Destruction of hydrogen bonds of poly(N-isopropylacrylamide) aqueous solution by trimethylamine N-oxide

Trimethylamine N-oxide (TMAO) is a compatible or protective osmolyte that stabilizes the protein native structure through non-bonding mechanism between TMAO and hydration surface of protein. However, we have shown here first time the direct binding mechanism for naturally occurring osmolyte TMAO with hydration structure of poly(N-isopropylacrylamide) (PNIPAM), an isomer of polyleucine, and subsequent aggregation of PNIPAM. The influence of TMAO on lower critical solution temperature (LCST) of PNIPAM was investigated as a function of TMAO concentration at different temperatures by fluorescence spectroscopy, viscosity (η), multi angle dynamic light scattering, zeta potential, and Fourier transform infrared (FTIR) spectroscopy measurements. To address some of the basis for further analysis of FTIR spectra of PNIPAM, we have also measured FTIR spectra for the monomer of N-isopropylacrylamide (NIPAM) in deuterium oxide (D(2)O) as a function of TMAO concentration. Our experimental results purportedly elucidate that the LCST values decrease with increasing TMAO concentration, which is mainly contributing to the direct hydrogen bonding of TMAO with the water molecules that are bound to the amide (-CONH) functional groups of the PNIPAM. We believed that the present work may act as a ladder to reach the heights of understanding of molecular mechanism between TMAO and macromolecule.     

Electrochemical disk generation and ring identification of carbanions from organomercurials in acetonitrile

A rotating disk-ring electrode was used for study of a series of organomercury compounds R₂Hg, where R = CN, CF(NO₂)₂, C₆F₅, PhCC, p-NO₂C₆H₄OCC, PhSCH₂CC, PhCOCH₂, CH₂CN, CCl₂CCl, 2-phenyl-o-carboranyl. Reduction of these compounds at a Pt-disk in acetonitrile is a two-electron process and results in generation of the carbanion R^?. The carbanions generated at the disk interact with the solvent during their convective diffusion to the ring electrode where there may be oxidized. The main reaction in solution, shown using chromatography-mass spectrometry techniques, is acid-base interaction of carbanions with the solvent acetonitrile, which acts as a Brönsted acid. Reaching the ring, the carbanions may be oxidized at anodic potentials of the ring; oxidation potentials depend significantly on carbanion structure (e.g.+0.28 V (vs. SCE), for PhCC^? and +2.20 V for CN^?. It is shown that PK_a value of the carbanions do not correlate with the oxidation potentials, however, a linear correlation is observed between pK_a values and a special parameter called the efficiency coefficient.     

Myrotoxins: a new class of macrocyclic trichothecenes

An isolate of $\text{Myrothecium roridum}$ which is a pathogen on tomatoes in Texas produces a new class of C27 macrocyclic trichothecenes which contains a nonconjugated diene system that includes a vinyl ether group.     

Chelating Behaviour of Substituted 3-4 Aryl-Hydrazo-Pentane-2, 4-Dione: Part VI. Potentiometric and Infrared Studies of the Ligands and Their Divalent Metal Complexes

The dissociation constants of 3-phenylhydrazo-pentane-2, 4-dione and its o-, m-, p-carboxy derivatives, and the stability constants of complexes of divalent metal ions with the o-carboxy derivative are determined by pH-metric method. The ir-spectra of the ligands and some divalent metal complexes with the o-derivative are discussed.     

Isolation,identification, and keratinolytic activity of several feather-degrading bacterial isolates

Several feather-degrading bacterial isolates were isolated from Egyptian soil. These isolates were able to degrade chicken feather, when grown on basal medium containing 1% native feather as a source of energy, carbon, and nitrogen. Feather waste, generated in large quantities as a byproduct of commercial poultry processing, is nearly pure keratin, which is not easily degradable by common proteolytic enzymes. The isolates were identified according to the morphological characteristics, biochemical tests, and API 50 CHBBacillus system. Proteolytic and keratinolytic activities of these isolates were monitored throughout the cultivation of the bacterial isolates on feather. Resulting soluble proteins, which were released as a result of the biodegradation of feather, were demonstrated by SDS-PAGE.     

Matériaux composites à base de graves et de liants polymères II: Ozonisation du polyéthylène et dosage des hydropéroxydes et des péroxydes derivés

The study of the oxidation of low density polyethylene is carried out under fluidized conditions in air and ozone. Special attention is paid to the formation of peroxides and hydroperoxides. Their production is optimized according to various parameters (temperature, time, quantity of ozone, flow of the gaseous current) using an experimental design method. Peroxides and hydroperoxides are titrated by a colorimetric method using diphenylpicrylhydrazyl as reagent. A correlation between i.r. carbonyl ratio and the yield of peroxides has been established.     

