Non-Contact Measurement of Adsorbed Cytochrome c with Optical Waveguide Spectrometry; The Effect of Distance between Waveguide and Protein on the Spectral Sensitivity

Abstract

Optical waveguide spectrometry with non-contact conditions was performed with the aim of widening the choice of substrate material. The visible absorption spectrum of cytochrome c (cyt.c) adsorbed on a quartz glass or gold surface was detected with the evanescent wave from a co-faced waveguide. A clear correlation was observed between absorbance of cyt.c and the gap between the waveguide surface and the protein.

Electron Transfer Reaction of Cytochrome c at the Electrode Surface Analyzed with Noncontact Optical Waveguide Spectroscopy

“…The absorbance at 409 nm after subtracting the base line was 0.031 when latex beads with diameter of 120 nm were used. This value approximately agreed with that of cyt.c adsorbed on a quartz glass (0.024) [14] estimated under the same condition such as the number of reflection, gap distance and so on. To analyze the redox activity of cyt.c adsorbed on the ITO electrode, the potential was applied to the noncontact cell system.…”

“…It was revealed that the OWG spectrum of the molecules adsorbed on the substrate, which is not in contact with the waveguide surface, could be detected when the gap is properly controlled. In a previous article, we determined the relation between the absorbance of the spectrum and the gap between the target substrate and the waveguide [14]. Latex beads with appropriate diameter were found to be effective as the gap controller.…”

Dynamic Analysis of Adsorption-Desorption Equilibrium of Sublimed Aromatic Molecules Using Polarized Optical Waveguide Spectroscopy

“…13 It was also reported that a redox reaction on the electrode surface can be detected dynamically, while not being affected by diffusion. 14,15 We have proposed a non-contact OWG spectroscopy as a powerful technique to analyze molecules on various surfaces, even opaque substrates. 13 Moreover, OWG spectrometry is expected to be simultaneously collaborated with fluorescence spectra.…”

Optical Waveguide Spectroscopy

“…A combination of OWG spectroscopy with electrochemical methods can give even better information [21][22][23][24][25]. OWG spectroelectrochemistry is useful technique for sensitive and simple analysis of redox reaction of molecules dissolved in a small amount of solution [22] or adsorbed on opaque electrodes [23,24]. Figure 7.2 shows the spectral change due to the redox reaction of Methylene blue.…”