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1.
Enzyme-catalyzed hydrolyzations of starch by α-amylase have been studied in various two-phase systems, consisting of water
and a water-immiscible organic solvent. The hydrolytic conversion of soluble starch to malto-oligosaccharides by α-amylase
was greatly accelerated in 10% (v/v) water content of water-dodecane two-phase systems. However, a rapid inactivation of the
enzyme has been observed in these systems. Addition of surfactant to these systems, such as polyoxyethylene (20) sorbitan monopalmitate (Tween 60) or bis(2-ethylhexyl) sodium sulfosuccinate (AOT), was effective for the enzyme stability.
Effects of enzyme immobilization on the stability of α-amylase, using Ca-alginate and chitosan beads, also have been studied.
The stability of immobilized enzyme was clearly enhanced in a 5–10% (v/v) water content two-phase system, whereas the free
enzyme was inactivated within 41 h, remaining at a relative activity of 47–76% after 41 h of treatment. Furthermore, scanning
electron micrographs (SEM) were taken to observe the effect of the two-phase system on the hydrolysis of starch. Potato starch
granules have been extremely swelled and burst out in the stirred 10% (v/v) water content system, which did not contain enzymes. 相似文献
2.
K. T. Normurodova Sh. Kh. Nurmatov B. Kh. Alimova O. M. Pulatova Z. R. Akhmedova A. A. Makhsumkhanov 《Chemistry of Natural Compounds》2007,43(4):454-457
Partially purified enzyme preparation with specific activities of 153.7 U/mg for α-amylase and 0.15 U/mg for protease was
produced by selective adsorption on starch. Enzymes were purified until homogeneous electrophoretically by gel-filtration
over HW-55 TSK-gel with specific activities of 245 U/mg for α-amylase and 1.44 U/mg for protease. The optimum temperature
and pH for purified α-amylase activity are 40–50°C and pH 6.0. The effects of various metal ions on the activity and stability
of the enzyme were studied.
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Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 374–376, July–August, 2007. 相似文献
3.
Three strains ofBacillus licheniformis were isolated and screened for α-amylase production by solid-state fermentation. Of these, IS-2 gave relatively higher enzyme
production (32±2.3 U/[g·min]) and was selected for improvement after treatment withN-methylN-nitroN-nitroso guanidine (NG) or nitrous acid (NA) to enhance its hydrolytic potential. Among the mutant variants, NA-14 gave higher
enzyme production (98±1.6 U/[g·min]), and hence, was selected for kinetic and thermal characterization. M1 as a moistening
agent (pH 7.0, optimized) supported 2.65-fold improved amylolytic activity by the derepressed mutant 72 h after inoculation.
The values of product yield coefficient (Y
p/x=1833.3 U/g) and specific rate constant (q
p=25.46 U/[g·h]) with starch were severalfold improved over those from other carbon sources and the other cultures. The purified
enzyme from NA-14 was most active at 40°C; however, the activity remained almost constant up to 44°C. The NA-induced random
mutagenesis substantially improved the enthalpy (ΔH
D=94.5±11 kJ/mol) and entropy of activation (ΔS=−284±22 J/[mol·K]) for α-amylase activity and substrate binding for starch hydrolysis. The results of this study (117.8±5.5
U/[g·min]) revealed a concomitant improvement in the endogenous metabolism of the mutant culture for α-amylase production. 相似文献
4.
H. Brückner 《Chromatographia》1987,24(1):725-738
Summary The enantiomeric resolution of N-methyl-DL-α-amino acids (NMe-AA) and DL-α-alkyl-α-amino acids (AAA) was achieved by ligand-exchange
(LE) high performance liquid chromatography (HPLC) using silica bonded L-amino acids as the chiral selector (Chiral ProCu,
Chiral HyproCu, Chiral ValCu, Nucleosil Chiral-1). Using aqueous solutions of copper sulfate or acetate adjusted to pH 4–6
and the addition of acetonitrile (10–20%) or methanol (10–40%), baseline resolution occurred in many cases. By comparison
with enantiomers of known optical configuration, the elution order of a number of NMe-AA and AAA could be determined and on-line
polarimeter detection enabled the assignment of the optical rotation, elution order and configuration of AAA enantiomers.
Using a preparative column (300mm × 20mm i.d.) packed with Chiral ProCu, a baseline resolution of 60mg DL-α-methylphenylalanine
was achieved. Further, LE-TLC, using a chiral stationary phase (“Chiralplate”), enabled the chiral separation of very hydrophobic
AAA, characterized by increasingly large alkyl side chains,viz. the homologous series α-ethylalanine to α-nonylalanine and α-propyl-α-amino-n-butyric acid to α-hexyl-α-amino-n-butyric acid.
