Saturation transfer electron paramagnetic resonance spectroscopy of spin labeled tobacco mosaic virus protein.

Abstract The coat protein of Tobacco Mosaic Virus is covalently labeled with a maleimide spin label at the single SH-group of the protein. Saturation transfer electron paramagnetic resonance spectroscopy, a technique that is sensitive to very slow molecular motion with rotational correlation times τ c in the range 10 −7 to 10 −3 sec, shows the dissociation of large oligomers of spin labeled protein with τ c ∼10 −4 sec at pH 5.5 to smaller oligomers at higher pH.