Concerted electron-proton transfer (EPT) in the oxidation of tryptophan with hydroxide as a base.
Tryptophan is unique among the redox-active amino acids owing to its weakly acidic indolic proton (pK(a) ≈ 16) compared to the -O-H proton of tyrosine (pK(a) = 10.1) or the -S-H proton of cysteine (pK(a) = 8.2). Stopped-flow and electrochemical measurements have been used to explore the roles of proton-coupled electron transfer and concerted electron-proton transfer (EPT) in tryptophan oxidation. The results of these studies have revealed a role for OH(-) as a proton acceptor base in EPT oxidation of N-acetyl-tryptophan but not for other common bases. The reorganizational barrier for (N-acetyl-tryptophan)(+/•) self-exchange is also estimated.
Department of Chemistry, University of North Carolina at Chapel Hill, North Carolina 27599-3290, USA.
Christopher J
CJ
Gagliardi
Robert A
RA
Binstead
H Holden
HH
Thorp
Thomas J
TJ
Meyer
D055664:Electrochemical Techniques; D004579:Electron Transport; D004583:Electrons; D006878:Hydroxides / Q000737:chemistry*; D010084:Oxidation-Reduction; D011522:Protons; D014364:Tryptophan / Q000737:chemistry*
D006878:Hydroxides; D011522:Protons; D014364:Tryptophan; C031356:hydroxide ion