Affinity cleaving

Kiessling, L. L., Griffin, L. C., Dervan, P. B. (1992). Flanking sequence effects within the pyrimidine triple-helix motif characterized by affinity cleaving, Biochemistry, 31 2829. 

Myers has discovered a related reaction of the natural product neocarzinostatine 8 (simplified structure). As in the case of the Bergman cyclization a diradical intermediate is generated by a chemical activation step taking place at the reaction site, where it then can cleave DNA. Because of this feature, together with its discriminating affinity towards different DNA strands, neocarzinostatine is regarded as a potential antitumor agent. 

The HSAB principle predicts that the equilibrium should lie to the right, because the hard acid CH3CO should have a greater affinity for the hard base RO than for the soft base RS . Indeed, thiol esters are easily cleaved by OR or hydrolyzed by... 

However, no evidence for even a transitory existence of -(X-Y) has been obtained except in the cases of X = Y = halogen or CNS (ref. 575a). and it is probable that the breakdown is concerted with reduction. The mole of cleavage appears to be governed by the relative electron affinities of X- and Y-, for example, hypobromous acid and hydroxylamine are cleaved by reducing ions as follows... 

In addition, HIV-1 infection also induces the secretion of certain metallo-proteinases (MMP-2, MMP-9) that are capable of cleaving the N-terminus of SDF-1 but not that of the P-chemokines, and this decreases SDF-1 affinity for CXCR4 binding (227-229). Proteolytic modification of SDF-1 by a serum factor(s) that is different from CD26 and MMPs, which results in reduced anti-HIV activity, has been described as well (230). How SDF-1 proteolytic... 

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