1 research outputs found
NMR studies of bio-systems at high pressure
No full textDipalmitoylphosphatidylcholine/cholesterol bilayer membranes were studied using \sp2H and \sp{31}P NMR spectroscopy over the pressure range from 1 bar to 5 kbar. The phase diagram was constructed, structure and dynamics of the bilayers were examined. The pressure dependence of the dynamic and conformational characteristics were studied using \sp{31}P NMR spectroscopy at 50\sp\circC over the pressure range from 1 bar to 5 kbar. Cholesterol is able to maintain the mobility of the head groups despite the ordering of hydrocarbon chains in clear contrast to the same in pure DPPC bilayers where large changes in the head group motion was evident. Limited interdigitation of the chain region was evident in the presence of 20 mol% cholesterol. The spin lattice relaxation times cross over from fast to slow correlation time regime with the main phase transition from the liquid crystal to gel phase.Pressure induced reversible unfolding of lysozyme was investigated by high resolution proton magnetic resonance spectroscopy by following the proton spectra of the following residues: His-15\sp{\varepsilon1}, Trp-28\sp{\varepsilon3}, Leu-17\sp{\delta\sp2}, Cys-64\sp\alpha and Trp-108\sp{\varepsilon3}. The experiments were performed at pH = 3.9 and 68.5\sp\circC in the pressure range from 1 bar to 5 kbar both in the absence and presence tri-N-acetylglucosamine (tri-NAG). Small but statistically significant differences in V were found for residues located in different regions of the protein. The effect of tri-NAG binding to lysozyme was to change of V from 10.3 0.6 to cm\sp3/mol to 18.1 1.7 cm\sp3/mol for the Trp-108\sp{\varepsilon3} residue which is located close to the active site. It is important to note that the Cys-64\sp\alpha residue also senses the binding of the substrate analog. The ability to detect statistically significant differences for V of individual residues located in different regions of lysozyme represents the main result of these experiments.The pressure induced unfolding of -helix, the helix-coil transition, of poly-N\sp5- (3-hydroxypropyl)-L-glutamine was investigated by high resolution \sp1H and \sp{13}C NMR spectroscopy and circular dichroism in aqueous medium and 7:3 methanol/water mixture at different temperatures. The line widths and spin lattice relaxation times were measured as a function of pressure over the range 1 bar to 5 kbar. Pressure induces an anomalous line width behavior facilitating exploration of the changes in H-bonding interactions associated with the helix-coil transition process. The current results provide reinforcing evidence for the proposed existence of an intermediate conformational state between the random coil and the -helix. A calibration curve for the estimation of the helix content in PHPG solutions was constructed.Made available in DSpace on 2011-05-07T12:27:16Z (GMT). No. of bitstreams: 2
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Previous issue date: 1993Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding ([email protected]) on 2011-05-07T14:41:14Z
Item is restricted indefinitely.Restriction data tranferred 2014-07-01T11:17:48-05:00
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