Fourier secondary structure content

In conclusion, the analysis of spectra properly recorded to 185 nm, or lower where possible, can give useful estimates of secondary structure content, but the content of turns and of P-structure should be interpreted with caution. Fourier transform infrared spectroscopy (FTIR) provides better estimates of the latter. When using the results of far-UV CD determination to characterize reproducibility of folding for different samples, it is important first to compare the spectra visually and to look for possible trends or factors that may explain small differences, rather than to rely solely on comparison of derived secondary structure contents. 

FSD spectra are frequently curve-fit to obtain an estimate of the secondary structure content of the protein being examined. This is justifiable because, in theory, Fourier self-deconvolution should not affect the relative areas of component bands. In practice however, it was found that this assumption is not valid. The relative areas of bands at the edges of the amide I region are increased by FSD. Therefore the following procedure was used for structural analysis. 

Secondary structure is most easily assessed by spectroscopic methods, in particular circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR). These techniques can be used to determine the content of a-helices, /3-sheets and, with... 

Low-resolution optical spectroscopic measurements established that the PrPc—>PrPSc conversion is accompanied by a major decrease in a-helical content and an increase in (3-sheet structure [101-104]. However, the secondary structure of PrPSc remains controversial, with the estimated content of a-helical structure ranging from 0%, as assessed by circular dichroism spectroscopy [104], to 0-21%, as inferred from Fourier-transform infrared measurements [101-103, 105]. These low resolution spectroscopic measurements are subject to considerable uncertainty thus, caution should be exercised when using global secondary structure estimates for constructing specific high-resolution structural models of PrPSc. 

A benefit of peptide synthesis is that one can easily fine tune amino acid content (i.e. primary structure) of peptides to customize final molecular conformations, gelation times, or other molecular interactions. This allows the creation of an array of peptides with minute differences in sequences but vast differences in final properties. Characterization is important to understanding the secondary structures formed by individual peptides and, consequently, the higher order structures that are formed during gelation. To confirm and characterize second order stracture, two spectroscopic methods, circular dichroism spectroscopy (CD) and Fourier-transform infrared spectroscopy (FUR) are frequently used. Both methods examine light absorption... 

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