Protein folding stands as one of the major interdisciplinary challenges of the last fifteen years, involving biology, chemistry, medicine and physics. In this book solvent effects, and the related hydrophobic effect, on proteins are investigated. Using a simple lattice model of proteins, in which the solvent is semi-explicitly taken into account, thermodynamical quantities can be investigated and the crucial role the solvent plays in protein folding can be demonstrated. Of particular relevance is our observation that a simple model, in which the potential energy is described in terms of the interactions between amino-acids only, does not correctly reproduce solvent effects. Approaches like this, in which solvent effects are treated implicitly, are commonly employed in many of more sophisticated models for protein folding dynamics. Our results are then of great importance as they suggest the treatment of the solvent in these models may need to be re-examined.

Protein Actions: Principles and Modeling is aimed at graduates, advanced undergraduates, and any professional who seeks an introduction to the biological, chemical, and physical properties of proteins. Broadly accessible to biophysicists and biochemists, it will be particularly useful to student and professional structural biologists and molecular biophysicists, bioinformaticians and computational biologists, biological chemists (particularly drug designers) and molecular bioengineers. The book begins by introducing the basic principles of protein structure and function. Some readers will be familiar with aspects of this, but the authors build up a more quantitative approach than their competitors. Emphasizing concepts and theory rather than experimental techniques, the book shows how proteins can be analyzed using the disciplines of elementary statistical mechanics, energetics, and kinetics. These chapters illuminate how proteins attain biologically active states and the properties of those states. The book ends with a synopsis the roles of computational biology and bioinformatics in protein science.

"Metropolis Monte Carlo (MC) simulations were performed with positively charged peptides in aqueous solution to study changes in peptide conformations at solid/liquid interface, and its effects on protein aggregation. Intermediate-resolution diblock model peptide, comprising of 10 units of ALA (non-polar) and LYS (polar) amino acid residues, was used for the simulations. In the first approach to modeling, solvent effects were considered explicitly. The explicit model was then used to study two peptide molecules, in helical structure, at solid/liquid interface. In order to increase the number of peptide molecules in the simulation box, with reduced computational cost, an implicit solvent model was developed with nonadditive hydrogen bonding and hydrophobic interaction potentials. The implicit model was used to simulate two peptides of helical structure at charged surfaces (to compare with the explicit model), and ten peptides of random coil structure with and without charged surfaces. The peptides were observed to always move towards the negatively charged surface and orient with residues of complimentary charge settling close to the surface, maximizing the electrostatic interactions. On reaching the surface, the peptides partially lose their secondary structure and clusters around the hydrophobic ends; this restructuring and dehydration of the peptides provides the entropic drive for adsorption and subsequent misfolding events. The 2- peptide-water-surface system in explicit model was also simulated with periodic switching of surface charge polarity, to induce a "shaking effect" in order to observe possible peptide configurational changes"--Abstract, page iii.

The almost universal presence of water in our everyday lives and the very `common' nature of its presence and properties possibly deflects attention from the fact that it has a number of very unusual characteristics which, furthermore, are found to be extremely sensitive to physical parameters, chemical environment and other influences. Hydrogen-bonding effects, too, are not restricted to water, so it is necessary to investigate other systems as well, in order to understand the characteristics in a wider context. Hydrogen Bond Networks reflects the diversity and relevance of water in subjects ranging from the fundamentals of condensed matter physics, through aspects of chemical reactivity to structure and function in biological systems.

Computational modeling is emerging as a powerful new approach to study and manipulate biological systems. Multiple methods have been developed to model, visualize, and rationally alter systems at various length scales, starting from molecular modeling and design at atomic resolution to cellular pathways modeling and analysis. Higher time and length scale processes, such as molecular evolution, have also greatly benefited from new breeds of computational approaches. This book provides an overview of the established computational methods used for modeling biologically and medically relevant systems.