Direct observation of differential UV photolytic degradation among the tryptophan residues of gramicidin A in sodium dodecyl sulfate micelles.
Gramicidin A, incorporated into sodium dodecyl sulfate micelles, was exposed to ultraviolet light and discovered by two-dimensional (TOCSY) NMR spectroscopy to undergo differential photolytic degradation. The four tryptophan residues of gramicidin A were found to be unequally sensitive to ultraviolet radiation. Tryptophan 9 was the most sensitive to ultraviolet photolysis, while tryptophan 11 was the least sensitive. Tryptophans 13 and 15 have approximately the same susceptibility to photolytic degradation by the ultraviolet light. Rate constants for the photolytic degradation of the four tryptophan residues were obtained from the dependence of the TOCSY spectrum upon the time of photolysis.
McKim
S
S
Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville 72701.
Hinton
J F
JF
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D006096:Gramicidin / Q000737:chemistry / Q000528:radiation effects*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008823:Micelles; D008958:Models, Molecular; D010782:Photolysis; D011487:Protein Conformation / Q000528:radiation effects*; D012967:Sodium Dodecyl Sulfate; D014364:Tryptophan / Q000528:radiation effects*; D014466:Ultraviolet Rays
D008823:Micelles; D006096:Gramicidin; D012967:Sodium Dodecyl Sulfate; D014364:Tryptophan