Departamento de Química-CCE, Universidade Estadual de Londrina, Londrina, PR 86051-990, Brazil.
Amino Acids. 2011 Jan;40(1):205-14. doi: 10.1007/s00726-010-0635-y. Epub 2010 Jun 4.
In the present paper, the adsorption of cysteine on hematite, magnetite and ferrihydrite was studied using FT-IR, electron paramagnetic resonance (EPR), Mössbauer spectroscopy and X-ray diffractometry. Cysteine was dissolved in artificial seawater (two different pHs) which contains the major constituents. There were two main findings described in this paper. First, after the cysteine adsorption, the FT-IR spectroscopy and X-ray diffractometry data showed the formation of cystine. Second, the Mössbauer spectroscopy did not show any increase in the amount of Fe(2+) as expected due the oxidation of cysteine to cystine. An explanation could be that Fe(2+) was oxidized by the oxygen present in the seawater or there occurred a reduction of cystine by Fe(2+) generating cysteine and Fe(3+). The specific surface area and pH at point of zero charge of the iron oxides were influenced by adsorption of cysteine. When compared to other iron oxides, ferrihydrite adsorbed significantly (p < 0.05) more cysteine. The pH has a significant (p < 0.05) effect only on cysteine adsorption on hematite. The FT-IR spectroscopy results showed that cystine remains adsorbed on the surface of the iron oxides even after being mixed with KCl and the amine and carboxylic groups are involved in this interaction. X-ray diffractometry showed no changes on iron oxides mineralogy and the following precipitated substances were found along with the iron oxides after drying the samples: cysteine, cystine and seawater salts. The EPR spectroscopy showed that cysteine interacts with iron oxides, changing the relative amounts of iron oxides and hydroxide.
在本论文中，使用傅里叶变换红外光谱（FT-IR）、电子顺磁共振（EPR）、穆斯堡尔光谱和 X 射线衍射法研究了半胱氨酸在赤铁矿、磁铁矿和水铁矿上的吸附。半胱氨酸溶解在含有主要成分的人工海水中（两种不同的 pH 值）。本文描述了两个主要发现。首先，半胱氨酸吸附后，FT-IR 光谱和 X 射线衍射数据表明胱氨酸的形成。其次，穆斯堡尔光谱并没有像预期的那样由于半胱氨酸氧化为胱氨酸而导致 Fe(2+) 量增加。一种解释可能是 Fe(2+) 被海水中的氧氧化，或者胱氨酸被 Fe(2+) 还原生成半胱氨酸和 Fe(3+)。铁氧化物的比表面积和零电荷点 pH 值受到半胱氨酸吸附的影响。与其他铁氧化物相比，水铁矿吸附的半胱氨酸明显更多（p < 0.05）。pH 值仅对半胱氨酸在赤铁矿上的吸附有显著影响（p < 0.05）。FT-IR 光谱结果表明，即使在与 KCl 和胺混合后，胱氨酸仍保留在铁氧化物表面上，并且涉及到胺和羧酸基团的相互作用。X 射线衍射未显示铁氧化物的矿物学发生变化，并且在干燥样品后，在铁氧化物中发现了以下沉淀物质：半胱氨酸、胱氨酸和海水盐。EPR 光谱表明半胱氨酸与铁氧化物相互作用，改变了铁氧化物和氢氧化物的相对含量。
