and bead arrays. Modified nucleotides
labelled with dye compounds of the present disclosure may be used
for sequencing templates on essentially any type of array,
including but not limited to those formed by immobilisation of
nucleic acid molecules on a solid support.
[0078] However, the modified nucleotides labelled with dye
compounds of the disclosure are particularly advantageous in the
context of sequencing of clustered arrays. In clustered arrays,
distinct regions on the array (often referred to as sites, or
features) comprise multiple polynucleotide template molecules.
Generally, the multiple polynucleotide molecules are not
individually resolvable by optical means and are instead detected
as an ensemble. Depending on how the array is formed, each site on
the array may comprise multiple copies of one individual
polynucleotide molecule (e.g. the site is homogenous for a
particular single- or double-stranded nucleic acid species) or even
multiple copies of a small number of different polynucleotide
molecules (e.g. multiple copies of two different nucleic acid
species). Clustered arrays of nucleic acid molecules may be
produced using techniques generally known in the art. By way of
example, WO 98/44151 and WO00/18957, each of which is incorporated
herein, describe methods of amplification of nucleic acids wherein
both the template and amplification products remain immobilised on
a solid support in order to form arrays comprised of clusters or
"colonies" of immobilised nucleic acid molecules. The nucleic acid
molecules present on the clustered arrays prepared according to
these methods are suitable templates for sequencing using the
modified nucleotides labelled with dye compounds of the
disclosure.
[0079] The modified nucleotides labelled with dye compounds of the
present disclosure are also useful in sequencing of templates on
single molecule arrays. The term "single molecule array" or "SMA"
as used herein refers to a population of polynucleotide molecules,
distributed (or arrayed) over a solid support, wherein the spacing
of any individual polynucleotide from all others of the population
is such that it is possible to individually resolve the individual
polynucleotide molecules. The target nucleic acid molecules
immobilised onto the surface of the solid support can thus be
capable of being resolved by optical means in some embodiments.
This means that one or more distinct signals, each representing one
polynucleotide, will occur within the resolvable area of the
particular imaging device used.
[0080] Single molecule detection may be achieved wherein the
spacing between adjacent polynucleotide molecules on an array is at
least 100 nm, more particularly at least 250 nm, still more
particularly at least 300 nm, even more particularly at least 350
nm. Thus, each molecule is individually resolvable and detectable
as a single molecule fluorescent point, and fluorescence from said
single molecule fluorescent point also exhibits single step
photobleaching.
[0081] The terms "individually resolved" and "individual
resolution" are used herein to specify that, when visualised, it is
possible to distinguish one molecule on the array from its
neighbouring molecules. Separation between individual molecules on
the array will be determined, in part, by the particular technique
used to resolve the individual molecules. The general features of
single molecule arrays will be understood by reference to published
applications WO00/06770 and WO 01/57248, each of which is
incorporated herein by reference. Although one use of the modified
nucleotides of the disclosure is in sequencing-by-synthesis
reactions, the utility of the modified nucleotides is not limited
to such methods. In fact, the nucleotides may be used
advantageously in any sequencing methodology which requires
detection of fluorescent labels attached to nucleotides
incorporated into a polynucleotide.
[0082] In particular, the modified nucleotides labelled with dye
compounds of the disclosure may be used in automated fluorescent
sequencing protocols, particularly fluorescent dye-terminator cycle
sequencing based on the chain termination sequencing method of
Sanger and co-workers. Such methods generally use enzymes and cycle
sequencing to incorporate fluorescently labelled dideoxynucleotides
in a primer extension sequencing reaction. So called Sanger
sequencing methods, and related protocols (Sanger-type), utilize
randomised chain termination with labelled dideoxynucleotides.
[0083] Thus, the present disclosure also encompasses modified
nucleotides labelled with dye compounds which are
dideoxynucleotides lacking hydroxyl groups at both of the 3' and 2'
positions, such modified dideoxynucleotides being suitable for use
in Sanger type sequencing methods and the like.