Presented at the Eleventh International Symposium on Column Liquid Chromatography, June 28–July 3, 1987, Amsterdam, The Netherlands.
Parts of the results have also been presented at ANAKON ’87, May 11–14, Baden-Baden, FRG, and the Tenth American Peptide Symposium,
May 23–28, 1987, St. Louis, MO, USA. 相似文献
5.
G. D'Andrea V. Mucciante F. Fantauzzi 《Journal of Thermal Analysis and Calorimetry》2001,65(3):737-743
At 298.15 K, the solubilization of hen ovotransferrin at buffered pH 7.8 (0.08 M Tris⋅HCl buffer, containing 0.1 M CaCl2) and the solubilization of α-chymotrypsin (from bovine pancreas) at non-buffered pH 3.0 (0.001 M HCl) both resulted in large
exothermic reactions, being the apparent ΔHs –2485 in the first case and –780.1 kJ mol–1 in the second case, respectively. By contrast, the complete hydrolysis of ovotransferrin (pH 7.8) achieved by using a-chymotrypsin
(pH 3.0) gave an endothermic reaction with ΔH=+31.84 kJ mol–1.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Konsoula Z Liakopoulou-Kyriakides M Perysinakis A Chira P Afendra A Drainas C Kyriakidis DA 《Applied biochemistry and biotechnology》2008,149(2):99-108
A hyperthermophilic α-amylase encoding gene from Pyrococcus woesei was transferred and expressed in Xanthomonas campestris ATCC 13951. The heterologous α-amylase activity was detected in the intracellular fraction of X. campestris and presented similar thermostability and catalytic properties with the native P. woesei enzyme. The recombinant α-amylase was found to be stable at 90 °C for 4 h and within the same period it retained more than
50% of its initial activity at 110 °C. Furthermore, X. campestris transformants produced similar levels of recombinant α-amylase activity regardless of the carbon source present in the growth
medium, whereas the native X. campestris α-amylase production was highly dependent on starch availability and it was suppressed in the presence of glucose or other
reducing sugars. On the other hand, xanthan gum yield, which appeared to be similar for both wild type and recombinant X. campestris strains, was enhanced at higher starch or glucose concentrations. Evidence presented in this study supports that X. campestris is a promising cell factory for the co-production of recombinant hyperthermophilic α-amylase and xanthan gum. 相似文献
7.
G. Kh. Khisamutdinov G. G. Rozantsev V. I. Slovetsky A. A. Fainzilberg 《Russian Chemical Bulletin》1998,47(8):1605-1606
Difluoroamine does not react with tetranitromethane and fluoro-, chloro-, and bromotrinitromethanes in DMF and in acidic media
(CF3COOH, ClSO3H, FSO3H, and oleum), but reacts with α-fluoro- and α-(difluoroamino)-α,α-dinitrotoluenes to give substitution products of the difluoroamino
group for both the nitro groups,viz., PhC(NF2)2F and PhC(NF2)3, respectively.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1647–1649, August, 1998. 相似文献
8.
I. M. Chung Mohd Ali A. Ahmad C. Y. Yu K. H. Ma J. G. Gwag Y. J. Park 《Chemistry of Natural Compounds》2005,41(6):650-653
One new compound 3,7,11,15,19-pentamethyl-9α,10α,11α,17α,18α-pentahydroxy-n-tetracosan-1-oxy-p-hydroxycaffeoate (oryzaterpenyl
caffeoate) (1), together with three known fatty acids linoleic acid, stearic acid and myristic acid were isolated and identified from the
rice grain of Oryza sativa. The structure of the new compound was elucidated by 1D and 2D NMR spectroscopic techniques (1H-1HCOSY, 1H-13C HETCOR) aided by EI-MS, and IR spectra.
__________
Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 535–537, November–December, 2005. 相似文献
9.
F. I. Guseinov 《Russian Chemical Bulletin》1998,47(4):663-665
α,α-Dichloro-β-oxoaldehyde diethyl acetals decompose under the action of bases (NaOH, MeONa) with cleavage of the carbon-carbon
bond and formation of carboxylic acids or their esters and the dichloroacetaldehyde diethyl acetal carbanion. The latter reactsin situ with benzaldehyde to form stable α-chloro-α,β-epoxyacetal. α-Chloro-α-formyl-γ-butyrolactone diethyl acetal is transformed
into α-chloro-α-diethoxymethyl-γ-hydroxybutyric acid under the action of an alkali.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 685–687, April, 1998. 相似文献
10.
