Time-Resolved Optical Waveguide Spectroscopy for Studying Protein Adsorption Kinetics

Abstract

A time-resolved evanescent wave absorption technique is employed in studying the adsorption of a mammalian protein (cytochrome c) from an electrolyte-free solution on a hydrophilic glass surface. The method combines the sensitivity of a fast-scan spectral analyzer and surface specificity of slab optical waveguide (SOWG) technique. While proteins are viewed to undergo an overall irreversible adsorption process brought about by structural changes that occur after the initial adsorption phase, we have used an SOWG technique to investigate the first stage of the adsorption process while no noticeable changes have taken place. Absorbance data within the first two seconds after contact fit well into the reversible adsorption model characteristic of Langmuir-type adsorption but the goodness-of-fit diminishes as the protein molecules spend more time on the surface.

Hemoglobin Adsorption to Silica Monitored with Polarization-Dependent Evanescent-Wave Cavity Ring-Down Spectroscopy

“…Another particularly sensitive set of techniques that has shown significant impact in the study of protein adsorption is methods that use the absorption of the evanescent wave adjacent to an optical waveguide. ,,− For example, a waveguide method has been used recently to study the adsorption of lysozyme and fibronectin with impressive sensitivity and time resolution . One advantage that EW-CRDS has over waveguide methods is that the absorbance is measured at a single location on the surface, permitting the potential of scanning microscopy or other position-dependent studies such as combinatorial studies of protein interactions with surfaces …”

Identification of adsorption states of heptyl viologen cation radicals in a thin deposition layer by slab optical waveguide spectroscopy utilizing indium-tin-oxide electrodes

“…We have been studying the adsorption process and adsorbed states of various molecules on solid|liquid interfaces by time-resolved SOWG spectroscopy [22][23][24][25]. The improvement and development of the light incident methods has been allowed us to carry out the highly sensitive time-resolved SOWG measurements [26][27][28][29][30]. By synchronizing spectroscopic observations with electrochemical measurements, we have carried out detailed observations of adsorbed molecules with the potential dependent change on the electrode surface successfully [31][32][33][34][35].…”

In situ observation of the initial adsorption process of heptylviologen cation radicals by slab optical waveguide spectroscopy synchronized with electrode potential modulation methods

“…Our recent improvement of the SOWG instrument based on the light incidence method utilizing a glycerol drop has enabled us to observe time-dependent adsorption behavior [8][9][10][11], and to obtain the standard Gibbs energy (DG) value due to the adsorption process of proteins on solid|liquid interfaces. The additional development of the highly sensitive spectroelectrochemical SOWG spectroscopy has also allowed us to carry out a detailed observation of adsorbed molecules with the potential dependent change on the electrode surface [12][13][14].…”