Effect on protein stability

Disulfides. The introduction of disulfide bonds can have various effects on protein stability. In T4 lyso2yme, for example, the incorporation of some disulfides increases thermal stability others reduce stability (47—49). Stabili2ation is thought to result from reduction of the conformational entropy of the unfolded state, whereas in most cases the cause of destabili2ation is the introduction of dihedral angle stress. In natural proteins, placement of a disulfide bond at most positions within the polypeptide chain would result in unacceptable constraint of the a-carbon chain. 

Alber, T. Mutational effects on protein stability. Annu. Rev. Biochem. 58 765-798, 1989. 

T. W. Randolph, Phase separation of excipients during lyophilization Effects on protein stability, J. Pharm. Sci., 86(11), 1198 (1997). 

Some drugs can also increase the amount of active CYP enzyme via effects on protein stabilization or the transcriptional apparatus. This process is called induction. 

Thus we note that cations (and anions) in proteins would have a very general effect on protein stability, either through cross-linking (similar to the effects of disulfide bridges) or through a general electrostatic effect... 

Lu, S. M., and Hodges, R. S. (2004). Defining the minimum size of a hydrophobic cluster in two-stranded alpha-helical coiled-coils Effects on protein stability. Prot. Sci. 13, 714-726. 

Yang, A. and B. Honig. (1994). Structural origins of pH and ionic strength effects on protein stability. Acid denaturation of sperm whale apomyoglobin. J. Mol. Biol. 237 602-14. 

Once a range of suitable pH and ionic strength are selected, the effect on protein stability is evaluated for the final selection of an optimal formulation pH. Only when the optimal pH and addition of common salts do not render the desired solubility are other additives considered. This adds to the complexity of the formulation and the challenge of maintaining stability. Recently, an empirical approach to determine protein phase diagrams using various biophysical techniques has been used to facilitate identification of optimal formulation conditions (Fan etal., 1995). 

Alber, T. A. (1989). Mutational effects on protein stability. Ann. Rev. Biochem. 58, 765-798. Branden, C., Tooze, J. (1991). Introduction to Protein Stiucture, Garland Publishing, New York and London. 

Strength Effects on Protein Stability—Acid Denaturation of Sperm Whale Apomyoglobin. 

Anton, M., J. R6sgen, M. Sinev, L. M. R Holthanzen, and D. W. Bolen. 2011. Osmolyte effects on protein stability and solubility A balancing act between backbone and side-chains. Biophysical Chemistry. 159, 90. 

It is not possible to measure preferential interactions between solutes and proteins in frozen samples. Therefore, it is not known if cryoprotectants are actually preferentially excluded from frozen proteins. However, a recent study by Heller et al. [82] has provided direct evidence that the influence of a solute on protein chemical potential accounts for the solute s effect on protein stability during freezing. First, it was found with infrared spectroscopy that hemoglobin s secondary structure was perturbed in the frozen state. To test the effect of increasing the protein s chemical potential on inhibiting freezing-induced structural perturbation, hemoglobin was... 

A.-S. Yang and B. Honig, /. Mol. Biol., 237, 602 (1994). Structural Origins of pH and Ionic Strength Effects on Protein Stability. Acid Denaturation of Sperm WTiale Apomyoglobin. 

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