Florêncio José A. Eiras-Stofella Daura R. Soccol Carlos R. Raimbault Maurice Guyot Jean P. Fontana José D. 《Applied biochemistry and biotechnology》2000,84(1-9):721-730
The microheterogeneous native amylolytic complex secreted by the isolate A6 of Lactobacillus plantarum revealed a selective enzyme specificity loss when submitted to a limited proteolysis under a suboptimum pH condition. A clear
electrophoretic profile change toward just one shorter, more acidic, and equally active polypeptide fragment resulted from
the pronase E pretreatment. Although the whole enzyme activity remained apparently unaffected for soluble starch, the native
parallel activity on intact and nongelatinized starch granules either from cereals or tubers was dramatically reduced. This
phenomenon was more clearly documented by scanning electron microscopy using the easiest accessible native substrate: wheat
starch granules. The anion-exchange-purified native enzymes from L. plantarum displayed a different optimum pH curve when compared with the thermotolerant α-amylase from Bacillus licheniformis. The α-amylases from the lactic-acid-producing A6 isolate presented an electrophoretic profile easily distinguishable from
those from B. liqueniformis and B. subtilis species. 相似文献
11.
The purified α-amylase of Geobacillus thermoleovorans had a molecular mass of 26 kDa with a pI of 5.4, and it was optimally active at 100 °C and pH 8.0. The T
1/2 of α-amylase at 100 °C increased from 3.6 to 5.6 h in the presence of cholic acid. The activation energy and temperature
quotient (Q
10) of the enzyme were 84.10 kJ/mol and 1.31, respectively. The activity of the enzyme was enhanced strongly by Co2+ and Fe2+; enhanced slightly by Ba2+, Mn2+, Ni2+, and Mg2+; inhibited strongly by Sn2+, Hg2+, and Pb2+, and inhibited slightly by EDTA, phenyl methyl sulfonyl fluoride, N-ethylmaleimide, and dithiothreitol. The enzyme activity was not affected by Ca2+ and ethylene glycol-bis (β-amino ethyl ether)-N,N,N,N-tetra acetic acid. Among different additives and detergents, polyethylene glycol 8000 and Tween 20, 40, and 80 stabilized
the enzyme activity, whereas Triton X-100, glycerol, glycine, dextrin, and sodium dodecyl sulfate inhibited to a varied extent.
α-Amylase exhibited activity on several starch substrates and their derivatives. The K
m and K
cat values (soluble starch) were 1.10 mg/ml and 5.9 × 103 /min, respectively. The enzyme hydrolyzed raw starch of pearl millet (Pennisetum typhoides) efficiently. 相似文献
12.
Zh. V. Zhilina V. V. Gumenyuk Yu. S. Nekrasov V. N. Babin L. V. Snegur Z. A. Starikova A. I. Yanovsky 《Russian Chemical Bulletin》1998,47(9):1781-1784
9-(α-Ferrocenylethyl)adenine was prepared by the reaction of adenine with α-hydroxyethylferrocene in a two-phase aqueous-organic
medium in the presence of HBF4. The structure of the resulting compound was established by X-ray diffraction analysis.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1828–1831, September, 1998. 相似文献
13.
Cyclopentanone or cyclohexanone were condensed with aromatic aldehydes to give corresponding α,α′-bis(R-benzylidene)cyclopentanones or α,α′-bis(R-benzylidene)cyclohexanones. The reaction was catalyzed by potassium hydrogen sulfate with a yield of 84–95% under
solvent-free conditions. 相似文献
14.
Klaus Burger Jan Spengler Lothar Hennig Rainer Herzschuh Samy A. Essawy 《Monatshefte für Chemie / Chemical Monthly》2000,131(5):463-473
Summary. Homochiral Nα-methyl-2,3-diaminopropionic and Nα-methyl-2,4-diaminobutyric acid derivatives 8a,b were obtained via a stereoconservative four-step synthesis starting from hexafluoroacetone protected L-aspartic and L-glutamic acid 2a,b, respectively. Hexafluoroacetone protected ω-isocyanato-α-methylamino acids 4a,b– the key intermediates of the synthesis – are versatile building blocks for amino acid and peptide modification and promising
candidates for combinatorial chemistry. Upon reaction with alcohols, compounds 4 give activated N
ω-urethane protected ω-amino-α-methylamino acid derivatives 5–7; upon reaction with amines, ω-ureido-α-methylamino acid derivatives 10–12 and 3-methylamino-pyrrolidin-2-ones 13 are available.
Received November 17, 1999. Accepted November 26, 1999 相似文献
15.
