Water Dynamics at Protein Interfaces: Ultrafast Optical Kerr Effect Study

The behavior of water molecules surrounding a protein can have an important bearing on its structure and function. Consequently, a great deal of attention has been focused on changes in the relaxation dynamics of water when it is located at the protein surface. Here we use the ultrafast optical Kerr effect to study the H-bond structure and dynamics of aqueous solutions of proteins. Measurements are made for three proteins as a function of concentration. We find that the water dynamics in the first solvation layer of the proteins are slowed by up to a factor of 8 in comparison to those in bulk water. The most marked slowdown was observed for the most hydrophilic protein studied, bovine serum albumin, whereas the most hydrophobic protein, trypsin, had a slightly smaller effect. The terahertz Raman spectra of these protein solutions resemble those of pure water up to 5 wt % of protein, above which a new feature appears at 80 cm–1, which is assigned to a bending of the protein amide chain

Temperature dependence of protein dynamics simulated with three different water models

The effect of variation of the water model on the temperature dependence of protein and hydration water dynamics is examined by performing molecular dynamics simulations of myoglobin with the TIP3P, TIP4P, and TIP5P water models and the CHARMM protein force field at temperatures between 20 and 300 K. The atomic mean-square displacements, solvent reorientational relaxation times, pair angular correlations between surface water molecules, and time-averaged structures of the protein are all found to be similar, and the protein dynamical transition is described almost indistinguishably for the three water potentials. The results provide evidence that for some purposes changing the water model in protein simulations without a loss of accuracy may be possible

Normes de concrétude, de valeur d'imagerie, de fréquence subjective et de valence émotionnelle pour 867 mots.

Summary : Concreteness, imageability, subjective frequency and emotionality ratings for 866 words. This article presents concreteness, imageability, subjective and emotional valence norms for a set of 866 words. The norms were collected front 97 participants, all French native speakers whose mean age was 23. Descriptive statistics and correlational analyses have been performed on these norms and on other estimated (age of acquistion, conceptual familiarity, image variability) and objective (word frequency) published indexes. The correlational analyses reveal the composite nature of certain estimations. In particular, subjective frequency and imageability are highly correlated with the other variables. Concreteness is highly correlated only with imageability and emotional valence, the lutter which is weakly correlated with the other variables. Researchers must have at their disposal such information in order to select stimuli in factorial studies or to perform multiple regression analyses. Key words : concreteness, imageability, subjective frequency, emotional valence.Résumé Cet article présente des normes de concrétude, de valeur d'imagerie, de fréquence subjective et de valence émotionnelle pour 866 mots. Ces normes ont été collectées auprès de 97 participants de langue maternelle française, âgés de 23 ans en moyenne. Des statistiques descriptives et des analyses corrélationnelles ont été conduites sur ces normes et sur d'autres indices normatifs déjà publiés (âge d'acquisition, familiarité conceptuelle, variabilité d'imagerie) et objectifs (fréquence objective). Les analyses de corrélation révèlent la nature composite des estimations. En particulier, la fréquence subjective et la valeur d'imagerie sont fortement corrélées à l'ensemble des variables. La concrétude est fortement corrélée uniquement à la valeur d'imagerie et à la valence émotionnelle, laquelle est faiblement corrélée avec les autres variables. Les chercheurs doivent disposer de telles indications pour sélectionner du matériel dans le cadre d'expériences ayant recours à des plans factoriels ou pour réaliser des analyses de régression multiple. Mots-clés: concrétude, valeur d'imagerie, fréquence subjective, valence émotionnelle.Bonin Patrick, Méot Alain, Aubert Louis-F., Malardier Nathalie, Niedenthal Paula M., Capelle-Toczek M.-C. Normes de concrétude, de valeur d'imagerie, de fréquence subjective et de valence émotionnelle pour 866 mots. In: L'année psychologique. 2003 vol. 103, n°4. pp. 655-694

Carboxyl Group Enhanced CO Tolerant GO Supported Pt Catalysts: DFT and Electrochemical Analysis

The effect of residual oxygen species in as-prepared Pt nanoparticle on partially reduced graphene oxide (Pt/PRGO) and partially reduced carboxylated-GO (Pt/PR­(GO–COOH)) supports was investigated using electrochemical CO stripping and density functional theory (DFT) analysis. Pt/PRGO and Pt/PR­(GO–COOH) revealed a clear negative shift in CO-stripping onset potential compared to commercial Pt/carbon black. DFT analysis confirmed that the presence of a −COOH group provides the most resistance for CO adsorption. This CO-Pt binding energy is significantly lower than that observed in the presence of an −OH group, which is the most abundant oxygen group in carbon supports. The Pt-CO dissociation energies (on a 42-atom graphene sheet) in the presence of various oxygen groups, in descending order, were OH > CO ≈ C–O–C > COOH. Although single-bonded carbon–oxygen groups (−OH and C–O–C) are more abundant on the GO basal plane and play an important role in Pt nanoparticle nucleation and distribution on graphene sheets, the double-bonded carbon–oxygen (CO and COOH) groups are more abundant residual species post Pt nanoparticle growth and play a vital role in enhancing CO tolerance