Peptides protein denaturation

Salt (ionic strength) gradients in lEC discussed in Section 5.4.3.3 are frequently used in the separation of complex peptides, proteins, and other biopolymer samples as a complementary technique to RP solvent gradient separations, often in a 2D setup [99,100]. The gradients usually start at a low salt (chloride, sulfate, etc.) concentration and typically run from 0.005 to 0.5 M. A buffer is used to control the pH acetonitrile and methanol may be added to improve the resolution and urea to improve the solubility of proteins that are difficult to dissolve. Ion exchangers with not strongly hydrophobic matrices usually prevent protein denaturation in aqueous mobile phases. 

One of the most important causes of poor resolution in protein and large peptide analysis with conventional phases is slowness of mass transport and of sorption/desorption. When selecting a column for a protein separation, it is important to look for obtaining rapid separations in order to limit protein denaturation. 

In addition to improving drug absorption, permeation enhancers that form mixed micelles with peptides or proteins may also provide protection against metabolic processes, including protease-dependent inactivation, efflux transport, and protein denaturation, all of which could lead to reduced bioavailabUity. A permeation enhancer that may also inhibit some competing metabolic processes could greatly improve the poor and inconsistent bioavailabiUty of some short and cyclic polypeptides such as cyclosporine (11 aa cyclic peptide) (Figure 13.11). 

The third approach has provided several successful results, though its application is usually limited to low molecular-weight peptides or non-peptide drugs. The liposome formulations, however, suffer from difficulties of storage or reconstruction and unpredictable distribution. Immobilization into insoluble polymeric particles is difficult in the case of structured proteins, as it normally involves the use of organic solvents. Moreover, protein denaturation and degradation may occur... 

Native protein denatured protein-------------> peptides + amino adds... 

Hence, although the specific numerical values reported for ATPase rates of stress-70 proteins show some variation, possibly attributable to differences in specific protein preparation and assay procedures utilized by different individuals, the consensus scheme that these data show is that in the absence of substrate peptide, the stress-70 proteins have a low basal ATPase rate, typically found to be 0.01-0.03 (mol ATP/mol stress-70 protein min). This can be enhanced severalfold either by binding of peptides or denatured proteins, or (as demonstrated by the effect of grpE and dnaJ proteins on dnaK) by the action of ancillary proteins. To the extent that the observations on HSC70 can be generalized to other members of the stress-70 protein family, peptide binding appears to relieve the attenuation of ATPase activity and allow it to proceed at the rate characteristic of the ATPase fragment of the protein alone. 

Research on amyloid fibrils was facilitated by the fact that fibrils similar to the ones found in vivo can be formed in vitro from peptides and denatured proteins. However, stmcture determination of amyloid fibrils has proven to be difficult due to the... 

Although proteins and peptides are minor constituents of wine, they make a significant contribution to the quality of product and play an important role in the wine quality as they affect taste, clarity, and stability. Chitinases and TLP persist through the vinification process and may cause hazes and sediments in bottled wines during the storage due to protein denaturing and aggregating with mechanisms not fully... 

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