Acoustic phonon quantization and low-frequency Raman spectra of spherical viruses

Abstract

Low-frequency vibrational modes are calculated using elastic continuum approximation model for spherical viruses immersed in a medium. The blueshift in the vibrational modes is observed with decrease in the virus particle size. To incorporate the effect of surrounding environment, the anisotropic and finite medium is taken into account. The presence of medium significantly affects the Raman peaks representing acoustic modes and results into the linewidth broadening accompanied by damping of modes. The estimated damping constant and quality factor suggest less loss of energy of the fundamental breathing mode in the virus-glycerol configuration. The temperature effect on the virus results into the redshift of the low-frequency Raman peaks with increase in temperature. Significant differences in Raman spectra of wet and dry lysozyme are observed. The conformational changes are more prominent at low temperature for virus-water configuration suggesting that water works as a low energy barrier for conformational changes of spherical virus.

A note on the breathing mode of an elastic sphere in Newtonian and complex fluids

“…In addition, biological nanoparticles such as viruses have also been modeled as elastic spheres in the studies of their vibration characteristics in different media, motivated by the idea of destroying viruses in a living host with ultrasound waves via resonance. [5][6][7][8][9] The resonant frequencies and damping characteristics of mechanical nanostructures with various shapes have been measured by a variety of experimental techniques. [10][11][12] From the modeling perspective, acoustic vibrations of elastic bodies are classical problems in continuum mechanics.…”

Raman Spectroscopy of Head and Neck Cancer: Separation of Malignant and Healthy Tissue Using Signatures Outside the “Fingerprint” Region

“…Low-frequency Raman shift signatures are typically associated with crystalline structures and are used in the pharmaceutical industry for dosage analysis [31]. Morphological vibrations of whole virus have been of interest to researchers and also result in low-frequency Raman shifts [32,33,34], however these shifts are extremely low and generally fall outside the region of our observations. While these peaks are not likely due to the HPV virus itself, the differences in the observed peaks could be indicative of the integration of viral DNA into the cell and the expression of oncogenes.…”

Viruses as nanoparticles: Structureversuscollective dynamics

“…As described above, the model used to estimate the frequencies of the virus nanoparticles modes is the elastic sphere model, which is generally thought as more appropriate because of the relatively strong stiffness of viral capsids [16,22,32,35]. Applying this model to a virus of 190 nm, i.e., using elastic constants that are typical of viral matter [16], yields spheroidal mode frequencies of 4 GHz for the quadrupolar S 1 2 mode and 9 GHz for the breathing S 1 0 mode.…”

“…As polymer colloids, they show high monodispersity, quasipherical morphology and are able, in the case of the two iridoviruses, to form well-ordered assemblies. These high-quality morphological aspects lead to postulate the existence of nanosphere vibration modes in viruses [24,[32][33][34][35]. These modes have been demonstrated to exist and to be well probed in a variety of nanoparticle systems [10], including ordered assemblies of PS colloids [36][37][38][39].…”