Copolyesterification between poly(butylene terephthalate), terephthalic acid and hydroquinone diacetate: a kinetic analysis

The kinetics of liquid crystalline copolyester synthesis via melt transesterification between poly(butylene terephthalate) (PBT), terephthalic acid (TA) and hydroquinone diacetate (HQDA) is examined. Two different copolyester compositions PBT30/(HQDA+TA) 70 and PBT 50/(HQDA+TA) 50 mol% ratio were synthesized. The ratio of HQDA to TA was kept constant for all the reactions.The copolyesters were synthesized via melt polycondensation route at 265°C, 275°C and 285°C using two different transesterification catalysts, zinc acetate and dibutyl tin oxide. A key postulation assumed in this work is that the reaction originates between TA and HQDA to form a dimer which slices PBT chain. The copolyesterification rate constant for a system containing butylene glycol a more nonpolar moiety compared to ethylene glycol in poly(ethylene terephthalate) has been determined. The activation energy values for the different copolymer systems has also been determined. The rate constants for the uncatalyzed and catalyzed copolyesterification reaction and the activation energy values for the reaction have been determined.     

Synthesis and characterization of [Cu(Phca2en)(PPh3)X] (X=Cl, Br, I, NCS, N3) complexes: crystal structures of [Cu(Phca2en)(PPh3)Br] and [Cu(Phca2en)(PPh3)I]

New mixed-ligand copper(I) complexes, [Cu(Phca₂en)(PPh₃)X], [Phca₂en = N,N′-bis(β-phenylci-nnamaldehyde)-1,2-diiminoethane and X=Cl (1), Br (2), I (3), NCS (4), N₃ (5)] have been synthesized and characterized by various techniques. ¹H and ¹³C-NMR and IR spectral data of these copper(I) complexes are compared with the free ligand to elucidate some structural features. The structures of [Cu(Phca₂en)(PPh₃)Br] (2) and [Cu(Phca₂en)(PPh₃)I] (3) have been determined from single-crystal data showing that the coordination geometry around copper atom is a distorted tetrahedron. Furthermore, these Cu(I) complexes exhibit supramolecular motifs of the type multiple phenyl embraces resulting from attractive interactions between phenyl rings of PPh₃ moieties. The presence of the C–H…Cu weak intramolecular hydrogen bonds, due to the trapping of C–H bonds in the vicinity of the metal atoms, is also reported.     

Square-wave voltammetric (SWV) determination of Captopril in reconstituted serum and pharmaceutical formulations

A simple, fast and sensitive square-wave voltammetric (SWV) method for the determination of trace amounts of Captopril in pharmaceutical formulation and reconstituted serum is reported. A three-electrode system containing the static mercury drop electrode (SMDE) working electrode, Pt auxiliary electrode and Ag/AgCl reference electrode was used throughout. Sodium sulfite was used as both supporting electrolyte and oxygen removing agent. No nitrogen purging is needed for oxygen removal from sample solution. Calibration graph showed good linearity in the concentration range of 0.5-50.0 μg mL⁻¹ of Captopril and regression coefficient of 0.9957 is obtained. R.S.D. for eight replicate measurements and LOD of the proposed method are 1.2% and 6.28 × 10⁻³ μg mL⁻¹, respectively. The effect of various parameters (equilibration time, scan increment, pulse height, drop size, frequency and sodium sulfite concentration) on the determination were investigated. The procedure was successfully applied to the determination of Captopril in pharmaceutical formulation and reconstituted serum.     

Ketoconazol‐Triiodide Ion Pair Complex as a Suitable Carrier in an Iodide Selective Membrane Electrode

A novel membrane sensor for selective monitoring of iodide, consisting of a triiodide‐ketoconazole ion pair complex dispersed in a PVC matrix, plasticized with a mixture of 2‐nitrophenyl octyl ether and dioctylphtalate with unique selectivity toward iodide ions, is described. The influence of membrane composition, pH of test solution and foreign ions on the electrode performance were investigated. The optimized membrane demonstrates a near‐Nernstian response for iodide ions over a wide linear range from 1.0 × 10^?2 to 1.0 × 10^?5 M, at 25 ± 1 °C. The electrode could be used over a wide pH range 3–10 and has the advantages of high selectivity, fast response time and good lifetime (over 4 months). It was successfully used as indicator electrode in potentiometric titrations and direct potentiometric assay of iodide ions.     

