Spectra tobacco mosaic virus

Figure 3.2 shows the fluorescence and phosphorescence emission spectrum from tobacco mosaic virus coat protein. These spectra are fairly typical of the tryptophan emission spectra observed from proteins at room temperature. 

Differences between the spectra of fluorescence and phosphorescence are immediately obvious. For all tryptophans in proteins the phosphorescence spectrum, even at room temperature, is structured, while the fluorescence emission is not. (Even at low temperatures the fluorescence emission spectrum is usually not structured. The notable exceptions include a-amylase and aldolase, 26 protease, azurin 27,28 and ribonuclease 7, staphylococcal endonuclease, elastase, tobacco mosaic virus coat protein, and Drosophila alcohol dehydrogenase 12. )... 

Figure 13 TEM micrograph of wild-type tobacco mosaic virus coated with gold nanoparticles. Scale bar corresponds to 50 nm. Inset shows EDX spectrum and presence of gold (Cu peaks are from grid). (Reprinted with permission from Ref. 70. 2003 American Chemical Society)...

The detection of optically active absorption bands is usually prevented by technical barriers, for they generally lie in the far ultraviolet region of the spectrum. Yet, largely as a result of instrumental improvements, the first measurements of Cotton effects associated with helical polypeptides have very recently been achieved. Simmons and Blout (1960) first measured a minimum in the rotatory dispersion of tobacco mosaic virus protein at 232... 

A detailed experimental study of the isotropic component of light scattered from dilute solutions of tobacco mosaic virus (a rod-like molecule with L = 3000 A and cross section diameter = 180 A) has been perfomed by Cummins et al. (1969) using spectrum analysis techniques. These authors found that the measured spectrum fit the theory described above rather well. Wada et al. (1971) repeated these experiments using an autocorrelator with similar results. 

Such a "self-beating experiment on biologically interesting molecules was first published by Dubin et al. (14), who made measurements of bovine serum albumin, ovalbumin, lysozyme, and polystyrene latex spheres. They also studied tobacco mosaic virus and DNA and found that the nonsphericity of these molecules leads to deviations from the Lenentzian spectrum. A theoretica] analysis by Pecoia (IS), which predicts angular-dependent, multi-Lorentzian spectra, can be used to obtain shape information of such molecules. 

Fig. 19.1. Tip-enhanced Raman (TERS) spectroscopic analysis of a single tobacco mosaic vims (TMV) particle (A) AFM image of the single virus and (B) TERS spectrum of the virus particle with an excitation wavelength of 568.2 nm showing contributions of protein and DNA...

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