Optimization of microfluidization for the homogeneous distribution of cellulose nanocrystals (CNCs) in biopolymeric matrix

Microfluidization, which is a high-pressure homogenization technique, was used to develop highly dispersed cellulose nanocrystal (CNC) reinforced chitosan based nanocomposite films. A three factor central composite design with five levels was designed to systematically optimize the microfluidization process. The three factors were the CNC content, the microfluidization pressure and the number of microfluidization cycles. Response surface methodology was used to obtain relationship between the mechanical properties of the nanocomposite films and the factors. Polynomial equations were generated based on the regression analysis of the factors and the predicted properties of the nanocomposite films were in good agreement with the experimental results. Microfluidization effectively reduced the CNC–chitosan aggregates and improved the mechanical properties of the nanocomposite films. Microscopic analysis of the microfluidized nanocomposite films revealed a 10–15 times reduction in the size of the aggregates compared to the non-microfluidized CNC/chitosan films and an increase in the root mean square surface roughness (Rq).     

Oversampling Free Energy Perturbation Simulation in Determination of the Ligand-Binding Free Energy

Determination of the ligand-binding affinity is an extremely interesting problem. Normally, the free energy perturbation (FEP) method provides an appropriate result. However, it is of great interest to improve the accuracy and precision of this method. In this context, temperature replica exchange molecular dynamics implementation of the FEP computational approach, which we call replica exchange free energy perturbation (REP) was proposed. In particular, during REP simulations, the system can easily escape from being trapped in local minima by exchanging configurations with high temperatures, resulting in significant improvement in the accuracy and precision of protein–ligand binding affinity calculations. The distribution of the decoupling free energy was enlarged, and its mean values were decreased. This results in changes in the magnitude of the calculated binding free energies as well as in alteration in the binding mechanism. Moreover, the REP correlation coefficient with respect to experiment ( R^REP = 0.85 ± 0.15 ) is significantly boosted in comparison with the FEP one ( R^FEP = 0.64 ± 0.30 ). Furthermore, the root-mean-square error (RMSE) of REP is also smaller than FEP, RMSE^REP = 4.28 ± 0.69 versus RMSE^FEP = 5.80 ± 1.11 kcal/mol, respectively. © 2019 Wiley Periodicals, Inc.     

Charge-Tagged DNA Radicals in the Gas Phase Characterized by UV/Vis Photodissociation Action Spectroscopy

Adenosine radicals tagged with a fixed-charge group were generated in the gas phase and structurally characterized by tandem mass spectrometry, deuterium labeling, and UV/Vis action spectroscopy. Experimental results in combination with Born–Oppenheimer molecular dynamics, ab initio, and excited-state calculations led to unambiguous assignment of adenosine radicals as N-7 hydrogen atom adducts. The charge-tagged radicals were found to be electronically equivalent to natural DNA nucleoside radicals.     

Application of Lectin Microarrays for Biomarker Discovery

Many proteins in living organisms are glycosylated. As their glycan patterns exhibit protein-, cell-, and tissue-specific heterogeneity, changes in the glycosylation levels could serve as useful indicators of various pathological and physiological states. Thus, the identification of glycoprotein biomarkers from specific changes in the glycan profiles of glycoproteins is a trending field. Lectin microarrays provide a new glycan analysis platform, which enables rapid and sensitive analysis of complex glycans without requiring the release of glycans from the protein. Recent developments in lectin microarray technology enable high-throughput analysis of glycans in complex biological samples. In this review, we will discuss the basic concepts and recent progress in lectin microarray technology, the application of lectin microarrays in biomarker discovery, and the challenges and future development of this technology. Given the tremendous technical advancements that have been made, lectin microarrays will become an indispensable tool for the discovery of glycoprotein biomarkers.     

Charge‐Tagged DNA Radicals in the Gas Phase Characterized by UV/Vis Photodissociation Action Spectroscopy

Adenosine radicals tagged with a fixed‐charge group were generated in the gas phase and structurally characterized by tandem mass spectrometry, deuterium labeling, and UV/Vis action spectroscopy. Experimental results in combination with Born–Oppenheimer molecular dynamics, ab initio, and excited‐state calculations led to unambiguous assignment of adenosine radicals as N‐7 hydrogen atom adducts. The charge‐tagged radicals were found to be electronically equivalent to natural DNA nucleoside radicals.     

