Microwave spectrum, centrifugal distortion, dipole moment and conformation of 2-methyl-1,3-dioxane

Microwave spectrum of 2-methyl-1,3-dioxane has been investigated in the frequency range 8–40 GHz. Rotational a-type and c-type transitions with J≤40 have been identified. Rotational constants A = 4658.122(2) MHz, B = 2503.221(1) MHz, C = 1783.950(1) MHz and centrifugal distortion constants for the ground vibrational state have been found. Dipole moment components μ_a = 1.43 ± 0.01 D, μ_c = 1.15±0.01 D and overall dipole moment μ = 1.84±0.02 D have been determined. The data obtained are in accord with the chair conformation of the molecule having equatorial arrangement of the methyl group. Original Russian Text Copyright ? 2006 by A. Kh. Mamleev, R. V. Galeev, L. N. Gunderova, M. G. Faizullin, and A. A. Shapkin __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 47, No.2, pp. 373–375, March–April, 2006.     

Antibacterial,antifungal and in vivo anticancer activities of chitin-binding lectins from Tomato (Solanum lycopersicum) fruits

A mixture of chitin-binding lectins from Tomato (Solanum lycopersicum) fruits, designated as Tomato chitin-binding lectins (TCLs), was isolated through affinity chromatography using an acetylated chitin column. Molecular weights of TCLs were determined to be 30 to 115 KDa which possessed mild toxicity with an LC₅₀ value of 521 µg/ml examined by the brine shrimp nauplii toxicity assay. Strong antibacterial activity of TCLs was found against Escherichia coli, Staphylococcus aureus and Shigella boydii at a concentration of 500 µg/ml by using disc diffusion method. Minimum inhibitory concentrations (MIC) of TCLs against Staphylococcus aureus and Escherichia coli were found to be 200 µg/ml and 140 µg/ml, respectively whereas minimum bactericidal concentrations (MBC) against the same bacterial species were 840 and 600 µg/ml, respectively. TCLs also exerted antibiofilm activity (53.32% at 250 μg/ml) against Escherichia coli. Strong antifungal activity of TCLs against Aspergillus niger was found at 600 µg/ml whereas the lectin mixture agglutinated A. niger spores at 200 µg/ml. TCLs exhibited 19.63% and 59.91% anti-proliferative activity against Ehrlich ascites carcinoma (EAC) cells in vivo in Swiss albino mice when intraperitonealy injected at doses 1.0 mg/kg/day and 2.0 mg/kg/day, respectively for five consecutive days. Morphological changes of apoptosis in EAC cells under fluorescence microscope and alteration of the expression of apoptosis-related genes (Fas, Caspase 8 and Caspase 3) had also been observed. MTT assay showed 27.61%, 38.74% and 49.23% of in vitro anticancer activity of the tomato lectins at concentrations of 37.5, 75 and 150 µg/ml, respectively.     

Evaluation of supports and methods for immobilization of enzyme cyclodextringlycosyltransferase

An experimental design with factorial planning was used for the immobilization of the enzyme cyclodextringlycosyltransferase (CGTase) from Bacillus firmus (strain no.37) to select the best combination of support, method of immobilization, and conditions that gives primarily higher average values for the specific immobilized enzyme activity, and secondarily, higher average values for the percentage of protein fixation. The experimental design factors were as follows: supports—controlled-pore silica, chitosan, and alumina; immobilization methods—adsorption, and two covalent bonding methods, either with γ-aminopropyltriethoxysilane or hexamethylenediamine (HEMDA); conditions—7°C without agitation and 26°C with stirring. The best combination of factors that lead to higher average values of the response variables was obtained with immobilization of CGTase in silica with HEMDA at 7°C. However, immobilization in chitosan at 7°C gave the highest immobilized CGTase specific activity, 0.25 μmole of β-CD/(min·mg protein). Physical adsorption gave low specific enzyme activities, and, in general, a high load of enzyme leads to lower specific enzyme activity.     

