Pyrolytic characteristics and kinetics of pistachio shell by thermogravimetric analysis

Pyrolytic characteristics and kinetics of pistachio shell were studied using a thermogravimetric analyzer in 50?C800?°C temperature range under nitrogen atmosphere at 2, 10, and 15?°C?min^?1 heating rates. Pyrolysis process was accomplished at four distinct stages which can mainly be attributed to removal of water, decomposition of hemicellulose, decomposition of cellulose, and decomposition of lignin, respectively. The activation energies, pre-exponential factors, and reaction orders of active pyrolysis stages were calculated by Arrhenius, Coats?CRedfern, and Horowitz?CMetzger model-fitting methods, while activation energies were additionaly determined by Flynn?CWall?COzawa model-free method. Average activation energies of the second and third stages calculated from model-fitting methods were in the range of 121?C187 and 320?C353?kJ?mol^?1, respectively. The FWO method yielded a compatible result (153?kJ?mol^?1) for the second stage but a lower result (187?kJ?mol^?1) for the third stage. The existence of kinetic compensation effect was evident.     

Stereoselective synthesis of both enantiomers of trans-2-(diphenylmethylideneamino)cyclopropanecarboxylic acid using a chiral pool approach and their incorporation in dipeptides

The stereoselective synthesis of (1R,2R)- and (1S,2S)-trans-2-(diphenylmethylideneamino)cyclopropanecarboxylic acid has been accomplished in six steps starting from (2S)- and (2R)-β-benzyl N-(tert-butoxycarbonyl)aspartate, respectively. The key-step in the reaction sequence is a stereoselective base-induced ring closure with a good trans diastereoselectivity. These novel trans-β-ACC derivatives could be incorporated in dipeptides employing a standard peptide coupling technique.     

Photophysics of aminoxanthone derivatives and their application as binding probes for DNA

Xanthones with amino substituents were synthesized to diminish the photoreactivity of the xanthone chromophore with DNA, with the objective of using these molecules to study their binding dynamics with DNA. The aminoxanthones showed a strong solvatochromic effect on their singlet and triplet excited-state photophysics, where polar solvents led to a decrease of the energies for the excited states. Quenching of the triplet excited states by nitrite anions was used to determine the binding dynamics, and a residence time in the microsecond time domain was estimated for the bound 2-aminoxanthone with DNA. The quenching experiments performed showed that this methodology will not be applicable to study the binding dynamics of a wide variety of guests with DNA.     

Two coupled enzymes perform in parallel the 'AND' and 'InhibAND' logic gate operations

The coupled activation of two enzymes: glucose dehydrogenase (GDH) and horseradish peroxidase (HRP), is used to construct the parallel-operating AND and InhibAND logic gates. The added substrates for the respective enzymes, glucose and H(2)O(2), act as the gate inputs, while the biocatalytically generated NADH and gluconic acid provide the output signals that follow the operations of the gates. The two gates are generated in the same vial, thus allowing the logic operations to take place in parallel, and the simultaneous readout of the functions of the gates.     

Linkage effects on binding affinity and activation of GPR30 and estrogen receptors ERalpha/beta with tridentate pyridin-2-yl hydrazine tricarbonyl-Re/(99m)Tc(I) chelates

We describe a new structural class of neutral tridentate pyridin-2-yl hydrazine chelates for labeling with tricarbonyl Re/99mTc(I) under aqueous conditions and investigate the receptor binding of synthetic estradiol derivatives with the novel G-protein-coupled receptor GPR30 and estrogen receptors ERalpha/beta. The steroid linkage affected the affinity and selectivity of estrogen binding with these receptors. Fluorescence assays based on calcium signaling demonstrate that membrane-permeable chelates 2 and 3 interact with the receptors in whole cells. These results suggest that in vitro assays will facilitate the development of targeted imaging agents for intracellular receptors and the feasibility of targeting GPR30 and ERalpha/beta for diagnostic tumor imaging.     

Myeloperoxidase-mediated oxidation of organophosphorus pesticides as a pre-step in their determination by AChE based bioanalytical methods

In order to improve the sensitivity of assays for inhibitors of the enzyme acetylcholine esterase (AChE), an effective method was developed for the conversion of the organophosphate pesticides (OPs) diazinon, malathion, chlorpyrifos, azinphos-methyl and phorate into more toxic inhibitors. This was accomplished by converting them from the thio form into their oxo form using the enzyme myeloperoxidase. The oxo forms, which are the only products of conversion, were determined by AChE bioassays, using either the free enzyme, or a flow injection analysis manifold with immobilized AChE and spectrophotometric detection. All modified OPs exhibited inhibitory power at ppb levels and within 10 min. The method is considered to represent an excellent means for improving the sensitivity of assays for determination of OPs.     

