The effect of n-, s- and t-butanol on the micellization and gelation of Pluronic P123 in aqueous solution

Thermodynamic and kinetics studies for adsorption of Pt ions complexes from the chloride solutions obtained by leaching chlorinated spent automotive catalysts on anionic exchange resin Diaion WA21J were carried out. It was found that only Si, Pt, Rh and Pd from the solution were selectively adsorbed on the resin Diaion WA21J more strongly. The adsorption equilibrium time for Pt ions was about 20 h. The isothermal adsorption of Pt ions was found to fit Langmuir, Freundlich and DKR models. The maximum monolayer adsorption capacities Q(max) and X(m) of Pt ions on the resin based on Langmuir and DKR model were 4.85, 5.36 and 5.69 mg/g as well as 5.01, 5.63 and 5.98 mg/g for temperatures 18°C, 28°C and 40°C, respectively. The apparent adsorption energy E(ad) based on DKR model were -11.79, -11.04 and -11.04 kJ/mol for the temperatures 18°C, 28°C and 40°C, respectively. Ion exchange was the mechanism involved in the adsorption process. The adsorption of Pt ions on the resin underwent pseudo-first-order kinetic process, and the apparent adsorption activation energy E(a,1) was 12.6 kJ/mol. The intraparticle diffusion of Pt ions was a main rate-controlling step in most of time of adsorption process.     

Polymorphism and isomerisation of an azobenzene derivative on gold

M-TBA (4-methoxy-3,30,5,50-tetra-tert-butylazobenzene) adsorbed on a gold (111) surface was found to form four different polymorphs, two of which isomerizable at -1.7 V, but with a low propensity for further isomerisation of nearby molecules (C. Dri, M. V. Peters, J. Schwarz, S. Hecht, L. Grill, Nat. Nanotechnol., 2008, 3, 649-653). Atomistic simulations investigate the origin of the effects.     

Super‐Resolution Imaging of Plasma Membrane Glycans

Much of the physiology of cells is controlled by the spatial organization of the plasma membrane and the glycosylation patterns of its components, however, studying the distribution, size, and composition of these components remains challenging. A bioorthogonal chemical reporter strategy was used for the efficient and specific labeling of membrane‐associated glycoconjugates with modified monosaccharide precursors and organic fluorophores. Super‐resolution fluorescence imaging was used to visualize plasma membrane glycans with single‐molecule sensitivity. Our results demonstrate a homogeneous distribution of N‐acetylmannosamine (ManNAc)‐, N‐acetylgalactosamine (GalNAc)‐, and O‐linked N‐acetylglucosamine (O‐GlcNAc)‐modified plasma membrane proteins in different cell lines with densities of several million glycans on each cell surface.     

Spectroscopic Identification of a Bidentate Binding Motif in the Anionic Magnesium–CO2 Complex ([ClMgCO2]−)

A magnesium complex incorporating a novel metal–CO₂ binding motif is spectroscopically identified. Here we show with the help of infrared photodissociation spectroscopy that the complex exists solely in the [ClMg(η²‐O₂C)]^? form. This bidentate double oxygen metal–CO₂ coordination has previously not been observed in neutral nor in charged unimetallic complexes. The antisymmetric CO₂ stretching mode in [ClMg(η²‐O₂C)]^? is found at 1128 cm^?1, which is considerably redshifted from the corresponding mode in bare CO₂ at 2349 cm^?1, suggesting that the CO₂ moiety has a considerable negative charge (～1.8 e^?). We also employed electronic structure calculations and kinetic analysis to support the interpretation of the experimental results.     

Communication: Vibrational spectroscopy of atmospherically relevant acid cluster anions: bisulfate versus nitrate core structures

Infrared multiple photon dissociation spectra for the smallest atmospherically relevant anions of sulfuric and nitric acid allow us to characterize structures and distinguish between clusters with a bisulfate or a nitrate core. We find that bisulfate is the main charge carrier for HSO(4)(-)·H(2)SO(4)·HNO(3) but not for NO(3)(-)·H(2)SO(4)·HNO(3). For the mixed dimer anion, we find evidence for the presence of two isomers: HSO(4)(-)·HNO(3) and NO(3)(-)·H(2)SO(4). Density functional calculations accompany the experimental results and provide support for these observations.     

