Hydrogen/deuterium fractionation factors of the aqueous ligand of cobalt in Co(H sub 2 O) sub 6 sup 2+ and Co(II)-substituted carbonic anhydrase

Journal Article · Wed Mar 29 04:00:00 EST 1989 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00189a052· OSTI ID:5174925

Kassebaum, J W; Silverman, D N ^[1]

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1. Univ. of Florida, Gainesville (USA)

The authors have measured the hydrogen/deuterium fractionation factor for the rapidly exchanging, water ligands of cobalt in Co(H{sub 2}O){sub 6}{sup 2+} and in two Co(II)-substituted isozymes of carbonic anhydrase. The fractionation factor was determined from NMR relaxation rates at 300 MHz of the protons of water in mixed solutions of H{sub 2}O and D{sub 2}O containing these complexes. In each case, the paramagnetic contribution to 1/T{sub 2} was greater than to 1/T{sub 1}, consistent with a chemical shift mechanism affecting 1/T{sub 2}. The fractionation factors obtained from T{sub 1} for Co(H{sub 2}O){sub 6}{sup 2+} and for the isozymes of Co(II)-substituted carbonic anhydrase were close to the fractionation factor for bulk water which is unity. The fractionation factors obtained from T{sub 2} were 0.73 {plus minus}0.02 for Co(H{sub 2}O){sub 6}{sup 2+} and 0.72 {plus minus} 0./02 for Co(II)-substituted carbonic anhydrase I, with a value of 0.77 {plus minus} 0.01 for isozyme II. They concluded that fractionation factors in these cases determined from T{sub 1} and T{sub 2} measured isotope preferences for different populations of ligand sites. They suggest that since T{sub 2} has a large contribution from a chemical shift mechanism, the fractionation factor determined from T{sub 2} has a large contribution of the fractionation of inner-shell ligands. The fractionation factors determined from T{sub 1} are close to unity, the value of the fractionation factor of bulk water, and contain a large contribution of the fractionation of outer-shell water.

• OSTI ID: 5174925
• Journal Information: Journal of the American Chemical Society; (USA), Journal Name: Journal of the American Chemical Society; (USA) Vol. 111:7; ISSN 0002-7863; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400105* -- Separation Procedures
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
CHEMICAL SHIFT
COBALT COMPLEXES
COMPLEXES
DEUTERIUM
DEUTERIUM COMPOUNDS
FRACTIONATION
HYDRATES
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPES
ISOTOPIC EXCHANGE
LIGANDS
LIGHT NUCLEI
MAGNETIC RESONANCE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ODD-ODD NUCLEI
RESONANCE
SEPARATION PROCESSES
SPECTRA
STABLE ISOTOPES
TRANSITION ELEMENT COMPLEXES