Spectroscopy, circular dichroic

Measuring Protein Sta.bihty, Protein stabihty is usually measured quantitatively as the difference in free energy between the folded and unfolded states of the protein. These states are most commonly measured using spectroscopic techniques, such as circular dichroic spectroscopy, fluorescence (generally tryptophan fluorescence) spectroscopy, nmr spectroscopy, and absorbance spectroscopy (10). For most monomeric proteins, the two-state model of protein folding can be invoked. This model states that under equihbrium conditions, the vast majority of the protein molecules in a solution exist in either the folded (native) or unfolded (denatured) state. Any kinetic intermediates that might exist on the pathway between folded and unfolded states do not accumulate to any significant extent under equihbrium conditions (39). In other words, under any set of solution conditions, at equihbrium the entire population of protein molecules can be accounted for by the mole fraction of denatured protein, and the mole fraction of native protein,, ie. 

N. Harada and K. Nakanishi, Circular Dichroic Spectroscopy-Exdton Coupling in Organic and Bioorganic Stereochemistry, Univ. Science Books, Mill Valley, CA, 1982. 

Spectrophotometric and spectrofluorimetric methods provide a wealth of information concerning structural determinations (identification, purity and precise measurement of concentration) and chemical changes in alkaloids. These techniques yield both quantitative and qualitative data on the effect of solvents, pH and other physiological conditions [141-143]. X-ray crystallography, H and NMR spectroscopy, infrared spectroscopy (IR) and circular dichroic spectroscopy were also used to study the physical properties... 

Harada, N. Nakanishi, K. Circular Dichroic Spectroscopy—Exciton Coupling in Organic Stereochemistry, Oxford University Press, Oxford, 1983. 

Figure 13. Definition of exciton chirality. Summation of the two Cotton effects (broken lines) separated by Davydov splitting A). gives the curves shown in solid lines. Adapted from N. Harada, K. Nakanishi. Circular Dichroic Spectroscopy - Exciton Coupling in Organic Stereochemistry, University Science Books. Mill Valley, California. 1983...

Harada N, Nakanishi K (1983) Circular dichroic spectroscopy exciton coupling in organic chemistry. University Science Books, Oxford... 

Owing to the instability of the isolated subunits of FqF, direct measurement of the secondary structure by circular dichroic spectroscopy or infrared spectroscopy has been limited to the subunits of TF, [30,78], For example, the secondary structures of TFj and its subunits are lost in the presence of 8 M urea, but restored on its removal [30]. The secondary structure has also been estimated from the amino acid sequence of EF, [11,21] by the method of Chou and Fassman [79]. Table 5.2 summarizes the contents of a-heUces and )8-sheets of subunits of TF, [30] and EF, [11]. Similar values were obtained for TF, and EF,. The CO-stretching vibrations of the a and subunits of TF, were 1648 cm and 1640 cm , respectively, indicating that the subunit has a greater amount of antiparallel )8-sheet structure than the subunit [80]. 

Directly measured on isolated subunits by circular dichroic spectroscopy [30]. 

Harada, N., Nakanishi, K. (1983), Circular Dichroic Spectroscopy University Science Books New York. 

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