Abstract: Compounds having the structure: ##STR1## wherein B represents 7-deazapurine, or pyrimidine moiety covalently bonded to the C.sup.1 '-position of the sugar moiety, provided that when B is 7-deazapurine, it is attached at the N.sup.9 -position of the 7-deazapurine and when B is pyrimidine, it is attached at the N.sup.1 -position;wherein A represents a moiety consisting of at least three carbon atoms which is capable of forming a detectable complex with a polypeptide when the compound is incorporated into a double-stranded ribonucleic acid, deoxyribonucleic acid duplex, or DNA-RNA hybrid;wherein the dotted line represents a chemical linkage joining B and A, provided that if B is 7-deazapurine, the linkage is attached to the 7-position of the deazapurine, and if B is pyrimidine, the linkage is attached to the 5-position of the pyrimidine; andwherein each of x, y and z represents ##STR2## either directly, or when incorporated into oligo- and polynucleotides, provide probes which are widely useful.