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Biomedical subjects

W Drost-Hansen

Publications and source records attributed to W Drost-Hansen.

6 recordsLinked to original sources

Temperature effects on cell-functioning--a critical role for vicinal water.

Interfacially modified water ('vicinal water') appears to extend over distances of several molecular diameters from an adjacent interface and possesses highly unusual thermal properties. Specifically, the vicinal water undergoes relatively abrupt changes over narrow temperature intervals centered around 15 degrees, 30 degrees, 45 degrees and 60 degrees C and these changes most likely reflect higher order (structural) phase transitions. Vicinal water occurs at all interfaces (independent of specific surface characteristics) and will therefore also be present in all biological cells. As a result, the effects of vicinal water ramify through all of cell biology and this explains many unexpected thermal anomalies seen in the temperature responses of a great variety of living systems. Thus, the concept of the thermal anomalies may explain such observations as abrupt changes in enzyme functioning; anomalous temperature effects in membrane processes; unusual cell volume responses to temperature; dramatic changes in erythrocyte sedimentation rates; anomalies in chromosome aberration rates; pasteurization temperature; upper and lower thermal limits for microbial growth; multiple growth optima and minima and body temperatures of mammals and birds.

Animals↗

Interaction of dolichol and dolichyl phosphate with phospholipid bilayers.

The thermotropic phase transition of dipalmitoylphosphatidylcholine vesicles reconstituted with dolichol or dolichyl phosphate was investigated as a function of the lipid-to-polyisoprenoid ratio by means of differential scanning calorimetry and fluorescence depolarization of the embedded probe 1,6-diphenyl-1,3,5-hexatriene. At the concentrations studied, dolichol and dolichyl phosphate lowered and broadened the transition temperature of dipalmitoylphosphatidylcholine bilayers. Dolichol was found to increase the motional freedom of the bilayer both below and above the transition temperature as determined by fluorescence depolarization. In contrast, low concentrations of dolichyl phosphate decreased the bilayer motional freedom below the transition temperature while high concentrations increased the motional freedom. Above the transition temperature, dolichyl phosphate decreased bilayer 'fluidity' at all concentrations. The data suggest that these polyisoprenoids perturb the bilayer lattice, with the neutral species dolichol increasing membrane 'fluidity', while dolichyl phosphate acts to 'stiffen' the membrane.

Calorimetry, Differential Scanning↗