Abu-Lail Nehal I, Camesano Terri A
Department of Chemical Engineering, Worcester Polytechnic Institute, 100 Institute Rd., Worcester, Massachusetts 01609, USA.
Biomacromolecules. 2003 Jul-Aug;4(4):1000-12. doi: 10.1021/bm034055f.
Biopolymers produced extracellularly by Pseudomonas putida KT2442 were examined via atomic force microscopy (AFM) and single molecule force spectroscopy. Surface biopolymers were probed in solutions with added salt concentrations ranging from that of pure water to 1 M KCl. By studying the physicochemical properties of the polymers over this range of salt concentrations, we observed a transition in the steric and electrostatic properties and in the conformation of the biopolymers that were each directly related to bioadhesion. In low salt solutions, the electrophoretic mobility of the bacterium was negative, and large theoretical energy barriers to adhesion were predicted from soft-particle DLVO theory calculations. The brush layer in low salt solution was extended due to electrostatic repulsion, and therefore, steric repulsion was also high (polymers extended 440 nm from surface in pure water). The extended polymer brush layer was "soft", characterized by the slope of the compliance region of the AFM approach curves (-0.014 nN/nm). These properties resulted in low adhesion between biopolymers and the silicon nitride AFM tip. As the salt concentration increased to > or =0.01 M, a transition was observed toward a more rigid and compressed polymer brush layer, and the adhesion forces increased. In 1 M KCl, the polymer brush extended 120 nm from the surface and the rigidity of the outer cell surface was greater (slope of the compliance region = -0.114 nN/nm). A compressed and more rigid polymer layer, as well as a less negative electrophoretic mobility for the bacterium, resulted in higher adhesion forces between the biopolymers and the AFM tip. Scaling theories for polyelectrolyte brushes were also used to explain the behavior of the biopolymer brush layer as a function of salt concentration.
通过原子力显微镜（AFM）和单分子力谱对恶臭假单胞菌KT2442胞外产生的生物聚合物进行了研究。在添加了从纯水到1 M KCl盐浓度的溶液中探测表面生物聚合物。通过研究该盐浓度范围内聚合物的物理化学性质，我们观察到空间和静电性质以及生物聚合物构象的转变，这些转变均与生物粘附直接相关。在低盐溶液中，细菌的电泳迁移率为负，并且根据软颗粒DLVO理论计算预测出较大的粘附理论能垒。低盐溶液中的刷状层由于静电排斥而伸展，因此空间排斥也很高（在纯水中聚合物从表面伸展440 nm）。伸展的聚合物刷状层是“柔软的”，其特征在于AFM进针曲线顺应区的斜率（-0.014 nN/nm）。这些性质导致生物聚合物与氮化硅AFM探针之间的粘附力较低。当盐浓度增加到≥0.01 M时，观察到向更刚性和压缩的聚合物刷状层的转变，并且粘附力增加。在1 M KCl中，聚合物刷从表面伸展120 nm，并且细胞外表面更刚性（顺应区斜率 = -0.114 nN/nm）。压缩且更刚性的聚合物层以及细菌较低的负电泳迁移率导致生物聚合物与AFM探针之间具有更高的粘附力。聚电解质刷的标度理论也被用于解释生物聚合物刷状层随盐浓度变化的行为。
