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

Mayumi Noto, David Keng, Iwao Teraoka, Stephen Arnold

Research output: Contribution to journalArticle


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.

Original languageEnglish (US)
Pages (from-to)4466-4472
Number of pages7
JournalBiophysical journal
Issue number12
StatePublished - Jun 2007


ASJC Scopus subject areas

  • Biophysics

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