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首页> 外文期刊>Structural Chemistry >Conformational changes of L-phenylalanine induced by near infrared radiation. ATR-FTIR studies
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Conformational changes of L-phenylalanine induced by near infrared radiation. ATR-FTIR studies

机译：近红外辐射引起的L-苯丙氨酸的构象变化。 ATR-FTIR研究

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In our previous work the influence of water evaporation on Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectra of L-phenylalanine (L-phe) in a function of pH (Olsztynska et al. Appl. Spectrosc. 60(9):1040, (14)) was studied. The presence of symmetric dimers of hydrogen-bonded amino acid was observed when simultaneously CO _2 - ionised and COOH unionised forms of the amino acid appear in the solution (near pK1). It is suggested that Near Infrared (NIR) radiation may induce partial protonation of CO _2 - groups at a neutral pH and formation the same type of dimers. The aim of this work was to study this hypothesis. Therefore, ATR-FTIR spectra of L-phe aqueous solution before and after NIR radiation (15 min., 700-2,000 nm) were obtained as a continuation of our earlier studies. Spectral characteristic bands of L-phe were described. The vibrational spectroscopic study of L-phe showed that it undergoes photochemical reactions under NIR exposure. It has been found that the irradiation process indeed induces a protonation of polar groups of L-phe at neutral pH what leads to forming of neutral forms and as a consequence hydrogen bonded dimers -C=O..HOOC-. Moreover, hydrophobic interactions strongly increase, what favours aggregation of L-phe molecules. The phenomenon is probably due to modifications of water structure around L-phe molecules. Intra-and intermolecular hydrogen bonds weaken which could favour aggregation and protonation of polar groups what induces also formation of symmetrical hydrogen bonds between protonated and deprotonated carboxylic groups.
机译：在我们以前的工作中，水的蒸发对L-苯丙氨酸（L-phe）的衰减全反射傅立叶变换红外（ATR-FTIR）光谱的影响是pH的函数（Olsztynska et al.Appl.Spectrosc.60（9）： 1040，（14））。当溶液中同时出现氨基酸的CO _2离子化和COOH工会化形式时，观察到氢键合氨基酸对称二聚体的存在（在pK1附近）。建议在中性pH值下近红外（NIR）辐射可诱导CO _2-基的部分质子化并形成相同类型的二聚体。这项工作的目的是研究这个假设。因此，获得了N-IR辐射前后（15分钟，700-2,000 nm）的L-phe水溶液的ATR-FTIR光谱，作为我们先前研究的延续。描述了L-phe的光谱特征带。 L-phe的振动光谱研究表明，它在近红外照射下会发生光化学反应。已经发现，辐照过程确实在中性pH下诱导了L-phe的极性基团的质子化，这导致形成中性形式，并且因此氢键合的二聚体-C ＝ O·HOOC-。而且，疏水性相互作用强烈增加，这有利于L-phe分子的聚集。这种现象可能是由于L-phe分子周围的水结构发生了变化。分子内和分子间的氢键减弱，这可能有利于极性基团的聚集和质子化，这也引起了质子化和去质子化的羧基之间对称氢键的形成。

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