Hovagimyan Karen G, Gerig John T
Department of Chemistry & Biochemistry, University of California, Santa Barbara, California 93106, USA.
J Phys Chem B. 2005 Dec 22;109(50):24142-51. doi: 10.1021/jp055075+.
The osmolyte trimethylamine N-oxide (TMAO) is one of a family of compounds found in living systems that can stabilize biomolecular tertiary structures. As a step in exploring the interactions between this material and polyamino acids, we have determined intermolecular 1H{1H} nuclear Overhauser effects (NOEs) between the protons of cyclo-alanylglycine and protons of solvent components in TMAO-water solutions. Comparison of the results to effects predicted on the basis of the molecular shape of the dipeptide and experimental translational diffusion coefficients suggests that both water and TMAO molecules have properties in the vicinity of the dipeptide that are different from those in the bulk solution. Changes of local concentrations of water and TMAO and changes in the diffusive behavior of these components near the dipeptide are rejected as possible explanations of the discrepancies between observed and calculated Overhauser effects. Rather, it is concluded that TMAO molecules, and the water molecules associated with them, participate to some extent in the formation of long-lived solute-solvent complexes. The aliphatic alcohol tert-butyl alcohol is structurally similar to TMAO. Overhauser effect studies of its interaction with cyclo-alanylglycine in tert-butyl alcohol-water suggest similar kinds of interactions are present in this system but that they are significantly weaker, presumably because of the lower polarity of this alcohol compared to TMAO.
渗透溶质三甲胺 N-氧化物（TMAO）是在生物系统中发现的一类能够稳定生物分子三级结构的化合物之一。作为探索这种物质与多氨基酸之间相互作用的一个步骤，我们已经测定了环丙氨酰甘氨酸的质子与 TMAO-水溶液中溶剂成分的质子之间的分子间 1H{1H}核 Overhauser 效应（NOE）。将结果与基于二肽分子形状预测的效应以及实验平移扩散系数进行比较，结果表明，在二肽附近，水和 TMAO 分子的性质与本体溶液中的不同。水和 TMAO 的局部浓度变化以及这些成分在二肽附近扩散行为的变化，都被排除作为观察到的和计算出的 Overhauser 效应之间差异的可能解释。相反，得出的结论是，TMAO 分子以及与之相关的水分子在一定程度上参与了长寿命溶质-溶剂复合物的形成。脂肪醇叔丁醇在结构上与 TMAO 相似。对其在叔丁醇-水中与环丙氨酰甘氨酸相互作用的 Overhauser 效应研究表明，该体系中存在类似的相互作用，但强度明显较弱，推测这是由于该醇与 TMAO 相比极性较低。
