Chemical immobilization of azido cellulose phenylcarbamate onto silica gel via Staudinger reaction and its application as a chiral stationary phase for HPLC

Azido cellulose phenylcarbamate (AzCPC) was synthesized regioselectively and chemically immobilized onto aminized silica gel to afford urea-bonded chiral stationary phases (CSPs). The obtained CSPs showed good enantioselectivity in HPLC towards various racemates using normal phase eluants (hexane/2-propanol, hexane/chloroform or hexane/2-propanol/chloroform).     

More Than Meets the Eye in Bacterial Cellulose: Biosynthesis,Bioprocessing, and Applications in Advanced Fiber Composites

Bacterial cellulose (BC) nanofibers are one of the stiffest organic materials produced by nature. It consists of pure cellulose without the impurities that are commonly found in plant‐based cellulose. This review discusses the metabolic pathways of cellulose‐producing bacteria and the genetic pathways of Acetobacter xylinum. The fermentative production of BC and the bioprocess parameters for the cultivation of bacteria are also discussed. The influence of the composition of the culture medium, pH, temperature, and oxygen content on the morphology and yield of BC are reviewed. In addition, the progress made to date on the genetic modification of bacteria to increase the yield of BC and the large‐scale production of BC using various bioreactors, namely static and agitated cultures, stirred tank, airlift, aerosol, rotary, and membrane reactors, is reviewed. The challenges in commercial scale production of BC are thoroughly discussed and the efficiency of various bioreactors is compared. In terms of the application of BC, particular emphasis is placed on the utilization of BC in advanced fiber composites to manufacture the next generation truly green, sustainable and renewable hierarchical composites.     

A Pressure Sensor Using Fiber Bragg Grating

In the present investigation, a Q-switched Nd:YAG laser is used to study the various aspects of diamond processing for fabricating integrated optic and UV optoelectronic devices. Diamond is a better choice of substrate compared to silicon and gallium arsenide for the fabrication of waveguides to perform operations such as modulation, switching, multiplexing, and filtering, particularly in the ultraviolet spectrum. The experimental setup of the present investigation consists of two Q-Switched Nd:YAG lasers capable of operating at wavelengths of 1064 nm and 532 nm. The diamond cutting is performed using these two wavelengths by making the “V”-shaped groove with various opening angle. The variation of material loss of diamond during cutting is noted for the two wavelengths. The cut surface morphology and elemental and structural analysis of graphite formed during processing in both cases are compared using scanning electron microscopy (SEM) and laser Raman spectroscopy. Both the Q-Switched Nd:YAG laser systems (at 1064 nm and 532 nm) show very good performance in terms of peak-to-peak output stability, minimal spot diameter, smaller divergence angle, higher peak power in Q-switched mode, and good fundamental TEM ₀₀ mode quality for processing natural diamond stones. Less material loss and minimal micro cracks are achieved with wavelength 532 nm whereas a better diamond cut surface is achieved with processing at 1064 nm with minimum roughness.     

Free porphyrin catalyzed direct C-H arylation of benzene with aryl halides

A general procedure for free porphyrin catalyzed direct C-H arylation of benzene was demonstrated. This air tolerant, transition-metal-free process provides a promising system for cheap and efficient synthesis of biaryls in a user-friendly approach.     

Parasite-based screening and proteome profiling reveal orlistat, an FDA-approved drug, as a potential anti Trypanosoma brucei agent