Screening, Gene Sequencing and Characterising of Lipase for Methanolysis of Crude Palm Oil

Staphylococcus sp. WL1 lipase (LipFWS) was investigated for methanolysis of crude palm oil (CPO) at moderate temperatures. Experiments were conducted in the following order: searching for the suitable bacterium for producing lipase from activated sludge, sequencing lipase gene, identifying lipase activity, then synthesising CPO biodiesel using the enzyme. From bacterial screening, one isolated specimen which consistently showed the highest extracellular lipase activity was identified as Staphylococcus sp. WL1 possessing lipFWS (lipase gene of 2,244 bp). The LipFWS deduced was a protein of 747 amino acid residues containing an α/β hydrolase core domain with predicted triad catalytic residues to be Ser474, His704 and Asp665. Optimal conditions for the LipFWS activity were found to be at 55 °C and pH 7.0 (in phosphate buffer but not in Tris buffer). The lipase had a K _M of 0.75 mM and a V _max of 0.33 mM?min^?1 on p-nitrophenyl palmitate substrate. The lyophilised crude LipFWS performed as good as the commonly used catalyst potassium hydroxide for methanolysis of CPO. ESI-IT-MS spectra indicated that the CPO was converted into biodiesel, suggesting that free LipFWS is a worthy alternative for CPO biodiesel synthesis.     

Determination of DDT in Animal Fats After Matrix Solid-Phase Dispersion Extraction Using an Activated Carbon Filter

A novel method for determining pp’-DDT, op’-DDT, pp’-DDE, and pp’-DDD contamination in animal fats (beef tallow, lard, and chicken fat) without using toxic organic solvents for sample preparation, followed by HPLC, has been developed. The sample is prepared by matrix solid-phase dispersion (MSPD) extraction with Toyobo-KF^®, an activated carbon fiber, as a new MSPD sorbent. The average recoveries (spiking levels: 0.2, 0.5, and 1.0 µg g^?1) ranged from 58 to 93%, with relative standard deviations of < 7%. The limits of quantitation were 0.18 µg g^?1.     

Spectrophotometric Determination of Cimetidine through Charge-transfer Reaction with 1,5-Dichloroanthraquinone as a π-Electron Acceptor

Cimetidine reacting with 1,5-dichloroanthraquinone in acetone solution can produce a charge-transfer complex that shows a strong absorption peak at 343 nm. The absorption value at 343 nm increased with cimetidine concentration in the range of 0.01—0.5 μg/mL, with regression coefficient of 0.9995 and detection limit of 0.006 μg/mL. This simple and sensitive method has been successfully applied to determine cimetidine in tablets and capsules, with average recovery of (98.47±0.92)% and (97.07±1.16)%, respectively. Furthermore, the mole ratio of the complex between cimetidine and 1,5-dichloroanthraquinone is 2∶1, and the mechanism of charge-transfer reaction is explored.     

Crinum latifolium mediated biosynthesis of gold nanoparticles and their anticandidal,antibiofilm and antivirulence activity

Candida spp. is one of the most common opportunistic human fungal pathogens, responsible for 90–100% of mucosal infections. Germ tube formation, hyphal morphogenesis, the production of tissue-damaging extracellular enzymes, and drug-resistant biofilm formation contribute to their pathogenicity, which can lead to systemic infections in the worst scenarios. Thus, there is an urgent need to discover new therapeutic agents to overcome the above virulence factors. Therefore, we aimed to prepare Crinum latifolium leaves-mediated biosynthesis of gold nanoparticles (AuNPs) that was characterized by various sophisticated techniques, and further their antifungal, antibiofilm, and anti-virulence activities was investigated. The AuNPs show a zone of inhibition between 19 and 22 mm for test strains of Candida spp. at 1000 µg/ml, whereas the MIC values were ranged from 250 to 500 µg/ml. AuNPs inhibit germ tube formation in C. albicans by 93.3% at 50 µg/ml. Furthermore, exposure to AuNPs significantly reduced the secretions of phospholipase, proteinase, hemolysin, esterase, and lipase. Confocal laser scanning microscopy (CLSM) investigation shows that 25 µg/ml of AuNPs significantly inhibit colonization and biofilm formation. Lastly, the interaction of Candidal cells with AuNPs revealed, ultrastructural changes in the cell wall and cell membranes as visualized by a transmission electron microscope (TEM).     