Effect of water-soluble polymers, polyethylene glycol and poly(vinylpyrrolidone), on the gelation of aqueous micellar solutions of Pluronic copolymer F127

The micellization of F127 (E(98)P(67)E(98)) in dilute aqueous solutions of polyethylene glycol (PEG6000 and PEG35000) and poly(vinylpyrrolidone) (PVP K30 and PVP K90) is studied. The average hydrodynamic radius (r(h,app)) obtained from the dynamic light scattering technique increased with increase in PEG concentration but decreased on addition of PVP, results which are consistent with interaction of the micelles with PEG and the formation of micelles clusters, but no such interaction occurs with PVP. Tube inversion was used to determine the onset of gelation. The critical concentration of F127 for gelation increased on addition of PEG and of PVP K30 but decreased on addition of PVP K90. Small-angle X-ray scattering (SAXS) was used to show that the 30 wt% F127 gel structure (fcc) was independent of polymer type and concentration, as was the d-spacing and so the micelle hard-sphere radius. The maximum elastic modulus (G(max)(')) of 30 wt% F127 decreased from its value for water alone as PEG was added, but was little changed by adding PVP. These results are consistent with the packed-micelles in the 30 wt% F127 gel being effectively isolated from the polymer solution on the microscale while, especially for the PEG, being mixed on the macroscale.     

Towards the Antimicrobial Finishing of Poly(isoprene)

Summary: Anionically polymerised (poly)isoprene was functionalized with cysteamine applying thiol-ene click chemistry. Subsequent quaternisation of the primary amino groups gave polymers with antimicrobial activity against Listeria monocytogenes, Eschericchia coli, Pseudomonas fluorescens and Staphylococcus aureus as revealed from tests performed according to the Japanese Industrial Standard Z2801:2000. The novel polymers feature sufficient thermal stability for the compounding with commodity polymers such as poly(propylene) and might be used as a non leaching additive to finish commodity polymers with antimicrobial acitivity.     

vmdICE: a plug-in for rapid evaluation of molecular dynamics simulations using VMD

Molecular dynamics (MD) is a powerful in silico method to investigate the interactions between biomolecules. It solves Newton's equations of motion for atoms over a specified period of time and yields a trajectory file, containing the different spatial arrangements of atoms during the simulation. The movements and energies of each single atom are recorded. For evaluating of these simulation trajectories with regard to biomedical implications, several methods are available. Three well-known ones are the root mean square deviation (RMSD), the root mean square fluctuation (RMSF) and solvent accessible surface area (SASA). Herein, we present a novel plug-in for the software "visual molecular dynamics" (VMD) that allows an interactive 3D representation of RMSD, RMSF, and SASA, directly on the molecule. On the one hand, our plug-in is easy to handle for inexperienced users, and on the other hand, it provides a fast and flexible graphical impression of the spatial dynamics of a system for experts in the field.     

Molecular Engineering To Enhance Reactivity and Selectivity in an Ultrafast Photoclick Reaction

Light-induced 9,10-phenanthrenequinone-electron-rich alkene ( PQ-ERA ) photocycloadditions are an attractive new type of photoclick reaction, featuring fast conversions and high biocompatibility. However, the tunability of the reaction was hardly investigated up to now. To this end, we explored the influence of substituents on both reaction partners and the reaction rate between the PQs and ERAs . We identified new handles for functionalization and discovered that using enamines as ERAs leads to drastically enhanced rates (>5400 times faster), high photoreaction quantum yields ( Φ_P , up to 65 %), and multicolor emission output as well as a high fluorescence quantum yield of the adducts ( Φ_F , up to 97 %). Further investigation of the photophysical and photochemical properties provided insights to design orthogonal reaction systems both in solution and on nanoparticle surfaces for ultrafast chemoselective functionalization by photoclick reactions.