Hydrogen bond-free flavin redox properties: managing flavins in extreme aprotic solvents
Hydrogen bond-free flavin redox properties: managing flavins in extreme aprotic solvents
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DOI：
10.1039/b801952e
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发表时间：
2008-01-01
影响因子：
3.2
通讯作者：
Dutton, P. Leslie
中科院分区：
文献类型：
--
作者：
Cerda, Jose F.;Koder, Ronald L.;Dutton, P. Leslie
我们报告了一个简单的，一步反应，转化核黄素，这是不溶于苯，四苯乙酰基核黄素（TPARP），这是可溶于这种溶剂中，以超过250 mM. Electrochemical分析TPARP单独和两个苯可溶性黄素受体的复合物：二苄基氨基吡啶（DBAP）和单苄基氨基吡啶（MBAP），证明该模型系统的行为类似于其他先前研究的黄素模型系统，其仅可溶于极性更强的溶剂如二氯甲烷。在苯和二氯甲烷中的结合滴定表明，TPARP与其配体的缔合常数在苯中比二氯甲烷高一个数量级以上，这是因为苯不竞争H-键，但二氯甲烷竞争H-键。在苯中加入DBAP后，TPARP的可见光谱中诱导的改变与转移到二氯甲烷中产生的差异非常相似，进一步表明黄素头基与二氯甲烷的氢键结合程度与其配体相似。这项工作强调了使用一个真正的非极性溶剂的氢键对任何仿生主客体模型系统的能量学的影响的分析的重要性。
We report a simple, single step reaction that transforms riboflavin, which is insoluble in benzene, to tetraphenylacetyl riboflavin (TPARF), which is soluble in this solvent to over 250 mM. Electrochemical analysis of TPARF both alone and in complexes with two benzene-soluble flavin receptors: dibenzylamidopyridine (DBAP) and monobenzylamidopyridine (MBAP), prove that this model system behaves similarly to other previously studied flavin model systems which were soluble only in more polar solvents such as dichloromethane. Binding titrations in both benzene and dichloromethane show that the association constants of TPARF with its ligands are over an order of magnitude higher in benzene than dichloromethane, a consequence of the fact that benzene does not compete for H-bonds, but dichloromethane does. The alteration induced in the visible spectrum of TPARF in benzene upon the addition of DBAP is very similar to the difference produced by transfer to dichloromethane, further indicating that the flavin head group engages in a similar degree of hydrogen bonding with dichloromethane as with its ligands. This work underlines the importance of using a truly nonpolar solvent for the analysis of the effects of hydrogen bonding on the energetics of any biomimetic host-guest model system.