Chan R, Chen Vicky, Bucknall M P
UNESCO Centre for Membrane Science and Technology, School of Chemical Engineering and Industrial Chemistry, The University of New South Wales, Sydney, NSW 2052, Australia.
Biotechnol Bioeng. 2004 Jan 20;85(2):190-201. doi: 10.1002/bit.10866.
Binary aqueous solutions of bovine serum albumin (BSA) and beta-lactoglobulin (bLG) were subject to flux-stepping and constant flux ultrafiltration to identify the apparent critical flux and to study the mechanisms and factors affecting fouling when the membrane is permeable to one protein component. Membranes from these filtration experiments were analyzed using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) to locate and quantify levels of fouling below and above the apparent critical flux. Hydrophilic (PLTK) regenerated cellulose and hydrophobic (PBTK) polysulfone asymmetric membranes were used, both of 30 kDa nominal molecular weight cut-off. For the hydrophilic PLTK membrane, protein deposition was shown to depend on electrostatic forces, exhibiting little or no fouling when the proteins had the same charge sign as that of the membrane. This was found to apply for both dilute equal mass-per-unit-volume and equimolar binary mixtures. For the PBTK membrane, hydrophobic protein-membrane attractive forces were sufficiently strong to cause deposition of bLG even in the presence of repulsive electrostatic forces. For the PBTK membrane deposition exceeded monolayer coverage below and above apparent critical flux conditions but for the PLTK membrane this generally occurred when the apparent critical flux was exceeded. MALDI-MS was shown to be a facile direct analytical technique for individually quantifying adsorbed proteins on membrane surfaces at levels as low as 50 fmol/mm(2). The high levels of compound specificity inherent to mass spectrometry make this approach especially suited to the quantification of individual components in mixed deposits. In this study, MALDI-MS was found to be successful in identifying and quantifying the protein species responsible for fouling.
对牛血清白蛋白（BSA）和β-乳球蛋白（bLG）的二元水溶液进行通量步进和恒通量超滤，以确定表观临界通量，并研究当膜对一种蛋白质成分具有渗透性时影响污染的机制和因素。使用基质辅助激光解吸电离质谱（MALDI-MS）对这些过滤实验中的膜进行分析，以定位和量化表观临界通量以下和以上的污染水平。使用了标称截留分子量为30 kDa的亲水性（PLTK）再生纤维素膜和疏水性（PBTK）聚砜不对称膜。对于亲水性PLTK膜，蛋白质沉积显示取决于静电力，当蛋白质与膜具有相同电荷符号时，几乎没有或没有污染。发现这适用于稀的等质量/单位体积和等摩尔二元混合物。对于PBTK膜，即使存在排斥性静电力，疏水的蛋白质-膜吸引力也足够强，足以导致bLG沉积。对于PBTK膜，在表观临界通量条件以下和以上，沉积都超过了单层覆盖，但对于PLTK膜，这通常在超过表观临界通量时发生。MALDI-MS被证明是一种简便的直接分析技术，可用于在低至50 fmol/mm²的水平上单独定量膜表面吸附的蛋白质。质谱固有的高化合物特异性使得这种方法特别适合于定量混合沉积物中的单个成分。在本研究中，发现MALDI-MS在识别和定量造成污染的蛋白质种类方面是成功的。
