Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700032, India.
J Phys Chem B. 2010 Jan 14;114(1):495-502. doi: 10.1021/jp908081r.
In this Article, we report the surface activity of the human globular blood protein, hemoglobin (Hb), at the air/water interface. The Langmuir-Blodgett technique is used for monolayer characterization. The adsorption growth-kinetics study shows that the adsorption process at the air/water interface is involved with two mechanisms: one diffusion with adsorption and the other rearrangement with unfolding. The kinetics is found to be dependent on pH and protein concentration in the subphase. The CD and FTIR studies suggest larger intermolecular aggregate and beta-sheet formation in the film lifted from the air/acidic water subphase. In alkaline pH and in isoelectric pH (6.8), not much variation is observed. The FE-SEM images support this observation. The acidic pH induced such conformational changes, and aggregation is explained with the argument of alpha-helix to beta-sheet conversion as well as the competition between protonation and deprotonation of the aromatic-amino acid residues at the air/water interface.
本文报道了人球形血蛋白血红蛋白（Hb）在气/水界面的表面活性。采用 Langmuir-Blodgett 技术对单层进行了特性描述。吸附生长动力学研究表明，气/水界面的吸附过程涉及两种机制：一种是扩散伴随吸附，另一种是重排伴随展开。动力学研究发现，吸附过程还依赖于亚相中的 pH 值和蛋白质浓度。圆二色性（CD）和傅里叶变换红外光谱（FTIR）研究表明，从空气/酸性水亚相提拉的薄膜中形成了更大的分子间聚集体和β-折叠结构。在碱性 pH 值和等电点（pH6.8）下，观察到的变化不大。FE-SEM 图像支持这一观察结果。酸性 pH 值诱导了这种构象变化，并且这种聚集可以通过α-螺旋向β-折叠的转变以及在气/水界面处芳香族氨基酸残基的质子化和去质子化之间的竞争来解释。
