13C-Nuclear Magnetic Resonance spectroscopy as a probe of enzyme environment—II: Effect of solvent and pH on 13C-chemical shifts in derivatized amino-acid models

The synthesis and characterization of side-chain derivatives of amino- and carboxy-protected lysine, serine and cysteine, and of two tripeptides is reported. Broad-band proton-decoupled ¹³C-nuclear magnetic resonance spectra have been determined and in almost all cases, each carbon resonance has been unambiguously assigned by a combination of off-resonance and specific decoupling techniques. The effect of solvent and pH on chemical shifts is discussed. The objective of these studies is to provide models relevant to the use of ¹³C-labelled electrophilic inhibitors as probes of enzyme active-site environment.