Inclusion complexation of warfarin withβ-cyclodextrins and its influence on absorption kinetics of warfarin in rat

The inclusion complexes of warfarin withβ-cyclodextrin, 2-hydroxypropyl-β-CD and methyl-β-CD have been investigated in aqueous solution. The apparent binding constants of warfarin are found to be 542±19, 442±18 and 112±6M^?1 respectively, calculated from the increments in fluorescence emission of the drug. The influence of theβ-CDs on the absorption rate of the drug is investigated within situ experiments in a chronically isolated internal loop, in the small intestine of the rat. The first-order disappearance (absorption) rate constant decreases to 3.6×10^?4 min^?1 inβ-CD, to 5.0×10^?4 min^?1 in 2-hydroxypropyl-β-CD and to 1.4×10^?3 min^?1 in methyl-β-CD compared to 3.2×10^?3 min^?1 in isotonic phosphate buffer (pH=7.4) solution, all of them showing a good agreement with the percentage of free warfarin in their complexed solutions: 16%, 18% and 47% calculated, respectively.     

Synthesis of two calix[4]arene diamide derivatives for extraction of chromium(VI)

The synthesis of four diamide derivatives of the p-tert-butylcalix[4]arenes from the reaction of 5,11,17,23-tetra-tert-butyl-25,27-diethoxycarbonylmethoxy-26,28-dihydroxycalix[4]arene 2 with various primary amines were reported. The ¹H and ¹³C NMR, data showed that the synthesized compounds exist in the cone conformation. The complexing properties of these compounds toward Cr₂O₇²⁻/HCr₂O₇⁻ anions are also studied. It has been observed that receptors 5 and 6 are better extractant than the compounds 3 and 4. The protonated alkyl ammonium form of 5 and 6 is an effective extractant for transferring HCr₂O₇⁻/Cr₂O₇²⁻ anions from an aqueous phase into a dichloromethane layer.     

Coupling between lysozyme and glycerol dynamics: microscopic insights from molecular-dynamics simulations

We explore possible molecular mechanisms behind the coupling of protein and solvent dynamics using atomistic molecular-dynamics simulations. For this purpose, we analyze the model protein lysozyme in glycerol, a well-known protein-preserving agent. We find that the dynamics of the hydrogen bond network between the solvent molecules in the first shell and the surface residues of the protein controls the structural relaxation (dynamics) of the whole protein. Specifically, we find a power-law relationship between the relaxation time of the aforementioned hydrogen bond network and the structural relaxation time of the protein obtained from the incoherent intermediate scattering function. We demonstrate that the relationship between the dynamics of the hydrogen bonds and the dynamics of the protein appears also in the dynamic transition temperature of the protein. A study of the dynamics of glycerol as a function of the distance from the surface of the protein indicates that the viscosity seen by the protein is not the one of the bulk solvent. The presence of the protein suppresses the dynamics of the surrounding solvent. This implies that the protein sees an effective viscosity higher than the one of the bulk solvent. We also found significant differences in the dynamics of surface and core residues of the protein. The former is found to follow the dynamics of the solvent more closely than the latter. These results allowed us to propose a molecular mechanism for the coupling of the solvent-protein dynamics.     

A Multivariate Approach to Evaluate Biomass Production,Biochemical Composition and Stress Compounds of <Emphasis Type="Italic">Spirulina platensis</Emphasis> Cultivated in Wastewater

The study was performed to investigate the effects of using cow effluent for the cultivation of Spirulina platensis on its biomass production and cell physiology. S. platensis was cultivated in three different cow effluents (CE) used as cultivation medium during 15 days. CE was prepared using dry cow manures, and it was further modified with supplement of NaNO₃ (CEN) and NaNO₃ + NaCl (CENS). High nitrate value stimulated chlorophyll-a and total protein content of the cyanobacterium and also biomass production in standards medium (SM) and CEN media. Total carbohydrate content of S. platensis grown in CE media was found to be higher (p < 0.05) than that of SM. Productions of biomass and biochemical compounds by the cyanobacterium grown on the CE and SM media were evaluated by using multivariate approach. Conductivity, oxidation reduction potential (ORP), salinity, pH, and TDS played important role (p < 0.01) in the biochemical composition. As an effective explanatory factor, ORP had a significant positive correlation with H₂O₂, whereas negatively correlated with chlorophyll-α, biomass production, filament length, and proline. Canonical correspondence analysis proposed that biochemical compounds of S. platensis were not only affected by salinity and nutrition of media but also by pH and ORP. The present study indicated that CEN as a low cost model medium had high potential for the production of biomass by S. platensis with high protein content.     

