Thermal Diffusion of a Stiff Rod-Like Mutant Y21M fd-Virus

Abstract

We investigated the thermal diffusion phenomena of a rod-like mutant filamentous fd-Y21M virus in the isotropic phase, by means of an improved infrared thermal diffusion forced Rayleigh scattering (IR-TDFRS) set-up crucial for measurements of slowly diffusing systems.Since this is the first thermal diffusion study of a stiff anisotropic solute, we investigate the influence of the shape anisotropy on the thermal diffusion behavior. The influence of temperature, fd-Y21M concentration and ionic strength in relation with the thermodiffusion properties is discussed. We characterize and eliminate the effect of these parameters on the absolute diffusion of the rods and show that diffusion determines the behavior of the Soret coefficient because the thermal diffusion coefficient is constant in the investigate regime. Our results indicate that for the thermal diffusion behavior structural changes of the surrounding water are more important than structural changes between the charged macroions. In the investigated temperature and concentration range, the fd-Y21M virus is thermophobic for the low salt content, while the solutions with the high salt content change from thermophobic to thermophilic behavior with decreasing the temperature. A comparison with recent measurements of other charged soft and biological matter systems shows that the shape anisotropy of the fd-virus becomes not visible in the results.

A computational approach to calculate the heat of transport of aqueous solutions

“…The solution changes from thermophobic at high temperatures, to thermophilic at low temperature, with the salt accumulating in the hot region in the latter case. The existence of temperature inversion effects in alkali halide aqueous solutions has been confirmed using state of the art thermal diffusion force Rayleigh scattering (TDRFS) [9,32,44] techniques as well as computer simulations [44]. This phenomenology can be consistently reproduced both experimentally and theoretically, and it is widely accepted.…”

Peptide model systems: Correlation between thermophilicity and hydrophilicity

“…To measure the thermodiffusion, we used IR-TDFRS, a transient grating technique. 33,34 Two infra-red laser beams are crossed inside the sample and create a holographic grating that creates a temperature grating due to the inherent absorption of water in that range. 35 Thermodiffusion leads to migration of the particles in that temperature gradient and a superimposed concentration grating.…”

Thermophoretic torque in colloidal particles with mass asymmetry

“…The thermodiffusive behavior of * j.olarte@imperial.ac.uk † mrubi@ub.edu ‡ f.bresme@imperial.ac.uk colloidal rods (fd viruses) was studied recently [13], and it has been shown that the heating of metallic nanorods in a polarized optical trap induces a thermal gradient around the rod and a torque that can be significant (∼10 2 pN nm) [14]. Theoretical and experimental studies of anisotropic particles under thermal gradients have uncovered fascinating behaviors that could open new routes to manipulate small colloids using thermal fields.…”