Cholest-5-ene-3 beta,4 beta-diyl diacetate

The title steroid, C31 H5004, is shown to pack in a highly anisotropic manner. Only a-face-to-/~-face contacts are found in the stacks formed along the b direction, there are only head-to-tail contacts in the c direction and the acetate groups lie in layers normal to c

A f-19 and deuterium nmr-study of two novel fluorosterols and their properties in model membranes and high-density-lipoprotein

Fluorine-19 nuclear magnetic resonance at 235 MHz has been used to characterize the NMR properties of two novel fluorinated sterols, 6,6-difluorocholestanol and 7,7-difluorocholestanol, and various 3-ester derivatives. F-19-F-19 and F-19-H-1 coupling constants in chloroform are reported. H-2-NMR studies of side-chain perdeuterated dimyristoylphosphatidylcholine (DMPC-d54) prove that the two unesterified fluorosterols affect model membrane dynamical properties in a manner analogous to cholesterol. In aqueous detergent the F-19 chemical shifts of both 6,6- and 7,7-difluorocholestanols are perturbed about 1 ppm upfield by esterification at the 3-position, suggesting that F-19-NMR may be a useful monitor of enzyme catalyzed sterol acylation in vitro. Finally 6,6-difluorocholestanol oleate has been incorporated into human high density lipoprotein (HDL) and its F-19 signals observed in this environment. The appearance of the spectrum, and the results of lipophilic relaxation probe experiments, indicate that the acyl sterol partitions into at least two environments, and exhibits slightly different chemical shift and homonuclear scalar coupling characteristics in each

Lipoprotein-associated phospholipase A(2) as an independent predictor of coronary heart disease

Background: Chronic inflammation is believed to increase the risk of coronary events by making atherosclerotic plaques in coronary vessels prone to rupture. We examined blood constituents potentially affected by inflammation as predictors of risk in men with hypercholesterolemia who were enrolled in the West of Scotland Coronary Prevention Study, a trial that evaluated the value of pravastatin in the prevention of coronary events. Methods: A total of 580 men who had had a coronary event (nonfatal myocardial infarction, death from coronary heart disease, or a revascularization procedure) were each matched for age and smoking status with 2 control subjects (total, 1160) from the same cohort who had not had a coronary event. Lipoprotein-associated phospholipase A(2), C-reactive protein, and fibrinogen levels and the white-cell count were measured at base line, along with other traditional risk factors. The association of these variables with the risk of coronary events was tested in regression models and by dividing the range of values according to quintiles. Results: Levels of C-reactive protein, the white-cell count, and fibrinogen levels were strong predictors of the risk of coronary events; the risk in the highest quintile of the study cohort for each variable was approximately twice that in the lowest quintile. However, the association of these variables with risk was markedly attenuated when age, systolic blood pressure, and lipoprotein levels were included in multivariate models. Levels of lipoprotein-associated phospholipase A(2) (platelet-activating factor acetylhydrolase), the expression of which is regulated by mediators of inflammation, had a strong, positive association with risk that was not confounded by other factors. It was associated with almost a doubling of the risk in the highest quintile as compared with the lowest quintile. Conclusions: Inflammatory markers are predictors of the risk of coronary events, but their predictive ability is attenuated by associations with other coronary risk factors. Elevated levels of lipoprotein-associated phospholipase A(2) appear to be a strong risk factor for coronary heart disease, a finding that has implications for atherogenesis and the assessment of risk

Role of the Skyrme tensor force in heavy-ion fusion

We make use of the Skyrme effective nuclear interaction within the time-dependent Hartree-Fock framework to assess the effect of inclusion of the tensor terms of the Skyrme interaction on the fusion window of the 16O–16O reaction. We find that the lower fusion threshold, around the barrier, is quite insensitive to these details of the force, but the higher threshold, above which the nuclei pass through each other, changes by several MeV between different tensor parametrisations. The results suggest that eventually fusion properties may become part of the evaluation or fitting process for effective nuclear interactions