The fluorescent nucleotide analogues (the 5'-mono-, di-, and triphosphates of lin-benzoguanosine, lin-benzoxanthosine, and lin-benzoinosine) have been prepared for use as dimensional probes of enzyme binding sites. They have quantum yields in aqueous solution of 0.39, 0.55, and 0.04 and fluorescent lifetimes of 6, 9, and approximately equal to 1.5 nsec, respectively. lin-Benzoinosine 5'-monophosphate is a substrate for xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2), providing lin-benzoxanthosine 5'-monophosphate, and lin-benzoinosine 5'-diphosphate is a substrate for polynucleotide phosphorylase (polyribonucleotide:orthophosphate nucleotidyltransferase. EC 2.7.7.8), giving poly(lin-benzoinosinic acid). The benzologues of the purine diphosphates are substrates for pyruvate kinase (ATP:pyruvate 2-O-phosphotransferase, EC 2.7.1.40), which is used to prepare the triphosphates.