Hydrodynamics and electrical properties characterization of Fish Type III Antifreeze Protein aggregates.

ANDRES SALVAY; SANTOS, J; HOWARD E

Montevideo, Uruguay

Congreso; 6th International Conference on Biological Physics and the 5th Southern Cone Biophysics Congress; 2007

  Antifreeze proteins (AFPs) are ice-binding proteins that depress the freezing point of water in a non-colligative manner, without a significant modification of the melting point. Found in the blood and tissues of some organisms (such as fish, insects, plants and soil bacteria), play an important role in subzero temperatures survival. Fish Type III AFP is present in members of the subclass Zoarcoidei. AFPIII is a small 7-kDa globular protein. The protein surface present a dominant hydrophilic and a dominant hydrophobic region, and result in the self-assembly of proteins when concentration reach the critical aggregation concentration (CAC) (Liu & Du J. Biol. Chem. (2004) 279, 6124). In the present work the formation of auto-organized structures was studied through the behavior of several physical properties. The dielectric permittivity spectra at low frequency, the conductivity, viscosity, and density of Fish Type III AFP solutions were measured at different concentrations around the CAC. The combination of the information obtained through electrical and hydrodynamics properties offers the possibility to control the formation of AFP molecular aggregates. The ensemble of the measurements also allows the characterization of the size and shape of micelles-like structures. We report also the shift of these properties when proteins are dissolved in deuterated water. Density and viscosity measurement of AFPIII solution in H2O at 3.5 mg/ml do not evidence appreciable difference with the values of density and viscosity of pure water.