Adsorption of the cysteine–tryptophan dipeptide at the Au(110)/liquid interface studied using reflection anisotropy spectroscopy

Controlling the formation of a monolayer of cytochrome P450 reductase onto Au surfaces

“…Experience with small molecules, the S-containing amino acids [29], decanethiol [30], and a cysteine-tryptophan dimer [31], leads us to expect that the protein molecules ( Fig. 1) will adsorb through the formation of a Au(110)-S linkage and that this will lead to a characteristic Au-S peak in the RAS at ∼2.54 eV.…”

Conformational change induced by electron transfer in a monolayer of cytochrome P450 reductase adsorbed at the Au(110)–phosphate buffer interface

“…1) and those of the adsorbed protein occurs for the applied potential of 0.056 V. This difference is very likely to be due to the replacement of the weakly adsorbed anions on the Au(110)-buffer interface by the CPR which makes a strong Au-S bond with the Au(110) surface [5,6]. Previous work shows [20][21][22] that this bond is not disrupted by variations in the applied potential so the anions will not be able to return to the surface as the potential is varied. The main differences between the RAS profiles of the adsorbed proteins and the Au(110)-interface are a reduction in the intensity of the broad positive peak centered on ∼2.0 eV and an increased, negative, intensity in the region of 2.5 to 3.5 eV.…”

“…Although the adsorbed protein does not become completely reduced this trend is also observed in the RAS profiles of the protein on the Au(110) surface particularly when the potential dependence of the RAS peak arising from the Au-S bond is taken into account. Previous studies of the RAS of the Au-S bond formed on Au(110) at −0.6 V by cysteine, cystine [20], a cysteine-tryptophan dipeptide [21], and decanethiol [22] show that it contributes a symmetric peak located at 2.5 eV with a width of ∼0.3 eV at full width at half maximum. In the RAS of these smaller molecules [20,21] adsorbed on Au(110) this feature remains sharp but reduces in intensity by 50% when the applied potential is increased to 0.0 V. This intensity variation is opposite to the behavior shown in Fig.…”

“…Previous studies of the RAS of the Au-S bond formed on Au(110) at −0.6 V by cysteine, cystine [20], a cysteine-tryptophan dipeptide [21], and decanethiol [22] show that it contributes a symmetric peak located at 2.5 eV with a width of ∼0.3 eV at full width at half maximum. In the RAS of these smaller molecules [20,21] adsorbed on Au(110) this feature remains sharp but reduces in intensity by 50% when the applied potential is increased to 0.0 V. This intensity variation is opposite to the behavior shown in Fig. 7 so as the potential is made more negative the increase in intensity of the Au-S peak at 2.5 eV is expected to mask, to some extent, the fall in intensity of the 2.7 eV contribution from the isoalloxazine rings.…”

“…As in previous work [7][8][9][20][21][22][23][24] we assume that the RAS of the adsorbed molecules is the sum of the contribution from the molecules and from the Au(110) surface together with the contribution from the Au-S bond. Figure 6 shows the difference between the RAS profiles of Figs.…”