Trypanosoma brucei is a parasite that causes African sleeping sickness in humans and nagana in livestock and is transmitted by the tsetse fly. There is an urgent need for the development of new drugs against African trypanosomiasis due to the lack of vaccines and effective drugs. Orlistat (also called tetrahydrolipstatin or THL) is an FDA-approved antiobesity drug targeting primarily the pancreatic and gastric lipases within the gastrointestinal tract. It shows potential activities against tumors, mycobacteria, and parasites. Herein, we report the synthesis and evaluation of an expanded set of orlistat-like compounds, some of which showed highly potent trypanocidal activities in both the bloodstream form (BSF) and the procyclic form (PCF) of T. brucei. Subsequent in situ parasite-based proteome profiling was carried out to elucidate potential cellular targets of the drug in both forms. Some newly identified targets were further validated by the labeling of recombinantly expressed enzymes in Escherichia coli lysates. Bioimaging experiments with a selected compound were carried out to study the cellular uptake of the drug in T. brucei. Results indicated that orlistat is much more efficiently taken up by the BSF than the PCF of T. brucei and has clear effects on the morphology of mitochondria, glycosomes, and the endoplasmic reticulum in both BSF and PCF cells. These results support specific effects of orlistat on these organelles and correlate well with our in situ proteome profiling. Given the economic challenges of de novo drug development for neglected diseases, we hope that our findings will stimulate further research towards the conversion of orlistat-like compounds into new trypanocidal drugs.     

Push–Pull archetype of reduced graphene oxide functionalized with polyfluorene for nonvolatile rewritable memory

A solution‐processable PFTPA‐convalently grafted reduced graphene oxide (RGO‐PFTPA) was synthesized by the 1,3‐dipolar cycloaddition of azomethine ylide. Bistable electrical switching and nonvolatile rewritable memory effects were demonstrated in a sandwich structure of indium tin oxide/RGO‐PFTPA/Al. The switch‐on voltage of the as‐fabricated device was around ?1.4 V, and the ON/OFF‐state current ratio was more than 10³. The ON–OFF transition process is reversible because the application of a high enough positive voltage can induce the reverse transfer of electrons, reducing the conductivity back to its initial OFF state. Both the OFF and ON states are accessible and very stable under a constant voltage stress of ?1 V for up to 3 h, or under a pulse voltage stress of ?1 V for up to 10⁸ continuous read cycles (pulse period = 2 μs, pulse width = 1 μs). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A New Model and Measurement Technique for Dynamic Shrinkage during Photopolymerization of Multi‐Acrylates

Summary: A novel experimental set‐up has been devised to measure simultaneously, in real time, the conversion and shrinkage of multi‐acrylates during photopolymerization. The data show that the current practice of assigning the excess volume entirely as excess free volume is inappropriate as this leads to an increasing fractional free volume with conversion. We propose to partition the excess volume into free and occupied volume components. The new model produces satisfactory results.

Experimental set‐up for the simultaneous collection of shrinkage and conversion data.     

Determination of peptide content and purity of DOTA-peptides by metal ion titration and UPLC: an alternative method to monitor quality of DOTA-peptides

PRRT requires high specific activities, thus at low molar ratio between DOTA-peptide and radioactivity. Therefore, the ingredients of the reaction, including (radio)metals and DOTA-peptide must be pure and the content known. Our aim was to quantify content and purity of DOTA-peptide by a base-to-base separation of DOTA-peptide and metal-DOTA-peptide by UPLC and UV-detection. Quantification of these peaks reveals an accurate and sensitive method to quantify purity and content of DOTA-peptides. Moreover, this technique enables monitoring of the (radio)labeling process and co-introduction of impurities, including metal ions.     

Simultaneous Determination of Cortisol,Cortisone, and 6β-Hydroxycortisol in Human Urine by UPLC with UV Detector and Application to Determine Diurnal Variations

In the present studies, a simple rapid ultra performance liquid chromatography (UPLC) method with UV detection for the simultaneous determination of cortisol, cortisone and 6β-hydroxycortisol in human urine was developed. The three analytes and the internal standard dexamethasone were separated on a Waters Acquity UPLC-Tunable UV system with an Acquity UPLC BEH C18 column (50 × 2.1 mm ID, 1.7 μm) using a gradient elution of methanol and water (containing 0.01% formic acid) with a run time of 7 min. The method was accurate and precise, over the ranges of 5–200 ng mL⁻¹ for cortisol, and 10–1,000 ng mL⁻¹ for both cortisone and 6β-hydroxycortisol, and showed good linearity (r ² > 0.999). This method was applied for the measurement of cortisol, cortisone and 6β-hydroxycortisol in samples collected over different periods as a tool to assess the activity of CYP3A and 11β-hydroxysteroid dehydrogenase type 2 enzymes.