HENRY M. SOBELL

X-RAY FIBER DIFFRACTION EVIDENCE FOR NEIGHBOR-EXCLUSION BINDING OF A PLATINUM METALLOINTERCALATION REAGENT TO DNA. P. J. Bond, R. Langridge, K.W. Jennette and S.J. Lippard, Proc. Nat. Acad. Sci. USA 72, No. 12, 4825-4829 (1975).

ABSTRACT: Good quality x-ray diffraction patterns have been obtained of polycrystalline fibers containing 2-hydroxyethanethiolato (2,2',2''-terpyridine) platinum (II) bound to calf thymus DNA by intercalation. The photographs strongly support the neighbor-exclusion binding model in which electron-dense platinum atoms are regularly distributed at 10.2-Angstrom intervals, every other interbase pair site.

This fiber diffraction study confirms the existence of neighbor-exclusion binding by this platinum organometallointercalator when it binds to DNA at high drug/DNA binding ratios. From the sharpness of the 10.2 and 5.1-Angstrom reflections, it is possible to estimate that the crystalline domain size is in the order of several hundred (intercalated) base pairs.