DYNAMICS OF PSEUDOMONAS-AERUGINOSA AZURIN AND ITS CYS3SER MUTANT AT SINGLE-CRYSTAL GOLD SURFACES INVESTIGATED BY CYCLIC VOLTAMMETRY AND ATOMIC-FORCE MICROSCOPY
Ep. Friis et al., DYNAMICS OF PSEUDOMONAS-AERUGINOSA AZURIN AND ITS CYS3SER MUTANT AT SINGLE-CRYSTAL GOLD SURFACES INVESTIGATED BY CYCLIC VOLTAMMETRY AND ATOMIC-FORCE MICROSCOPY, Electrochimica acta, 42(19), 1997, pp. 2889-2897
Cyclic voltammetry of Pseudomonas aeruginosa azurin on polycrystalline
gold is reversible (E-0 = 360 mV vs she; 50 mM ammonium acetate) but
the voltammetric signals decay with time constants of about 3 x 10(-3)
s(-1). No signal is observed for monocrystalline Au(111). Cys3Ser azu
rin is electrochemically inactive on either type of gold electrode but
shows a reversible although decaying peak (362 mV, 50 mM ammonium ace
tate; decay time constant approximate to 2 x 10(-3) s(-1)) on edge-pla
ne pyrolytic graphite. Ex situ and in situ atomic force microscopy (AF
M) of the azurins on Au(111) show initially arrays of protein structur
es of lateral 100-200 Angstrom and vertical approximate to 50 Angstrom
extension. These could be individual molecular images convoluted with
the tip curvature. As scanning proceeds the structures in the ex situ
mode collect into large two-dimensional assemblies while the adsorbed
protein in the in situ mode is largely swept into the solution, recov
ering the free Au(111) surface. The cyclic voltammetry and AFM data ar
e consistent with time dependent adsorption of the azurins on gold via
the disulphide bridge (wild-type) or free thiol group (Cys3Ser mutant
). (C) 1997 Published by Elsevier Science Ltd.