Smart functionalized thin gel layers for electrochemical sensors,biosensors and devices

Combining hydrogels sensitive to external stimuli with conducting surfaces opens new possibilities in electrochemistry. Thin hydrogel layers as unique electrode-modifying materials provide highly permeable matrix for easy diffusion of analytes. In addition, larger individuals, for example, nanoparticles and enzymes, can be straightforwardly immobilized in the polymeric networks at electrode surfaces. Such properties are strongly desired for construction of sensors and biosensors. In addition, sensitivity to external stimuli allows to significantly enhance or weaken the electroanalytical signal. Recently, a significant number of articles concerning switchable sensors/biosensors, switchable electrochemical systems and signal–responsive interfaces have been published. This report is also focused on the construction of various devices based on electrode surfaces modified with smart hydrogel layers, for example, logic gates and electroresponsive hydrogel layers as potentially advanced drug delivery systems, artificial muscles and electrochemical valves.     

Short but Weak: The Z-DNA Lone-Pair⋅⋅⋅π Conundrum Challenges Standard Carbon Van der Waals Radii

Current interest in lone-pair⋅⋅⋅π (lp⋅⋅⋅π) interactions is gaining momentum in biochemistry and (supramolecular) chemistry. However, the physicochemical origin of the exceptionally short (ca. 2.8 Å) oxygen-to-nucleobase plane distances observed in prototypical Z-DNA CpG steps remains unclear. High-level quantum mechanical calculations, including SAPT2+3 interaction energy decompositions, demonstrate that lp⋅⋅⋅π contacts do not result from n→π* orbital overlaps but from weak dispersion and electrostatic interactions combined with stereochemical effects imposed by the locally strained structural context. They also suggest that the carbon van der Waals (vdW) radii, originally derived for sp³ carbons, should not be used for smaller sp² carbons attached to electron-withdrawing groups. Using a more adapted carbon vdW radius results in these lp⋅⋅⋅π contacts being no longer of the sub-vdW type. These findings challenge the whole lp⋅⋅⋅π concept that refers to elusive orbital interactions that fail to explain short interatomic contact distances.     

Modification of blood serum DSC profiles by sauna treatments in cross-country skiers during the exercise cycle

Journal of Thermal Analysis and Calorimetry - The study has evaluated the effect of sauna treatments on the blood serum of professional cross-country skiers (3 women and 6 men) during two exercise...     

Heterogeneous azide–alkyne cycloaddition in the presence of a copper catalyst supported on an ionic liquid polymer/silica hybrid material

Heterogeneous copper catalysts were prepared by the deposition of CuI on a hybrid material consisting of silica and a polymer with imidazolium moieties. The solid materials were characterised using solid‐phase NMR, Fourier transform infrared, Raman and X‐ray photoelectron spectroscopies and Brunauer–Emmett–Teller measurements. The formation of copper–carbene complexes was proved from Raman spectra and the results were supported by density functional theory calculations. The catalyst could be recycled efficiently with low loss of copper. Metal leaching was proved to be facilitated by the use of conditions typical for a homogeneous system (the presence of a polar solvent or the addition of a tertiary amine). Besides simple model reactions, the best catalyst was found to be suitable for the synthesis of triazoles of more elaborate structure, such as ferrocene or steroid derivatives.     

Monitoring compartment-specific substrate cleavage by cathepsins B, K, L, and S at physiological pH and redox conditions

Background  

Cysteine cathepsins are known to primarily cleave their substrates at reducing and acidic conditions within endo-lysosomes. Nevertheless, they have also been linked to extracellular proteolysis, that is, in oxidizing and neutral environments. Although the impact of reducing or oxidizing conditions on proteolytic activity is a key to understand physiological protease functions, redox conditions have only rarely been considered in routine enzyme activity assays. Therefore we developed an assay to test for proteolytic processing of a natural substrate by cysteine cathepsins which accounts for redox potentials and pH values corresponding to the conditions in the extracellular space in comparison to those within endo-lysosomes of mammalian cells.     

Oligoether-strapped meso-pyrimidinylporphyrins

Bis(oligoether-strapped) zinc(II)-meso-pyrimidinylporphyrins were readily synthesized via nucleophilic aromatic substitution reactions of biscathechol-substituted tri- or tetraethylene glycol straps on the upper and lower faces of a Zn(II)-A₂B₂-meso-dichloropyrimidinylporphyrin precursor. The crown ether-like bridges surrounding the porphyrin core create peculiar cavities above and below the macrocyclic plane with appealing features for supramolecular host–guest chemistry.     

3He NMR studies on helium–pyrrole,helium–indole,and helium–carbazole systems: a new tool for following chemistry of heterocyclic compounds

The ³He nuclear magnetic shieldings were calculated for free helium atom and He–pyrrole, He–indole, and He–carbazole complexes. Several levels of theory, including Hartree–Fock (HF), Second‐order Møller‐Plesset Perturbation Theory (MP2), and Density Functional Theory (DFT) (VSXC, M062X, APFD, BHandHLYP, and mPW1PW91), combined with polarization‐consistent pcS‐2 and aug‐pcS‐2 basis sets were employed. Gauge‐including atomic orbital (GIAO) calculated ³He nuclear magnetic shieldings reproduced accurately previously reported theoretical values for helium gas. ³He nuclear magnetic shieldings and energy changes as result of single helium atom approaching to the five‐membered ring of pyrrole, indole, and carbazole were tested. It was observed that ³He NMR parameters of single helium atom, calculated at various levels of theory (HF, MP2, and DFT) are sensitive to the presence of heteroatomic rings. The helium atom was insensitive to the studied molecules at distances above 5 Å. Our results, obtained with BHandHLYP method, predicted fairly accurately the He–pyrrole plane separation of 3.15 Å (close to 3.24 Å, calculated by MP2) and yielded a sizable ³He NMR chemical shift (about ?1.5 ppm). The changes of calculated nucleus‐independent chemical shifts (NICS) with the distance above the rings showed a very similar pattern to helium‐3 NMR chemical shift. The ring currents above the five‐membered rings were seen by helium magnetic probe to about 5 Å above the ring planes verified by the calculated NICS index. Copyright © 2014 John Wiley & Sons, Ltd.