Taglioni J P, Fournier J
Biochimie. 1979;61(9):1055-63.
The divalent metal ion-thiamine diphosphate (TDP) complexes are of potential interest because such complexes are directly involved in enzymatic reactions. The binding of Ni2+ to TDP has been studied in order to gain some insight in the TDP-metal interactions which could help to understand the role of the metal ions in general in the enzymatic processes. A technique of pH titration is developped which brings definitive proof of metal-TDP bonding in aqueous solutions. The results indicate that the metal ion interacts both with the pyrophosphate group and the pyrimidine ring. The complexation decreases the pK for the phosphate ionization. The ring nitrogen is a some 12 times weaker ligand of Ni2+ than is pyrophosphate. The stability constants obtained for an ionic strength 0.5 in tetramethylammonium bromide are reported; the maximum of the apparent formation constant, between pH 4.5 and pH 7.5, occurs for pH 6.9. The poor solubility of nickel hydroxyde is responsible for increasing interaction in alcaline solution.
二价金属离子 - 硫胺二磷酸（TDP）配合物具有潜在的研究价值，因为这类配合物直接参与酶促反应。为了深入了解TDP与金属之间的相互作用，从而有助于理解金属离子在酶促过程中的总体作用，人们对Ni2+与TDP的结合进行了研究。开发了一种pH滴定技术，该技术为水溶液中金属 - TDP键合提供了确凿的证据。结果表明，金属离子与焦磷酸基团和嘧啶环均发生相互作用。络合作用降低了磷酸盐电离的pK值。环氮作为Ni2+的配体，其配位能力比焦磷酸弱约12倍。报告了在溴化四甲基铵中离子强度为0.5时获得的稳定常数；在pH 4.5至pH 7.5之间，表观形成常数的最大值出现在pH 6.9处。氢氧化镍的低溶解度导致在碱性溶液中相互作用增强。
