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Magnetic exchange paths in heterobinuclear complexes containing a μ-oxo-bis(μ-acetato)dimetal core
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Abstracts
Ho(j9
MAGNETIC EXCHANGE PATHS IN HETEROBINUCLEAR COMPLEXES CONTAINING A u-0X0-BIS(u-ACETATO)DIMETAL CORE.
K. Wieghardta, J. J. Girerdb a Ruhr-Universitat Bochum, FRG,
b Universite Paris-Sud, France.
We have synthesized and characterized a series of heterobinuclear complexes containing the u-oxo-bis(u-acetato)dimetal core with two different transition metals. Intramolecular ferromagnetic or antiferromagnetic spin exchange coupling has been ?bserve$ depending solely on the d” electronic configuration of M and M . The interacting magnetic orbitals are d,, and d,,.
HO70
NANOSECOND TRANSIENT ABSORPTION SPECTROSCOPY OF B-12. Eefei COENZYME Chen and Mark R. Chance, Georgetown University, Dept of Chemistry, Wash., DC 20057.
Laser photolysis of the photolabile Co(III)-C bond of Coenzyme B-12 mimics homolytic cleavage, resulting in the formation of a Co(I1) species and a deoxyadenosyl radical. The transient absorption difference spectrum of photolyzed B12 minus unphotolyzed B-12 at 5 nanoseconds and longer was observed. The power and wavelength dependence of the quantum yield was measured and found to be 0.21 at saturating powers. The apparently unphotolyzed 79% at 5 nanoseconds may be by geminate recombination. explained On microsecond recombination of timescales, diffusional deoxyadenosyl radicals and Co(I1) was observed.
HO71
Nh4R STUDIES OF THE Fe(I1) BINDING SITE OF ISOPENIClLLIN N SYNTHASE (IPNS). L.-J. Mlngl, L. Que, Jr.1, C. Frolik2, A. Kriauciunas2, and V. Chen2, 1De artment of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA. flLilly Research Laboratories, Lilly Corporation Center, Indianapolis, IN 46285, USA. IPNS, a nonheme high spin Fe(E)-dependent protein, catalyzes the formation of &penicillin N from L-aad-L-cys-D-val (ACV) with the concomitant reduction of 1 02 to 2 H20. The 1H NMR spectrum (300 MHz at 283 K) of IPNS reveals several hyperfineshifted signals. The ones at 68 ppm (3H, D20 exchangeable) and 43 ppm (2H) suggest the possible involvement of 3 His binding to the Fe(B). Anaerobic addition of ACV to the enzyme solution causes spectral changes indicating the formation of an enzyme-substrate (ES) complex. The addition of NO, an 02 analogue, to the ES complex also alters the NMR spectrum of the complex.
Abstracts
Ho(j9
MAGNETIC EXCHANGE PATHS IN HETEROBINUCLEAR COMPLEXES CONTAINING A u-0X0-BIS(u-ACETATO)DIMETAL CORE.
K. Wieghardta, J. J. Girerdb a Ruhr-Universitat Bochum, FRG,
b Universite Paris-Sud, France.
We have synthesized and characterized a series of heterobinuclear complexes containing the u-oxo-bis(u-acetato)dimetal core with two different transition metals. Intramolecular ferromagnetic or antiferromagnetic spin exchange coupling has been ?bserve$ depending solely on the d” electronic configuration of M and M . The interacting magnetic orbitals are d,, and d,,.
HO70
NANOSECOND TRANSIENT ABSORPTION SPECTROSCOPY OF B-12. Eefei COENZYME Chen and Mark R. Chance, Georgetown University, Dept of Chemistry, Wash., DC 20057.
Laser photolysis of the photolabile Co(III)-C bond of Coenzyme B-12 mimics homolytic cleavage, resulting in the formation of a Co(I1) species and a deoxyadenosyl radical. The transient absorption difference spectrum of photolyzed B12 minus unphotolyzed B-12 at 5 nanoseconds and longer was observed. The power and wavelength dependence of the quantum yield was measured and found to be 0.21 at saturating powers. The apparently unphotolyzed 79% at 5 nanoseconds may be by geminate recombination. explained On microsecond recombination of timescales, diffusional deoxyadenosyl radicals and Co(I1) was observed.
HO71
Nh4R STUDIES OF THE Fe(I1) BINDING SITE OF ISOPENIClLLIN N SYNTHASE (IPNS). L.-J. Mlngl, L. Que, Jr.1, C. Frolik2, A. Kriauciunas2, and V. Chen2, 1De artment of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA. flLilly Research Laboratories, Lilly Corporation Center, Indianapolis, IN 46285, USA. IPNS, a nonheme high spin Fe(E)-dependent protein, catalyzes the formation of &penicillin N from L-aad-L-cys-D-val (ACV) with the concomitant reduction of 1 02 to 2 H20. The 1H NMR spectrum (300 MHz at 283 K) of IPNS reveals several hyperfineshifted signals. The ones at 68 ppm (3H, D20 exchangeable) and 43 ppm (2H) suggest the possible involvement of 3 His binding to the Fe(B). Anaerobic addition of ACV to the enzyme solution causes spectral changes indicating the formation of an enzyme-substrate (ES) complex. The addition of NO, an 02 analogue, to the ES complex also alters the NMR spectrum of the complex.