Non-monotonic variation with salt concentration of the second virial coefficient in protein solutions

The osmotic virial coefficient $B_2$ of globular protein solutions is calculated as a function of added salt concentration at fixed pH by computer simulations of the ``primitive model''. The salt and counter-ions as well as a discrete charge pattern on the protein surface are explicitly incorporated. For parameters roughly corresponding to lysozyme, we find that $B_2$ first decreases with added salt concentration up to a threshold concentration, then increases to a maximum, and then decreases again upon further raising the ionic strength. Our studies demonstrate that the existence of a discrete charge pattern on the protein surface profoundly influences the effective interactions and that non-linear Poisson Boltzmann and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory fail for large ionic strength. The observed non-monotonicity of $B_2$ is compared to experiments. Implications for protein crystallization are discussed.Comment: 43 pages, including 17 figure

HIGHLY NONLINEAR OPTICAL EFFECTS IN LIQUID CRYSTALS

Le champ optique d'un laser continu est assez fort pour induire un grand changement de l'indice de réfraction d'un cristal liquide. La transition structurelle induite par un champ optique peut avoir lieu. La grande nonlinearité optique peut mener à des phénomènes d'optique nonlinéaire intéressants.CW laser fields are strong enough to induce a large refractive index change in a liquid crystal. Optical-field-induced structural transition can occur. The large optical nonlinearity can lead to some unusual highly nonlinear optical phenomena

Summer and fall habitat of North Atlantic right whales (Eubalaena glacialis) inferred from satellite telemetry

Author Posting. © National Research Council Canada, 2005. This article is posted here by permission of National Research Council Canada for personal use, not for redistribution. The definitive version was published in Canadian Journal of Fisheries and Aquatic Sciences 62 (2005): 527-543, doi:10.1139/F04-238.Satellite-monitored radio tags were attached to North Atlantic right whales (Eubalaena glacialis) in Grand Manan Basin of the lower Bay of Fundy during the summer and early fall seasons of 1989–1991 and 2000. Monte Carlo tests were used to examine the distribution of the tagged whales in space and time and with respect to a variety of environmental variables to characterize right whale habitat on their northern feeding grounds. These environmental variables included depth, depth gradient, climatological surface and bottom hydrographic properties, and remotely sensed surface temperature, chlorophyll concentration, and their respective horizontal gradients. Site fidelity in the Bay of Fundy was very low during 1989–1991 and high during 2000. When the tagged animals left the Bay, they did not frequently visit the deep basins of the Gulf of Maine and Scotian Shelf, where abundances of their primary copepod prey, Calanus finmarchicus, are thought to be high. Instead, right whales visited areas characterized by low bottom water temperatures, high surface salinity, and high surface stratification. No evidence was found that the tagged right whales associated with oceanic fronts or regions with high standing stocks of phytoplankton.This study was supported by the Office of Naval Research, National Marine Fisheries Service, Oregon State University Marine Mammal Endowment, and the Space Grant and Earth System Science fellowship programs of the National Aeronautics and Space Administration