Kinetic and Mechanistic Studies on the Reaction of the Vitamin B12 Complex Aquacobalamin with the HNO Donor Angeli’s Salt: Angeli’s Salt and HNO React with Aquacobalamin
化学
盐(化学)
无机化学
核化学
有机化学
作者
Harishchandra Subedi,Hanaa A. Hassanin,Nicola E. Brasch
出处
期刊:Inorganic Chemistry [American Chemical Society] 日期:2014-01-17卷期号:53 (3): 1570-1577被引量:27
We report the first studies on the reaction between an HNO donor compound and vitamin B12 complexes. Kinetic and mechanistic studies have been carried out on the reaction between the vitamin B12 derivative aquacobalamin (H2OCbl(+)/HOCbl; pKa = 7.8) and the HNO donor Angeli's salt. Studies were carried out with aquacobalamin in excess, since nitrite also reacts with aquacobalamin to form nitrocobalamin (NO2Cbl). At pH <9.90 aquacobalamin reacts directly with the monoprotonated form of Angeli's salt, HN2O3(-), to form nitroxylcobalamin (NO(-)-Cbl(III); NOCbl) and nitrite. At pH >10.80 the reaction instead switches predominantly to a mechanism in which spontaneous decomposition of Angeli's salt to give HNO and nitrite becomes the rate-determining step, followed by the rapid reaction between aquacobalamin and HNO/NO(-) to again give NOCbl. Both reactions proceed with a 1:1 stoichiometry and formation of nitrite is confirmed using the Griess assay.