Kinetics of the L‐aminoacylase‐catalyzed resolution of N‐acetyl‐DL‐butyrine

The kinetics of the asymmetric hydrolysis of N‐acetyl‐DL ‐butyrine catalyzed by L ‐aminoacylase to obtain optically pure L ‐butyrine is described. Some of the constants are determined from the initial reaction rates and others from long‐term experiments in batch reactors by the numerical integration of the reactor design equation and minimization of the kinetic parameters. The methodology described can be applied to the kinetic study of other complex biocatalytic systems. Studies on enzyme activation by adding different divalent metal ions and enzymatic deactivation are also included. © 2002 Society of Chemical Industry     

Influence of the degree of exfoliation of an organoclay on the flame‐retardant properties of cross‐linked ethylene‐co‐Propylene‐co‐diene monomer‐g‐Maleic anhydride‐based composites

Layered montmorillonite was synthesized by hydrothermal method, progressively modified by an alkylammonium and thoroughly characterized by elemental, thermal, and X‐ray diffraction (XRD) analysis. Pristine and modified clays were introduced in maleic anhydride‐modified ethylene‐co‐propylene‐co‐diene monomer matrix. XRD and transmission electron microscopy investigations showed microcomposite as well as intercalated or exfoliated nanocomposites morphologies depending on the organic content of the clay. The inhibitor character of the pristine clay on peroxides as crosslinking agent for rubbers was then demonstrated and overcome by using electron beam irradiation for specimens containing unmodified clay. Dynamic mechanical analyses and swelling measurements showed that it is possible to obtain the same degree of crosslinking of the polymer matrix by electron beam irradiation of the composites based on pristine clay specimens and conventional peroxide curing of modified‐clay‐based ones. Finally, flame‐retardant properties of different clays‐based composites showed a direct dependence on the degree of exfoliation. It was observed that the better the exfoliation, the higher is the flame retardancy. POLYM. COMPOS., 38:966–973, 2017. © 2015 Society of Plastics Engineers     

Metal‐ion‐retention properties of the poly(2‐acrylamido‐2‐methyl‐1‐propanosulfonic acid‐co‐4‐vinyl pyridine) resin

The water‐insoluble resin poly(2‐acrylamido‐2‐methyl‐1‐propanosulfonic acid‐co‐4‐vinyl pyridine), through a radical polymerization solution, was synthesized with ammonium persulfate as an initiator and N,N‐methylene bisacrylamide as a crosslinking reagent. The metal‐ion‐retention properties were studied by batch and column equilibrium procedures for the following metal ions: Hg(II), Cu(II), Cd(II), Zn(II), Pb(II), and Cr(III). These properties were investigated under competitive and noncompetitive conditions. The effects of the pH, maximum retention capacity, and regeneration capacity were studied. The resin showed a high retention ability for Hg(II) ions at pH 2.0. The retention of Hg(II) ions from a mixture of ions was greater than 90%. The resin showed a high selectivity for Hg(II) with respect to other metal ions. The Hg(II)‐loaded resin was able to be recovered with 4M HClO₄. The retention capacity was kept after four cycles of adsorption and desorption. The retention properties for Hg(II) were very similar with the batch and column methods. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3556–3562, 2003     

Improvement of the production of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate‐co‐4‐hydroxybutyrate) terpolyester by manipulating the culture condition

BACKGROUND: The aim of this work is to enhance the production of terpolyester poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate‐co‐4‐hydroxybutyrate) (P(3HB‐co‐3HV‐co‐4HB)) produced by a locally isolated bacterium, Cupriavidus sp. USMAA2‐4. The monomer composition was varied by supplementing different carbon precursors and by manipulating the culture condition through one‐stage cultivation. The effect of C/N ratio and different concentrations of carbon source and precursors were investigated in order to produce higher content of this terpolyester. Although research on this biodegradable polyester is abundant, studies on terpolyester P(3HB‐co‐3HV‐co‐4HB) are still limited. RESULTS: Supplementation of oleic acid in accumulation medium increased the bacterial growth and polyhydroxyalkanoate (PHA) accumulation. It was also shown that medium consisting of assorted carbon precursors at C/N 20 gave relatively high dry cell weight and P(3HB‐co‐3HV‐co‐4HB) content. Various compositions of terpolyester were obtained when the concentration of oleic acid and 4HB precursors were manipulated. The combination of oleic acid with γ‐butyrolactone and 1‐pentanol was found to be the best combination to produce high PHA content (81 wt%). The composition of monomer in P(3HB‐co‐3HV‐co‐4HB) was produced in the range 8–13 mol% for 3HV and 9–24 mol% for 4HB, respectively. CONCLUSIONS: The production of P(3HB‐co‐3HV‐co‐4HB) in shake‐flasks successfully produced 81 wt% of PHA content. This manipulated culture condition can be used at larger scale to provide modeling for the production of terpolyester in a bioreactor. Copyright © 2012 Society of Chemical Industry     

