Correlation of TrpGly and GlyTrp Rotamer Structure with W7 and W10 UV Resonance Raman Modes and Fluorescence Emission Shifts.
Correlation of TrpGly and GlyTrp Rotamer Structure with W7 and W10 UV Resonance Raman Modes and Fluorescence Emission Shifts.
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DOI：
10.1155/2012/735076
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发表时间：
2012-01-01
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影响因子：
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通讯作者：
Juszczak, Laura J
中科院分区：
文献类型：
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作者：
Eisenberg, Azaria Solomon;Juszczak, Laura J
色氨酸甘氨酸（TrpGly）和甘氨酰色氨酸（GlyTrp）二肽在pH 5.5和pH 9.3下显示荧光发射位移模式，其中TrpGly两性荧光发射仅蓝移。该图案与紫外共振拉曼（UVRR）W10带位置和W7费米双重带比的位移相匹配。从头计算结果表明，W7双峰的1340 cm（-1）带由三种模式组成，其中两种模式决定了二肽的W7带比。分子动力学模拟表明，二肽采取两种构象：一个与肽骨架延长，一个与吲哚卷曲的骨干。对这些构象至关重要的二面角是chi（1），并取三个离散值。只有TrpGly两性酶在延伸的骨架构象中花费相当多的时间，因为这是通过与末端胺阳离子的两个氢键稳定的。根据斯塔克效应模型，吡咯附近的正电荷使（1）L（a）跃迁保持在高能量，限制荧光发射红移，如对TrpGly两性荧光素所观察到的。氢键稳定的骨架为TrpGly两性酶所特有的C（亚甲基）-C（α）-C（羰基）W10对称延伸提供了基本原理。
Tryptophyl glycine (TrpGly) and glycyl tryptophan (GlyTrp) dipeptides at pH 5.5 and pH 9.3 show a pattern of fluorescence emission shifts with the TrpGly zwitterion emission solely blue shifted. This pattern is matched by shifts in the UV resonance Raman (UVRR) W10 band position and the W7 Fermi doublet band ratio. Ab initio calculations show that the 1340cm(-1) band of the W7 doublet is composed of three modes, two of which determine the W7 band ratios for the dipeptides. Molecular dynamics simulations show that the dipeptides take on two conformations: one with the peptide backbone extended; one with the backbone curled over the indole. The dihedral angle critical to these conformations is chi(1) and takes on three discrete values. Only the TrpGly zwitterion spends an appreciable amount of time in the extended backbone conformation as this is stabilized by two hydrogen bonds with the terminal amine cation. According to a Stark effect model, a positive charge near the pyrrole keeps the (1)L(a) transition at high energy, limiting fluorescence emission red shift, as observed for the TrpGly zwitterion. The hydrogen bond stabilized backbone provides a rationale for the C(methylene)-C(alpha)-C(carbonyl) W10 symmetric stretch that is unique to the TrpGly zwitterion.