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Examination of the secondary structure of proteins by deconvolved FTIR spectra
Author(s) -
Byler D. Michael,
Susi Heino
Publication year - 1986
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360250307
Subject(s) - chemistry , deconvolution , globular protein , analytical chemistry (journal) , root mean square , fourier transform , spectral line , resolution (logic) , gaussian , molecular physics , nuclear magnetic resonance , crystallography , mathematical analysis , mathematics , physics , statistics , chromatography , computational chemistry , quantum mechanics , astronomy , artificial intelligence , computer science
Fourier transform ir (FTIR) spectra of 21 globular proteins have been obtained at 2 cm −1 resolution from 1600 to 1700 cm −1 in deuterium oxide solution. Fourier self‐deconvolution was applied to all spectra, revealing that the amide I band of each protein except casein consists of six to nine components. The components are observed at 11 well‐defined frequencies, although all proteins do not exhibit components at every characteristic frequency. The root mean square (RMS) deviation of 124 individual values from the 11 average characteristic frequencies is 1.9 cm −1 . The observed components are assigned to helical segments, extended beta ‐segments, unordered segments, and turns. Segments with similar structures do not necessarily exhibit band components with identical frequencies. For instance, the lower frequency beta ‐structure band can vary within a range of approximately 15 cm −1 . The relative areas of the individual components of the deconvolved spectra were determined by a Gauss–Newton, iterative curve‐fitting procedure that assumed Gaussian band envelopes for the deconvolved components. The measured areas were used to estimate the percentage of helix and beta ‐structure for each of 21 globular proteins. The results are in good general agreement with values derived from x‐ray data by Levitt and Greer. The RMS deviation between 22 values ( alpha ‐ and beta ‐content of 11 beta ‐rich proteins measured by both techniques) is 2.5 percentage points; the maximum absolute deviation is 4 percentage points.