title: Deuterium exchange in arsenobetaine and dimethylarsinoylacetic acid.
abstract: Arsenobetaine occurs naturally in almost all marine animals and it is assumed to be the unreactive end-product of a detoxification pathway. To investigate the properties of arsenobetaine and its likely immediate biogenic precursor, dimethylarsinoylacetic acid, we studied the exchanges of the C-2 methylene protons of these compounds in D2O solution and showed them to be pH dependent first-order reactions. For arsenobetaine, the rate of exchange was highest at high pH values although exchange also occurred at low pH values. For dimethylarsinoylacetic acid, the rate was highest at low pH values although there was also exchange at high pH values. The half-life of the reaction was maximum for arsenobetaine at pH values of 5-6, and for dimethylarsinoylacetic acid at 6.5-8.5. Mechanisms are suggested for the exchange reactions involved.
authors.affiliation: Endocrine Disrupter Research Laboratory, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan. edmonds.john.s@nies.go.jp
authors.forename: John S
authors.initials: JS
authors.lastname: Edmonds
authors.forename: Makoto
authors.initials: M
authors.lastname: Nomachi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Morita
mesh_terms: D000085:Acetates / Q000737:chemistry*; D000818:Animals; D001152:Arsenicals / Q000737:chemistry*; D002021:Buffers; D003903:Deuterium / Q000737:chemistry*; D006838:Hydrocarbons; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008386:Marine Biology; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008956:Models, Chemical; D011522:Protons
chemical_list: D000085:Acetates; D001152:Arsenicals; D002021:Buffers; D006838:Hydrocarbons; D011522:Protons; C477455:dimethylarsinoylacetic acid; C030011:carbene; D003903:Deuterium; D008697:Methane; C038992:arsenobetaine