Bovine serum albumin (BSA) plays a role in the size of SDS micelle-like aggregates at the saturation binding: the ionic strength effect

The influence of ionic strength on the complexes formed by natural bovine serum albumin (BSA), pH 5.4 (near the isoelectric point), and sodium dodecyl sulfate (SDS) in aqueous buffered (sodium acetate) solution was investigated by using surface tension, fluorescence and small angle X-ray scattering (SAXS) techniques. Ionic strength was varied by changing sodium acetate buffer concentration from 0.020 to 0.5 M. Surface tension revealed that SDS:BSA saturation binding occurs at psp = 42 +/- 2 mM, independent of the solution ionic strength. Further, SAXS curves are consistent with the necklace and bead model, where micelle-like aggregates are randomly distributed along the partial unfolded protein. Micelle-like aggregates grow from small spheres at 10 mM SDS to small ellipsoids (upsilon = 1.3 , ratio between the largest and the shortest axes) near psp, in good agreement with micellar aggregation numbers obtained by fluorescence, independent of salt concentration. Protein-bound micelles stop growing above psp and further SDS addition induces free-micelle formation.     

Interactions between octyl-β-D-glucoside and α-amino acids or small peptides

The interactions between octyl--D-glucoside and glycine in water have been investigated by surface tension, viscosity, and density measurements. The results show that the -amino acid causes an unexpected lowering of the critical micellar concentration of octyl--D-glucoside. Such a finding has been interpreted in temss of dipole-dipole interactions between the hydrophilic site of the surfactant and the peptidic cosluttes. From three to seven amino acid molecules have been estimated to be coordinated with each glucoside unity in the micellar state. The research has been extended to glycine oligopeptides and L-lysine. The latter compound has effects similar to those observed with glycine whereas diglycine and triglycine show weaker effects on the micellization process.     

Regio- and Stereochemical Aspects of the Palladium-Catalyzed Desilylation-Arylation of Substituted Vinylsilanes

The palladium-catalyzed desilylation-arylation of substituted vinylsilanes by p-iodoanisole in the presence of bidentate phosphine ligands is described. Apart from enhancing the rate of the reaction considerably, heteroatom-based functional groups in the vinylsilane moiety have a profound influence on the regiochemistry. A catalytic cycle for the chelation-controlled desilylation-arylation reaction involving five- and six-membered chelate rings is proposed.     

Synthesis of linear and starlike polymers from poly(propylene glycol) methacrylate using controlled radical polymerization

The copper‐catalyzed atom transfer radical polymerization (ATRP) of poly(propylene glycol) methacrylate (PPGM) in solution to produce linear and starlike polymers is reported, using methylethyl ketone as the solvent and a temperature of 80 °C. The ATRP system used was efficient for polymerization of the functionalized monomer without protecting hydroxyl end groups of monomer. The polymerizations were consistent with “living” or controlled processes, as revealed by the linear evolution of molecular weight with conversion. Increasing the [M]₀:[I]₀ ratio resulted in increasing molecular weights, whereas the polydispersity indices remained low (M_w/M_n < 1.4) even at high conversion. Decreasing the [CuBr]₀:[I]₀ ratio resulted in lower conversions, slightly larger polydispersities, and decreased molecular weights, likely resulting from a lower initiation efficiency. Polymers were characterized by ¹H and ¹³C NMR; molecular weights of polymers with low degrees of polymerization were estimated by end‐group analysis from ¹³C NMR spectra obtained using distortionless enhancement by polarization transfer and the gated decoupling techniques. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 334–343, 2002     

The mechanism of Fe induced bond stability of uranyl(v)

The stabilization of uranyl(v) (UO₂¹⁺) by Fe(ii) in natural systems remains an open question in uranium chemistry. Stabilization of U^VO₂¹⁺ by Fe(ii) against disproportionation was also demonstrated in molecular complexes. However, the relation between the Fe(ii) induced stability and the change of the bonding properties have not been elucidated up to date. We demonstrate that U(v) – oaxial bond covalency decreases upon binding to Fe(ii) inducing redirection of electron density from the U(v) – oaxial bond towards the U(v) – equatorial bonds thereby increasing bond covalency. Our results indicate that such increased covalent interaction of U(v) with the equatorial ligands resulting from iron binding lead to higher stability of uranyl(v). For the first time a combination of U M_4,5 high energy resolution X-ray absorption near edge structure (HR-XANES) and valence band resonant inelastic X-ray scattering (VB-RIXS) and ab initio multireference CASSCF and DFT based computations were applied to establish the electronic structure of iron-bound uranyl(v).