[0084] Modified nucleotides labelled with dye compounds of the
present disclosure incorporating 3' blocking groups, it will be
recognized, may also be of utility in Sanger methods and related
protocols since the same effect achieved by using modified dideoxy
nucleotides may be achieved by using modified nucleotides having
3'-OH blocking groups: both prevent incorporation of subsequent
nucleotides. Where nucleotides according to the present disclosure,
and having a 3' blocking group are to be used in Sanger-type
sequencing methods it will be appreciated that the dye compounds or
detectable labels attached to the nucleotides need not be connected
via cleavable linkers, since in each instance where a labelled
nucleotide of the disclosure is incorporated; no nucleotides need
to be subsequently incorporated and thus the label need not be
removed from the nucleotide.
[0085] The present disclosure also provides kits including modified
nucleosides and/or nucleotides labelled with dyes. Such kits will
generally include at least one modified nucleotide or nucleoside
labelled with a dye set forth herein together with at least one
further component. The further component(s) may be one or more of
the components identified in a method set forth above or in the
Examples section below. Some non-limiting examples of components
that can be combined into a kit of the present disclosure are set
forth below.
[0086] In a particular embodiment, a kit can include at least one
modified nucleotide or nucleoside labelled with a dye set forth
herein together with modified or unmodified nucleotides or
nucleosides. For example, modified nucleotides labelled with dyes
according to the disclosure may be supplied in combination with
unlabelled or native nucleotides, and/or with fluorescently
labelled nucleotides or any combination thereof. Accordingly the
kits may comprise modified nucleotides labelled with dyes according
to the disclosure and modified nucleotides labelled with other, for
example, prior art dye compounds. Combinations of nucleotides may
be provided as separate individual components (e.g. one nucleotide
type per vessel or tube) or as nucleotide mixtures (e.g. two or
more nucleotides mixed in the same vessel or tube).
[0087] Where kits comprise a plurality, particularly two, more
particularly four, modified nucleotides labelled with a dye
compound, the different nucleotides may be labelled with different
dye compounds, or one may be dark, with no dye compounds. Where the
different nucleotides are labelled with different dye compounds it
is a feature of the kits that said dye compounds are spectrally
distinguishable fluorescent dyes. As used herein, the term
"spectrally distinguishable fluorescent dyes" refers to fluorescent
dyes that emit fluorescent energy at wavelengths that can be
distinguished by fluorescent detection equipment (for example, a
commercial capillary based DNA sequencing platform) when two or
more such dyes are present in one sample. When two modified
nucleotides labelled with fluorescent dye compounds are supplied in
kit form, it is a feature of some embodiments that the spectrally
distinguishable fluorescent dyes can be excited at the same
wavelength, such as, for example by the same laser. When four
modified nucleotides labelled with fluorescent dye compounds are
supplied in kit form, it is a feature of some embodiments that two
of the spectrally distinguishable fluorescent dyes can both be
excited at one wavelength and the other two spectrally
distinguishable dyes can both be excited at another wavelength.
Particular excitation wavelengths are 532 nm, 630 nm to 700 nm,
particularly 660 nm.
[0088] In one embodiment a kit includes a modified nucleotide
labelled with a compound of the present disclosure and a second
modified nucleotide labelled with a second dye wherein the dyes
have a difference in absorbance maximum of at least 10 nm,
particularly 20 nm to 50 nm. More particularly the two dye
compounds have Stokes shifts of between 15-40 nm where "Stokes
shift" is the distance between the peak absorption and peak
emission wavelengths.
[0089] In a further embodiment a kit can further include two other
modified nucleotides labelled with fluorescent dyes wherein the
dyes are excited by the same laser at 600 nm to 700 nm,
particularly 630 nm to 700 nm, more particularly 660 nm. The dyes
can have a difference in absorbance maximum of at least 10 nm,
particularly 20 nm to 50 nm. More particularly the two dye
compounds can have Stokes shifts of between 20-40 nm. Still yet
more particularly the two dye compounds can have a different
absorbance maximum above 600 nm, particularly above 640 nm.
Particular dyes which are spectrally distinguishable from
polymethine dyes of the present disclosure and which meet the above
criteria are polymethine analogues as described in U.S. Pat. No.
