Stability structural, of proteins

During the past 10 years, tremendous advances have occurred in protein science that are due, in large part, to combining experimental studies with sophisticated computer simulations. In particular, these techniques have revealed the critical role that water plays in the function and structural stability of proteins, an aspect largely ignored in the past (Ghosh et al., 2003). 

It is widely known that the cosolvents influence the structural stability of proteins and alter dynamic properties of water molecules [26,39]. It is, therefore, natural that the energy flow in protein should also be strongly influenced in the mixed solvent environment. When the energy flow from the protein to the ambient solvent is investigated from the view point of the solvent structural dynamics, it is, of course, necessary to develop some theoretical framewoiks, which are able to evaluate the spatial distributions of each solvent component around the large and flexible macromolecules. For this purpose, we developed the surficial KB theory [40], and applied it to examine the role of ectoine [24], a zwitterionic CS that protects protein function against environmental stresses. 

Another major area of impact of thermodynamics concerns the structural and functional stability as well as the activity of the proteins. The technical implications of knowledge in this field for reprocessing recombinant proteins by unfolding and refolding and for designing appropriate micro-environments and processing conditions in bioreactors and recovery equipment are evident. The lectures on conformational and structural stability of proteins are thus a key element in the course. 

Haynes C A and Norde W 1995 Structural stabilities of adsorbed proteins J. Colloid Interface Sci. 169 313-28... 

Noncovalent Forces Stabilizing Protein Structure. Much of protein engineering concerns attempts to alter the stmcture or function of a protein in a predefined way. An understanding of the underlying physicochemical forces that participate in protein folding and stmctural stabilization is thus important. 

The most frequent of the domain structures are the alpha/beta (a/P) domains, which consist of a central parallel or mixed P sheet surrounded by a helices. All the glycolytic enzymes are a/p structures as are many other enzymes as well as proteins that bind and transport metabolites. In a/p domains, binding crevices are formed by loop regions. These regions do not contribute to the structural stability of the fold but participate in binding and catalytic action. 

Formulation strategies for stabilization of proteins commonly include additives such as other proteins (e.g., serum albumin), amino acids, and surfactants to minimize adsorption to surfaces. Modification of protein structure to enhance stability by genetic engineering may also be feasible, as well as chemical modification such as formation of a conjugate with polyethylene glycol. 

Globular proteins are known to act as polymeric stabilizers of protein structure in solution. Wang and Hanson [106] review the mechanisms of protein stabilization by serum albumin, and it has been included in... 

Stabilization of proteins against those degradative processes with retention of structure and function through removal of water requires an understanding of the process of lyophilization or freeze-drying. 

S. N. Timasheff, Stabilization of protein structure by solvent additives, in Stability of Protein Pharmaceuticals, Part B In Vivo Pathways of Degradation and Strategies for Protein Stabilization (T. J. Ahern and M. C. Manning, eds.), Plenum Press, New York, 1992, pp. 265-285. 

The structure and structural stability of globular proteins in aqueous solution are the result of various interactions inside the protein molecule, between the protein and the water, and among the water molecules (Norde 2003a). The... 

The sorbent materials are supplied as finely dispersed colloidal particles, whose surfaces are smooth. Some of their properties are presented in Table 3. The sorbents cover different combinations of hydrophobicity and sign of the surface charge. Thus, the model systems presented allow systematic investigation of the influences of hydrophobicity, electric charge, and protein structural stability on protein adsorption. 

Many polypeptides undergo covalent modification after (or sometimes during) their ribosomal assembly. The most commonly observed such PTMs are listed in Table 2.7. Such modifications generally influence either the biological activity or the structural stability of the polypeptide. The majority of therapeutic proteins bear some form of PTM. Although glycosylation represents the most common such modification, additional PTMs important in a biopharmaceutical context include carboxylation, hydroxylation, sulfation and amidation these PTMs are now considered further. 

Lee, B. and Vasmatis, G. 1997. Stabilization of protein structures. Current Opinion in Biotechnology 8, 423-428. 

Fig. 6. Structural stability of major ampullate silk protein in constrained Nephila edulis. The graph shows a time series of circular dichroism spectra of major ampullate (MA) protein at 1% w/v in distilled water. The spiders prior to dissection were prevented from spinning, but fed and watered for at least 2 weeks. With time, the secondary structure of silk protein is becoming more and more disordered. The arrow indicates increasing time (days). Note that the amino acid composition of the silk protein was similar to that of a native N. edulis spider. Interestingly, silk protein extracted from the constrained spider did not respond to denaturing conditions (detergents, alcohols, pH, and salts Dicko et al, 2004a, 2005).

Privalov, P.L. and S.J. Gill. 1988. Stability of protein structure and hydrophobic interaction. Adv Protein Chem 39 191-234. 

Sequence inversion and racemization have been associated with uncatalyzed formation of the cyclic dipeptides and has been shown to greatly complicate the kinetics of formation. Cyclic dipeptide formation, by uncatalyzed processes, is rapid enough to pose an apparent threat to the stability of proteins and a possible rationale for the posttranslational N-acetylation of proteins that have been observed in higher organisms. The rate of DKP formation will also depend on the carbonyl ester protecting groups or the structures of the peptide-resin linkage in the solid-phase mode. Furthermore, cyclization is a concentration-independent reaction and demands the use of dilute solutions. ... 

Like most other approaches to structural analysis of proteins, however, DSC is most valuable when it is not the only source of structural information concerning a given protein. DSC can provide evidence concerning the number of domains, or "cooperative unfolding units" into which a protein is divided, the stabilities of the individual domains. 

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