Chiral Resolution and Pharmacological Characterization of the Enantiomers of the Hsp90 Inhibitor 2‐Amino‐7‐[4‐fluoro‐2‐(3‐pyridyl)phenyl]‐4‐methyl‐7,8‐dihydro‐6H‐quinazolin‐5‐one Oxime

Heat‐shock protein 90 (Hsp90) is a molecular chaperone involved in the stabilization of key oncogenic signaling proteins, and therefore, inhibition of Hsp90 represents a new strategy in cancer therapy. 2‐Amino‐7‐[4‐fluoro‐2‐(3‐pyridyl)phenyl]‐4‐methyl‐7,8‐dihydro‐6H‐quinazolin‐5‐one oxime is a racemic Hsp90 inhibitor that targets the N‐terminal adenosine triphosphatase site. We developed a method to resolve the enantiomers and evaluated their inhibitory activity on Hsp90 and the consequent antitumor effects. The (S) stereoisomer emerged as a potent Hsp90 inhibitor in biochemical and cellular assays. In addition, this enantiomer exhibited high oral bioavailability in mice and excellent antitumor activity in two different human cancer xenograft models.     

Self‐assembled structures in polystyrene‐block‐polyisoprene‐blend‐polystyrene and polystyrene‐block‐poly(methyl methacrylate)‐blend‐polystyrene or ‐blend‐poly(methyl methacrylate) in the strong segregation regime

This study deals with the investigation of microphase‐separated morphology and phase behaviour in blends of polystyrene‐block‐polyisoprene with homopolystyrene and blends of polystyrene‐block‐poly(methyl methacrylate) with homopoly(methyl methacrylate) or homopolystyrene in the strong segregation regime using small‐angle X‐ray scattering and transmission electron microscopy as a function of composition, molecular weight of homopolymers, r_M and temperature. Parameter r_M = M_H/M_C (where M_H is the molecular weight of homopolymer and M_C that of the corresponding block copolymer) was selected to encompass behaviour of the chains denoted as a ‘wet brush’ (i.e. r_M < 1). The relative domain spacing D/D_o increases in the regime 0 < r_M?1 with increasing concentration of homopolymer w_P and increasing r_M but depends on the specific implemented morphology. We tested a new approximate D/D_o versus w_P relation in the strong segregation regime using block copolymers of high molecular weights. It is shown that the parameters r_M and χ^3/2N determine the slope of the D/D_o versus w_P relation in the strong segregation regime and the new approximation generally matches the experimental data better than the approximations used so far. Copyright © 2010 Society of Chemical Industry     

Characterization of 4,6‐Diazido‐N‐nitro‐1,3,5‐triazine‐2‐amine

4,6‐Diazido‐N‐nitro‐1,3,5‐triazine‐2‐amine (DANT) was prepared with a 35 % yield from cyanuric chloride in a three step process. DANT was characterized by IR and NMR spectroscopy (¹H, ¹³C, ¹⁵N), single‐crystal X‐ray diffraction, and DTA. The crystal density of DANT is 1.849 g cm⁻³. The cyclization of one azido group and one nitrogen atom of the triazine group giving tetrazole was observed for DANT in a dimethyl sulfoxide solution using NMR spectroscopy. An equilibrium exists between the original DANT molecule and its cyclic form at a ratio of 7 : 3. The sensitivity of DANT to impact is between that for PETN and RDX, sensitivity to friction is between that for lead azide and PETN, and sensitivity to electric discharge is about the same as for PETN. DANT′s heat of combustion is 2060 kJ mol⁻¹.     

