Unfolding transition

Kellermayer et aJ., 1997] Kellermayer, M., Smith, S., Granzier, H., and Bustamante, C. Folding-unfolding transition in single titin modules characterized with laser tweezers. Science. 276 (1997) 1112-1116... 

Fig. 8. Dependence of (A) corrected diffusion coefficient (D), (B) steady-state fluorescence intensity, and (C) corrected number of particles in the observation volume (N) of Alexa488-coupled IFABP with urea concentration. The diffusion coefficient and number of particles data shown here are corrected for the effect of viscosity and refractive indices of the urea solutions as described in text. For steady-state fluorescence data the protein was excited at 488 nm using a PTI Alphascan fluorometer (Photon Technology International, South Brunswick, New Jersey). Emission spectra at different urea concentrations were recorded between 500 and 600 nm. A baseline control containing only buffer was subtracted from each spectrum. The area of the corrected spectrum was then plotted against denaturant concentrations to obtain the unfolding transition of the protein. Urea data monitored by steady-state fluorescence were fitted to a simple two-state model. Other experimental conditions are the same as in Figure 6.

Bovine a -lactalbumin (BLA) is a protein whose structure appears to be unusually malleable and, as such, has been the focus of many studies of what is termed the molten globule transition. At low pH, BLA expands and is said to lose tertiary structure, but it maintains substantial secondary structure in a partial unfolding transition (molten globule... 

Navon A, Ittah V, Laity JH, et al. Local and long-range interactions in the thermal unfolding transition of bovine pancreatic ribonuclease A. Biochemistry 2001 40 93-104. 

Li A. and Daggett V. Identification and characterization of the unfolding transition state of chymotrypsin inhibitor 2 by molecular dynamics simulations. J. Mol. Biol. 

Figure 13.1 Microcalorimetry scans displaying Tm values for interleukin-1 receptor (IL-1R type I). The inlay displays the unfolding of IL-1R (I) showing the ACp measured as the baseline difference between the native (N) and denatured (D) states for two independent scans. Thermal unfolding of IL-1R (I) is composed of three cooperative unfolding transitions, labeled 1, 2, and 3.

The unfolding behavior of multidomain proteins in the presence of preservatives has also been evaluated. For example, IL-1R (type I) has three domains that correspond to three unfolding transitions as measured by microcalorimetry and depicted in Figure 13.1.31 All three transitions exhibit some shift to lower Tm in the presence of the three preservatives tested (i.e., 0.065% phenol, 0.1% metacresol, and 0.9% benzyl alcohol), in comparison to a control containing no preservative. Such a destabilization could have consequences for the shelf-life of the product. Another example of the impact of preservatives on a multidomain protein is illustrated in Figure 13.5. The protein is fused to a single IgCi, Fc. The... 

Liggins, J.R., F. Sherman, A.J. Mathews, and B.T. Nall. 1994. Differential scanning calorimetric study of the thermal unfolding transitions of yeast iso-1 and iso-2 cytochromes c and three composite isozymes. Biochemistry 33 9209-9219. 

VJ Hilser, CD Worosila, E Freire. Analysis of thermal-induced proteins folding/ unfolding transitions using free-solution capillary electrophoresis. Anal. Biochem. 208 125-131 (1993). 

Kellermayer MSZ, Smith SB, Granzier HL, Bustamante C. Folding-unfolding transitions in single titin molecules characterized with laser tweezers. Science 1997 276 1112-1126. 

Daggett, V., Validation of protein-unfolding transition states identified in molecular dynamics simulations. Biochem Soc Symp, 2001(68) 83-93. 

Mel nikov, S.M., Sergeyev, V.G., Yoshikawa, K., Takahashi, H. and Hatta, I. (1997a) Cooperativity or phase transition Unfolding transition of DNA cationic surfactant complex. J. Chem. Phys., 107, 6917-6924. 

Yoshikawa, Y., Nomura, S.M., Kanbe, T. and Yoshikawa, K. (2000) Controlling the folding/ unfolding transition of the DNA-histone HI complex by direct optical manipulation. Chem. Phys. Lett., 330, 77-82. 

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. 

Freire, E., van Osdol, W. W., Mayorga, O. L. and Sanchez-Ruiz, J. M. (1990). Calorimetrically determined dynamics of complex unfolding transitions in proteins. Annu. Rev. Biophys. Biophys. Chem. 19, 159-188. 

Fig. 8. Experimental ( — ) and theoretical heat capacity functions for the thermal folding/unfolding transition of phosphoglycerate kinase at pH 6.5 in the presence of 0.7 M GuHCl. The heat denaturation transition is characterized by a single peak, whereas the cold denaturation displays two peaks corresponding to the independent unfolding of the N and C domains. The experimental curve has been published before (Griko et al., 1989). As discussed in the text, the theoretical curve does not represent the best fit to the experimental data, but rather the calculated curve using structural information in conjunction with thermodynamic information for elementary interactions. [Reprinted from Freire et al. (1991).]...

Go N, Abe H (1981) Noninteracting local-structure model of folding and unfolding transition in globular proteins. I. formulation, Biopolymers 20 991-1011... 

The ability of modern HPLC techniques to yield quantitative data on rate constants for polypeptide or protein folding and unfolding transitions as well as to detect conformational intermediates with relaxation half-times of similar (or larger) magnitude to the mass transport time (i.e., rconf rmasstransfer, where Tmasstransfer > 10 sec) also has important ramifications in the selection... 

Fig. 2.2. GdnHCl-induced unfolding transition curves for authentic and recombinant goat a-lactalbumin [22], The filled diamonds indicate the unfolding transition of the methionine-free recombinant protein produced by CNBr cleavage. The unfolding was carried out at 25° C in the presence of 1 mM CaCB, 50 mM NaCl, and 50 mM sodium cacodylate (pH 7.0). The transitions were monitored by CD measurements at 222 nm (circles and diamonds) and at 270 nm (triangles), and the transition curves were normalized between the native and fully unfolded baselines. The black line with symbols represents the authentic form, and the gray line with symbols represents the recombinant form. Reproduced with permission from [22]...

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