Design,synthesis, antimicrobial evaluations and in silico studies of novel pyrazol-5(4H)-one and 1H-pyrazol-5-ol derivatives

A new series of 1,4-disubstituted 3-methylpyrazol-5(4H)-one derivatives were synthesized by reacting various substituted aromatic aldehydes with 3-methylpyrazol-5(4H)-one derivatives through Knoevenagel condensation by conventional as well as by exposure to microwave irradiations. After that newly synthesized compounds of 1,4-disubstituted 3-methyl-1H-pyrazol-5-ol were prepared from these derivatives by reduction reaction of sodium borohydride at 0–5 °C. Sixty-four heterocyclic compounds containing a pyrazole moiety were synthesized with good to excellent yields (51 to 91%). Compounds (3d, 3m, 4a, 4b, 4d, and 4g) showed potent antibacterial activity against MSSA (Methicillin-susceptible strains of Staphylococcus aureus) and MRSA (Methicillin-resistant strains of Staphylococcus aureus) with MIC (the minimum inhibitory concentration) ranging between 4 and 16 µg/mL as compared to ciprofloxacin (MIC = 8–16 µg/mL). Compounds (4a, 4h, 4i, and 4l) showed potent antifungal activity against Aspergillus niger with MIC ranging between 16 and 32 µg/mL as compared to fluconazole (MIC = 128 µg/mL). In particular, compound 4a exhibited the strongest activity among the synthesized compounds in both bacterial and fungal strains with MIC ranging between 4 and 16 µg/mL. Furthermore, the nine most active compounds showed a good ADMET (absorption, distribution, metabolism, excretion, and toxicity) profile in comparison to ciprofloxacin and fluconazole as reference drugs. Molecular docking predicted that DHFR (dihydrofolate reductase) protein from Staphylococcus aureus and NMT (N-myristoyl transferase) protein from Candida albicans are the most suitable targets for the antimicrobial activities of these potent compounds.     

Phytochemical prospection,evaluation of antibacterial activity and toxicity of extracts of Libidibia ferrea (Mart. ex Tul.) L.P. Queiroz

Libidibia ferrea (Mart. ex Tul.) L.P. Queiroz is a arboreal species found in the Caatinga from Northeast of Brazil that has been used in popular medicine as an anti-inflammatory, healing, analgesic and for the treatment of respiratory system disorders. Therefore, the objective of this work was to evaluate the composition of ethanol extracts from the leaves and inner bark of Libidibia ferrea, as well as to verify its antibacterial activity and as a potential inhibitor of the TetK efflux pump in Staphylococcus aureus strains, in addition to investigating the toxicity of the extracts in a Drosophila melanogaster model. The analysis and quantification of the extracts markers was performed by High Performance Liquid Chromatography (HPLC). To determine the Minimum Inhibitory Concentration (MIC) broth microdilution tests were carried out. The evaluation of efflux pump inhibition was performed by modifying the MIC of antibiotics and ethidium bromide. Mortality and negative geotaxis tests were used to verify the toxicity of extracts on D. melanogaster. Hydrolysable tannins (gallic acid and ellagic acid) and flavonoids were found in HPLC analysis. The extracts did not show antibacterial activity, demonstrating a MIC ≥ 1024 µg/mL, however the ethanolic extract of the leaves decreased the MIC of the antibiotic from 64 µg/mL to 16 µg/mL, but this effect is not associated with the inhibition of the efflux pump. The extracts did not show toxicity in a D. melanogaster model. This is the first study to evaluate the antibacterial activity of L. ferrea extracts on the IS-58 strain of S. aureus, as well as the first to investigate its toxicity using D. melanogaster. From the results, further studies are needed to determine the mechanisms of action of the extract with other antibiotics.     

