Spectacular induced-fit process for guest binding by a calix[6]arene Zn(II) funnel complex

The host properties of a calix[6]arene cone capped by a Zn(II) tris-imidazole core at the small rim and decorated by three NH(2) substituents at the large rim are described and compared to the hexa-tBu parent complex. It is shown that the replacement of three bulky tBu substituents by three hydrophilic and small NH(2) groups has three major impacts: the receptor is now soluble in aqueous media, it accepts large guests such as dimethyldopamine and, most interestingly, undergoes a spectacular induced-fit behavior for guest binding.     

Advances in Biohybridized Planar Polymer Membranes and Membrane-Like Matrices

The past few decades have seen increasing growth in the field of biomimetic membranes and thus also a rapid expansion of their biomedical and technological applications. Versatility, stability and scalability have moved biohybrid polymer membranes into the limelight. This review focuses on planar, soft polymer membranes and polymer-based matrices and their role as a host for different types of biomolecules. Because biomimetic polymer platforms present an extensive, ever-growing field, we limit ourselves mostly to the discussion of producing planar polymer membranes on solid supports that lend themselves to functionalization by biomolecules. We present an overview of the major highlights and challenges associated with the biohybridization of such polymer platforms. In particular, we elaborate on procedures developed to maintain optimal peptide and membrane protein performance in a customized polymer membrane or membrane-like environment. Finally, we discuss a number of applications of such biohybridized polymer platforms and contemplate future developments to further exploit their potential.     

Determination of synthetic polypeptide conformations and molecular geometrical parameters by nonaqueous CE

The aim of this work was to study changes in homopolypeptide chain conformation as a function of the number of residues by the modeling of the electrophoretic mobility. For this purpose, the frictional coefficients of poly(N(epsilon)-trifluoroacetyl-L-lysine) with different number of residues (up to 11) were determined from the absolute ionic mobilities and modeled by the hydrodynamic frictional coefficient of an equivalent cylinder. This approach allowed determination of geometrical parameters of the polypeptide chain in a liquid phase (nonaqueous solution of the BGE). The fact that the BGE and analyte are dissolved in mixed (methanol-ACN) organic solvent implied to take into account different effects and corrections that are generally not considered in aqueous solvent: namely, the effect of ion-pairs between constituents of the BGE for the calculation of the ionic strength, the effect of ion-pairs between the solutes and the electrolyte counterions and the correction due to the dielectric friction (Hubbard-Onsager equations). In addition, the influence of the ionic strength on the electrophoretic mobility was corrected using the Pitts equation, and the effect of lateral charges due to a slight deprotonation of the -NH- group in the lateral chain was also considered. From this modeling, molecular geometrical parameters relative to the linear and helico?dal conformations were obtained with very good correlation coefficients. Interestingly, this work also points out that the use of ionic mobility modeling for extracting molecular geometrical parameters can also be applied to end-charged polypeptides with slightly charged lateral chains (3% of elementary charge per residue).     

Evaluation of the pH- and thermal stability of the recombinant green fluorescent protein (GFP) in the presence of sodium chloride

The thermal stability of recombinant green fluorescent protein (GFP) in sodium chloride (NaCl) solutions at different concentrations, pH, and temperatures was evaluated by assaying the loss of fluorescence intensity as a measure of denaturation. GFP, extracted from Escherichia coli cells by the three-phase partitioning method and purified through a butyl hydrophobic interaction chromatography (HIC) column, was diluted in water for injection (WFI) (pH 6.0-7.0) and in 10 mM buffer solutions (acetate, pH 5.0; phosphate, pH 7.0; and Tris-EDTA, pH 8.0) with 0.9-30% NaCl or without and incubated at 80-95 degrees C. The extent of protein denaturation was expressed as a percentage of the calculated decimal reduction time (D-value). In acetate buffer (pH 4.84+/-0.12), the mean D-values for 90% reduction in GFP fluorescence ranged from 2.3 to 3.6 min, independent of NaCl concentration and temperature. GFP thermal stability diluted in WFI (pH 5.94+/-0.60) was half that observed in phosphate buffer (pH 6.08+/-0.60); but in both systems, D-values decreased linearly with increasing NaCl concentration, with D-values (at 80 degrees C) ranging from 3.44, min (WFI) to 6.1 min (phosphate buffer), both with 30% NaCl. However, D-values in Tris-EDTA (pH 7.65+/-0.17) were directly dependent on the NaCl concentration and 5-10 times higher than D-values for GFP in WFI at 80 degrees C. GFP pH- and thermal stability can be easily monitored by the convenient measure of fluorescence intensity and potentially be used as an indicator to monitor that processing times and temperatures were attained.     