The role of Fe in the increased stability of uranyl(v) is clarified by using state of the art uranium metalorganic chemistry, advanced X-ray spectroscopic approaches and computations.     

Iron-catalyzed hydroxylation of β-ketoesters with hydrogen peroxide as oxidant

The hydroxylation of β-ketoesters was studied using simple iron catalysts and 30 wt % hydrogen peroxide as the terminal oxidant. The highest activity and yield were achieved in the presence of iron(III) chloride. Cyclic β-ketoesters could be smoothly hydroxylated in 75-90% yield. For linear β-ketoester and β-ketoamide, the chloro-substituted products were obtained.     

In Vitro Cytotoxic Protective Effect of Alginate-Encapsulated Capsaicin Might Improve Skin Side Effects Associated with the Topical Application of Capsaicin

Chronic neuropathic pain, particularly peripheral pain, is a cause of great concern for diabetic patients. Current treatments include numerous agents such as capsaicinoids, a known deterrent of neuropathic pain despite the inconvenience associated with local side effects. In this context, the current work aims to elucidate the potential mechanisms involved in cytotoxicity by capsaicin and proposes an efficient formulation of capsaicin in alginate microcapsules, which significantly reduces side effects from capsaicin topical administration. For this, human dermal fibroblast cells were treated with alginate-microencapsulated capsaicin extracts and screened for potential cytotoxic effects produced by the treatment. Cell viability and morphology were examined, as well as oxidative stress status and anti-inflammatory potential. Our results show that the alginate encapsulated formulation of capsaicin exerted lower cytotoxic effects on human dermal fibroblasts as measured by cell viability and reactive oxygen species (ROS) production. Furthermore, the expression profiles of inflammatory cytokines were significantly altered by the treatment as compared with the control culture.     

Effective Preparation of [18F]Flumazenil Using Copper-Mediated Late-Stage Radiofluorination of a Stannyl Precursor

(1) Background: [¹⁸F]Flumazenil 1 ([¹⁸F]FMZ) is an established positron emission tomography (PET) radiotracer for the imaging of the gamma-aminobutyric acid (GABA) receptor subtype, GABA_A in the brain. The production of [¹⁸F]FMZ 1 for its clinical use has proven to be challenging, requiring harsh radiochemical conditions, while affording low radiochemical yields. Fully characterized, new methods for the improved production of [¹⁸F]FMZ 1 are needed. (2) Methods: We investigate the use of late-stage copper-mediated radiofluorination of aryl stannanes to improve the production of [¹⁸F]FMZ 1 that is suitable for clinical use. Mass spectrometry was used to identify the chemical by-products that were produced under the reaction conditions. (3) Results: The radiosynthesis of [¹⁸F]FMZ 1 was fully automated using the iPhase FlexLab radiochemistry module, affording a 22.2 ± 2.7% (n = 5) decay-corrected yield after 80 min. [¹⁸F]FMZ 1 was obtained with a high radiochemical purity (>98%) and molar activity (247.9 ± 25.9 GBq/µmol). (4) Conclusions: The copper-mediated radiofluorination of the stannyl precursor is an effective strategy for the production of clinically suitable [¹⁸F]FMZ 1.     

Desymmetrization of glycerol derivatives with peptide-based acylation catalysts

[reaction: see text] Nucleophile-loaded peptides have been evaluated as catalysts for the desymmetrization of glycerol derivatives through an enantioselective acylation process. Enantiomeric excesses of up to 97% have been obtained for the monoacylated products. A range of other substrates have been examined that shed light on the mechanistic basis of the desymmetrizations.