Figure 4.
(A) Oxidation of Trp- and Tyr-containing peptides on carbon paste electrodes. (a) Differential pulse voltammograms and (b) chronopotentiograms for (A1) Tyr- and Trp-containing luteinizing hormone releasing hormone, (A2) Tyr-containing neurotensin, and (A3) Trp-containing bombesin. 10 nM peptide was adsorbed for 5 min at accumulation potential of 0.1 V followed by chronopotentiogram or DP voltammogram recording. CPS: Istr 5 μA; DPV scan rate, 5 mV/s. Y refers to Tyr and W to Trp residues. Adapted with permission from ref (159). Copyright 1996 Elsevier. (B) Oxidation peak of 2 μM human serum albumin (HSA) denatured in 8 M urea at glassy carbon electrode. (C) Dependences of square wave voltametric peak heights (−■−) and changes in fluorescence emission at 334 nm (− –○– −) on urea concentration. 1 μM HSA was incubated overnight with different urea concentrations (indicated in the figure) at 4 °C. Oxidation peak height of HSA denatured in 8 M urea was taken as 1. In the fluorescence measurements, intensity at 334 nm produced by 1 μM HSA incubated in the absence of urea was taken as 1. Adapted with permission from ref (218). Copyright 2012 Elsevier.