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N Janes

Publications and source records attributed to N Janes.

23 records · Page 2Linked to original sources
PubMed1991

The role of anionic phospholipids in membrane adaptation to ethanol.

In rats chronically fed-ethanol, liver microsomes and mitochondria, brain synaptosomes and reconstituted vesicles of their respective membrane phospholipids are resistant to disordering by ethanol in vitro (membrane tolerance) after 35 days of ethanol exposure. (Taraschi et al, 1986a; Rottenberg et al, 1981). Specific phospholipids from ethanol-fed rats, i.e. phosphatidylinositol (PI) from liver microsomes, cardiolipin (CL) from hepatic mitochondria and phosphatidylserine (PS) from brain synaptosomes confer tolerance to reconstituted vesicles of membrane phospholipids from control rats. In liver microsomes, PI was the only lipid that exhibited a significant decrease in both the polyunsaturate pool and the ratio of the total olefinic content to the saturated fatty acid content. The fatty acid composition of cardiolipin was perturbed by chronic ethanol administration as evidenced by a significant increase in oleic acid (18:1) and a significant decrease in linoleic acid (18:2). These alterations produced a more saturated cardiolipin with a decreased (4.4%) unsaturation index (UI) and a 60% reduction in the UI/saturated fatty acid index. These fatty acid modifications, which arise in response to long term ethanol ingestion, represent an adaptive shift in lipid metabolic pathways that do not appear to be (solely) responsible for membrane tolerance.

Alcoholism↗
PubMed1990

1H NMR dipolar echo decay spectroscopy: a sensitive probe of membrane structure.

The structural and motional properties of membrane lipids in various physical states and macroscopic organizations are elucidated by 1H NMR dipolar echo decay spectroscopy (DECODE). Multilamellar lipid dispersions in the gel (L beta') and liquid-crystalline (L alpha) states and a nonbilayer, hexagonal (HII) phase are readily distinguished, a dynamic profile within these phases is identified, and dipolar order parameters are obtained in the fluid phases. The method is suitable for any pulsed NMR spectrometer. DECODE provides the first depth-dependent assay of lipid order that does not rely on isotopic labeling or exogenous probe.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1988

Phosphorus-31 nuclear magnetic resonance spectroscopic study of the canine pancreas: applications to acute alcoholic pancreatitis.

The first nuclear magnetic resonance spectroscopic study of the canine pancreas is described. Both in-vivo, ex-vivo protocols and nmr observables are discussed. The stability of the ex-vivo preparation based on the nmr observables is established for at least four hours. The spectra obtained from the in-vivo and ex-vivo preparations exhibited similar metabolite ratios, further validating the model. Metabolite levels were unchanged by a 50% increase in perfusion rate. Only trace amounts of phosphocreatine were observed either in the intact gland or in extracts. Acute alcoholic pancreatitis was mimicked by free fatty acid infusion. Injury resulted in hyperamylasemia, edema (weight gain), increased hematocrit and perfusion pressure, and depressed levels of high energy phosphates.

Alcoholism↗
PubMed1981

First observation of amino acid side chain dynamics in membrane proteins using high field deuterium nuclear magnetic resonance spectroscopy.

We have obtained the first deuterium NMR spectra of an individual membrane protein, bacteriorhodopsin in the purple membrane of Halobacterium halobium R1. Biosynthetic isotopic enrichment with [gamma-2H6]valine and high field Fourier transform operation permitted rapid data acquisition on intact membranes, including measurement of relaxation times. At some temperatures high quality spectra could be obtained in less than 1 s. [U-14C]Valine tracer studies indicate that less than or equal to 2% of valine added to the growth medium is broken down and incorporated into other membrane constituents. The NMR results indicate that the valine side chain is a rather rigid structure. Motion about C alpha-C beta is slow (less than 10(5) s-1) at growth temperature, While motion about C beta-C gamma is as expected fast (much greater than 10(5) s-1) at all accessible temperatures. The activation energy for methyl group rotation from spin-lattice relaxation data between -75 and 53 degrees C is approximately 2.4 kcal/mol, in good agreement with previous 1H NMR studies on solid alkanes. Preliminary data on [gamma-2H6]valine-labeled Acholeplasma laidlawii B (PG9) cell membranes are also presented. Our results strongly suggest that it should now be possible to observe in great detail the motions of any type of amino acid side chain in membrane proteins, including the effects of lipid composition on protein dynamics.

Amino Acids↗