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Nuclear magnetic resonance (NMR) studies of nickel-iron hybrid hemoglobins (Hb)

Conference · · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)
OSTI ID:5206735
; ; ;
Ni-Fe hybrid Hbs, ..cap alpha..(Ni)/sub 3/..beta..(Fe)/sup 2/ and ..cap alpha..(Fe)/sub 2/..beta..(Ni)/sub 2/, have been studied by proton NMR. ..cap alpha..(Fe)/sub 2/..beta..(Ni)/sub 2/, ..cap alpha..(Ni)/sub 2/..beta..(Fe)/sub 2/, and ..cap alpha..(Ni)/sub 2/..beta..(Ni)/sub 2/ show exchangeable proton resonances at +14 and +11 ppm, T-state markers. Upon binding of CO to ..cap alpha..(Fe)/sub 2/..beta..(Ni)/sub 2/, these T-state markers disappear with a concomitant appearance of a R-state marker at +10.8 ppm at pH 6.5 to 8.5. On the other hand, the complementary hybrid, ..cap alpha..(Ni)/sub 2/..beta..(Fe-CO)/sub 2/, shows the two T-state markers at low pHs. Upon raising pH, the amplitude of the T-state markers is decreased and accompanied by an appearance of the R-state marker. Electronic absorption spectra and hyperfine-shifted proton resonances at different pHs indicate that these ligand-induced structural changes are accompanied by the changes in the coordination and spin states of Ni-PP in ..cap alpha..(Ni)/sub 2/-subunits. In the deoxy T-state, the ..cap alpha..(Ni)/sub 2/-subunits are dominantly in a tetra-coordinated (S = 0) state, whereas, in the R-state, the penta-coordinated (S = 1) state is markedly increased in the ..cap alpha..(Ni)/sub 2/-subunits. Thus, hyperfine-shifted proximal His NH proton resonances of the ..cap alpha..(Ni)/sub 2/-subunits are observable only in the R-state. The Ni-PP in the ..beta..(Ni)/sub 2/-subunits, however, always takes a penta-coordinated (S = 1) state regardless of the medium conditions and the state of ligation in the partner ..cap alpha..(Fe)/sub 2/-subunits. Thus, hyperfine-shifted proximal His NH proton resonances of the ..beta..(Ni)/sub 2/-subunits are always observable.
Research Organization:
Univ. of Pennsylvania, Philadelphia
OSTI ID:
5206735
Report Number(s):
CONF-8606151-
Conference Information:
Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 45:6
Country of Publication:
United States
Language:
English

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Related Subjects

550201 -- Biochemistry-- Tracer Techniques
550600* -- Medicine
59 BASIC BIOLOGICAL SCIENCES
62 RADIOLOGY AND NUCLEAR MEDICINE
ABSORPTION SPECTRA
BARYONS
BIOCHEMICAL REACTION KINETICS
CARBOXYLIC ACIDS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
GLOBIN
HADRONS
HEMOGLOBIN
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
IRON
KINETICS
MAGNETIC RESONANCE
METALS
NICKEL
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PH VALUE
PIGMENTS
PORPHYRINS
PROTEINS
PROTONS
REACTION KINETICS
RESONANCE
SPECTRA
TRANSITION ELEMENTS