Detection of protein orientation on the silica microsphere surface using transverse electric/transverse magnetic whispering gallery modes.

The state of adsorbed protein molecules can be examined by comparing the shifts in a narrow line resonance wavelength of transverse electric (TE) and transverse magnetic (TM) whispering gallery modes (WGM) when the molecules adsorb onto a transparent microsphere that houses WGM. In adsorption of bovine serum albumin (BSA) onto an aminopropyl-modified silica microsphere, the TM/TE shift ratio indicated highly anisotropic polarizability of BSA in the direction normal to the surface, most likely ascribed to anchoring the heart-shaped protein molecule by one of its tips. The polarization-dependent resonance shift was confirmed when the surrounding refractive index was uniformly changed by adding salt, which would simulate adsorption of large objects.

Nanolayer characterization through wavelength multiplexing of a microsphere resonator.

We optically characterize nanolayer (<150 nm) formation in situ on a silica microsphere in an aqueous environment by simultaneously following the shifts of whispering-gallery modes at two wavelengths. This approach was inspired by layer perturbation theory, which indicates that these two measurements can be used to determine independently both the thickness and the optical dielectric constant. The theory is verified for extreme cases and used to characterize a biophysically relevant hydrogel nanolayer with an extremely small excess refractive index of 0.

Activity of Candida rugosa lipase immobilized on gamma-Fe2O3 magnetic nanoparticles.

We report the stability and enzymatic activity of Candida rugosa Lipase (E.C.3.