Folding stabilization

Liquid paraffin dansylatmdes 10-fold, stabilization >10h spray solution, 67% in n-hexane [245]... 

Triton X-100 ethoxyquin (antioxidant in spices) > 200-fold, stabilization > 15 h spray solution, 33% in benzene the fluorescence of aflatoxin Bi is reduced by 10 to 15% [292]. 

These studies conducted in solution and in the solid state revealed a common 3i4-helical fold stabilized by H-bonds closing 14-membered rings formed between NH and C=0 +2 (see Fig. 2.12A and C). It is noteworthy that the 3i4-helix of j -peptides with L-amino acid-derived chirality centers (Fig. 2.12 A) and the a-helix have opposite polarity and helicity. 

Detailed NMR conformational analysis of y -peptides 139-141 (Fig. 2.35) in pyri-dine-d5 revealed that y-peptides as short as four residues adopt a 2.6-hehcal fold stabilized by H-bonds between C=0 and NH +3 which close 14-membered pseudocycles [200, 201]. The 2.614-helical structure of a low energy conformer of y-hex-apeptide 141 as determined from NMR measurements in pyridine-d5 [200], is shown in Fig. 2.36A and B). Determination of the structure of y" -peptides in CD3OH was hampered by the much lower dispersion of the diasterotopic H-C(a) protons compared to their dispersion in pyridine-d5. However, the characteristic and properly resolved i/ir-2 NOE crosspeacks between H-C(y) and NH +2 in the NH/H-C(y) region of the ROESY spectrum were an indication that the 2.6-helical structure is at least partially populated in CD3OH. 

J.-L. Popot, D. M. Engelman (2000) Helical membrane protein folding, stability and evolution. Annu. Rev. Biochem., 69 881-923... 

Human epidermal growth factor Triton X-100 (0.02% w/v) Eibronectin (0.05% w/v) Solution 2 fold increased stability at 60°C -1.5 fold stability increase at 60°C [19]... 

Kidric, M., Fabian, H., Brzin, J., Popovic, T., and Pain, R.H. 2002. Folding, stability, and secondary structure of a new dimeric cysteine proteinase inhibitor. Biochem. Biophys. Res. Commun. 297 962-967. 

Litowski, J. R., and Hodges, R. S. (2001). Designing heterodimeric two-stranded alpha-helical coiled-coils The effect of chain length on protein folding, stability and specificity./. Pept. Res. 58, 477-492. 

Several attempts have been made to improve the PB by accounting for the effects of ion size, ion correlation, and fluctuations of ion distributions. The resultant modified models have led to improved predictions for the ion effects in RNA/DNA folding stability. 

From the partition function, we can predict a variety of ion-dependent folding properties such as the ion-binding properties and the ion-dependence of the folding stability. 

To predict the ion-dependent folding stability for a short DNA helix, we use a two-state model. Specifically, we assume that the conformational ensemble of the system consists of two states double-stranded (ds) helix as the folded state and single-stranded (ss) hehces (stabilized by the single-stranded self-stacking) as the unfolded state. For a given ionic condition... 

Na+, Mg2 1) and temperature T, using the TBI model (Fig. 22.1), we compute the electrostatic free energies for the duplex GES and the unfolded state GE, respectively. The electrostatic contribution to the folding stability is... 

The ion-dependence of AGe shows how the ionic condition affects the folding stability and how the changes in ionic conditions induce the fold-ing/unfolding transition. 

To predict the total folding stability also requires the result for the nonelectric part of the free energy difference AGne. Assuming the ion-independence of AGNE, we can estimate AGne from the empirical parameters measured at 1 MNa+ (SantaLucia, 1998) ... 

More work needs to be done to develop increasingly accurate representations of the electronic states of peptides and various side chain chromophores. Once this is completed, the models are in place to examine interactions between these states for a given protein conformation. An accurate and flexible model which can calculate CD spectra of a variety of protein structures would be invaluable in the study of protein folding, stability, and structure. 

Elastin is not a true rubber as it is not self-lubricating. It has elastic properties only in the presence of water. At rest, elastin is tightly folded, stabilized by hydrophobic interactions between nonpolar residues this has been termed an oiled coil. On stretching, these hydrophobic interactions are broken, and the nonpolar residues are exposed to water. This conformation is thermodynamically unstable, and once the stretching force is removed, the elastin recoils to its resting state. 

Kowalski, J. M., R. N. Parekh, J. Mao and K. D. Wittrup. Protein folding stability can determine the efficiency of escape from endoplasmic reticulum quality control. J Biol Chem (1998) 273(31) 19453-8. 

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