Thursday, March 19, 2009

Arsenic Mechanisms Probed

Detection of trivalent arsenic [As(III)] complex with DNA: A spectroscopic investigation
Authors: S. M. Mandal ab; A. K. Ghosh a; B. R. Pati b; A. K. Das a
a Department of Biotechnology, Indian Institute of Technology, West Bengal, India
b Department of Microbiology, Vidyasagar University, West Bengal, India
Toxicological & Environmental Chemistry, Volume 91, Issue 2 March 2009 , pages 219 - 224

Arsenite [As(III)] is well known to exert mutagenic or carcinogenic effects. Arsenic (III) binds proteins with its cystine-SH group to DNA. Overall binding constant K = 1.12 104 M-1 and exponential decay constant T1 = 271 s for DNA-As (III) interaction were measured spectrophometrically at ╬╗max = 260 nm. Fourier transform infrared (FTIR) spectrometric method was used to charac-terize and determine the arsenite binding site in DNA-As(III) interaction. FTIR spectroscopic results showed that As(III) indirectly binds to the nitrogen bases of DNA and predominantly affected the H-bonded OH and NH bands, whereas no interaction was found with phosphate groups. No transitions from B to A or B to Z was observed in B-DNA structure.
BrooklynDodger(s) (Comment)s: Toxicology and Environmental Chemistry published papers from and with a developing world focus (if India is still the developing world.) Aresenic in ground water for drinking is clearly a bigger issue in Asia than the US and Europe. The Dodger(s) has(had) wondered whether arsenic toxicity arose from arsenic substituting for phosphorous, being just below in the periodic table, sort of like lead substituting for calcium. This paper suggests it's arsenate reacting with DNA rather than arsenic inserting itself.

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