Comparison between the self‐assembling behaviors of PLLA‐PEO‐PLLA triblock copolymers and PLLA‐PEO‐PPO‐PEO‐PLLA pentablock copolymers

Poly(L ‐lactic acids) (PLLAs) were grafted to both ends of poly(ethylene oxide) (PEO) to produce biocompatible amphiphilic PLLA‐PEO‐PLLA triblock copolymers. The self‐assembling behaviors of two PLLA‐PEO‐PLLA copolymers in aqueous solutions were examined by Dynamic Light Scattering and Transmission Electron Microscopic techniques. PLLA‐PEO‐PLLA formed spherical micelles, whereas PLLA‐PEO‐PPO‐PEO‐PLLA pentablock copolymers were reported to produce vesicles. It is believed that the PPO segment within the PLLA‐PEO‐PPO‐PEO‐PLLA pentablock copolymers has a dominant role in the formation of vesicles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and Characterization of 1‐Azido‐2‐Nitro‐2‐Azapropane and 1‐Nitrotetrazolato‐2‐Nitro‐2‐Azapropane

1‐Azido‐2‐nitro‐2‐azapropane ( 1 ) was synthesized in high yield from 1‐chloro‐2‐nitro‐2‐azapropane and sodium azide. 1‐Nitrotetrazolato‐2‐nitro‐2‐azapropane ( 2 ) was synthesized in high yield from 1‐chloro‐2‐nitro‐2‐azapropane and silver nitrotetrazolate. The highly energetic new compounds ( 1 and 2 ) were characterized using vibrational (IR and Raman) and multinuclear NMR spectroscopy (¹H, ¹³C, ¹⁴N), elemental analysis and low‐temperature single crystal X‐ray diffraction. 1‐Azido‐2‐nitro‐2‐azapropane ( 1 ) represents a covalently bound liquid energetic material which contains both a nitramine unit and an azide group in the molecule. 1‐Nitrotetrazolato‐2‐nitro‐2‐azapropane ( 2 ) is a covalently bound room‐temperature stable solid which contains a nitramine group and a nitrotetrazolate ring unit in the molecule. Compounds 1 and 2 are hydrolytically stable at ambient conditions. The impact sensitivity of compound 1 is very high (<1 J) whereas compound 2 is less sensitive (<6 J).     

Computational Study of the Lipase‐Mediated Desymmetrisation of 2‐Substituted‐Propane‐1,3‐Diamines

The enantioselectivity displayed by the lipase from Pseudomonas cepacia towards a wide range of prochiral 2‐substituted‐propane‐1,3‐diamines was studied by means of molecular dynamics simulations (MDS). In all cases the enzyme allows the recovery of the corresponding amino carbamates of R configuration. However, the enantioselectivity is only synthetically useful if no ortho substituent is present and the aromatic ring is directly bonded to the 2‐carbon of the 1,3‐diamine core. Analysis of the MDS trajectories revealed that the homologation of 2‐aryl substituents by means of a methylene group lowers enantioselectivity by alleviating the conformational tension of the slow‐reacting orientations due to unfavourable intramolecular contacts between the ortho carbons of the aryl group and the nucleophilic nitrogen, as well as between the chiral carbon and the oxyanion. Additionally, the relative solvent accessible surfaces of the atoms of the aryl ring nicely correlate with the effect of the location of the substituent on enantioselectivity.     

Preparation of organo‐soluble co‐polyimides using N‐methyl‐2‐pyrrolidone as the solvent via one‐pot high‐temperature polymerization

A series of organo‐soluble co‐polyimides (co‐PIs) were successfully synthesized from 3,3′,4,4′‐benzophenonetetracarboxylic‐dianhydride (BTDA), 1,4‐bis‐(4‐amino‐2‐trifluoromethyl‐phemoxy)‐benzene (p‐6FAPB) and 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (BIA) via the one‐pot high‐temperature polymerization using N‐methyl‐2‐pyrrolidone (NMP) as the solvent. The imidization reaction of poly(amic acid)s in solution state was discussed in detail by attenuated total reflectance‐Fourier transform infrared spectra (ATR‐FTIR), and the results illustrate that the introduced benzimidazole moiety has a catalytic activity on the imidization process. The number‐average molecular weights and polydispersity index of these PIs measured by gel permeation chromatography range from 1.11 × 10⁵ to 2.20 × 10⁵ and 1.82 to 3.84, respectively. The prepared co‐PIs exhibit sufficient solubility in some polar solvents and high optical transparency. Meanwhile, these co‐PI films show good mechanical performances, and the strength and modulus of the sample with the molar ratio of p‐6FAPB/BIA = 5/5 reach 183 MPa and 4.71 GPa, respectively. Moreover, the obtained co‐PIs possess high glass transition temperatures (T_g) (above 260 °C) and good thermal stability with 5% weight loss temperature in the range of 502–531 °C in the nitrogen atmosphere. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45497.     