Chloroplast Biogenesis 77: Two Novel Monovinyl and Divinyl Light-Dark Greening Groups of Plants and Their Relationship to the Chlorophyll a Biosynthetic Heterogeneity of Green Plants

Abstract— On the basis of the steady-state accumulation of divinyl (DV) or monovinyl (MV) protochlorophyllide (Pchlide) a in darkness (D) or in the light (L), green plants have been classified into three different greening groups namely dark divinyl-light divinyl (DDV-LDV), dark monovinyl-light divinyl (DMV-LDV) and dark monovinyl-light monovinyl (DMV-LMV) (Ionannides et al., Biochem. Syst. Ecol. 22, 211-220,1994). Interruption of the L phase of the photoperiod by a brief period of darkness (LD condition) revealed a predominance of different chlorophyll (Chl) a biosynthetic routes, depending upon the greening group affiliation of the plant species. For example, in DMV-LDV and DMV-LMV plants, the predominant Chl a biosynthetic routes under the LD condition appear to be the MV Chi a biosynthetic route and/or a mixed DV-MV Chi a biosynthetic route that bifurcates at the level of DV Pchlide a. On the basis of DV and MV Pchlide a accumulation rates after re-darkening, this greening group is designated as a light-dark MV (LDMV) subgroup. In DDV-LDV plants, the predominant LD Chi a biosynthetic routes appear to be the DV Chi a biosynthetic route and/or a mixed DV-MV Chi a biosynthetic route that bifurcates at the level of DV Chlide a. This greening group is designated as a light-dark DV (LDDV) subgroup. It is proposed that upon inhibiting the conversion of Pchlide a to Chi a by interruption of the L phase of the photoperiod by a brief period of D, the rates of DV and MV Pchlide a regeneration may reflect the carryover rates of DV and MV Pchlide a biosynthesis in L instead of reflecting a differential use of DV and MV carboxylic biosynthetic rates in D. It is also shown that in LDMV plants, MV Chlide a and MV Chi a are formed without the participation of [4-vinyl] Chlide a reductase. On the basis of recently published evidence, it is also argued that Pchlide oxidoreductase-A (POR-A) may be active in LDDV plants, while POR-B may predominate in LDMV plant species. The evolutionary significance of the LDDV and LDMV greening subgroups is discussed.     

A simple colorimetric method for the assay of penicillin G salt and penicillamine by oxidation with iodate

A simple colorimetric procedure is described for determination of penicillin G salt and penicillamine. It is based on oxidation with potassium iodate at room temperature and measurement of the liberated iodine at 520 nm after extraction with carbon tetrachloride. Compared with other procedures, this method proved to be more rapid, highly reproducible and reasonably accurate. The relative standard deviation did not exceed 0.9% and 0.4% for penicillin and penicillamine, respectively. The procedure has been successfully applied to pharmaceutical preparations containing either of the two compounds.     

Vector and Cell Line Engineering Technologies Toward Recombinant Protein Expression in Mammalian Cell Lines

The rapid growth of global biopharmaceutical market in the recent years has been a good indication of its significance in biotechnology industry. During a long period of time in recombinant protein production from 1980s, optimizations in both upstream and downstream processes were launched. In this regard, one of the most promising strategies is expression vector engineering technology based on incorporation of DNA opening elements found in the chromatin border regions of vectors as well as targeting gene integration. Along with these approaches, cell line engineering has revealed convenient outcomes in isolating high-producing clones. According to the fact that more than 50% of the approved therapeutic proteins is being manufactured in mammalian cell lines, in this review, we focus on several approaches and developments in vector and cell line engineering technologies in mammalian cell culture.     

Functionalization of cellulose nanocrystal powder by non-thermal atmospheric-pressure plasmas

Cellulose - Despite promising characteristics such as the biodegradability and the environmentally benign nature of cellulose nanocrystal (CNC) based composites, their poor dispersion and...