5,268,486 (for example Cy5) or WO 0226891 (Alexa 647; Molecular
Probes A20106) or unsymmetrical polymethines as disclosed in U.S.
Pat. No. 6,924,372, each of which is incorporated herein by
reference.
[0090] In an alternative embodiment, the kits of the disclosure may
contain nucleotides where the same base is labelled with two
different compounds. A first nucleotide may be labelled with a
compound of the disclosure. A second nucleotide may be labelled
with a spectrally distinct compound, for example a `red` dye
absorbing at greater than 600 nm. A third nucleotide may be
labelled as a mixture of the compound of the disclosure and the
spectrally distinct compound, and the fourth nucleotide may be
`dark` and contain no label. In simple terms therefore the
nucleotides 1-4 may be labelled `green`, `red`, `red/green`, and
dark. To simplify the instrumentation further, four nucleotides can
be labelled with a two dyes excited with a single laser, and thus
the labelling of nucleotides 1-4 may be `green 1`, `green 2` `green
1/green 2`, and dark.
[0091] Nucleotides may contain two dyes of the present disclosure.
Dyes where R.sub.1 and R.sub.4 are H absorb at a lower wavelength
than where R.sub.1 and R.sub.4 are alkyl. A kit may contain two or
more nucleotides labelled with dyes of the disclosure. A kit may
contain a nucleotide labelled with a compound of the disclosure
where R.sub.1 and R.sub.4 are H, and a second nucleotide labelled
with a compound of the disclosure where R.sub.1 and R.sub.4 are
alkyl. Kits may contain a further nucleotide where a portion of the
nucleotide is labelled with a compound of the disclosure where
R.sub.1 and R.sub.4 are H, and a second portion of the nucleotide
labelled with a compound of the disclosure where R.sub.1 and
R.sub.4 are alkyl. Kits may further contain an unlabelled
nucleotide.
[0092] Although kits are exemplified above in regard to
configurations having different nucleotides that are labelled with
different dye compounds, it will be understood that kits can
include 2, 3, 4 or more different nucleotides that have the same
dye compound.
[0093] In particular embodiments a kit may include a polymerase
enzyme capable of catalyzing incorporation of the modified
nucleotides into a polynucleotide. Other components to be included
in such kits may include buffers and the like. The modified
nucleotides labelled with dyes according to the disclosure, and
other any nucleotide components including mixtures of different
nucleotides, may be provided in the kit in a concentrated form to
be diluted prior to use. In such embodiments a suitable dilution
buffer may also be included. Again, one or more of the components
identified in a method set forth herein can be included in a kit of
the present disclosure.
[0094] It is noted that, as used in this specification and the
appended claims, the singular forms "a", "an" and "the" include
plural referents unless expressly and unequivocally limited to one
referent. It will be apparent to those skilled in the art that
various modifications and variations can be made to various
embodiments described herein without departing from the spirit or
scope of the present teachings. Thus, it is intended that the
various embodiments described herein cover other modifications and
variations within the scope of the appended claims and their
equivalents.
Experimental Details
2,3,3-Trimethyl-1-phenyl-3H-indolium-5-sulfonate (1)
##STR00010##
[0096] 2-Methylene-3,3-trimethyl-1-phenyl-2,3-dihydro-1H-indole (1
g, 4.25 mmol) was dissolved in 1 ml of sulphuric acid at
temperature <5.degree. C. and 1 ml fuming sulphuric acid (20%)
was added with stirring. The solution was stirred at room
temperature 1 h then heated at 60.degree. C. for 3 h. Product
precipitated with diethyl ether washed with acetone and ethanol.
Yield 0.7 g (52%). The structure was confirmed by NMR.
2-(2-Anilinovinyl-1)-3,3-trimethyl-1-phenyl-3H-indolium-5-sulfonate
(2-1)
##STR00011##
[0097] Reaction Scheme:
##STR00012##
[0099] A mixture of
2,3,3-trimethyl-1-phenyl-3H-indolium-5-sulfonate (0.63 g) and ethyl
N-phenylformimidate (0.5 g) was heated at 70.degree. C. for 30 min.