Low‐Cost‐Membranen für die Vanadium‐Redox‐Flow‐Batterie

Vanadium redox‐flow batteries are a technology that can be used to store fluctuating energies from solar and wind power. In order to reduce the manufacturing costs of the batteries, e.g., cheaper raw materials can be used. By using polystyrene‐based polymers for membrane production, conductivities comparable to perfluorosulfonic acid membranes can be achieved. A way to produce these heterogeneous membranes consisting of disperse and continuous phase is shown.     

Cellulose nanofibers prepared by the N‐methylmorpholine‐N‐oxide method

The process of electrospinning is very suitable for obtaining fibers with a diameter on a nanometer scale. Such fibers can be spun from almost all kinds of known polymers, copolymers, and polymer blends. In this work, we present cellulose nanofibers obtained by the electrospinning process from spinning dopes containing cellulose dissolved in an N‐methylmorpholine‐N‐oxide/water system. Under different electrospinning process conditions, cellulose fibers, a nonwoven fiber network, and a cellulose membrane were obtained. The fibers were examined with scanning electron microscopy. The diameters of the fibers were in the submicrometer range. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1855–1859, 2005     

Optimization and investigation of the governing parameters in electrospinning the home‐made poly(l‐lactide‐co‐ε‐caprolactone‐diOH)

Poly(l ‐lactide‐co‐ε‐caprolactone‐diOH) (PCLA) with (ABA)_n type is synthesized using poly(lactic acid) (PLA) and poly(ε‐caprolactone) di‐OH (PCL‐diOH) via chain extending method. FT‐IR, ¹H‐NMR, and GPC data demonstrate that PLA and PCL‐diOH have reacted completely. The product is electrospun into ultrafine fibers subsequently. The optimum electrospinning parameters obtain from an orthogonal experiment are a solvent ratio (DMF/DCM) of 5/5, a polymer concentration of 28 wt %, a collector distance of 20 cm and a voltage of 18 kV. As a result, the average diameter of fibers is 0.77 µm and the uniformity is above 80%. Via range analysis, it is found that the order of the influence on diameter is solvent ratio, applied voltage, collector distance, and polymer concentration, successively. Single effect of the four governing factors on diameter and morphology is also experimentally investigated. This may provide clues for obtaining fibers with various structures by controlling the parameters. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3600–3610, 2013     

N‐Alkyl‐, 1‐C‐Alkyl‐, and 5‐C‐Alkyl‐1,5‐dideoxy‐1,5‐imino‐(l)‐ribitols as Galactosidase Inhibitors

A series of 1,5‐dideoxy‐1,5‐imino‐(l )‐ribitol (DIR) derivatives carrying alkyl or functionalized alkyl groups were prepared and investigated as glycosidase inhibitors. These compounds were designed as simplified 4‐epi‐isofagomine (4‐epi‐IFG) mimics and were expected to behave as selective inhibitors of β‐galactosidases. All compounds were indeed found to be highly selective for β‐galactosidases versus α‐glycosidases, as they generally did not inhibit coffee bean α‐galactosidase or other α‐glycosidases. Some compounds were also found to be inhibitors of almond β‐glucosidase. The N‐alkyl DIR derivatives were only modest inhibitors of bovine β‐galactosidase, with IC₅₀ values in the 30–700 μm range. Likewise, imino‐l ‐ribitol substituted at the C1 position was found to be a weak inhibitor of this enzyme. In contrast, alkyl substitution at C5 resulted in enhanced β‐galactosidase inhibitory activity by a factor of up to 1000, with at least six carbon atoms in the alkyl substituent. Remarkably, the ‘pseudo‐anomeric’ configuration in this series does not appear to play a role. Human lysosomal β‐galactosidase from leukocyte lysate was, however, poorly inhibited by all iminoribitol derivatives tested (IC₅₀ values in the 100 μm range), while 4‐epi‐IFG was a good inhibitor of this enzyme. Two compounds were evaluated as pharmacological chaperones for a GM1‐gangliosidosis cell line (R301Q mutation) and were found to enhance the mutant enzyme activity by factors up to 2.7‐fold.     

