Size-controlled macromolecule

A substrate for detecting the presence of a mutation in a gene, said substrate comprising a molecular layer of a plurality of regularly spaced size-controlled, cone shaped macromolecules, wherein each of said macromolecule comprises a polymer comprising a linear region and a plurality of branched regions in which a plurality of termini on the branched region are covalently bound to the substrate, and the terminus of the linear region is fixed with a target-specific oligonucleotide via a functional group, wherein said polymer is of the formula:

• Z—NH—[R1]m—C—{[R2—C]a—{(R3—C)b—[(R4—C)c—(R5—Y)x]y}z}n
• wherein
• each of m, a, b, and c is independently 0 or 1;
• x is 1 when c is 0 or when c is 1, x is 3;
• y is 1 when b is 0 or when b is 1, y is 3;
• z is 1 when a is 0 or when a is 1, z is 3;
• n is 3;
• each of R1, R2, R3, R4, and R5 is independently a moiety of the formula
• —CH2OCH2CH2C(═O)—;
• Z is said target-specific oligonucleotide;
• and
• Y is carboxylic acid terminal group that is bound to the substrate;
• provided the product of n, x, y, and z is at least 3, and wherein
• said macromolecules are spaced at regular intervals between about 0.1 nm and about 100 nm between the linear functionalized groups.