Axisymmetric Fractional Diffusion with Mass Absorption in a Circle under Time-Harmonic Impact

The axisymmetric time-fractional diffusion equation with mass absorption is studied in a circle under the time-harmonic Dirichlet boundary condition. The Caputo derivative of the order 0<α≤2 is used. The investigated equation can be considered as the time-fractional generalization of the bioheat equation and the Klein–Gordon equation. Different formulations of the problem for integer values of the time-derivatives α=1 and α=2 are also discussed. The integral transform technique is employed. The outcomes of numerical calculations are illustrated graphically for different values of the parameters.     

Hesperetin—Between the Ability to Diminish Mono- and Polymicrobial Biofilms and Toxicity

Hesperetin is the aglycone of citrus flavonoid hesperidin. Due to the limited information regarding hesperetin antimicrobial potential and emerging need for novel antimicrobials, we have studied its antimicrobial activity (microdilution assay), antibiofilm activity with different assays in two models (mono- and polymicrobial biofilm), and toxicity (MTT and brine shrimp lethality assays). Hesperetin inhibited growth of all Candida isolates (minimal inhibitory concentration, MIC, 0.165 mg/mL), while it’s inhibitory potential towards Staphylococcus aureus was lower (MIC 4 mg/mL). Hesperetin (0.165 mg/mL) reduced ability of Candida to form biofilms and moderately reduced exopolysaccharide levels in biofilm matrix. Effect on the eradication of 24 h old C. albicans biofilms was promising at 1.320 mg/mL. Inhibition of staphylococcal biofilm formation required higher concentrations of hesperetin (<50% inhibition with MIC 4 mg/mL). Establishment of polymicrobial C. albicans-S. aureus biofilm was significantly inhibited with the lowest examined hesperetin concentration (1 mg/mL) in crystal violet and CFU assays. Hesperetin toxicity was examined towards MRC-5 fibroblasts (IC₅₀ 0.340 mg/mL) and in brine shrimp lethality assay (LC₅₀ > 1 mg/mL). Hesperetin is efficient in combating growth and biofilm formation of Candida species. However, its antibacterial application should be further examined due to the cytotoxic effects provoked in the antibacterial concentrations.     

Preparative-Scale Biocatalytic Oxygenation of N-Heterocycles with a Lyophilized Peroxygenase Catalyst

A lyophilized preparation of an unspecific peroxygenase variant from Agrocybe aegerita (rAaeUPO-PaDa-I-H) is a highly effective catalyst for the oxygenation of a diverse range of N-heterocyclic compounds. Scalable biocatalytic oxygenations (27 preparative examples, ca. 100 mg scale) have been developed across a wide range of substrates, including alkyl pyridines, bicyclic N-heterocycles and indoles. H₂O₂ is the only stoichiometric oxidant needed, without auxiliary electron transport proteins, which is key to the practicality of the method. Reaction outcomes can be altered depending on whether hydrogen peroxide was delivered by syringe pump or through in situ generation using an alcohol oxidase from Pichia pastoris (PpAOX) and methanol as a co-substrate. Good synthetic yields (up to 84 %), regioselectivity and enantioselectivity (up to 99 % ee) were observed in some cases, highlighting the promise of UPOs as practical, versatile and scalable oxygenation biocatalysts.     

Creep relaxation and stress relaxation of PS-HI/SEBS blends

For the selection of the polymer materials and polymer blends for various fields of applications the stability of material under constant deformation and constant load are very important. In this paper, the copolymers high-impact polystyrene, PS-HI, styrene-ethylene/buthylene-styrene block copolymer, SEBS, and their blends PS-HI/SEBS were investigated. The investigations were done by DMA analysis. The secondary viscoelastic functions, creep, creep modulus, stress and flexural relaxation modulus were investigated in creep and stress relaxation experiment at temperatures 25, 35, 45, 55 and 65°C during 1 h. The master curves were created by time-temperature correspondence principle, TTC. The correlation of the secondary viscoelastic functions with time, temperature and content of the hard, PS, phase was discussed.