The application of ellipsometry of the study of the adsorption behavior of proteins and synthetic macromolecules at the air-water interface has been investigated. It is shown that for macromolecules the amount adsorbed per unit area, Γ, as determined by ellipsometry, only has a well-defined physical meaning if the refractive-index increment remains constant up to high concentrations present in the adsorbed layer. It has been found experimentally that this conditioned is fulfilled for proteins. The ellipsometric Γ values of some protein agree satisfactorily with those obtained by two independent techniques has been used to investigate the adsorption from solution of κ-casein, bovine serum albumin, and polyvinyl alcohol. For bovine serum albumin, Γ reaches a plateau value of 2.9 mg/m2 for concentrations ≥ 0.05 wt%. The thickness of the adsorbed molecules. For κ-casein, Γ steadily increases with increasing centration and multilayers are formed. The technique provides interesting information on conformational changes in adsorbed macromolecules, on the rate of the process, and on the conditions under which these occur.

Ellipsometry as a tool to study the adsorption behavior of synthetic and biopolymers at the air–water interface

A comprehensive review of protein adsorption at solid-liquid interfaces is presented, including a brief review of protein structure and the principles of protein adsorption. Adsorption-based biocompatibility hypotheses and correlations are discussed, including surface charge, interface energetics, passivation, protein-resistant surfaces, and the role of adsorbed immunoglobulins and complement. New methods for the study of protein adsorption are discussed, including total internal reflection techniques (absorbance, fluorescence, and Raman) and ellipsometry. Qualitative “rules of thumb” of protein adsorption are also presented.

Protein adsorption and materials biocompatibility: A tutorial review and suggested hypotheses

Differential reflection spectroscopy of very thin surface films

A prism–film coupler has been discussed recently by Tien, Ulrich, and Martin as a device to couple efficiently a laser beam into thin-film dielectric light guides. This coupler also allows an accurate measurement of the spectrum of propagating modes from which the refractive index and the thickness of the film can be determined. We present here a theory of the prism–film coupler. The physical principles involved are illustrated by a method that combines wave and ray optics. We study the modes in the thin-film light guide and their modification by the effect of coupling. We also calculate the field distributions in the prism and the film, the power transfer between the prism and the film, and derive a condition of optimum operation. In one example, 81% of the laser power can be fed into any desired mode of propagation in the film.

Theory of Prism–Film Coupler and Thin-Film Light Guides

Surface plasmon resonance (SPR) imaging is a surface-sensitive spectroscopic technique for measuring interactions between unlabeled biological molecules with arrays of surface-bound species. In this paper, SPR imaging is used to quantitatively detect the hybridization adsorption of short (18-base) unlabeled DNA oligonucleotides at low concentration, as well as, for the first time, the hybridization adsorption of unlabeled RNA oligonucleotides and larger 16S ribosomal RNA (rRNA) isolated from the microbe Escherichia coli onto a DNA array. For the hybridization adsorption of both DNA and RNA oligonucleotides, a detection limit of 10 nM is reported; for large (1500-base) 16S rRNA molecules, concentrations as low as 2 nM are detected. The covalent attachment of thiol-DNA probes to the gold surface leads to high surface probe density (1012 molecules/cm2) and excellent probe stability that enables more than 25 cycles of hybridization and denaturing without loss in signal or specificity. Fresnel calculations are...

https://execdeanagriculture.rutgers.edu/pdfs/goodman-074.pdf

Surface Plasmon Resonance Imaging Measurements of DNA and RNA Hybridization Adsorption onto DNA Microarrays

Explicit formulas are derived for the mean-square electric fields induced by plane electromagnetic radiation in a two-phase, three-phase, and N-phase stratified medium. The first (incident) and last phases are semi-infinite in extent. Boundaries separating phases are plane and parallel. Phases are isotropic with arbitrary optical constants. Simple relationships follow for special cases such as at the critical angle for a two-phase system. Equations for reflectance, transmittance, and phase changes on reflectance and transmittance are given. Details are given concerning the energy absorption process, especially in the two- and three-layer cases. Equations for the N-layer case are in terms of characteristic matrices which can be readily programmed for a computer.

Electric Fields Produced by the Propagation of Plane Coherent Electromagnetic Radiation in a Stratified Medium

Expanded formulas for attenuated total reflection and the derivation of absorption rules for single and multiple ATR spectrometer cells

On the determination of optical constants by a two-angle internal reflection method

New procedures have been devised for studying small energy losses in optical coatings. The ability to have large electromagnetic fields of the desired distribution in a multilayer system is used to optimize single and multiple reflection spectroscopy for the characterization of thin layers and interphase regions. The analysis is based on Poynting’s theorem for radiation absorption. Linearized equations are derived for these low-loss cases, and experimental setups for maximum sensitivity are discussed. It is shown how to reduce complex multiphase spectroscopic data to optical constants which represent material properties. It is shown how losses caused by one absorbing species can be analyzed in the presence of another. Both experimental and computer simulated data are analyzed. Typical data reducing procedures are given for mirror coatings, lens coatings, losses due to impurities throughout a film, and losses due to contaminants at a film phase boundary.

reflection spectroscopy of optical coatings

In 1962 we performed the following experiments. Silver chloride internal reflection elements were coated with thin palladium films and infra red internal reflection spectra taken with organic liquids contacting the metal films. A metal film 40 A thick gave spectra of the organics similar to attenuated total reflection (ATR) spectra. A thicker film (ca. 175 A thick per chemical analysis) having a resistance of 40 Ω per square also gave spectra of the organics, but with less intensity. These simple experiments showed that spectra of the region close to the electrode could be taken through a thin metal electrode. These results were reported by Hansen and Osteryoung(1) with the suggestion that this type of optical set-up could be used to study electrochemical reactions in situ. It was also suggested that an electrical conductor like germanium could serve as both internal reflection element and electrode. Later in 1962 glass multiple reflection elements were coated with various metals, and spectra of dyes taken in the visible. When the metal film was made an electrode in an electrochemical cell, and a potential applied, large changes in reflectance were observed. These were the beginnings of a fruitful coupling of two fields, internal reflection spectroscopy and electrochemistry.

Wilford N. Hansen

Papers

Electric Fields Produced by the Propagation of Plane Coherent Electromagnetic Radiation in a Stratified Medium

Expanded formulas for attenuated total reflection and the derivation of absorption rules for single and multiple ATR spectrometer cells

On the determination of optical constants by a two-angle internal reflection method

reflection spectroscopy of optical coatings

Spectroscopic Observation of an Electrochemical Reaction by Means of Internal Reflection