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Biomedical subjects

M Bloom

Publications and source records attributed to M Bloom.

At least 109 records · Page 6Linked to original sources
PubMed1979

Deuterium magnetic resonance study of cholesteryl esters in membranes.

The ternary systems EYL:H2O (50:50 wt %) containing 1 and 5 mol % cholesteryl palmitate-d31 or 1 and 5 mol % cholesteryl palmitate-16,16,16,16-d3 have been studied. Cholesteryl palmitate-d31 gave a unique deuterium magnetic resonance spectrum corresponding to a homogeneous (delta vQ = 3 and 12 kHz) and a solid phase (deltaVQ = 38 and 118 kHz). From the characteristic spectra and spin-lattice relaxation times, a procedure for calculating the amount of each phase present in the ternary mixture is given resulting in a maximum value of homogeneously dissolved cholesteryl palmitate of 0.2 +/- 0.1 mol % and a solid fraction above 0.2 mol %. The most probable order parameter for the (-CD2)n portion of the homogeneous fraction of cholesteryl palmitate-d31 was determined from the quadrupolar splittings to be S = 0.1 which is less than one-half that of the order parameter found for the lecithin chains. Possible explanations for the diminution of the order parameter for cholesteryl ester in bilayers are discussed.

Cholesterol Esters↗
PubMed1979

Persistence of infectious Friend virus in spleens of mice after spontaneous recovery from virus-induced erythroleukemia.

Persistent infectious virus was detected in the majority of spleens of (C57BL/10 X A.BY)F1 mice after spontaneous recovery from Friend virus-induced erythroleukeima. The Friend murine leukemia helper virus (F-MuLV) was detected in titers up to 3 X 10(5) PFU/g of spleen. The defective spleen focus-forming virus (SFFV) was present in much lower titers and could be detected in cell-free spleen homogenates only after amplification of virus titer by growth of virus in vitro on SC1 cells. The incidence of cells producing F-MuLV alone in spleens after recovery from leukemia was 0.003 to 0.3%, and the incidence of cells producing both F-MuLV and SFFV was less than 0.0001 to 0.01%. In most recovered mouse spleens there appeared to be a selective reduction of SFFV relative to F-MuLV.

Animals↗
PubMed1978

Fatty acyl chain order in lecithin model membranes determined from proton magnetic resonance.

Proton magnetic resonance (1H NMR) has been used to compare the local orientational order of acyl chains in phospholipid bilayers of multilamellar and small sonicated vesicular membranes of dipalmitoyllecithin (DPL) at 50 degrees C and egg yolk lecithin (EYL) at 31 degrees C. The orientational order of the multilamellar systems was characterized using deuterium magnetic resonance order parameters and 1H NMR second moments. 1H NMR line shapes in the vesicle samples were calculated using vesicle size distributions, determined directly using electron microscopy, and a theory of motional narrowing, which takes into account the symmetry properties of the bilayer systems. The predicted non-Lorentzian line shapes and widths were found to be in good agreement with experimental results, indicating that the local orientational order (called "packing" by many workers) in the bilayers of small vesicles and in multilamellar membranes is substantially the same. This results was found to be true not only for the largest 1H NMR line associated with the nonterminal methylene protons but also for the resolved 1H NMR lines due to the alpha-CH2 and the terminal CH3 positions on the acyl chain. Analysis of the vesicle 1H NMR spectra of EYL taken with different medium viscosities yielded a value of approximately 4 X 10(-8) cm2 s-1 for the lateral diffusion constant of the phospholipid molecules at 31 degrees C.

Fatty Acids↗
PubMed1977

Deuterium magnetic resonance studies of the interaction of lipids with membrane proteins.

The deuterium magnetic resonance spectra of lipid-protein particles containing cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) isolated from beef heart mitochondria and the specifically deuterated lipid 1-(16,16,16-trideuteropalmitoyl)-2-palmitoleoyl phosphatidylcholine are presented. These reconstituted particles are of uniform lipid and protein content; however, the spectra clearly show two environments characterized by distinctly different residual quadrupolar splittings or order parameters. The less-ordered environment shows a splitting similar to but slightly less than that of the pure lipid alone at a given temperature. The more restricted environment appears to be induced by the presence of the protein. The amount of the restricted lipid is clearly temperature dependent with a 2- to 3-fold decrease in relative amount from 2 to 22 degrees. The rate of exchange of lipid between the free and restricted environments is slower than 10(3)/sec. The significance of these phenomena is discussed.

Chemical Phenomena↗