Guaianolide Sesquiterpene Lactones from Centaurothamnus maximus

Centaurothamnus maximus (family Asteraceae), is a leafy shrub indigenous to the southwestern Arabian Peninsula. With a paucity of phytochemical data on this species, we set out to chemically characterize the plant. From the aerial parts, two newly identified guaianolides were isolated: 3β-hydroxy-4α(acetoxy)-4β(hydroxymethyl)-8α-(4-hydroxy methacrylate)-1αH,5αH, 6αH-gual-10(14),11(13)-dien-6,12-olide (1) and 15-descarboxy picrolide A (2). Seven previously reported compounds were also isolated: 3β, 4α, 8α-trihydroxy-4-(hydroxymethyl)-lαH, 5αH, 6βH, 7αH-guai-10(14),11(13)-dien-6,12-olide (3), chlorohyssopifolin B (4), cynaropikrin (5), hydroxyjanerin (6), chlorojanerin (7), isorhamnetin (8), and quercetagetin-3,6-dimethyl ether-4’-O-β-d-pyranoglucoside (9). Chemical structures were elucidated using spectroscopic techniques, including High Resolution Fast Atom Bombardment Mass Spectrometry (HR-FAB-MS), 1D NMR; ¹H, ¹³C NMR, Distortionless Enhancement by Polarization Transfer (DEPT), and 2D NMR (¹H-¹H COSY, HMQC, HMBC) analyses. In addition, a biosynthetic pathway for compounds 1–9 is proposed. The chemotaxonomic significance of the reported sesquiterpenoids and flavonoids considering reports from other Centaurea species is examined.     

Electrochemical determination of sulfaguanidine using COOH-MWCNT coated GC electrode

The electrochemical behavior of sulfaguanidine was investigated in PBS buffer aqueous solutions. Cyclic voltammograms have shown that (1) the Sg provided a well-defined irreversible oxidation peak (2) the signal-to-background current ratio is 3 times higher at COOH-MWCNT coated GCE than that of bare GCE and (3) the modifying GCE surface by COOH-MWCNT led to a significant improvement (2.7 folds) of the electrochemical response. It has been shown that Sg oxidizes according to a diffusion-controlled mechanism. A linear calibration curve was obtained for the oxidation of Sg at 10–70 μM. The COOH-MWCNT coated GCE has also been successfully used for the determination of Sg in real samples.     

Pharmacological Justification for the Medicinal Use of Plumeria rubra Linn. in Cardiovascular Disorders

Plumeria rubra (L.) is a traditional folkloric medicinal herb used to treat cardiovascular disorders. The present investigation was methodically planned to investigate the pharmacological foundations for the therapeutic effectiveness of P. rubra in cardiovascular illnesses and its underlying mechanisms. Ex vivo vaso-relaxant effects of crude leaf extract of P. rubra were observed in rabbit aorta ring preparations. Hypotensive effects were measured using pressure and force transducers connected to the Power Lab data acquisition system. Furthermore, P. rubra displayed cardioprotective properties in rabbits when they were exposed to adrenaline-induced myocardial infarction. In comparison to the intoxicated group, the myocardial infarction model showed decreased troponin levels, CK-MB, LDH, ALT, ALP, AST, and CRP, as well as necrosis, apoptosis, oedema, and inflammatory cell enrollment. P. rubra has revealed good antioxidant properties and prolonged the noradrenaline intoxicated platelet adhesion. Its anticoagulant, vasorelaxant, and cardioprotective effects in both in vivo and ex vivo investigations are enabled by blocking L-type calcium channels, lowering adrenaline, induced oxidative stress, and tissue tear, justifying its therapeutic utility in cardiovascular disorders.     

Crystallographic and first-principles density functional theory study on the structure,noncovalent interactions,and chemical reactivity of 1,5-benzodiazepin-2-ones derivatives

The present work arose out of a desire to fundamentally understand the molecular geometry, weak interactions, electron density delocalization, and chemical reactivity features of 1,5-benzodiazepines-containing family. Herein, a complete X-ray crystallographic study, supported by trustworthy sets of computational approaches, has been reported for two organic crystals. Quantifying intramolecular and intermolecular interactions by Hirshfeld-Becke surfaces analysis conjointly with noncovalent interaction-reduced density gradient topological study revealed that supramolecular assemblies are stabilized by N-H ^… O (inter) and O-H ^… N (intra) hydrogen bonds, Cg ^… Cg (π ^… π) and C-H(O) ^… π intercontacts, as well as Van der Waals interactions and steric effects. The long-range-corrected functional wB97XD, which uses Grimme's D2 dispersion model, seems to be just right for our systems. The quantum theory of atoms in molecules analysis confirms that both significant O1-H1…N1 and N2-H2A…O2 H-bonds are weak and electrostatic in nature. Furthermore, global reactivity indices computed via the conceptual density functional theory framework allows these molecules to be classified as moderate electrophiles and marginal nucleophiles. The active sites favorable for nucleophilic/electrophilic attacks were also predicted based on local Parr functions. Finally, a comparative evaluation on the aromaticity character and π-π stacking ability has been done for different (pseudo) rings.