Anti‐HIV‐1 Peptide Derivatives Based on the HIV‐1 Co‐receptor CXCR4

The human immunodeficiency virus type 1 (HIV‐1) uses CD4 and the co‐receptor CCR5 or CXCR4 in the process of cell entry. The negatively charged extracellular domains of CXCR4 (CXCR4‐ED) interact with positive charges on the V3 loop of gp120, facilitating binding via electrostatic interactions. The presence of highly conserved positively charged residues in the V3 loop suggests that CXCR4‐ED‐derived inhibitors might be broadly effective inhibitors. Synthetic peptide derivatives were evaluated for anti‐HIV‐1 activity. The 39‐mer extracellular N‐terminal region (NT) was divided into three fragments with 10‐mer overlapping sites ( N1 – N3 ), and these linear peptides were synthesized. Peptide N1 contains Met 1–Asp 20 and shows significant anti‐HIV‐1 activity. Extracellular loops 1 and 2 (ECL1 and 2) were mimicked by cyclic peptides C1 and C2 , which were synthesized by chemoselective cyclization. Cyclic peptides C1 and C2 show higher anti‐HIV‐1 activity than their linear peptide counterparts, L1 and L2 . The cytotoxicities of C1 and C2 are lower than those of L1 and L2 . These results indicate that Met 1–Asp 20 segments of the NT and cyclic peptides of ECL1 and ECL2 are potent anti‐HIV‐1 drug candidates.     

Non‐Isothermal Kinetic Study of the Thermal Decomposition of Melamine 3‐Nitro‐1,2,4‐triazol‐5‐one Salt

Study on thermal behavior of 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) salts was required to obtain important data for application purposes. These compounds have been shown to be useful intermediates for gun propellant ingredients, high energetic ballistic modifiers for solid propellants and other potential applications. In this paper, thermal decomposition and non‐isothermal kinetics of melamine 3‐nitro‐1,2,4‐triazol‐5‐one salt (MNTO) were studied under non‐isothermal conditions by DSC and TG methods. The kinetic parameters were obtained from analysis of the DSC and TG curves by Kissinger and Ozawa methods. The critical temperature of thermal explosion (T_b) was 574 K. The results show that MNTO is thermally more stable than NTO when compared in terms of the critical temperature of thermal explosion. Finally, the values of ΔS^#, ΔH^#, and ΔG^# of its decomposition reaction were calculated.     

1,2,3,4‐Tetrachloro‐5,5‐dimethoxy‐cyclopenta‐1,3‐diene: Diels Alder Reactions and Applications of the Products Formed

Readily available 1,2,3,4‐tetrachloro‐5,5‐dimethoxy‐ cyclopenta‐1,3‐diene ( 2 ) is an excellent cyclic diene for Diels—Alder reaction with a vast variety of dienophiles. The products so formed (norbornene derivatives) constitute important building blocks for the synthesis of diverse complex natural as well as non‐natural products. Apart from very high endo selectivity associated with Diels—Alder reactions, there are several other fascinating features associated with these bicyclic products which make them convenient entities in the synthesis of complex molecules. The most important is the rigid framework that act as a powerful template to provide high degree of selectivity and directional nature to various substituents. The proposed article is intended to focus on Diels‐Alder reactions of 2 and the applications of norbornene derivatives in organic synthesis.     

Studies on ethylene‐propylene‐diene rubber modification by N‐chlorothio‐N‐butyl‐benzenesulfonamide

N‐Chlorothiosulfonamides have been used to modify ethylene‐propylene‐diene rubber (EPDM) to enhance the compatibility of EPDM in, e.g., natural rubber (NR)/butadiene rubber (BR)/EPDM blends for ozone resistance. N‐Chlorothio‐N‐butyl‐benzenesulfonamide (CTBBS) was selected as a representative for N‐chlorothiosulfonamides. In this study, we found that CTBBS behaves differently with various types of EPDM. Three types of EPDM were selected: ethylidene norbornene (ENB)‐EPDM, hexadiene (HD)‐EPDM, and dicyclopentadiene (DCPD)‐EPDM. HD‐EPDM showed the greatest effectiveness toward CTBBS‐modification. However, this EPDM is not commercially available anymore. On the opposite side, DCPD‐EPDM showed the lowest reactivity so that almost no modification could be realized. The result with ENB‐EPDM was, that upon application of CTBBS to ENB‐EPDM, gelation occurred and, therefore, a low amount of modification was achieved. With the limited modification efficiency for ENB‐EPDM, there is no significant improvement when applying the modified ENB‐EPDM into NR/BR/EPDM blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009