Numerical simulations of surface plasmon resonance system for monitoring DNA hybridization and detecting protein lipid film interactions

This paper presents a simple method to extract information about thin organic films from surface plasmon resonance (SPR) spectra. From numerical simulations it was found that a shift (Delta theta(SPR)) of an absorption peak in the SPR spectrum was directly proportional to the product of the thin organic film thickness and the refractive index difference between the thin organic film and a buffer soaking the sample. It was also found that Delta theta(SPR) was not sensitive to the thin organic film support of a gold film and a glass cover slip. Relationships between Delta theta(SPR) and distributions of macromolecule structures, in the thin organic films were theoretically established. Formulae were derived for a homemade SPR system to calculate length, transverse area, density and surface concentration of macromolecules in the thin organic film. The validity of these treatments was checked by precisely measuring the size of a single distearoylphosphatidylcholine molecule on a gold-supported phospholipid film; by quantitatively monitoring hybridization of synthesized oligonucleotides strands based on a biotin/avidin system; and by quantitatively detecting the steric hindrance of rabbit C-reactive protein specifically bound to phospholipid monolayers composed of synthesized lipids.