Computational Models of Hen Egg White Lysozyme Physisorption to Silica- and Mica-like Surfaces

Protein-surface adsorption phenomena play a crucial role in a variety of fields, including medicine, molecular and cell biology, biotechnology, phar- maceutical sciences, and biophysics. It is therefore desirable to develop accu- rate models to describe them. Hen-Egg-White-Lysozyme (HEWL) adsorption to silica- and mica-like surfaces entails minimal conformational changes, rendering it an ideal system for rigid-body Brownian dynamics simulations. Experimen- tal studies revealed that the fluorescence attached to HEWL exhibits a sharp overshoot followed by a trough as a function of time. This work identifies two inconsistencies in the explanation previously used by the authors to interpret the experiment. A reorientation does not seem to be the main driving factor for the overshoot. Furthermore, I examine previously used electrostatic potential models based on the Poisson-Boltzmann equation (PBE) used by Romanowska et al. and Reinhardt et al.. It is found that even though different orientations of HEWL- FITC on the surface are possible, the required amount of adsorbed proteins and corresponding reorientation is attained only with the linearized PBE-potential. The study provides a possible explanation why reaching the critical overshoot value with non-linearized PBE-based models poses difficulties. Overcoming this problem is an indispensable step in developing Brownian-dynamics-based atomic- detail multi-molecule models for protein-surface adsorption.