Ion pair, reverse-phase chromatograms of reaction mixtures consisting of a ZnPc succinimidyl ester and an oligonucleotide along with control reactions consisting of the native ZnPc dye and an oligonucleotide. (a) Reactions with succinimidyl ester 4 (—, reaction with C6-O1; ---, C12-O1; ···, ZnPc 2; · – · – ·, gradient composition). (b) Reaction with succinimidyl ester 4 and a control reaction with the native ZnPc 2 dye (—, reaction with succinimidyl ester 4; ···, reaction with ZnPc 2; · – · – ·, gradient composition).