An orange melt formed. The product triturated with diethyl ether
and filtered off. Yield 0.7 g (84%).
2-(2-Acetanilidovinyl-1)-3,3-trimethyl-1-phenyl-3H-indolium-5-sulfonate
(2-2)
##STR00013##
[0100] Reaction Scheme:
##STR00014##
[0102] A mixture of
2,3,3-trimethyl-1-phenyl-3H-indolium-5-sulfonate (0.63 g),
N,N'-diphenylformimidine (0.5 g), acetic acid (1 ml) and acetic
anhydride (2 ml) was heated at 70.degree. C. for 3 hours and then
at 50.degree. C. overnight. A yellow solution formed. The product
was filtered off and washed with diethyl ether. Yield 0.69 g
(75%).
1,2-dimethyl-1-(4-sulfonatobutyl)-3-phenyl-1H-benzo[e]indolium
(3)
##STR00015##
[0103] Reaction Scheme:
##STR00016##
[0105] N-(2-Naphtyl),N-phenylhydrazine hydrochloride (19.51 mmol,
5.28 g), 5-methyl-6-oxoheptanesulfonic acid (17.18 mmol, 3.70 g)
and anhydrous ZnCl.sub.2 (17.18 mmol, 2.34 g) in absolute ethanol
(30 ml) were stirred at room temperature for 30 min, then at
80.degree. C. for 2 h. the reaction progress was checked by TLC
(10% H.sub.2O in CH.sub.2CN). After completion the reaction was
cooled down and the solvent removed under vacuum. The residue was
dissolved in DCM and purified by flash column on silica-gel. Yield:
3.06 g, 42%.
[0106] Proton NMR: (MeOH-D4): 8.28 (0.5H, d, J=8 Hz); 8.05-8.02
(1H, m); 7.89 (0.5H, d, J=8 Hz); 7.75-7.66 (3H, m); 7.65-7.60 (1H,
m); 1.49-1.43 (1.5H, m); 7.31-7.25 (2H, m); 7.16 (0.5H, d, J=9 Hz);
7.07 (0.5H, appt, J=7.4 Hz); 6.61 (0.5H, d, J=8 Hz); 2.85-2.35 (4H,
m); 1.88 (3H, appd, J=9 Hz); 1.75-1.4 (5H, m); 1.35-1.25 (0.5H, m);
1.1-0.95 (0.5H, m); 0.8-0.65 (0.5H, m); 0.58-0.45 (0.5H, m).
1,2-Dimethyl-1-(3-sulfonatopropyl)-3-phenyl-1H-benzo[e]indolium
(4)
##STR00017##
[0107] Reaction Scheme:
##STR00018##
[0109] The title compound was prepared as the previous compound
from N-(2-naphtyl)-N-phenylhydrazine hydrochloride and
4-methyl-5-oxopentanesulfonic acid. The product was purified by
flash column on silicagel. Yield: 40%. Structure confirmed by NMR
spectrum.
2,3-Dimethyl-3-(4-sulfonatobutyl)-1-phenyl-3H-indolium (5)
##STR00019##
[0110] Reaction Scheme:
##STR00020##
[0112] N,N-Diphenylhydrazine hydrochloride (0.01 mol, 2.2 g),
5-methyl-6-oxoheptanesulfonic acid (0.017 mol, 3.0 g) in glacial
acetic acid (20 ml) were stirred at room temperature
(.about.20.degree. C.) for an hour then at 100.degree. C. for 3
hours (TLC check). The reaction mixture was cooled down and the
solvent removed under vacuum. The residue was washed with diethyl
ether and purified by flash column on silicagel. Yield: 2 g (56%).
Structure confirmed by NMR spectrum.