Hippurathydrolase,ein neues Enzym aus Mikroorganismen, 2. Mitt.: Enzymeigenschaften

Characteristic properties of the new enzymehippurate hydrolase are reported:

1. The Michaelis constant for hippurate hydrolysis is 5.5·10^?4 mole/l at 5° and pH 7.5. The specific activity of the purified enzyme preparation is 7.5 μmole/minute · mg enzyme protein at 37° and pH 7.5. The pH optimum is 7.5.
2. The effects of temperature on the reaction rate and on the stability of the enzyme were determined.
3. The effects of various inhibitors (HgCl₂, pCMB, EDTA, 8-hydroxyquinoline) and cations were studied. Participation of metal ions in the catalytic function ofhippurate hydrolase was not detectable.

     

Validated assay for the simultaneous quantification of total vincristine and actinomycin‐D concentrations in human EDTA plasma and of vincristine concentrations in human plasma ultrafiltrate by high‐performance liquid chromatography coupled with tandem mass spectrometry

A sensitive, specific and efficient high‐performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) assay for the simultaneous determination of total vincristine and actinomycin‐D concentrations in human plasma and an assay for the determination of unbound vincristine are presented. Electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI) and heated electrospray ionization (H‐ESI) were tested as ionization interfaces. For reasons of robustness ESI was chosen followed by tandem mass spectrometry (ESI‐MS/MS). For the plasma assay a 30 µL aliquot was protein precipitated with acetonitrile/methanol (50:50, v/v) containing the internal standard vinorelbine and 10 µL volumes were injected onto the HPLC system. To determine unbound vincristine, ultrafiltrate was produced from plasma using 30 kDa centrifugal filter units. The plasma ultrafiltrate was mixed with methanol (50:50, v/v), internal standard vinorelbine was added and 20 µL aliquots were injected onto the HPLC system. Separation was achieved on a 50 × 2.1 mm i.d. Xbridge C₁₈ column using 1 mM ammonium acetate/acetonitrile (30:70, v/v) adjusted to pH 10.5 with ammonia, run in a gradient with methanol at a flow rate of 0.4 mL/min. HPLC run time was 6 min. The assay quantifies in plasma vincristine from 0.25 to 100 ng/mL and actinomycin‐D from 0.5 to 250 ng/mL using plasma sample volumes of only 30 µL. Vincristine in plasma ultrafiltrate can be quantified from 1 to 100 ng/mL. Validation results demonstrate that vincristine and actinomycin‐D can be accurately and precisely quantified in human plasma and plasma ultrafiltrate with the presented methods. The assays are now in use to support clinical pharmacological studies in children treated with vincristine and actinomycin‐D. Copyright © 2009 John Wiley & Sons, Ltd.     

Facile Biosynthesis of Silver Nanoparticles Using <Emphasis Type="Italic">Descurainia sophia</Emphasis> and Evaluation of Their Antibacterial and Antifungal Properties

The objective of the present study was to evaluate efficiency of silver nanoparticles (Ag-NPs) biosynthesis using Descurainia sophia as a novel biological resource. The resulting synthesized Ag-NPs were characterized using UV visible spectroscopy, X-ray diffraction, transmission electron microscopy and dynamic light scattering (DLS). The UV–Vis spectra gave surface plasmon resonance at ~420 nm. TEM images revealed formation spherical shaped Ag-NPs with size ranged from to 1–35 nm. DLS confirmed uniformity of the synthesized Ag-NPs with an average size of ~30 nm. Following, the antibacterial and antifungal activities of the synthesized Ag-NPs were investigated. The concentration 25 µg/ml of the Ag-NPs showed maximum inhibitory effect on mycelium growth of Rhizoctonia solani (More than 86 % inhibition), followed by 15 µg/ml (55 % inhibition) and 10 µg/ml (63 % inhibition). The minimum inhibitory concentration and minimum bactericidal concentration of Ag-NPs against Agrobacterium tumefaciens (strain GV3850) and A, rhizogenes (strain 15843) were 4 and 8 µg/ml, respectively. The Ag-NPs were stable in vitro for 3 months without any precipitation or decrease of antifungal effects. Finally, it could be concluded that D. sophia can be used as an effective method for biosynthesis of nanoparticles, especially Ag-NPs.     