Catalyst Engineering for the Selective Reduction of CO2 to CH4: A First-Principles Study on X-MOF-74 (X=Mg,Mn, Fe,Co, Ni,Cu, Zn)

The conversion of carbon dioxide (CO₂) into more valuable chemical compounds represents a critical objective for addressing environmental challenges and advancing sustainable energy sources. The CO₂ reduction reaction (CO₂RR) holds promise for transforming CO₂ into versatile feedstock materials and fuels. Leveraging first-principles methodologies provides a robust approach to evaluate catalysts and steer experimental efforts. In this study, we examine the CO₂RR process using a diverse array of representative cluster models derived from X-MOF-74 (where X encompasses Mg, Mn, Fe, Co, Ni, Cu, or Zn) through first-principles methods. Notably, our investigation highlights the Fe-MOF-74 cluster's unique attributes, including favorable CO₂ binding and the lowest limiting potential of the studied clusters for converting CO₂ to methane (CH₄) at 0.32 eV. Our analysis identified critical factors driving the selective CO₂RR pathway, enabling the formation CH₄ on the Fe-MOF-74 cluster. These factors involve less favorable reduction of hydrogen to H₂ and strong binding affinities between the Fe open-metal site and reduction intermediates, effectively curtailing desorption processes of closed-shell intermediates such as formic acid (HCOOH), formaldehyde (CH₂O), and methanol (CH₃OH), to lead to selective CH₄ formation.     

Finite Element Analysis of Elasto-plastic Plate Bending Problems using Transition Rectangular Plate Elements

In this work, the finite element analysis of the elasto-plastic plate bending problems is carried out using transition rectangular plate elements. The shape functions of the transition plate elements are derived based on a practical rule. The transition plate elements are all quadrilateral and can be used to obtain efficient finite element models using minimum number of elements. The mesh convergence rates of the models including the transition elements are compared with the regular element models. To verify the developed elements, simple tests are demonstrated and various elasto-plastic problems are solved. Their results are compared with ANSYS results.The English text was polished by Keren Wang.     

Organic vapor sensing properties and characterization of α-naphthylmethacrylate LB thin films

Determination of organic vapor sensing properties of α-Naphthylmethacrylate (α-NMA) monomer based Langmuir-Blodgett (LB) thin films was aimed in this study. LB thin film fabrication was performed on quartz glass and quartz crystal substrates in order to investigate the characterization and organic vapor properties of α-NMA materials by using UV-Visible, Atomic Force Microscopy (AFM) and Quartz Crystal Microbalance (QCM) techniques. π-A isotherm graph was taken and a suitable surface pressure value were primarily determined as 13?mN m^?1 for successful α-NMA LB thin film fabrication. Transfer ratio value was found to be ≥ 0.93 for quartz glass and quartz crystal substrates. The typical frequency shift per layer was obtained as 16.93?Hz/layer and the deposited mass onto a quartz crystal was calculated as 271.30?ng/layer (1.02?ng mm^?2). The sensing responses of α-NMA LB films against dichloromethane, chloroform, toluene and m-xylene were measured by QCM system. Dichloromethane created the maximum shift in the resonance frequency than other organic vapors used in this study. Results exhibited that α-NMA LB thin films were potential candidates for organic vapor sensing applications, especially high sensitive detection of dichloromethane at room temperature.     

Redox active polymer metal chelates for use in flexible symmetrical supercapacitors: Cobalt-containing poly(acrylic acid) polymer electrolytes

The novel polymer metal chelate electrolytes(polychelates)were prepared by incorporation of cobalt sulfate(Co)into poly(acrylic acid)(PAA)host matrix.Quasi-solid state supercapacitor devices were fabricated using polychelates,PAA-Co X(X:3,5,7,and 10)where X represents the doping fraction(w/w)of Co in PAA.All polymer metal electrolytes were showed excellent bending-stretching properties,thermal stability and electrochemical durability with an optimum ionic conductivity of 3.15×10^-4 S cm^-1.Hierarchically porous activated carbon and nano-sized conductive carbon were used to form carbon composite symmetrical device electrodes.The electric double-layer capacitor(EDLC)and redox reactions of Co-incorporated polychelates at the interfaces of porous activated carbon provided an optimum specific capacitance of 341.33 F g^-1 with a device of PAA-Co7,which is at least 15 times enhancement compared to the device of pristine PAA.The PAA-Co7 device also provided energy density of 21.25 Wh kg^-1 at a power density of 117.69 W kg^-1.A prolonged cyclic stability of the device exhibited superior capacitive performance after 10,000 charge-discharge cycles and the maintained 90%of its initial performance.In addition,the supercapacitor with a dimension of 1.5 cm×3 cm containing PAA-Co7 successfully operated the red-blue-green(RGB)LED light.     

Photophysical behavior of a novel 4-aza-indole derivative in different solvents: reverse solvatochromism

Research on Chemical Intermediates - The photophysical properties of a new 4-aza-indole derivative [ethyl...