Larsen Travis H, Branco Monica C, Rajagopal Karthikan, Schneider Joel P, Furst Eric M
Department of Chemical Engineering and Center for Molecular and Engineering Thermodynamics, University of Delaware, 150 Academy Street, Newark, Delaware 19716, USA.
Macromolecules. 2009 Nov 10;42(21):8443-8450. doi: 10.1021/ma901423n.
The gelation kinetics of four β-hairpin oligopeptides that have been designed to exhibit responsive behavior to changes in environmental conditions, such as pH, ionic strength and temperature, are characterized using multiple particle tracking microrheology and circular dichroism (CD) spectroscopy. The peptides, predominantly an alternating sequence of valine and lysine residues, differ by a point substitution of a single amino acid near a type II'β-turn sequence. The rate of gelation becomes faster for point substitutions which reduce the total charge of the peptide. Similarly, increasing the ionic strength reduces or screens intra- and inter-molecular electrostatic repulsions, again leading to faster gelation kinetics. CD measurements show that the concentration of folded peptide at the gel point decreases as the gelation kinetics become slower, possibly indicating a relationship between the assembly rate and the resulting gel microstructure. Finally, a model is developed based on the electrostatic barrier to peptide folding and association which agrees semi-quantitatively with the microrheology results. This represents a first step towards understanding the role of peptide charge and physico-chemical conditions in the self-assembly of these peptide hydrogelators.
使用多粒子跟踪微流变学和圆二色性（CD）光谱对四种β-发夹寡肽的凝胶化动力学进行了表征，这些寡肽被设计用于表现出对环境条件变化（如pH值、离子强度和温度）的响应行为。这些肽主要是缬氨酸和赖氨酸残基的交替序列，在II'型β-转角序列附近因单个氨基酸的点突变而有所不同。对于降低肽总电荷的点突变，凝胶化速率会加快。同样，增加离子强度会减少或屏蔽分子内和分子间的静电排斥，再次导致更快的凝胶化动力学。CD测量表明，随着凝胶化动力学变慢，凝胶点处折叠肽的浓度降低，这可能表明组装速率与所得凝胶微观结构之间存在关系。最后，基于肽折叠和缔合的静电屏障建立了一个模型，该模型与微流变学结果半定量一致。这是理解肽电荷和物理化学条件在这些肽水凝胶剂自组装中的作用的第一步。
