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
- 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), Vol. 111:7; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
COBALT COMPLEXES
FRACTIONATION
DEUTERIUM
ISOTOPIC EXCHANGE
DEUTERIUM COMPOUNDS
HYDRATES
CHEMICAL SHIFT
LIGANDS
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
COMPLEXES
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
ODD-ODD NUCLEI
RESONANCE
SEPARATION PROCESSES
SPECTRA
STABLE ISOTOPES
TRANSITION ELEMENT COMPLEXES
400105* - Separation Procedures
400202 - Isotope Effects
Isotope Exchange
& Isotope Separation