TYROSINE HYDROGEN-BONDING AND ENVIRONMENTAL-EFFECTS IN PROTEINS PROBED BY ULTRAVIOLET RESONANCE RAMAN-SPECTROSCOPY
TYROSINE HYDROGEN-BONDING AND ENVIRONMENTAL-EFFECTS IN PROTEINS PROBED BY ULTRAVIOLET RESONANCE RAMAN-SPECTROSCOPY
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DOI：
10.1021/bi00415a007
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发表时间：
1988-07-26
期刊：
影响因子：
2.9
通讯作者：
PRENDERGAST, FG
中科院分区：
文献类型：
--
作者：
HILDEBRANDT, PG;COPELAND, RA;PRENDERGAST, FG
本文报道了在229 nm激发下的紫外共振拉曼光谱，测定了水溶液中的酪氨酸、鸡的卵泡样第三结构域蛋白[OMCHI3(-)]和恰恰拉卡的卵泡样第三结构域蛋白[OMCHA(-)]以及α。1 -, .alpha。2-和。β。-嘌呤苷元。在此激发波长下，苯丙氨酸的干扰最小，可以确定Tyr环模式的频率。8a和8b。.nu。8b频率随着Tyr h键给能程度的降低而降低，对于去质子化的酪氨酸达到一个极限值。这个氢键强度的光谱指标是通过在氢键受体溶液中使用模型化合物对甲酚来校准的，其氢键形成焓可以从文献中得到。通过这种校准，可以估计Tyr为氢键供体的蛋白质中的Tyr氢键焓；OMCHA3（-）和。alpha的值分别为13.7、9.6和11.2 kcal/mol。1-或。2-)和。分别-purothionin。1176 cm-1 .nu。在229 nm处激发的Tyr条带和在200 nm处激发的Tyr 830/850-cm-1费米双重态的强度比都与估计的氢键焓有很强的相关性，但在purothionins上看到了很大的偏差，反映了这些蛋白质的Tyr残基的特殊环境，被认为是被限制在疏水口袋中。强的摩尔强度约为。1000 cm - 1 .nu。水溶液中苯丙氨酸的12波段约为大多数蛋白质中观察到的值的一半。在苯丙氨酸水溶液中加入乙二醇可增加其强度，其值与在蛋白质中所见的值相似。蛋白质环境对芳烃UVRR强度的影响预计是普遍的。
Ultraviolet resonance Raman spectra with 229-nm excitation are reported for aqueous tyrosine and for ovomucoid third domain proteins from chicken [OMCHI3(-)] and from chachalaca [OMCHA(-)], as well as .alpha.1-, .alpha.2-, and .beta.-purothionin. At this excitation wavelength interference from phenylalanine is minimized, and it is possible to determine the frequencies of the Tyr ring modes .nu.8a and .nu.8b. The .nu.8b frequency decreases with the degree of Tyr H-bound donation, reaching a limiting value for deprotonated tyrosine. This spectroscopic indicator of H-bond strength was calibrated by using the model compound p-cresol in H-bond acceptor solutions for which the enthalpy of H-bond formation can be obtained from the literature. With this calibration it is possible to estimate Tyr H-bond enthalpies in proteins for which Tyr is a H-bond donor; values of 13.7, 9.6, and 11.2 kcal/mol were found for OMCHA3(-) and for .alpha.1- (or .alpha.2-) and .beta.-purothionin, respectively. The intensity of the 1176-cm-1 .nu.9a band of Tyr excited at 229 nm and also the intensity ratio of the Tyr 830/850-cm-1 Fermi doublet excited at 200 nm both correlate strongly with the estimated H-bond enthalpies, but large deviations are seen for the purothionins, reflecting a special environment for the Tyr residue of these proteins, which is believed to be constrained in a hydrophobic pocket. The molar intensity of the strong .apprx. 1000-cm-1 .nu.12 band of phenylalanine in aqueous solution is about half the value observed in most proteins. Addition of ethylene glycol to aqueous phenylalanine increases the intensity, which attains a value similar to those seen in proteins. Protein environmental effects on UVRR intensities for aromatics are expected to be common.