Torreggiani A, Tamba M, Bonora S, Fini G
Istituto I.S.O.F. (C.N.R.), Via P. Gobetti 101, 40129 Bologna, Italy.
Biopolymers. 2003;72(4):290-8. doi: 10.1002/bip.10406.
A comparative Raman and FTIR study of histamine (Hm), a small hormone present in a wide selection of living organisms, and its complexes with copper(II) at different pH values was carried out. Both the Raman and IR spectra present some marker bands useful for the identification of the structure of the species predominating in the Cu(II) aqueous and alcoholic systems. In particular, Raman spectroscopy appears to be a useful tool for analyzing the tautomeric equilibrium of the imidazole ring of Hm, because some bands (i.e., nuC(4)dbond;C(5)) appear at different wavenumbers, depending on whether the imidazole moiety is in the N(tau)-H (tautomer I) or N(pi)-H (tautomer II) protonated form. In aqueous solutions the manner in which Hm binds to Cu(II) depends on the pH. At basic pH the most relevant species formed are a dimer, Cu(2)L(2)H(-2), and a monomeric complex, CuL or CuL(2). On the contrary, by decreasing the pH, Hm acts as a mono- or bidentate ligand, giving rise to two types of monomeric complexes, CuLH and CuL or CuL(2). With respect to the Cu(II)-Hm alcoholic system, both the aminic group and the imidazole ring (tautomer I) take part in the Cu(II) coordination, leading to the formation of the CuL or CuL(2) monomeric complex.
对组胺（Hm）进行了拉曼光谱和傅里叶变换红外光谱（FTIR）的对比研究，组胺是一种存在于多种生物体内的小分子激素，还研究了其在不同pH值下与铜（II）形成的配合物。拉曼光谱和红外光谱都呈现出一些特征谱带，有助于识别在铜（II）的水体系和醇体系中占主导地位的物种结构。特别是，拉曼光谱似乎是分析组胺咪唑环互变异构平衡的有用工具，因为一些谱带（即νC(4)=C(5)）出现在不同的波数处，这取决于咪唑部分是处于N(τ)-H（互变异构体I）还是N(π)-H（互变异构体II）质子化形式。在水溶液中，组胺与铜（II）的结合方式取决于pH值。在碱性pH值下，形成的最主要物种是二聚体Cu(2)L(2)H(-2)和单体配合物CuL或CuL(2)。相反，随着pH值降低，组胺作为单齿或双齿配体，产生两种类型的单体配合物CuLH和CuL或CuL(2)。对于铜（II）-组胺醇体系，氨基和咪唑环（互变异构体I）都参与铜（II）的配位，导致形成CuL或CuL(2)单体配合物。
