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971.
Liaqat Ali Samina Ali Javid Hussain Ahmed Al‐Harrasi Abdul Latif Khan Syed Tasleem Hussain Shah Tania Shamim Rizvi 《Helvetica chimica acta》2014,97(4):556-560
The isolation and structure elucidation of a new triterpenic acid named floccosic acid ( 1 ) is reported on the basis of the 1D‐ and 2D‐NMR assignments. This secondary metabolite was isolated as a new constituent, along with the known triterpenoids, betulinic acid and β‐amyrin. All these compounds were purified by repeated column chromatography of the MeOH extract of Nepeta floccosa. The structure elucidation of the new compound was accomplished by the combined mass spectrometry (MS), infrared (IR) and ultraviolet (UV) absorption spectroscopy, one‐ (1H‐ and 13C‐) and two‐dimensional (H? C correlations; HMBC and HSQC) NMR techniques. The known compounds were identified by comparison of their physical and spectroscopic data with those reported in the literature. 相似文献
972.
An facile and efficient protocol for the synthesis of 13-aryl-indeno[1,2-b]naphtha[1,2-e]pyran- 12(13H)- ones has been developed that proceeds via the one-pot three-component sequential reaction of an aromatic aldehyde with β-naphthol and 2H-indene-1,3-dione under solvent-free conditions in the presence of a poly(4-vinylpyridinium)hydrogen sulfate (P(4-VPH)HSO4) catalyst. The catalyst can be reused several times, making this procedure facile, practical, and sustainable. The simple experimental procedure, solvent-free reaction conditions, use of an inexpensive catalyst, short react time, and excellent yields are some of the major advantages of this methodology. 相似文献
973.
Cold water fish gelatin films: Effects of cross-linking on thermal, mechanical, barrier, and biodegradation properties 总被引:1,自引:0,他引:1
Bor-Sen Chiou Roberto J. Avena-Bustillos Haani Jafri Syed H. Imam William J. Orts 《European Polymer Journal》2008,44(11):3748-3753
Gelatin was extracted from Alaska pollock (Theragra chalcogramma) and Alaska pink salmon (Oncorhynchus gorbuscha) skins and cast into films. The fish gelatin films’ tensile, thermal, water vapor permeability, oxygen permeability, and biodegradation properties were compared to those of bovine and porcine gelatin films. In addition, fish gelatin films were cross-linked with glutaraldehyde. Pollock and salmon gelatin films had comparable tensile properties, but had lower tensile strength and percent elongation than mammalian gelatin films. The lower strength and elongation might have been due to lower structural gelatin levels present in fish gelatin films. The addition of cross-linkers had little effect on tensile properties and melting temperatures of fish gelatin films. Pollock gelatin films had the lowest water vapor and oxygen permeability values, whereas mammalian gelatin films had the highest permeability values. Cross-linking resulted in lower water vapor permeability for salmon gelatin films and higher oxygen permeability for pollock gelatin films. However, all fish gelatin films had better water vapor and oxygen barrier properties than mammalian gelatin films. Also, fish gelatin films degraded faster than mammalian gelatin films. 相似文献
974.
Meera Moydeen Abdul Hameed Syed Ali Padusha Mohamed Khan Badr M. Thamer Nirmala Rajkumar Hany El-Hamshary Mohamed El-Newehy 《先进技术聚合物》2023,34(1):6-23
Electrospinning procedures such as blend electrospinning, coaxial electrospinning, and emulsion electrospinning have been used for the fabrication of electrospun nanofibers (ENFs) for biomedical applications. These ENFs are attracted great interest especially in drug delivery applications due to their small size, high surface area-to-volume, and porosity. The aim of this review is to focus on the controlled release mechanism among the different electrospinning methods, and the selectivity of hydrophilic, water-soluble polymers as a carrier for drug. The mechanism for the drug delivery depends mainly on the method of drug loading, polymeric interactions, and the nature of polymer swelling, erosion, or degradation. This review compressed on the literature survey about the fabrication of nanofibers by different electrospinning methods, factors affecting the nanofiber morphologies, selectivity of polymeric blends for successful controlled release behavior, and the mechanism involved in the drug release steps. 相似文献
975.