Indocarbocyanine I-2 (6)
##STR00021##
[0113] Chemical Name
2-{(5-[1-phenyl-3,3-dimethyl)-1,2-dihydro-3H-indol-2-ylidene]-1-propen-1-y-
l}-3,3-dimethyl-1-(5-carboxypenthyl)-indolium-5-sulfonate
Reaction Scheme:
##STR00022##
[0115]
3,3-Dimethyl-1-(5-carboxypenthyl-2-(4-anilinovinyl)-3H-indolium-5-s-
ulfonate (0.46 g) and 2,3,3-Trimethyl-1-phenyl-3H-indolium
perchlorate (0.34 g) in mixture of acetic anhydride (2 ml) and
acetic acid (1 ml) were stirred at room temperature
(.about.25.degree. C.) for 0.5 hour. Then to this solution pyridine
(0.5 ml) was added. The reaction mixture was stirred at 80.degree.
C. for 3 h. Completion of the reaction was checked by TLC (20%
H.sub.2O in CH.sub.3CN) and by UV measurement. Once the reaction
finished, the red coloured mixture was cooled down and the solvents
were removed under vacuum. The residue was purified by C18 flash
column (TEAB 0.1 M in water and acetonitrile).
[0116] Yield: 0.33 g (55%).
Indocarbocyanine I-4 (7)
##STR00023##
[0117] Chemical Name
Triethylammonium
2-{(5-[(4-sulfonatobutyl)-1-phenyl-3-methyl)-1,2-dihydro-3H-indol-2-ylide-
ne]-1-propen-1-yl}-3,3-dimethyl-1-(5-carboxypenthyl)-indolium-5-sulfonate
Reaction Scheme:
##STR00024##
[0119]
3,3-Dimethyl-1-(5-carboxypenthyl-2-(4-anilinovinyl)-3H-indolium-5-s-
ulfonate (0.46 g) and
2,3-dimethyl-3-(4-sulfonatobutyl)-1-phenyl-3H-indolium (0.36 g) in
mixture of acetic anhydride (2 ml) and acetic acid (1 ml) were
stirred at room temperature (.about.25.degree. C.) for 0.5 hour.
Then to this solution pyridine (1 ml) was added. The reaction
mixture was stirred at 80.degree. C. for 3 h/completion of the
reaction checked by TLC (20% H.sub.2O in CH.sub.3CN)/and by UV
measurement). Once the reaction finished, the red coloured reaction
mixture was cooled down and most of the solvents were removed under
vacuum. The residue was purified by C18 flash column (TEAB 0.1 M in
water and acetonitrile). Yield: 0.29 g (35%).
Indocarbocyanine I-5 (8)
##STR00025##
[0120] Chemical Name
2-{(5-[(3-phenyl-1,1-dimethyl)-2,3-dihydro-1H-benzo[e]indol-2-ylidene]-1-p-
ropen-1-yl}-3,3-dimethyl-1-(5-carboxypenthyl)-indolium-5-sulfonate
Reaction Scheme:
##STR00026##
[0122]
3,3-Dimethyl-1-(5-carboxypenthyl-2-(4-anilidovinyl)-3H-indolium-5-s-
ulfonate (0.46 g) and 1,1,2-trimethyl-3-phenyl-3H-indolium
perchlorate (0.39 g) in mixture of acetic anhydride (1 ml) and
acetic acid (1 ml) were stirred at room temperature
(.about.25.degree. C.) for 0.5 hour. Then to this solution pyridine
(1 ml) was added. The reaction mixture was stirred at 60.degree. C.
for 3 h/the reaction progress checked by TLC (20% H.sub.2O in
CH.sub.3CN)/and by UV measurement. Once the reaction finished, the
red coloured reaction mixture was cooled down and most of the
solvents were removed under vacuum. The residue was purified by C18
flash column (TEAB 0.1 M in water and acetonitrile).
[0123] Yield: 0.38 g (54%).
