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This thesis is devoted to understanding solute-solvent interactions in folded and unfolded proteins. To this end, we have studied partial molar volume, V°, and adiabatic compressibility, K°S, of 20 amino acid side chains using low weight molecular model compounds, N-acetyl amino acid amide and its derivatives, between 18°C and 55°C. We used our data to develop an additive scheme for calculating the partial specific volume and adiabatic compressibility of fully extended polypeptide chains as a function of pH and temperature. We compared our calculated volumetric characteristics of the fully extended conformations of apocytochrome c and apomyoglobin with the experimental values measured in neutral pH (for apocytochrome c) or acidic pH (for apomyoglobin). The comparison between the calculated and experimental volumetric characteristics suggested that neither apocytochrome c nor apomyoglobin are fully unfolded and retain solvent-inaccessible amino acid residues. To study cosolvent-solute interactions, we determined V° and K° S of amino acid side chains and glycyl units as a function of urea concentration. We analyzed these data within the framework of a statistical thermodynamic formalism to determine the association constants, k, for the reaction in which urea binds to each of the amino acid side chains and the glycyl unit replacing two water molecules in solvation shell. Our determined k range from 0.04 to 0.39 M with the average of 0.16 +/- 0.09 M. There was no apparent correlation between the values of k and the ratio of polar to nonpolar solvent accessible surface areas. This study supports a direct interaction model in which urea denatures a protein by concerted action via favorable interactions with a wide range of protein groups. In addition, we have presented buffer ionization effect on the volume of protein denaturation could be significant with the potential to affect not only its magnitude but also its sign using a pressure perturbation calorimetric technique. Our results identified buffer ionization as an important determinant of protein transition volume that needs to be carefully taken into account. Results described in this work provide fundamental understanding of solute-solvent interaction in both folded and unfolded proteins.
This monograph presents the molecular theory and necessary tools for the study of solvent-induced interactions and forces. After introducing the reader to the basic definitions of solvent-induced interactions, the author provides a brief analysis of the statistical thermodynamics. The book thoroughly overviews the connection of those interactions with thermodynamics and consequently focuses on specifically discussing the hydrophobic-hydrophilic interactions and forces. The importance of the implementation of hydrophilic interactions and forces in various biochemical processes is thoroughly analyzed, while evidence based on theory, experiments, and simulated calculations supporting that hydrophilic interactions and forces are far more important than the corresponding hydrophobic effects in many biochemical processes such as protein folding, self-assembly of proteins, molecular recognitions, are described in detail. This title is of great interest to students and researchers working in the fields of chemistry, physics, biochemistry, and molecular biology.
This work covers advances in the interactions of proteins with their solvent environment and provides fundamental physical information useful for the application of proteins in biotechnology and industrial processes. It discusses in detail structure, dynamic and thermodynamic aspects of protein hydration, as well as proteins in aqueous and organic solvents as they relate to protein function, stability and folding.
A variety of complementary techniques and approaches have been used to characterize peptide and protein unfolding induced by temperature, pressure, and solvent. Volume 62, Unfolded Proteins, assembles these complementary views to develop a more complete picture of denatured peptides and proteins. The unifying observation common to all chapters is the detection of preferred backbone confirmations in experimentally accessible unfolded states. Peptide and protein unfolding induced by temperature, pressure, and solvent Denatured peptides and proteins Detection of preferred backbone confirmations in experimentally accessible unfolded states
This book deals with a subject that has been studied since the beginning of physical chemistry. Despite the thousands of articles and scores of books devoted to solvation thermodynamics, I feel that some fundamen tal and well-established concepts underlying the traditional approach to this subject are not satisfactory and need revision. The main reason for this need is that solvation thermodynamics has traditionally been treated in the context of classical (macroscopic) ther modynamics alone. However, solvation is inherently a molecular pro cess, dependent upon local rather than macroscopic properties of the system. Therefore, the starting point should be based on statistical mechanical methods. For many years it has been believed that certain thermodynamic quantities, such as the standard free energy (or enthalpy or entropy) of solution, may be used as measures of the corresponding functions of solvation of a given solute in a given solvent. I first challenged this notion in a paper published in 1978 based on analysis at the molecular level. During the past ten years, I have introduced several new quantities which, in my opinion, should replace the conventional measures of solvation thermodynamics. To avoid confusing the new quantities with those referred to conventionally in the literature as standard quantities of solvation, I called these "nonconventional," "generalized," and "local" standard quantities and attempted to point out the advantages of these new quantities over the conventional ones.
Since the first attempts to model proteins on a computer began almost thirty years ago, our understanding of protein structure and dynamics has dramatically increased. Spectroscopic measurement techniques continue to improve in resolution and sensitivity, allowing a wealth of information to be obtained with regard to the kinetics of protein folding and unfolding, and complementing the detailed structural picture of the folded state. Concurrently, algorithms, software, and computational hardware have progressed to the point where both structural and kinetic problems may be studied with a fair degree of realism. Despite these advances, many major challenges remain in understanding protein folding at both the conceptual and practical levels. Computational Methods for Protein Folding seeks to illuminate recent advances in computational modeling of protein folding in a way that will be useful to physicists, chemists, and chemical physicists. Covering a broad spectrum of computational methods and practices culled from a variety of research fields, the editors present a full range of models that, together, provide a thorough and current description of all aspects of protein folding. A valuable resource for both students and professionals in the field, the book will be of value both as a cutting-edge overview of existing information and as a catalyst for inspiring new studies. Computational Methods for Protein Folding is the 120th volume in the acclaimed series Advances in Chemical Physics, a compilation of scholarly works dedicated to the dissemination of contemporary advances in chemical physics, edited by Nobel Prize-winner Ilya Prigogine.
Covering experiment and theory, bioinformatics approaches, and state-of-the-art simulation protocols for better sampling of the conformational space, this volume describes a broad range of techniques to study, predict, and analyze the protein folding process. Protein Folding Protocols also provides sample approaches toward the prediction of protein structure starting from the amino acid sequence, in the absence of overall homologous sequences.
The book will discuss classes of proteins and their folding, as well as the involvement of bioinformatics in solving the protein folding problem. In vivo and in vitro folding mechanisms are examined, as well as the failures of in vitro folding, a mechanism helpful in understanding disease caused by misfolding. The role of energy landscapes is also discussed and the computational approaches to these landscapes.