Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Super Highway, Gadap Road, Karachi 74600, Pakistan.
Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Super Highway, Gadap Road, Karachi 74600, Pakistan.
J Photochem Photobiol B. 2017 Aug;173:231-239. doi: 10.1016/j.jphotobiol.2017.05.033. Epub 2017 May 29.
The effect of metal ion complexation on the photolysis of riboflavin (RF) using various metal ions (Ag, Ni, Co, Fe, Ca, Cd, Cu, Mn, Pb, Mg, Zn, Fe) has been studied. Ultraviolet and visible spectral and fluorimetric evidence has been obtained to confirm the formation of metal-RF complexes. The kinetics of photolysis of RF in metal-RF complexes at pH7.0 has been evaluated. The apparent first-order rate constant (k) for the photolysis of RF and the formation of lumichrome (LC) and lumiflavin (LF) (0.001M phosphate buffer) and LC, LF and cyclodehydroriboflavin (CDRF) (0.2-0.4M phosphate buffer) have been determined. The values of k indicate that the rate of photolysis of RF is promoted by divalent and trivalent metal ions. The second-order rate constants (k' ) for the interaction of metal ions with RF are in the order: Zn>Mg>Pb>Mn>Cu>Cd>Fe>Ca>Fe>Co>Ni>Ag. In phosphate buffer (0.2-0.4M), an increase in the metal ion concentration leads to a decrease in the formation of LC compared to that of CDRF by different pathways. The photoproducts of RF have been identified and RF and the photoproducts have simultaneously been assayed by a multicomponent spectrometric method. The mode of photolysis of RF in metal-RF complexes has been discussed.
研究了不同金属离子（Ag、Ni、Co、Fe、Ca、Cd、Cu、Mn、Pb、Mg、Zn、Fe）对核黄素（RF）光解的金属离子络合效应。通过紫外可见光谱和荧光证据证实了金属-RF 配合物的形成。在 pH7.0 下评估了 RF 在金属-RF 配合物中的光解动力学。确定了 RF 的光解和光色氨酸（LC）和光黄素（LF）（0.001M 磷酸盐缓冲液）以及 LC、LF 和环脱水核黄素（CDRF）（0.2-0.4M 磷酸盐缓冲液）形成的表观一级速率常数（k）。k 值表明 RF 的光解速率被二价和三价金属离子促进。金属离子与 RF 相互作用的二级速率常数（k'）顺序为：Zn>Mg>Pb>Mn>Cu>Cd>Fe>Ca>Fe>Co>Ni>Ag。在磷酸盐缓冲液（0.2-0.4M）中，金属离子浓度的增加导致 LC 的形成相对于 CDRF 的形成减少，这是通过不同途径实现的。已经鉴定了 RF 的光产物，并且通过多组分光谱法同时测定了 RF 和光产物。讨论了 RF 在金属-RF 配合物中的光解模式。
