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51.
Creaser E.H.; Murali C.; Britt K.A. 《Protein engineering, design & selection : PEDS》1990,3(6):523-526
By protein engineering we have investigated changes to two aminoacid residues (Trp93 and Ser48) in the substrate pocket of yeastalcohol dehydrogenase 1. Upon changing Thr48 to serine we producedan enzyme which has markedly greater activity towards aliphaticalcohols with chain length up to 8, together with a generalincrease in catalytic activity (V/K). Changes at position 93were less pronounced, with the Phe enzyme being more activethan the parent towards the range of alcohols but with the alanineenzyme showing very little difference from the wild-type. Enzymeswith the double changes at 48 and 93 showed increased activitytowards alcohols with 38 carbons but the increases werenot additive over the single changes. The enzymes with changesat the two positions would metabolize both stereoisomers of2-octanol whereas the parent ADH would attack only one of them.None of the engineered enzymes would attack cyclohexanol oraromatic alcohols. The results are in general agreement withthe prediction that reducing the size of amino acids in thesubstrate pocket would enhance the ability to oxidize alcoholslarger than ethanol. 相似文献
52.
A series of novel copolymer superabsorbents based on monomer acrylamide (AM), potassium methacrylate (KMA), and 2‐hydroxyethyl methacrylate (HEMA) were prepared by copolymerization using ammonium persulfate (APS) as an initiator and N,N‐methylenebisacrylamide (MBA) as a crosslinking agent. The synthetic variables (the monomer concentration, crosslinker concentration, and initiator concentration) were also studied. The experimental results of superabsorbent polymers (SAPs) show a better absorbency in both water and NaCl solutions. The copolymers were characterized by IR spectroscopy. The water retention in the soil was enhanced using the above superabsorbents. The use of SAPs for the growth of groundnut plants was also investigated. SAPs can be considered for water‐managing materials for agriculture and horticulture purposes in desert and drought‐prone areas. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1795–1801, 2002 相似文献
53.
Preparation and surface- active properties of polyoxyethylene-glycol (600) monoesters of fatty acids
T. Chandrasekhara Rao Y. Sita Rama Sastry R. Subbarao Gollamudi Lakshminarayana 《Journal of the American Oil Chemists' Society》1977,54(1):15-16
Polyoxyethyleneglycol (PEG-600) monoesters of undecylenic, lauric, myristic, palmitic, stearic, oleic, ricinoleic and 12-hydroxystearic
acids were prepared in 80-85% yield by reacting PEG with boric acid, esterifying the resultant borate with fatty acid, and
selectively hydrolyzing the borate ester; their surface active properties were evaluated. Increase in acyl chain length increased
the surface tension. The presence of a double bond or hydroxyl group in C18 series improved the wetting and emulsifying proper-ties. Unsaturation in the fatty acid chain reduced the foaming power. 相似文献
54.
G. Venkateswara Rao R. Subbarao K. T. Achaya 《Journal of the American Oil Chemists' Society》1970,47(8):292-294
Hydroxylation of safflower and linseed oils by routes involving halogen compounds is described. A product containing 20.5%
Br was obtained by treatment of safflower oil in CCl4 solution with N-bromosuccinimide (NBS) in presence of benzoyl peroxide and UV illumination. Bromine was totally removed using
Ag2O in 50% dioxan; the resulting hydroxyl value (HV) was only 100, against an expected HV of 180, perhaps because of dehydration
and ether formation. Using other silver salts, bromine replacement with hydroxyl was always incomplete. Such residual bromine
was totally replaced by hydrogen, without altering other characteristics, by treatment of the product with zinc amalgam in
acetic acid. Linseed oil by similar NBS bromination (Br 22.2%) and Ag2O treatment gave a product with Br 2.9%, HV 74, conj. diene 15% and conj. triene 4%. Halogenreplacement difficulties also
attended the hydrobromination of these oils at the double bonds, followed by hydroxylation. Addition of hypochlorous or hypobromous
acid to safflower oil, followed by total replacement of halogen with hydrogen using zinc amalgam, yielded products of HV 75
and 83 respectively. The degree of hydroxylation was only half of that expected from the loss of unsaturation. 相似文献
55.
The Starch–Casein‐based edible films containing with or without neem (Melia azadirachta) extract was prepared. The neem based free films were also heat pressed and all of them were assessed for inhibition of pathogenic organisms namely E. coli, Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Pseudomonas spp., and Salmonella, using disc diffusion assay. The Glass‐transition temperature (Tg) and thermal properties of the films were determined with the help of DSC and DMA. Tensile strength (TS), elongation at break (EAB), water vapor transmission rate (WVTR), and oxygen transmission rate (OTR) of the films were also determined. Incorporation of neem extract to edible film did not affect any of the physical properties except microbial, and the films were effective in inhibiting the growth of pathogens, since the inhibition zones varied from 15 mm as large as 24 mm. However, the heat‐pressed films containing neem extract led higher the Tg, TS, and modulus, while the EAB was marginally affected, indicating the toughening of the film and as expected, the heat pressing of films decreased the WVTR and marginally affected OTR. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3948–3954, 2006 相似文献
56.
