Search

Cobalamin-dependent methionine synthase (5-methyltetrahydrofolate-homocysteine methyltransferase, EC 2.1.1.13) has been isolated from Escherichia coli B in homogeneous form. The enzyme is isolated in an inactive form with the visible absorbance properties of cob(II)alamin. The inactive enzyme exhibits an electron paramagnetic resonance (EPR) spectrum at 38 K that is characteristic of cob(II)alamin at acid pH, where the protonated dimethylbenzimidazole substituent is not coordinated with the cobalt nucleus (base-off cobalamin). An additional, variable component of the EPR spectrum of the inactive enzyme has the characteristics of a cob(III)alamin-superoxide complex. Previous work by others [Taylor, R.T., & Weissbach, H. (1969) Arch. Biochem. Biophys. 129, 745-766. Fujii, K., & Huennekens, F.M. (1979) in Biochemical Aspects of Nutrition (Yagi, K., Ed.) pp 173-183, Japan Scientific Societies, Tokyo] has demonstrated that the enzyme can be activated by reductive methylation using adenosylmethionine as the methyl donor. We present data indicating that the conversion of inactive to methylated enzyme is correlated with the disappearance of the EPR spectrum as expected for the conversion of paramagnetic cob(II)alamin to diamagnetic methylcobalamin. When the methyl group is transferred from the methylated enzyme to homocysteine under aerobic conditions, cob(II)alamin/cob(III)alamin-superoxide enzyme is regenerated as indicated by the return of the visible absorbance properties of the initially isolated enzyme and partial return of the EPR spectrum. Our enzyme preparations contain copper in approximately 1:1 stoichiometry with cobalt as determined by atomic absorption spectroscopy.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclinic crystals of native bovine superoxide dismutase and its monocyano derivative were studied by means of electron paramagnetic resonance spectroscopy. Through computer simulation of the spectra, the directions of the principal axes of the magnetic tensors (g and A) have been found with respect to the crystal principal axes and with respect to the positions of atoms bear the Cu(II) as previously determined by x-ray crystallography (Richardson, J. S., Thomas, K. A., and Richardson, D. C. (1975) Biochem. Biophys. Res. Commun. 63, 986-992; Tainer, J. A., Getzoff, E. D., Richardson, J. S., and Richardson, D. C. (1980) in 2SOD: Cu, Zn-Superoxide Dismutase Complete Atomic Coordinates (Richardson, D. C., and Richardson, J. S., eds) Brookhaven Protein Structure Data Bank). In the native protein, the direction of the gz axis of Cu(II) was found to lie perpendicular to the rough plane formed by the four imidazole nitrogen atoms coordinated to the Cu(II). The direction of gy is approximately along the His 44N-Cu-His 46N direction, and gx is in the direction of the Cu-His 61-Cu-N bond. The A is coaxial with g within 15 degrees C. A substantial shift occurs in the direction of gz when CN- binds to the Cu(II), suggesting a change in the coordination configuration of the metal.

This is a case study of ninety-two patients served by an outpatient service of a state psychiatric hospital in a rural area in west central New York State. The purpose was to identify variables associated with success (tenure in the community) and lack of success (number of readmissions within last year and five years and one subsequent year). Using a stepwise multiple regression analysis, age and living with others were positively correlated with success and negatively correlated with rehospitalizations within one year. Over a five-year period, affective disorders, inconsistency in taking medication, and having a hobby were correlated with multiple hospitalizations. In the year following data collection, readmissions were related only to inconsistency in taking medication. Mental health practitioners are advised to carefully follow up persons at highest risk of returning to the hospital.

Crisis intervention, with its emphasis on focused treatment in a limited time frame, is adaptable to social work practice in hospitals. The author discusses the crisis intervention model in relation to the hospitalized patient and his or her family and examines three kinds of crises: those caused by illness or injuries, by hospitalization itself, and by treatment procedures.

When the di- or trimethylamine dehydrogenases (trimethylamine:(acceptor) oxidoreductase (demethylating), EC 1.5.99.7) of certain methylotrophic bacteria are reduced by two electrons with substrate unusual EPR signals arise at g = 2 and g = 4 (Steenkamp, D.J. and Beinert, H. (1982) Biochem. J. 207, 233-239; 241-252) indicative of spin-spin interaction between the FMN and iron-sulfur compounds of these enzymes. An attempt is made to understand, describe and simulate these spectra in terms of a triplet state with possible contributions from both dipolar and anisotropic exchange (J) interactions. No direct measurement of J is available, but various approaches to setting limits to J are outlined. According to these, J approximately 0.4 to 3 cm-1 or 15 to 50 cm-1. The spectra show, in the g = 2 region, a pair of rather sharp inner and a pair of broad outer lines; the latter broaden as well as move out from the center with increasing time (after substrate addition) and substrate concentration, while there is little change of g = 4. The best fits to such spectra were obtained by assuming distribution of D and E values, depending on substrate effects and arriving presumably from 'g-strain'. The fact that both shapes and intensities at g = 2 and g = 4 could be reproduced simultaneously at two frequencies indicates that the assumptions underlying our approaches and interpretations are permissible and reasonable, although we cannot claim their uniqueness. The distance between the centers of the spin densities of the flavin radical and the Fe-S cluster is thought to lie between the limits 3 to 5 A if the asymmetries in the spin-spin interaction are magnetic dipole-dipole in origin. Because there is an indication that the interaction is anisotropic exchange, the upper limit is less stringent.