Dye Conjugate (I-5-1) pppT-I-2
Reaction Scheme:
##STR00027##
[0124] Preparation:
[0125] Anhydrous DMA (5 mL) and Hunig's Base (0.06 mL) were added
to the dried sample of the dye (I-2) (60 mg). A solution of TSTU,
(0.25 g) in 5 mL of dry DMA was then added to this. The red colour
of activated ester developed. The reaction mixture was stirred at
room temperature for 1 h. According to TLC (20% H.sub.2O in
CH.sub.3CN) the activation was completed. After activation was
completed this solution was added to the solution of pppT-LN3 (0.23
g) in water (7 mL). The reaction mixture was stirred at room
temperature under nitrogen atmosphere for 3 h. The coupling
progress was checked by TLC (20% H.sub.2O in acetonitrile). The
reaction mixture was cooled down to .about.4.degree. C. with an
ice-bath, then a solution of 0.1 M TEAB (5 mL) in water was added
and the mixture was stirred at room temperature for 10 min. The
reaction mixture was applied to column with .about.50 g of DEAE
sephadex resin suspension in 0.05 M TEAB solution in water and
washed with TEAB (concentration gradient from 0.1 M up to 0.5 M).
Coloured fractions were collected and evaporated then co-evaporated
again with water to remove more TEAB and vac down to dryness. The
residue was then re-dissolved in TEAB 0.1 M. This solution was
filtered through a syringe filter 0.2 nm pore size into a corning
flask and stored in the freezer. The product was purified by HPLC
using C18 reverse phase column with acetonitrile-0.1 M TEAB.
[0126] Yield 67%.
Dye Conjugate (I-5-2) pppT-I-4
Reaction Scheme:
##STR00028##
[0127] Preparation:
[0128] Anhydrous DMA (5 mL) and Hunig's Base (0.06 mL) were added
to the dried sample of the dye (I-2) (82 mg). A solution of TSTU,
(0.25 g) in 5 mL of dry DMA was then added to this. The red colour
of activated ester developed soon. The reaction mixture was stirred
at room temperature for 1 h. After activation was completed (TLC:
15% H.sub.2O in CH.sub.3CN) this solution was added to the solution
of pppT-LN3 (0.23 g) in water (7 mL). The reaction mixture was
stirred at room temperature under nitrogen atmosphere for 3 h. The
reaction mixture was cooled down to .about.4.degree. C. with an
ice-bath, then a solution of 0.1 M TEAB (5 mL) in water was added
and the mixture was stirred at room temperature for 10 min. The
reaction mixture was applied to column with .about.75 g of DEAE
Sephadex resin suspension in 0.05 M TEAB solution in water and
washed with TEAB (concentration gradient from 0.10 M up to 0.75 M).
Red coloured fractions were collected, the solvent evaporated and
then the residue co-evaporated again with water to remove more TEAB
and vac down to dryness. The dye was then re-dissolved in TEAB 0.1
M. This solution was filtered through a syringe filter 0.2 nm pore
size and the product was purified by HPLC using C18 reverse phase
column with acetonitrile-0.1 M TEAB. Yield 70%.
TABLE-US-00001 TABLE 1 efficiency Dye Kd uM Vmax s-1
uM.sup.-1s.sup.-1 pppT DEG527 4.29 1.67 0.4 pppT Dy681 0.39 0.88
2.3 pppT I-2 0.33 1.51 4.5
[0129] Table 1 demonstrates that the incorporation ratio of the
3'-azidomethylthymidine triphosphate labelled with the dye I-2 is
more than 10 times faster when compared with
3'-azidomethylthymidine triphosphate analogues labelled with
alternative dyes.
TABLE-US-00002 TABLE 2 Pol 217 Pol 957 EA Kd uM Kd uM ffT-Deg527
3.00 1.80 Dark ffT -- 0.55 ffT-I-2 0.25 0.14
[0130] Table 2 demonstrates that the binding affinity of
3'-azidomethylthymidine triphosphate labelled with the dye I-2 is
more than 10 times more efficient when compared with
3'-azidomethylthymidine triphosphate analogues labelled with
alternative dyes and is also more efficient than unlabelled
3'-azidomethylthymidine triphosphate.
[0131] The dyes as shown by example I-2 are particularly
advantageous for the efficient incorporations of their labelled
nucleotide analogues. This is due to their much higher binding
affinity (lower Kd) to the polymerase. The nucleotides with higher
binding affinity can be used with the same incorporation efficiency
as nucleotides with lower affinities, but at a much lower
concentration. The amount of nucleotide required per cycle of
sequencing reagent is therefore reduced without lower the quality
of the sequencing data obtained.
* * * * *