Shukor MY Masdor N Baharom NA Jamal JA Abdullah MP Shamaan NA Syed MA 《Applied biochemistry and biotechnology》2008,144(3):283-291
A heavy-metal assay has been developed using bromelain, a protease. The enzyme is assayed using casein as a substrate with
Coomassie dye to track completion of hydrolysis of casein. In the absence of inhibitors, casein is hydrolysed to completion,
and the solution is brown. In the presence of metal ions such as Hg2+ and Cu2+, the hydrolysis of casein is inhibited, and the solution remains blue. Exclusion of sulfhydryl protective agent and ethylenediaminetetraacetic
in the original assay improved sensitivity to heavy metals several fold. The assay is sensitive to Hg2+ and Cu2+, exhibiting a dose–response curve with an IC50 of 0.15 mg l−1 for Hg2+ and a one-phase binding curve with an IC50 of 0.23 mg l−1 for Cu2+. The IC50 value for Hg2+ is found to be lower to several other assays such as immobilized urease and papain assay, whilst the IC50 value for Cu2+ is lower than immobilized urease, 15-min Microtox™, and rainbow trout. 相似文献
976.
Shukor MY Habib SH Rahman MF Jirangon H Abdullah MP Shamaan NA Syed MA 《Applied biochemistry and biotechnology》2008,149(1):33-43
A molybdate-reducing bacterium has been locally isolated. The bacterium reduces molybdate or Mo6+ to molybdenum blue (molybdate oxidation states of between 5+ and 6+). Different carbon sources such as acetate, formate,
glycerol, citric acid, lactose, fructose, glucose, mannitol, tartarate, maltose, sucrose, and starch were used at an initial
concentration of 0.2% (w/v) in low phosphate media to study their effect on the molybdate reduction efficiency of bacterium. All of the carbon sources
supported cellular growth, but only sucrose, maltose, glucose, and glycerol (in decreasing order) supported molybdate reduction
after 24 h of incubation. Optimum concentration of sucrose for molybdate reduction is 1.0% (w/v) after 24 h of static incubation. Ammonium sulfate, ammonium chloride, valine, OH-proline, glutamic acid, and alanine (in
the order of decreasing efficiency) supported molybdate reduction with ammonium sulfate giving the highest amount of molybdenum
blue after 24 h of incubation at 0.3% (w/v). The optimum molybdate concentration that supports molybdate reduction is between 15 and 25 mM. Molybdate reduction is optimum
at 35 °C. Phosphate at concentrations higher than 5 mM strongly inhibits molybdate reduction. The molybdenum blue produced
from cellular reduction exhibits a unique absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. The
isolate was tentatively identified as Serratia marcescens Strain Dr.Y6 based on carbon utilization profiles using Biolog GN plates and partial 16s rDNA molecular phylogeny. 相似文献
977.
Shukor MY Rahman MF Shamaan NA Lee CH Karim MI Syed MA 《Applied biochemistry and biotechnology》2008,144(3):293-300
Molybdenum-reducing activity in the heterotrophic bacteria is a phenomenon that has been reported for more than 100 years.
In the presence of molybdenum in the growth media, bacterial colonies turn to blue. The enzyme(s) responsible for the reduction
of molybdenum to molybdenum blue in these bacteria has never been purified. In our quest to purify the molybdenum-reducing
enzyme, we have devised a better substrate for the enzyme activity using laboratory-prepared phosphomolybdate instead of the
commercial 12-phosphomolybdate we developed previously. Using laboratory-prepared phosphomolybdate, the highest activity is
given by 10:4-phosphomolybdate. The apparent Michaelis constant, K
m for the laboratory-prepared 10:4-phosphomolybdate is 2.56 ± 0.25 mM (arbitrary concentration), whereas the apparent V
max is 99.4 ± 2.85 nmol Mo-blue min−1 mg−1 protein. The apparent Michaelis constant or K
m for NADH as the electron donor is 1.38 ± 0.09 mM, whereas the apparent V
max is 102.6 ± 1.73 nmol Mo-blue min−1 mg−1 protein. The apparent K
m and V
max for another electron donor, NADPH, is 1.43 ± 0.10 mM and 57.16 ± 1.01 nmol Mo-blue min−1 mg−1 protein, respectively, using the same batch of molybdenum-reducing enzyme. The apparent V
max obtained for NADH and 10:4-phosphomolybdate is approximately 13 times better than 12-phoshomolybdate using the same batch
of enzyme, and hence, the laboratory-prepared phosphomolybdate is a much better substrate than 12-phoshomolybdate. In addition,
10:4-phosphomolybdate can be routinely prepared from phosphate and molybdate, two common chemicals in the laboratory. 相似文献
978.
