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.
Noto
Mayumi
M
Microparticle Photophysics Laboratory, Polytechnic University, Brooklyn, New York 11201, USA.
Keng
David
D
Teraoka
Iwao
I
Arnold
Stephen
S
D000327:Adsorption; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D004574:Electromagnetic Fields; D008280:Magnetics; D008422:Materials Testing / Q000379:methods*; D008863:Microspheres; D011485:Protein Binding; D011487:Protein Conformation; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000648:ultrastructure*; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
D020099:Coated Materials, Biocompatible; D012710:Serum Albumin, Bovine; D012822:Silicon Dioxide