Thermal degradation of polyisobutylene studied using factor-jump thermogravimetry

The overall activation energy of the thermal degradation of polyisobutylene has been measured using factor-jump thermogravimetry to be 206±1 kJ/mole over the range 365 to 405° in N₂ at 800 mm Hg pressure and flowing at 4 mm/s over the sample. This is consistent with some values reported for thermal degradation in vacuum and in solution. In 5 mm Hg of N₂, an apparent activation energy of 218±2 kJ/mole was found, and in vacuum the apparent activation energy is 238±13 kJ/mole. Troublesome bubbling made the vacuum values difficult to measure. Substitution of reasonable values for the activation energies of initiation,E _i , termination,E _t , and the activation energy,E _a , for vacuum degradation in the equationE _a =E _i /2E _d -E _t /2 yields an activation energy E_d=84 kJ/mole for the unzipping reaction. This equation presupposes a degradation mechanism of random initiation, unzipping, and bimolecular termination. Substitution of reasonable values for the heat of polymerization, ΔH, in the definition ΔH=E _p ?e _d suggests that the activation energy of the polymerization reaction at 375° is approximately 30 kJ/mole.     

Development and Validation of a High Performance Liquid Chromatographic Method for the Determination of Voriconazole Content in Tablets

This paper describes the validation of an isocratic HPLC method for the assay of voriconazole in tablets. The method employs a Merck LiChrospher^? 100 RP-8 (125 × 4.6 mm I.D., 5 μm particle size) column, with a mobile phase of methanol : triethylamine solutions 0.6 %, pH 6.0 (50:50, v/v) and UV detection at 255 nm. A linear response (r > 0.9999) was observed in the range of 20.0–100.0 μg mL⁻¹. The method showed good recoveries (average 100.4%) and the relative standard deviation intra and inter-day were ≤ 1.0 %. Validation parameters as specificity and robustness were also determined. The method can be used for both quality control assay of voriconazole in tablets and for stability studies as the method separates voriconazole from its degradation products and tablet excipients.     

Purification and Biochemical Characterization of a Novel Alkaline (Phospho)lipase from a Newly Isolated Fusarium solani Strain

An extracellular lipase from Fusarium solani strain (F. solani lipase (FSL)) was purified to homogeneity by ammonium sulphate precipitation, gel filtration and anion exchange chromatography. The purified enzyme has a molecular mass of 30 kDa as estimated by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The 12 NH₂-terminal amino acid residues showed a high degree of homology with a putative lipase from the fungus Necteria heamatoccocae. It is a serine enzyme, like all known lipases from different origins. Interestingly, FSL has not only lipase activity but also a high phospholipase activity which requires the presence of Ca²⁺ and bile salts. The specific activities of FSL were about 1,610 and 2,414 U/mg on olive oil emulsion and egg-yolk phosphatidylcholine as substrates, respectively, at pH 8.0 and 37 °C. The (phospho)lipase enzyme was stable in the pH range of 5–10 and at temperatures below 45 °C.     