P. P. Onys'ko 《Russian Chemical Bulletin》1998,47(9):1763-1767
N-(α-Hydroxypolyhaloalkyl)amides react with trivalent phosphorus chlorides to give α-(acylamino)polyhaloalkylphosphoryl compoundsvia phosphorotropic rearrangement of intermediate phosphites or phosphinites.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1810–1814, September, 1998. 相似文献
16.
Electrophilic cyclization of β-geranyl acetate promoted by mercury(II) trifluoroacetate leads to mixtures of α- and γ-5αH-cyclogeranyl acetate derivatives and 6α-hydroxy-5αH-and 6α-hydroxy-5βH-cyclogeranyl acetate derivatives mercurated at the C-3 atom. The ratio of the unsaturated and hydroxymercurated products
depends on the reaction conditions. α-Geranyl acetate reacts with mercury(II) trifluoroacetate to give a mixture of 6α-hydroxy-5αH-and 6α-hydroxy-5βH-geranyl acetates, mercurated at C-9, with an equatorial mercurated methylene group at C-4. The mercury-containing groups
in mercurated cyclogeranyl derivatives can easily be reduced or replaced by an oxygen-containing functional group; this constitutes
a convenient route to polyfunctional cyclogeranyl derivatives that are difficult to obtain.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1320–1324, July, 1997. 相似文献
17.
Francesco Alfani Maria Cantarella Nicoletta Spreti Raimondo Germani Gianfranco Savelli 《Applied biochemistry and biotechnology》2000,88(1-3):1-15
α-Chymotrypsin (α-CT) activity was tested with N-glutaryl-l-phenylalanine p-nitroanilide in buffered media with added cationic surfactants. The effect of the commercial cetyltrimethylammonium
bromide (CTABr) was compared with that of three other surfactants with ethyl (CTEABr), propyl (CTPABr), and butyl (CTBABr)
head groups. These were synthesized and purified in this laboratory. Surfactant head groups provided distinct environments
that largely modulated the catalytic performance. Larger alkyl head group hydrophobicity led to a marked enhancement of α-CT
activity. CTBABr-rich media induced the highest superactivity.
Kinetic measurements were performed in Tris-HCl buffer at a surfactant concentration either below or above CMC, and α-CT superactivity
occurred in both media. Positive interactions between the enzyme and surfactants happened independently of thesupramolecular
organization of the medium. The reaction followed the Michaelis-Menten kinetics. The substrate to micelle aggregates binding
constant was used to calculate the substrate concentration available for catalysis. The k
cat to k
m ratio was in CTBABr-rich media always higher than in pure buffer and depended on the surfactant concentration. α-CT superactivity
depended on the pH value of buffer solution. Enzyme inactivation followed a single-step mechanism in pure buffer and a series
mechanism in the presence of a surfactant. The rate of activity decay obeyed a first-order kinetics. 相似文献
18.
Summary An HPLC method was developed for the simultaneous assay of intermediate (α-aminonitrile and α-amino acid amide) and end products
(α-amino acid) in process streams of α-amino acid synthesis. Applications are given for Ala, Val and Leu. α-Aminonitriles
were stable in a phosphate buffer pH 3, which was subsequently used for sample handling and chromatography. The α-aminonitrile,
the corresponding acid amide and α-amino acid were separated using a buffered ion-pair mobile phase on an RP column and were
detected fluorimetrically after post-column reaction with fluorescamine. Linearity and precision of the method are given. 相似文献
19.
The hydrolysis of 1,2-dichlorotetramethyldisilane was studied at different temperatures. At reduced temperatures, the hydrolysis
gave permethylcyclo(oxadisilanes) [(Me2Si)2O]n (n = 2 and 3) and α,ω-dihydroxypermethyloligo(oxadisilanes) HO[(SiMe2)2O]mH (m = 1–5). The formation of the latter was proved by the GC-MS method.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 722–724, April, 2006. 相似文献
20.
A. Yu. Sizov A. N. Kovregin R. N. Serdyuk M. V. Vorob’ev V. A. Porosyatnikov A. A. Tsvetkov D. O. Korneev A. F. Ermolov 《Russian Chemical Bulletin》2006,55(7):1200-1208
A route to α-hydropolyfluoroalkanethiols and polyfluorothioacyl halides via thermal splitting of benzyl polyfluoroalkyl sulfides under the action of phosphorus pentoxide was proposed. The thiols obtained
were used as starting materials for the synthesis of α-hydropolyfluoroalkanesulfenyl chlorides. The properties of the resulting
F,S-containing compounds were studied.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1156–1163, July, 2006. 相似文献