Methods and compositions for determining the sequence of nucleic acid molecules

A composition comprising first and second compounds of the formula Tms—L—X, wherein

• Tms has the formula
• wherein
• G is (CH2)1-6 wherein a hydrogen on one and only one of the CH2 groups of each G is replaced with —(CH2)c-Amide-T4;
• Amide is
• R1 is hydrogen or C1-10 alkyl;
• c is an integer ranging from 0 to 4;
• and
• m is an integer ranging from 1 to 50 such that when m is greater than 1, G, c, Amide, R1 and T4 are independently selected;
• T5 is an organic moiety of the formula C1-25N0-9O0-9S0-3P0-3HαFβIδ wherein the sum of α, β and δ is sufficient to satisfy the otherwise unsatisfied valencies of the C, N, O, S and P atoms;
• and T5 includes a tertiary or quaternary amine or an organic acid;
• and m is an integer ranging from 0-49;
• L is a chemical group which, upon exposure to light of selected wavelength, allows cleavage of Tms from X;
• and
• X is nucleic acid;
• with the proviso that m in the first compound is different from m in the second compound, but the Tms groups in the first and second compounds are otherwise identical.