Role of the solvent in the dynamical transitions of proteins: the case of the lysozyme-water system

We study the dynamics of hydration water in the protein lysozyme in the temperature range 180 K相似文献   

Effective methods for the biotinylation of azamacrocycles

The biotin-(strept)avidin interaction remains a gold standard of model biological recognition events. The biotinylation of azamacrocycles permits the investigation of signal transduction between this recognition event and the metal center of an azamacrocycle complex, of wide potential interest in biosensing. There are no generally applicable procedures in the literature for such functionalizations. We report here a comprehensive investigation into the attachment of biotin to TACN, cyclen, and cyclam. Effective methods have been found for each ring. The efficacy of the functionalization is critically dependent on the nature of the azamacrocycle.     

Preparation and characterization of rapid magnetic recyclable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript>@TiO<Subscript>2</Subscript>–Sn photocatalyst

Effective procedure to synthesize Fe₃O₄@SiO₂@TiO₂–Sn magnetically separable photocatalyst by a combination of co-precipitation, sol–gel and photodeposition methods was introduced. Products were characterized by XRD, SEM, VSM, EDS, DRS, TEM, ICP-OES and IR techniques. The dimensions of catalyst particle size were evaluated by scanning electron microscopy, and results approved nanoscale size for product. In addition, studying the magnetic nature by VSM analysis showed superparamagnetic properties for all samples. XRD pattern indicates that TiO₂ coated on Fe₃O₄@SiO₂ core well crystallized at 400 °C in anatase phase. Synthesized photocatalyst shows good photocatalytic performance in decolorization of rhodamine B aqueous solution. The composite nanoparticles showed high recycling efficiency and stability over five separation cycles.     

An investigation on ordered algebraic hyperstructures

In this paper, we present some basic notions of simple ordered semihypergroups and regular ordered Krasner hyperrings and prove some results in this respect. In addition, we describe pure hyperideals of ordered Krasner hyperrings and investigate some properties of them. Finally, some results concerning purely prime hyperideals are proved.     

Insights into hofmeister mechanisms: anion and degassing effects on the cloud point of dioctanoylphosphatidylcholine/water systems

Water dispersions of dioctanoylphosphatidylcholine (diC8PC) exhibit upper consolute curves. How they are affected by some salts and other additives (D2O, urea) has already been explored and the phase separation has been interpreted within the framework of the Blankschtein-Thurston-Benedek (BTB) model. This deduces the chemical potential gain in micellar growth (Deltamu) and the intermicellar interaction coefficient (C) as fitting parameters from the coexistence curves. But, the specific mechanisms that drive such phenomena have remained obscure. To identify these mechanisms, we investigate the effects of a range of anions on the cloud points of diC8PC/H2O systems and extract the phenomenological parameters of the BTB model. We show how these parameters, for micellar growth, i.e., surface, intramolecular interactions, and for interaggregate interactions, i.e., bulk solute effects, are connected to anionic polarizabilities. Nonelectrostatic (NES) quantum mechanical fluctuation (Lifshitz or dispersion) forces missing from conventional theories are then shown to regulate lyotropic Hofmeister effects, both explicitly and implicitly.     

Structure of SDS micelles with propylene carbonate as cosolvent: a PGSE-NMR and SAXS study

The effect of propylene carbonate on SDS micelles was investigated by means of pulsed gradient spin-echo (PGSE) NMR, small-angle X-ray scattering (SAXS), conductivity and ion-selective electrode (ISE) measurements. The knowledge of the cosolvent partition between continuous phase and micelles (obtained by means of PGSE-NMR) allowed the identification of relevant dilution paths. Along these paths the system is composed of identical micelles that become more and more diluted. The extrapolation of measured self-diffusion coefficient to infinite dilution (where direct and hydrodynamic interactions are negligible) permits the determination of hydrodynamic size of the micelles. Moreover, the micelle ionization degree (measured by means of ISE) combined with PGSE-NMR and conductivity data furnishes an estimate of the aggregation number without any assumptions on micellar shape. On the other hand, troublesome hydrodynamic interactions are irrelevant to SAXS, and scattering data collected at fixed composition can be analyzed according to a reasonable model by exploiting the insight on the propylene carbonate partition gained through PGSE-NMR. By means of these approaches, we have found that propylene carbonate acts mainly as cosurfactant for the SDS micelles, decreasing their size and aggregation number by increasing the mean headgroup area of SDS.     

Order Types of Convex Bodies

We prove a Hadwiger transversal-type result, characterizing convex position on a family of non-crossing convex bodies in the plane. This theorem suggests a definition for the order type of a family of convex bodies, generalizing the usual definition of order type for point sets. This order type turns out to be an oriented matroid. We also give new upper bounds on the Erdős–Szekeres theorem in the context of convex bodies.     

Divergent and stereoselective synthesis of dafachronic acids

A new divergent synthesis of DAF-12 ligands, namely Δ⁴- and Δ⁷-dafachronic acid, is described starting from the natural bile acid hyodeoxycholic acid. Homologation of the side chain followed by stereoselective reduction of the Δ²⁴ olefinic linkage, 6α-dehydroxylation and C₃-oxidation affords dafachronic acids in good yields and high diastereoselectivity making this approach easily accessible and scalable.