Development and validation of a dried blood spot–HPLC assay for the determination of metronidazole in neonatal whole blood samples

A selective and sensitive high-performance liquid chromatography method with UV detection for the determination of metronidazole in dried blood spots (DBS) has been developed and validated. DBS samples [spiked or patient samples] were prepared by applying blood (30 µL) to Guthrie cards. Discs (6 mm diameter) were punched from the cards and extracted using water containing the internal standard, tinidazole. The extracted sample was chromatographed without further treatment using a reversed phase system involving a Symmetry® C18 (5 µm, 3.9?×?150 mm) preceded by a Symmetry® guard column of matching chemistry and a detection wavelength of 317 nm. The mobile phase comprised acetonitrile/0.01?M phosphate solution (KH₂PO₄), pH 4.7, 15:85, v/v, with a flow rate of 1 mL/min. The calibration was linear over the range 2.5–50 mg/mL. The limits of detection and quantification were 0.6 and 1.8 µg/mL, respectively. The method has been applied to the determination of 203 DBS samples from neonatal patients for a phamacokinetic/pharmacodynamic study.     

Bioprospecting Dodonaea viscosa Jacq.; a traditional medicinal plant for antioxidant,cytotoxic, antidiabetic and antimicrobial potential

Purpose of studyDodonaea viscosa Jacq. is an ethnomedicinal plant that has been extensively used for the treatment of gout, rheumatism and pain. Current study was undertaken to mine its antioxidant, antimicrobial, cytotoxic and antidiabetic potential. Chromogenic assays were employed to establish plant’s multimode antioxidant profile whereas HPLC fingerprinting was performed to quantify polyphenols. Standard brine shrimp lethality, MTT and SRB assays proved its cytotoxicity potential.ResultsAmong all the extracts (flower, leaf, stem and root), maximum extract recovery (22% w/w), gallic acid equivalent total phenolic content (20.11 ± 0.11 ug GAE/mg DW), ascorbic acid equivalent total antioxidant capacity (22.5 ± 0.07 µg/mg DW) and total reducing power (31.1 ± 1.13 µg/mg DW) were recorded in the distilled water + acetone extract of leaf. The acetone extract of leaf showed maximum quercetin equivalent total flavonoid content (4.78 ± 0.13 µg/mg DW). HPLC-DAD analysis revealed significant amount of rutin, vanillic acid, coumaric acid, ferulic acid, gallic acid, syringic acid, cinnamic acid, gentisic acid, catechin, caffeic acid, apigenin and myricetin in the different plant parts. Maximum scavenging potential was exhibited by methanol + ethyl acetate stem extract (IC₅₀ = 23.8 µg/ml). The highest antibacterial potential was found in flower (85.7%) and root (71.4%) extracts. The ethanol + ethyl acetate (1:1) leaf extract showed noteworthy toxicity against brine shrimps (LC₅₀ = 95.46 µg/ml) while a notable antiproliferative activity against THP-1 (IC₅₀ = 3.4 µg/ml) and Hep G2 (IC₅₀ = 20 µg/ml) cell lines was shown by ethanol + ethyl acetate extracts (1:1) of stem and root, respectively. A moderate inhibition of α-amylase enzyme was observed in all parts of the plant.ConclusionThe results of the present study suggest D. viscosa as a potential source of antioxidant, anticancer and α-amylase inhibitory phytochemicals.     

Ecofriendly synthesis of silver nanoparticles using Kei-apple (Dovyalis caffra) fruit and their efficacy against cancer cells and clinical pathogenic microorganisms

