Motions and electrostatic interactions in natural and semisynthetic myoglobins: a carbon-13 nuclear magnetic resonance study
It is expected that the internal motions of amino acid side chains and protein backbone segments influence and are in turn affected by charge-charge and related interactions, steric constraints, hydrophobic forces, and hydrogen bonding. As an initial test of this theory /sup 13/C-enriched glycine, alanine, and isoleucine have been substituted for the amino terminal valine of sperm whale myoglobin using semisynthetic techniques. /sup 13/C-NMR has been used to analyze the motions of the side chain and the protonation state of the alpha amino group as a function of pH. The addition of a single methyl group to the side chain can alter the alpha amino pK value by as much as 0.3 pH units indicating a delicately balanced set of change-charge interactions between the alpha amino group and the rest of the protein. Further evidence in support of the state theory was found upon examination of the internal motions of seven of nine isoleucine vectors. These motions were extracted from natural abundance /sup 13/C-NMR relaxation data. The results suggest a strong possibility that concerted motions are important. Also, an increase in temperature from 32/sup 0/C to 52/sup 0/C leads to an electrostatically driven tightening of the myoglobin structure as evidenced by no significant increase in motion amplitude of most of the vectors.
- Research Organization:
- Indiana Univ., Bloomington (USA)
- OSTI ID:
- 6704136
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
MYOGLOBIN
CONFIGURATION INTERACTION
CONFORMATIONAL CHANGES
MOLECULAR STRUCTURE
CARBON 13
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
NUCLEAR MAGNETIC RESONANCE
CARBON ISOTOPES
CARBOXYLIC ACIDS
EVEN-ODD NUCLEI
GLOBIN
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
PORPHYRINS
PROTEINS
RESONANCE
STABLE ISOTOPES
550201* - Biochemistry- Tracer Techniques