Ansari R Kazi TG Jamali MK Arain MB Sherazi ST Jalbani N Afridi HI 《Journal of AOAC International》2008,91(2):400-407
A simple and fast procedure is proposed for the extraction of iron (Fe), copper (Cu), and nickel (Ni) in 16 varieties of sunflower seed oil samples using an ultrasonic bath. The experimental parameters of the ultrasonic-assisted extraction (UAE) method were optimized to improve the sensitivity and detect the metals at trace levels in minimum time. Conventional wet acid digestion method was used for comparative purposes. The optimum recovery of all 3 metals was obtained by UAE for 7 min, while the separation of aqueous and organic phases after extraction using centrifugation (UAE-2) required 3 min, as compared to the conventional equilibration method (UAE-1) that required 90 min. The respective recoveries of Cu, Fe, and Ni obtained with UAE-2 were in the range of 95.8-97.5, 93.5-98.3, and 95.6-98.2%, respectively, for different varieties of sunflower oil samples. Accuracy was determined by the standard addition method. Under the optimum operating conditions, the limits of detection obtained from the standard addition curves were 21.7, 20.4, and 35.6 ng/mL for Fe, Cu, and Ni, respectively. The fact that all varieties of sunflower oil contain significant amounts of Fe, Cu, and Ni indicates the deterioration of sunflower oil quality immediately after extraction from seeds, which poses a threat to oil quality and human health. 相似文献
979.
We report the synthesis and spectroscopic characterization of nanohybrid structures consisting of an azobenzene compound grafted on the surface of zinc oxide nanoparticles. Characteristic bathochromic shifts indicate that the azobenzene photochromic molecules self-assemble onto the surface of the nanocrystals. The extent of packing is dependent on the shape of the nanoparticle. ZnO nanorods, with flat facets, enable a tighter organization of the molecules in the self-assembled monolayer than in the case of nanodots that display a more curvated shape. Consistently, the efficiency of photochromic switching of the self-assembled monolayer on ZnO nanoparticles is also shown to be strongly affected by nanoparticle shape. 相似文献
980.
Zeglinski J Nolan M Bredol M Schatte A Tofail SA 《Physical chemistry chemical physics : PCCP》2012,14(10):3435-3443
Strontium can be substituted into the calcium sublattice of hydroxyapatite without a solubility limit. However, recent ab initio simulations carried out at 0 K report endothermic nature of this process. There is also striking discrepancy between experimentally observed preference of Sr doping at Ca-II sites and the first principles calculations, which indicate that a Ca-I site is preferred energetically for the Sr substitution. In this paper we combine insights from Density Functional Theory simulations and regular configurational entropy calculations to determine the site preference of Sr doping in the range of 0-100 at% at finite temperatures. In addition, samples of Sr-HA are synthesized and refinement of the relevant structural information provides benchmark information on the experimental unit cell parameters of Sr-HA. We find that the contribution of the entropy of mixing can efficiently overcome the endothermic excess energy at a temperature typical of the calcining step in the synthesis route of hydroxyapatite (700-950 °C). We observe that the most preferential substitution pattern is mixed substitution of Sr regardless of the concentration. For a wet chemical method, carried out at a moderate temperature (90 °C), the mixed doping is still slightly favourable at higher Sr-concentrations, except the range at 20% Sr, where Site II substitution is not restricted energetically and equally possible as the mixed doping. We observe a close correspondence between our theoretical results and available experimental data. Hence it should be possible to apply this theory to other divalent dopants in HA, such as Zn(2+), Mg(2+), Pb(2+), Cu(2+), Ba(2+), Cd(2+) etc. 相似文献