Green fabrication has become a safe approach for producing nanoparticles. Plant-based biogenic synthesis of silver nanoparticles (AgNPs) has emerged as a possible alternative to traditional chemical production. In this paper, we provide a low-cost, green synthesis of AgNPs utilizing using Kei-apple (Dovyalis caffra) fruit extract. Ultraviolet–visible (UV–Vis) spectroscopy, Fourier Transform Infrared (FTIR), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Scanning-Electron Microscope (SEM), and Dynamic Light Scattering (DLS) analyses were used to characterize green produced AgNPs. The formation of AgNPs was shown to have a surface resonance peak of 415 nm in UV–visible spectra, and FTIR spectra verified the participation of biological molecules in Synthesis of AgNPs. The TEM revealed that the biosynthesized AgNPs were mostly spherical in form, with size range of 12–53 nm. XRD diffractogram was used to demonstrate the face cubic centre (fcc) character of AgNPs. Excellent anticancer activity of AgNPs was recorded where more than 80% of Prostate Cancer (PC-3) cell lines was inhibited by 100–150 µg/mL of AgNPs, while 38% only was recorded using AgNO₃ and 55.62% was recorded D. caffra fruit extract at 150 µg/mL. Destructions of PC-3 cell was observed as a result of exposed to AgNPs, followed by D. caffra fruit extract, while minor alterations were recorded as exposed to AgNO₃. The 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging using AgNPs was three fold using fruit extract at 100 µg/mL indicating good antioxidant activity. Excellent inhibitory activity of AgNPs was recorded against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Aspergillus fumigatus with inhibition diameter zone 28.22 ± 0.25 mm, 23.21 ± 0.35 mm, 27.25 ± 0.03 mm, 28.40 ± 0.15 mm, 29.23 ± 0.44 mm, and 9.52 ± 0.5 mm, respectively compared with AgNO₃. D. caffra fruits considered a promising and safe source for fabrication of AgNPs with multi-biological functions.     

Preparation of a very stable immobilized Solanum tuberosum epoxide hydrolase

The covalent immobilization of the Solanum tuberosum epoxide hydrolase (StEH) was explored using highly activated Sepabeads-epoxy or Glyoxyl-agarose based supports. A Glyoxyl-agarose immobilizate, prepared under optimized experimental conditions, led to a material exhibiting excellent thermal and chemical stability. The key step of this immobilization process was the use of 164 kDa dextran as an additive during immobilization, which prevented the enzyme from inactivation at the high pH (pH 10) necessarily used for performing this immobilization. This afforded a Glyoxyl-agarose-StEH immobilizate with 80% initial enzymatic activity retention and a stabilization factor of at least 300 at 60 °C, as compared to the free enzyme. The high enantio- and regio-selectivity properties of this novel biocatalyst were shown to be nearly identical to those of the free enzyme.     

Volumetric, viscometric and refractive index behavior of some α-amino acids in aqueous tetrapropylammonium bromide at different temperatures

Densities, ρ, viscosities, η, and refractive indices, n _D, of glycine (Gly), DL-alanine (Ala), DL-valine (Val) (0.05, 0.10, 0.15, 0.20, 0.25 mol kg^?1), and L-leucine (Leu) (0.02, 0.05, 0.10 mol kg^?1) in water and in 0.20 mol kg^?1 aqueous tetrapropylammonium bromide (TPAB) have been measured at 298.15, 303.15, 308.15, and 313.15 K. The density data have been utilized to calculate apparent molar volumes, ?_v, partial molar volumes at infinite dilution, ?_v°, and partial molar volumes of transfer, ? _v°(tr) of amino acids. The viscosity data have been analyzed by means of Jones-Dole equation to obtain Falkenhagen coefficient, A, and Jones-Dole coefficient, B, free energy of activation of viscous flow per mole of solvent, Δµ₁°*, and solute, Δµ₂°*, and enthalpy, ΔH*, and entropy of activation, ΔS*, of viscous flow. The refractive index data have been used to calculate molar refractivity, R _D, of amino acids in aqueous tetrapropylammonium bromide solutions. It has been observed that ?_v°, B-coefficient and Δµ₂°* vary linearly with increasing number of carbon atoms in the alkyl chain of amino acids, and they were split to get contributions from the zwitterionic end groups (NH₃ ⁺, COO^-) and methylene group (CH₂) of the amino acids. The behavior of these parameters has been used to investigate the solute-solute and solute-solvent interactions as well as the effect of tetrapropylammonium cation (C₃H₇)₄N⁺ on these interactions.