Aliphatic semisynthetic amino terminal variants of myoglobin: enrichment with carbon-13, determination and interpretation of terminal pK values and motions

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5819796

Busch, M R

The synthesis of a series of myoglobins substituted in the amino terminal residue to provide variation in the aliphatic nature of the side chain and enrichment in /sup 13/C was accomplished by semisynthetic methods. The replacements of valine, the native first residue, included /sup 13/C enriched glycine, alanine, valine, leucine, and isoleucine. The products were extensively characterized and found to be virtually indistinguishable by most physical methods. /sup 13/C NMR spectroscopy showed significant differences in the amino terminal pK value, ranging from 7.72 for myoglobin to 7.15 for myoglobin. Consideration of the electrostatic effects of the charge array indicated a balance of interactions at this site not significantly altered by variations in the side chain. By examination of the crystal structure, consideration of earlier work regarding the interactions of the side chain of Leu-2, and data regarding the motions of the terminal residue, it was concluded that the interaction of the side chain of the first residue with the hydrophobic cluster formed primarily by close contact of invariant residues Leu-2 and Leu-137 was the primary cause for the reduction in the terminal pK values seen for the larger aliphatics. By restricting the freedom of the residue, this interaction limits the available hydration volume, and consequently favors the unprotonated form of the amine. The concurrent observation of both functional elements in the series of ..cap alpha.. amino terminal residues brings out the interrelated consequences for the two categories of solvent interactions controlling structural and functional properties in a graded way.

• Research Organization: Indiana Univ., Bloomington (USA)
• OSTI ID: 5819796
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALANINES
AMINO ACIDS
CARBON 13
CARBON ISOTOPES
CARBOXYLIC ACIDS
CHEMICAL PREPARATION
ELECTROPHYSIOLOGY
EVEN-ODD NUCLEI
GLOBIN
GLYCINE
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
LEUCINE
LIGHT NUCLEI
MOLECULAR STRUCTURE
MYOGLOBIN
NMR SPECTRA
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHYSIOLOGY
PIGMENTS
PORPHYRINS
PROTEINS
SPECTRA
STABLE ISOTOPES
SYNTHESIS
TRACER TECHNIQUES
VALINE