Molecular and thermal studies of carbon fiber precursor polymers with low thermal‐oxidative stabilization characteristics 下载免费PDF全文
In this investigation, terpolymers, copolymers, and homopolymer of acrylonitrile with dimethylaminopropyl acrylamide (DMAPA), itaconic acid (IA) viz., poly(acrylonitrile‐ran‐3‐dimethylaminopropyl acrylamide‐ran‐itaconic acid) [P(AN‐DMAPP‐IA)], poly(acrylonitrile‐co‐3, dimethylaminopropyl acrylamide) [P(AN‐DMAPP)] were synthesized with varying amounts of comonomers using solution polymerization process. The chemical structure, composition, bonding network were determined employing infrared, 1H and, 13‐carbon nuclear magnetic resonance spectroscopic techniques. Molecular characteristics of as‐synthesized polymers such as different kinds of average molecular weights, molecular weight distribution were estimated applying solution viscometry and size exclusion chromatography. The influence of comonomers (DMPAA, IA) on the thermal stabilization characteristics of acrylonitrile terpolymers in comparison with copolymers and homopolymers of acrylonitrile were studied using differential scanning calorimetry (DSC), hyphenated thermal techniques (thermal gravimetry coupled with differential thermal analyzer).The DSC curves of P(AN‐DMAPP‐IA) exhibit a distinct broader bimodal peaks with thermal exotherm initiating at as low as 165 °C, and followed by two peaks with temperature difference of 42 °C, releasing the evolved heat at a release rate of 0.7–0.11 J g?1s?1over 10 min as compared to 1.2, 7.5 J g?1s?1 in 4.5, 2 min as observed in P(AN‐DMAPP), polyacrylonitrile, respectively. The thermal stability of P(AN‐DMAPP‐IA) and P(AN‐DMAPP), as evidenced by TGA‐DTA was found to be higher than PAN homopolymers. Specific heat capacity measurements confirmed the DSC results. Bulk densities of P(AN‐DMAPP‐IA) were in the range 0.31–0.35 g/cc. These results confirm the low‐temperature stabilization characteristics and suitability of P(AN‐DMAPP‐IA) as low cost carbon fiber precursor polymers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46381. 相似文献
57.
K. R. Murali 《Journal of Materials Science: Materials in Electronics》2008,19(4):369-371
Cerium oxide(CeO2) thin films were deposited by the sol–gel dip coating technique using cerium chloride, acrylamide and N,N bis methylene acrylamide. The as deposited films were heat-treated at different temperatures in air. X-ray diffraction studies
indicated the films to be of single phase CeO2. Optical bandgap in the range of 3.53–3.60 eV was obtained from optical studies. Laser Raman studies exhibited Raman bands
around 457 cm−1. 相似文献
58.
K. R. Murali J. Abirami T. Balasubramanian 《Journal of Materials Science: Materials in Electronics》2008,19(3):217-222
Zinc sulphide thin films were deposited by the pulse plating technique using AR grade Zinc sulphate and sodium thiosulphate
precursors. The pH of the deposition bath was adjusted to 2. The duty cycle was varied in the range of 20–60%. Total deposition
time was kept constant as 60 min in all the cases. X-ray diffraction studies indicated the formation of single phase cubic
zinc sulphide films. After heat treatment the crystal structure transformed to hexagonal structure. Optical absorption measurements
indicated a band gap values in the range of 3.6–4.0 eV as the duty cycle decreased. EDAX studies yielded a composition of
the films deposited at 50% duty cycle is Zn = 48%, S = 52%. XPS studies indicated the formation of ZnS. The Zn 2p and S 3p
peaks are observed. AFM studies indicated a rms value of surface roughness of 55 nm for the films deposited at a duty cycle
of 60%. 相似文献
59.
60.
G. Murali Dhar B. N. Srinivas M. S. Rana Manoj Kumar S. K. Maity 《Catalysis Today》2003,86(1-4):45-60
Support effects form important aspect of hydrodesulfurization (HDS) studies and mixed oxide supports received maximum attention in the last two decades. This review will focus attention on studies on mixed oxide supported Mo and W catalysts. For convenience of discussion, these are divided into Al2O3 containing mixed oxide supports, TiO2 containing mixed oxide supports, ZrO2 containing mixed oxide supports and other mixed oxide supports containing all the rest. TiO2 containing mixed oxides received maximum attention, especially TiO2–Al2O3 supported catalysts. A brief discussion about their prospects for application to ultradeep desulfurization is also included. An overview of the available literature with emphasis on research carried out in our laboratory form the contents of this publication. 相似文献