Electron paramagnetic resonance studies on hepatic microsomal cytochrome P-450 from a marine teleost fish.
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Aminobenzoates↗
Biomedical subjects
M Chevion
Publications and source records attributed to M Chevion.
High resolution EPR studies of the fine structure of heme proteins. Third harmonic detection approach.
When third harmonic detection is applied in EPR studies of the superhyperfine structure of nitrosyl derivatives of a number of human hemoglobin variants, significant resoltuion enhancement is obtained. This has allowed a detailed analysis of the number of superhyperfine lines, their g-values and their splittings, and has led to a more complete understanding of the interaction between the axial ligands of the heme iron. Sudies of the effect of the modulation amplitude on EPR line-shapes revealed that the amplitude required to resolve fine structure in the third harmonic mode is 3-10 times larger than that used to record an undistorted first derivative spectrum. The application of this approach for other systems is discussed, and practical guidelines for its use are given.
Electron Spin Resonance Spectroscopy↗
Membrane studies of Streptococcus pyogenes and its L-form growing in hypertonic and physiologically isotonic media. An electron spin resonance spectroscopy approach.
Electron spin resonance spectroscopy (ESR) was used to compare the lipid organization, thermal stability and the physical state of the membrane of a human pathogen, Streptococcus pyogenes and its osmotically fragile L-form with this same L-form now adapted to grow under physiologically isotonic conditions (physiological L-form). Comparison of the hyperfine splittings of a derivative of 5-ketostearic acid spin label, I(12, 3), after incorporation into the membrane, revealed that the lipid chain rigidity of these membranes is in the order physiological L-form greater than osmotically fragile L-form greater than streptococcus. The signal intensity (of the center magnetic field line) versus temperature analysis showed two transitions for these membranes. The first with melting points of 45, 26 and 36 degrees C and second transition at 70, 63 and 60 degrees C for the physiological L-form, osmotically fragile L-form and streptococcal membranes, respectively. This same order of membrane lipid chain rigidity was seen from the cooperativities obtained for each of these systems from analysis based on the expression for an n-order reaction. The I(12, 3) and other probes with the paramagnetic group close to the methyl end of the molecule suggested that this difference in lipid chain rigidity between these organisms resides in the environment closer to the lipid head group region rather than in the hydrophobic lipid core. Another major finding was the binding of I(12, 3) at two or more different sites in each of the membranes examined. This change in lipid chain rigidity now provides an explanation to account for the survival of a previously osmotically fragile L-form in physiologically isotonic media by focusing on changes in the physical nature of its membrane. In so doing, it adds to and reinforces the speculation of the potential survival in vivo and involvement in pathogenesis of osmotically fragile aberrant forms of bacteria.
Cell Membrane↗
Incorporation of D-alanine into the membrane of Streptococcus pyogenes and its stabilized L-form.
A principal aim of this study was to explain our earlier finding of a lack of d-alanine in the glycerol teichoic acid from the membrane of a stabilized L-form of Streptococcus pyogenes (B. M. Slabyj and C. Panos, 1973. J. Bacteriol. 114:934-942). It was found that the incorporation of d-alanine into the membrane teichoic acid of S. pyogenes requires either supernatant fraction or two enzymes from supernatant fraction, stimulator (d-alanine activating enzyme) and d-alanine:membrane acceptor ligase, plus membrane fragments, ATP and Mg(2+). A similar system from the L-form is inoperative. Also, no incorporation is observed with L-form or coccal supernatant fractions when L-form membranes are used. However, d-alanine incorporation is observed when L-form enzymes are used with membrane fragments from the parental streptococcus. Thus, the L-form possesses the required soluble components for d-alanine incorporation but the L-form membrane cannot function as acceptor even though it contains d-alanine-deficient membrane teichoic acid. These results suggest that a defect has occurred in the membrane of this stabilized L-form for d-alanine incorporation into membrane teichoic acid.
Adenosine Triphosphate↗
TPEN, a transition metal chelator, improves myocardial protection during prolonged ischemia.
In view of the hypothesis that free radicals induced damage during ischemia and reperfusion is mediated by transition metals, we investigated the effect of the potent metal chelator TPEN (N,N,N'N'-tetrakis(-)[2-pyridylmethyl]-ethylenediamine) on cardiac function after prolonged myocardial ischemia. Isolated working rat hearts were subjected to 12 hours of cold ischemic arrest followed by reperfusion for 1 hour. The study was carried out on five groups (nine hearts in each): (1) St. Thomas' Hospital cardioplegic solution; (2) St. Thomas' Hospital cardioplegic solution with 7.5 mumol/L TPEN; (3) protection conditions as in group 2, but with TPEN administration during preischemic and reperfusion periods; (4) University of Wisconsin solution; and (5) the same conditions as in group 4 with TPEN administration during the preischemic and reperfusion periods. Significant enhancement of hemodynamic recovery was observed in the presence of TPEN throughout the experiment. The recovery of cardiac output was 24% +/- 4% in group 3, as compared to 12% +/- 4% in group 1 (p < 0.01). The postischemic left ventricular pressure recovery was 57% +/- 4% in group 3, as compared to 18% +/- 7% in group 1 (p < 0.005). The hearts in group 5 recovered, reaching 29% +/- 2% of the preischemic cardiac output and at 65% +/- 2% of the left ventricular pressure recovery (p < 0.05 versus group 3). Lactate dehydrogenase was released throughout the reperfusion. TPEN addition to groups 2 and 3 did not significantly reduce lactate dehydrogenase release; however, TPEN in University of Wisconsin solution and throughout the experiment significantly decreased lactate dehydrogenase release.(ABSTRACT TRUNCATED AT 250 WORDS)
Adenosine Triphosphate↗