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H Kon

Publications and source records attributed to H Kon.

At least 91 records · Page 5Linked to original sources
PubMed1975

An interpretation of the three line EPR spectrum of nitric oxide hemeproteins and related model systems: the effect of the heme environment.

The EPR spectra of the nitric oxide (NO) derivatives of structurally perturbed Fe (II) hemeproteins show various patterns, all of which are characterized by the conspicuous three-line hyperfine splitting due to 14NO, in contrast to that of the native proteins. For the purpose of obtaining structural information from these three line spectra, the model systems were studied, which consist of NO, heme (or TPP-Fe(II), where TTP means alpha, beta, gamma, delta-tetraphenylporphine) and the nitrogenous base, pyridine or quinoline, which, respectively, give the native type or the three line (perturbed type) EPR spectrum. The ring proton paramagnetic shift of quinoline in this system shows that it is not coordinated to NO-TPP-Fe(II) as a normal axial ligand, in contrast to pyridine which gives the shift pattern of the ordinary axial ligation. This observation suggests that in the NO-hemeproteins some perturbations of the protein structure cause the rupture or distortion of the bond between the imidazole nitrogen on the fifth coordination site and the heme iron, resulting in the three line spectrum. The EPR study of the model systems, the pentacoordinated complex, NO-heme and NO-TPP-Fe(II), in various media revealed that the pentacoordinated species indeed exhibits, depending upon its environment, a variety of spectra, which closely reproduce the three line patterns observed in the perturbed proteins and some related model systems. Such spectral variation can be attributed to the difference in the degree of quenching the internal motion and/or the structural heterogeneity caused by molecular environment.

Electron Spin Resonance Spectroscopy↗
PubMed1973

Charge transfer between amine and carbonyl.

The transfer of a whole electron in the ground state can be demonstrated by the interaction of p-phenylenediamine and glyoxal, which leads to the formation of free radicals.

Aldehydes↗
PubMed1970

Electron spin resonance studies of lipid-protein interaction in human serum lipoproteins.

Spin-labeled derivatives of high density (HDL) and low density (LDL) lipoproteins from human serum were prepared with N-(1-oxyl-2,2,6,6-tetramethyl-4-piperidinyl)-maleimide. At the low ratios of spin label to protein employed, no changes in circular dichroism or immunochemical reactions were detected. The lipoprotein derivatives, labeled in their protein moieties, exhibited electron spin resonance spectra containing signals of strongly immobilized and weakly immobilized components. The strongly immobilized component was relatively more prominent in high density than in low density lipoproteins. Delipidation or addition of detergent greatly reduced the relative magnitude of the highly-immobilized signal. Reaction with specific antibodies did not alter the signals of spin-labeled lipoproteins or apoproteins. The signals of the reconstituted complex of spin-labeled apoHDL-phospholipid were indistinguishable from those of a spin-labeled apoHDL in the absence of lipid.

Chemical Phenomena↗