Fullerenes as Key Components for Low‐Dimensional (Photo)electrocatalytic Nanohybrid Materials

An emerging class of heterostructures with unprecedented (photo)electrocatalytic behavior, involving the combination of fullerenes and low‐dimensional (LD) nanohybrids, is currently expanding the field of energy materials. The unique physical and chemical properties of fullerenes have offered new opportunities to tailor both the electronic structures and the catalytic activities of the nanohybrid structures. Here, we comprehensively review the synthetic approaches to prepare fullerene‐based hybrids with LD (0D, 1D, and 2D) materials in addition to their resulting structural and catalytic properties. Recent advances in the design of fullerene‐based LD nanomaterials for (photo)electrocatalytic applications are emphasized. The fundamental relationship between the electronic structures and the catalytic functions of the heterostructures, including the role of the fullerenes, is addressed to provide an in‐depth understanding of these emerging materials at the molecular level.     

Pyridine-based Liquid-Phase Synthesis of Crystalline TiN and ZnSiN2 Nanoparticles

TiN and ZnSiN₂ nanoparticles are obtained via a novel pyridine-based synthesis route. This one-pot liquid-phase route strictly avoids all oxygen sources (including starting materials, surface functionalization, solvents), which is highly relevant in regard of the material purity and material properties. Colloidally stable suspensions of crystalline, small-sized TiN (5.4±0.4 nm) and ZnSiN₂ (5.2±1.1 nm) are instantaneously available from the liquid phase. Elemental analysis and electron energy loss spectroscopy confirm the purity of the compounds and specifically the absence of oxygen. The as-prepared ZnSiN₂ show yellowish emission (500-700 nm) already at room temperature with its maximum at 570 nm.     

Abraham Model Correlations for Triethylene Glycol Solvent Derived from Infinite Dilution Activity Coefficient,Partition Coefficient and Solubility Data Measured at 298.15 K

A gas chromatographic headspace analysis method was used to experimentally determine gas-to-liquid partition coefficients and infinite dilution activity coefficients for 29 liquid organic solutes dissolved in triethylene glycol at 298.15 K. Solubilities were also determined at 298.15 K for 23 crystalline nonelectrolyte organic compounds in triethylene glycol based on spectroscopic absorbance measurements. The experimental results of the headspace chromatographic and spectroscopic solubility measurements were converted to gas-to-triethylene glycol and water-to-triethylene glycol partition coefficients, and molar solubility ratios using standard thermodynamic relationships. Expressions were derived for solute transfer into triethylene glycol by combining our measured experimental values with published literature data. Mathematical correlations based on the Abraham model describe the observed partition coefficient and solubility data to within 0.16 log₁₀ units (or less).     

A versatile approach to hybrid thiadiazine-based molecules by the Ugi four-component reaction

Aiming at developing a versatile method for the generation of hybrid heterocyclic molecules, we describe a sequential approach comprising the formation of carboxy-functionalized 1,3,5-thiadiazines followed by the Ugi reaction with variation of the amino and the isonitrile components. The method enables the generation of structurally diverse molecular hybrids including peptide, lipid, steroidal and sugar moieties linked to the 1,3,5-thiadiazine scaffold.     

Global inversion theorems via coercive functionals on metric spaces

Let X$X$ and Y$Y$ be metric spaces. We give sufficient metric conditions for a local homeomorphism f:X→Y$f:X\to Y$ to be a global one. We achieve this by means of auxiliary coercive functionals; several expected global inversion theorems are obtained by choosing different functionals.