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UN H and SH H cross-relaxation in hydrated proteins

Journal Article · · Biophys. J.; (United States)
The frequency dependence of the proton spin-lattice relaxation time T1 of solid hydrated bovine serum albumin and alpha-chymotrypsin has been measured over 4.5 decades in the range 10(4) to 3 X 10(8) Hz mainly by the aid of the field-cycling technique. The comparison between H2O- and D2O-hydrated samples permitted the distinction of exchangeable and unexchangeable protons. In all cases the UN H cross-relaxation dips due mainly to the amide groups have been observed. In addition, in the case of the deuterium exchanged proteins a SH H quadrupole dip appears. The amide groups act as relaxation sinks due to the coupling of the amide proton to UN and adjacent protons. Outside of the dip regions the proton-proton coupling dominates. The fluctuations of the UN H and H H interactions are of a different type. The unexchangeable protons show a T1 dispersion outside of the quadrupole dip regions given by the exceptional power law T1 approximately v0.75 +/- 0.05. It is shown that apart from structural information of the UN spectra, UN H cross-relaxation spectroscopy permits the determination of correlation times in the range 10(-7) s less than tau less than 10(-4)S.
Research Organization:
Universitaet Ulm, Germany, F.R.
OSTI ID:
6257865
Journal Information:
Biophys. J.; (United States), Journal Name: Biophys. J.; (United States) Vol. 2; ISSN BIOJA
Country of Publication:
United States
Language:
English