Linking reagents for nucleotide probes

A linking reagent composition having the formula:

• Q--X.sup.1 --R.sup.2 (X.sup.3 --M).sub.n --T
• wherein:
• T is a DNA synthesis support attached to the end of R.sup.2 through a cleavable ester linkage,
• R.sup.2 comprises a chain of atoms which is 2-20 atoms in length joining X.sup.1 to T, wherein each R.sup.2 is stable to DNA synthesis and deprotection conditions,
• X.sup.1 is O, S, NH or NNH,
• Q is a nucleotide or a protecting group which may be removed to permit X.sup.1 to be coupled to the phosphorus group of a nucleotide,
• each X.sup.3 is independently a linker-arm joined at a first end to R.sup.2 and joined at a second end to M, wherein each X.sup.3 is stable to DNA synthesis and deprotection conditions,
• each M is independently a label stable to DNA synthesis and deprotection conditions or a protecting group which can be removed to permit X.sup.3 to be coupled to a label, and
• each n is a positive integer.

A linking reagent having the formula:

• ##STR6## wherein:
• Z is a reactive phosphorus-containing group, OH or a cleavable ester attached to a DNA synthesis support, wherein said reactive phosphorus-containing group is able to couple, to or is activatable for coupling to, an OH group of a first nucleotide;
• D is a protecting group which may be removed to permit said non-nucleotide linking reagent to be coupled to a second nucleotide;
• i is either 0, 1, 2 or 3, and j is either 0, 1, 2 or 3, provided that i+j is at least 1;
• L.sup.1 is a first linker-arm;
• L.sup.2 is either H or a second linker-arm;
• wherein said first linker-arm, and said second linker-arm each independently have the formula:
• (CH.sub.2).sub.k --NH--(CO--(CH.sub.2).sub.q NH).sub.r --M
• wherein each M is independently H, fluorenylmethoxycarbonyl, trifluoroacetyl or a label stable to DNA synthesis and deprotection conditions,
• each k is independently an integer between 0 and 4, inclusive,
• each q is independently an integer between 1 and 11, inclusive,
• each r is independently either 0, 1, or 2,
• provided that each k+1+(2+q)r in said first linker-arm, and in said second linker-arm are independently an integer between 1 and 25, inclusive.