Abu-Lail Nehal I, Camesano Terri A
Department of Chemical Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA.
Langmuir. 2006 Aug 15;22(17):7296-301. doi: 10.1021/la0533415.
The nature of the physical interactions between Escherichia coli JM109 and a model surface (silicon nitride) was investigated in water via atomic force microscopy (AFM). AFM force measurements on bacteria can represent the combined effects of van der Waals and electrostatic forces, hydrogen bonding, steric interactions, and perhaps ligand-receptor type bonds. It can be difficult to decouple these forces into their individual components since both specific (chemical or short-range forces such as hydrogen bonding) and nonspecific (long-range colloidal) forces may be present in the overall profiles. An analysis is presented based on the application of Poisson statistics to AFM adhesion data, to decouple the specific and nonspecific interactions. Comparisons with classical DLVO theory and a modified form of a van der Waals expression for rough surfaces were made in order to help explain the nature of the interactions. The only specific forces in the system were due to hydrogen bonding, which from the Poisson analysis were found to be -0.125 nN. The nonspecific forces of 0.155 nN represent an overall repulsive interaction. These nonspecific forces are comparable to the forces calculated from DLVO theory, in which electrostatic-double layer interactions are added to van der Waals attractions calculated at the distance of closest approach, as long as the van der Waals model for "rough" spherical surfaces is used. Calculated electrostatic-double layer and van der Waals interactions summed to 0.116 nN. In contrast, if the classic (i.e., smooth) sphere-sphere model was used to predict the van der Waals forces, the sum of electrostatic and van der Waals forces was -7.11 nN, which appears to be a large overprediction. The Poisson statistical analysis of adhesion forces may be very useful in applications of bacterial adhesion, because it represents an easy way to determine the magnitude of hydrogen bonding in a given system and it allows the fundamental forces to be easily broken into their components.
通过原子力显微镜（AFM）在水中研究了大肠杆菌JM109与模型表面（氮化硅）之间物理相互作用的性质。对细菌进行的AFM力测量可以代表范德华力和静电力、氢键、空间相互作用以及可能的配体-受体型键的综合作用。由于在整体分布中可能同时存在特异性（化学或短程力，如氢键）和非特异性（长程胶体）力，因此很难将这些力分解为各自的组成部分。本文基于将泊松统计应用于AFM粘附数据，对特异性和非特异性相互作用进行了解耦。为了帮助解释相互作用的性质，与经典的DLVO理论以及粗糙表面范德华表达式的修正形式进行了比较。系统中唯一的特异性力是由于氢键，通过泊松分析发现其为-0.125 nN。0.155 nN的非特异性力代表整体排斥相互作用。这些非特异性力与根据DLVO理论计算的力相当，在DLVO理论中，只要使用“粗糙”球形表面的范德华模型，就将静电双层相互作用加到在最接近距离处计算的范德华吸引力上。计算得到的静电双层和范德华相互作用之和为0.116 nN。相比之下，如果使用经典的（即光滑的）球-球模型来预测范德华力，静电和范德华力之和为-7.11 nN，这似乎是一个很大的高估。粘附力的泊松统计分析在细菌粘附应用中可能非常有用，因为它提供了一种简单的方法来确定给定系统中氢键的大小，并且可以轻松地将基本力分解为其组成部分。