Effect of aspect ratio of vertically aligned copper nanowires in the presence of cellulose nanofibers on the thermal conductivity of epoxy composites

The composites comprising vertically aligned network of copper nanowires (CuNWs) in the presence of cellulose nanofibers were fabricated by using the freeze‐templating method and the effect of aspect ratio (A/R) of CuNWs on the thermal conductivity of epoxy composites was investigated. The thermal conductivity of epoxy composites increased to 0.79 W m^?1 K^?1 at 1.12 vol% of high A/R CuNWs loading, corresponding to the thermal conductivity enhancement of 365% as compared to the pure epoxy. The thermal conductivity of vertically aligned higher A/R CuNWs/epoxy, which is 38.5% and 51.9% higher than those of the lower A/R CuNWs and the randomly aligned CuNWs, respectively. The application of the epoxy composites in heat dissipation was demonstrated by the temperature changes of composites on a hot plate with the increase of heating time. These results indicate that the thermally conductive composites in this study could be applied for thermal dissipating materials in electronic devices.     

A Keggin-Type Tungstovanadate-Based Hybrid Compound: Synthesis,Crystal Structure,and Electrocatalytic Oxidation of Ascorbic Acid

Russian Journal of Coordination Chemistry - A new V-centered Keggin polyoxometalate-based inorganic-organic hybrid (HPpz)3[VW12O40] (I) (Ppz = piperazine) has been hydrothermal synthesized and...     

Preparative isolation of arylbutanoid‐type phenol [(‐)‐rhododendrin] with peak tailing on conventional C18 column using middle chromatogram isolated gel column coupled with reversed‐phase liquid chromatography

Reversed‐phase liquid chromatography coupled with middle chromatogram isolated gel column was employed for the efficient preparative separation of the arylbutanoid‐type phenol [(‐)‐rhododendrin] from Saxifraga tangutica. Universal C18 (XTerra C18) and XCharge C18 columns were compared for (‐)‐rhododendrin fraction analysis and preparation. Although tailing and overloading occurred on the XTerra C18 column, the positively charged reversed‐phase C18 column (XCharge C18) overcame these drawbacks, allowing for favorable separation resolution, even when loading at a on a preparative scale (3.69 mg per injection). The general separation process was as follows. First, 365.0 mg of crude (‐)‐rhododendrin was enriched from 165 g Saxifraga tangutica extract via a middle chromatogram isolated gel column. Second, separation was performed on an XTerra C18 preparative column, from which 73.8 mg of the target fraction was easily obtained. Finally, the 24.0 mg tailing peak of (‐)‐rhododendrin on XTerra C18 column was selectively purified on the XCharge C18 analytical column. These results demonstrate that the tailing nonalkaloid peaks can be effectively used for preparative isolation on XCharge C18 columns.     

On the embedding of graphs into graphs with few eigenvalues

A graph is called of type k if it is connected, regular, and has k distinct eigenvalues. For example graphs of type 2 are the complete graphs, while those of type 3 are the strongly regular graphs. We prove that for any positive integer n, every graph can be embedded in n cospectral, non-isomorphic graphs of type k for every k ≥ 3. Furthermore, in the case k ≥ 5 such a family of extensions can be found at every sufficiently large order. Some bounds for the extension will also be given. © 1996 John Wiley & Sons, Inc.     

Facilely prepared aggregation-induced emission (AIE) nanocrystals with deep-red emission for super-resolution imaging

Organic nanocrystals (NCs) with high brightness are highly desirable for biological imaging. However, the preparation of NCs by a facile and fast method is still challenging. Herein, an aggregation-induced emission (AIE) luminogen of 4,4′-(5,6-difluorobenzo[c][1,2,5]thiadiazole-4,7-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (DTPA-BT-F) in the deep-red region is designed with intensive crystalline features to obtain NCs by kinetically controlled nanoprecipitation. The prepared AIE NCs with high brightness and good photo-stability are then applied in super-resolution imaging via stimulated emission depletion (STED) nanoscopy. As observed, the nanostructures in lysosomes of both fixed and live cells are well visualized with superior lateral resolutions under STED nanoscopy (full width at half maximum values, 107 and 108 nm) in contrast to that in confocal imaging (548 and 740 nm). More importantly, dynamic monitoring and long-term tracking of lysosomal movements in live HeLa cells, such as lysosomal contact, can also be carried out by using DTPA-BT-F NCs at a superior resolution. To the best of our knowledge, this is the first case of AIE NCs prepared by nanoprecipitation for STED nanoscopy, thus providing a new strategy to develop high performance imaging agents for super-resolution imaging.

AIE nanocrystals with high brightness in the deep-red region were facilely prepared by kinetically controlled nanoprecipitation. These nanocrystals were then applied in super-resolution cellular imaging via STED nanoscopy.