Salt Concentration and pH-Dependent Adsorption of Two Polypeptides on Planar and Divided Alumina Surfaces. In Situ IR Investigations

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• 作者：C. M. Pradier ; V. Humblot ; L. Stievano ; C. M&eacute ; thivier ; J. F. Lambert
• 刊名：Langmuir
• 出版年：2007
• 出版时间：February 27, 2007
• 年：2007
• 卷：23
• 期：5
• 页码：2463 - 2471
• 全文大小：244K
• 年卷期：v.23,no.5(February 27, 2007)
• ISSN：1520-5827

文摘

The adsorption of proteins is the first process to take place when a solid is immersed in a biological fluid; thoughnot yet thoroughly understood at a molecular level, this process is also known to be strongly influenced by the presenceof salt in solution or by pH changes. In the present work, poly-L-glutamic acid (PG) and poly-L-lysine (PL) wereselected to mimic the behavior of some protein fragments. Their adsorption was investigated by infrared spectroscopyin various modes, both on planar and on divided (powder) surfaces of aluminum oxide. These two peptides were shownto have different behaviors when adsorbed from solutions with or without CaCl₂ and at various pH values. Polarizationmodulation-reflection absorption infrared spectroscopy, applied in a special cell designed to characterize the solidsurface in contact with the liquid, enabled the observation of the influence of pH and salts upon polypeptide adsorption.At pH values higher than 5 and in the presence of CaCl₂ in solution, a net increase of the PG adsorbed amount isobserved, whereas no such effect could be detected for PL. Specific interactions between the COO^- groups on theside chains and the surface, or between those of two different molecules, was inferred. Interestingly, similar conclusionscould be drawn for the surface of alumina powders contacted with solutions of PG and PL and characterized byattenuated total reflectance IR. This work demonstrates the potential for IR investigations of solid oxide-liquidinterfaces combining the study of planar and finely divided surfaces.