Leberle K, Kempf I, Zundel G
Institut für Physikalische Chemie, Universität München, Federal Republic of Germany.
Biophys J. 1989 Apr;55(4):637-48. doi: 10.1016/S0006-3495(89)82861-9.
Films of O-phospho-L-serine-P-ethylester (PSE) were studied by infrared spectroscopy. PSE films were studied pure and as 1:1 mixture with LiOH, NaOH, KOH, and Ca(OH)2 as a function of the degree of hydration. The same investigations were performed if (L-glu)n was added to the system (ratio 1:1, PSE/glu residue). In the PSE molecules an intramolecular (I) COOH...-OP in equilibrium with COO-...HOP (II) hydrogen bond is present. In this bond a double minimum proton potential occurs and it shows large proton polarizability. This hydrogen bond is relatively stable as shown by the neutralization experiments. At low degree of hydration the cations are present at the phosphate groups. The Li ions polarize the intramolecular hydrogen bonds much more than the other cations, i.e., the weight of the proton-limiting structure COOH...-OP is increased by Li ions. Regarding these results one has to assume that such a hydrogen bond is also present in the phosphatidylserine head groups. It is discussed that such hydrogen bonds could be part of a lateral charge-conducting system in the polar surfaces of biological membranes. Such systems could connect proton-creating and proton-consuming centers at the membrane surface and conduct positive charge at an extremely high rate.
采用红外光谱法对O-磷酸-L-丝氨酸-P-乙酯（PSE）薄膜进行了研究。研究了纯PSE薄膜以及与LiOH、NaOH、KOH和Ca(OH)₂按1:1混合的薄膜，考察了其水合程度的影响。如果向体系中加入(L-谷)n（比例为1:1，PSE/谷氨酸残基），则进行相同的研究。在PSE分子中，存在分子内（I）COOH...-OP与COO-...HOP（II）氢键处于平衡状态。在该键中出现双极小质子势，且显示出较大的质子极化率。中和实验表明，这种氢键相对稳定。在低水合程度下，阳离子存在于磷酸基团处。锂离子对分子内氢键的极化作用比其他阳离子大得多，即锂离子增加了质子限制结构COOH...-OP的权重。基于这些结果，必须假定磷脂酰丝氨酸头部基团中也存在这样的氢键。有人讨论说，这种氢键可能是生物膜极性表面横向电荷传导系统的一部分。这样的系统可以连接膜表面产生质子和消耗质子的中心，并以极高的速率传导正电荷。
