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At least 919 records · Page 51Linked to original sources
PubMed1987

Partial synthesis and properties of a series of N-acyl sphingomyelins.

A series of sphingomyelins (SM) with different chain length fatty acids (C14:0, C16:0, C18:0, C20:0, C22:0, and C24:0) N-linked to the primary amino group of sphingosine have been synthesized starting with bovine brain SM. Two different acid hydrolysis procedures, butanolic HCl (H. Kaller, 1961. Biochem. Z. 334: 451-456) and methanolic HCl (R.C. Gaver and C.C. Sweeley. 1965. J. Am. Oil Chem. Soc. 42: 294-298), were used and the resultant sphingosylphosphocholine (SPC) was converted to SM using two acylation methods: using fatty acid imidazolide to yield the O-acyl, N-acyl SPC, followed by mild alkaline hydrolysis for selective deacylation at the O-acyl linkage, and selective acylation at the amino group of SPC using the free fatty acid in the presence of dicyclohexylcarbodimide. Following chromatographic purification, N-acyl SM were obtained in high yield (80-90%), and were characterized by a combination of thin-layer chromatography, high performance liquid chromatography, chemical analysis, optical rotation, circular dichroism, infrared spectroscopy, 13C NMR, and sphingosine base analysis. The N-acyl SM were chemically homogeneous with respect to fatty acid composition and the sphingosine base composition resembled that of the starting bovine brain SM. However, as a consequence of the epimerization at C-3 of SPC in both acid hydrolysis procedures, the resulting N-acyl SM consisted of mixtures of D-erythro and L-threo sphingomyelins. By differential scanning calorimetry hydrated C14:0 to C24:0 SM exhibited gel-liquid crystal transitions in the range 30-50 degrees C but the chain length dependence was complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Acylation↗
PubMed1979

Quantitative study on anomeric forms of glucose produced by alpha-glucosidases.

Anomeric forms of glucose produced from phenyl alpha-maltoside, maltose, or phenyl alpha-glucoside have been determined quantitatively by simultaneous measurements of optical rotation and reducing power, for eight kinds of glucose-producing 1,4-alpha-glucosyl hydrolases, including glucose-forming amylase from human urine, and alpha-glucosidases from pig serum, honey bee, buckwheat seed, rice seed, sugar beet seed, flint corn seed, and brewer's yeast. All the eight enzymes studied were found to produce alpha-glucose exclusively.

Animals↗
PubMed1985

Purification and identification of Streptomyces aureofaciens lD13 antibiotic.

Complete extraction of S. aureofaciens lD13 antibiotic was achieved by adding n-butanol to the clarified culture filtrate (v/2v) at pH 8.0. Using the column chromatography technique, 85.7% of the initial amount of the antibiotic was obtained in a purified form. Data of the Rf values of the antibiotic in different organic solvents revealed that it belongs to the tetracycline group. The antibiotic was chromatographically analyzed, using the thin-layer technique. UV and IR spectra, optical rotation, melting point as well as 15 colour reactions were also determined.

1-Butanol↗
PubMed1979

[Denaturation of beef liver glutamate dehydrogenase under the action of guanidine hydrochloride and a study of the possibility of the enzyme renaturation].

It was shown that denaturation of beef liver glutamate dehydrogenase under the action of guanidine hydrochloride results in a diplacement of the protein fluorescence maximum from 332 to 349 nm, in a decrease of optical rotation of the protein at 233 nm and in an appearance of negative bands in the difference absorbance spectrum with extrema at 279 and 287 nm. The transition of native enzyme into a denaturated state is observed within a narrow interval of guanidine hydrochloride concentrations. The middle point of the transition corresponds to approximately 2,2 M guanidine hydrochloride. The inactivation kinetics for glutamate dehydrogenase coincide with those of the enzyme spectral properties alterations due to denaturation. The attempts at renaturation of glutamate dehydrogenase by diluting the denaturated enzyme solution or by a dialysis against a buffer solution were unsuccessful.

Animals↗
PubMed1978

Studies on trypsin inhibitors. Part VIII. Synthesis of the protected octatriacontapeptide corresponding to the sequence 15-52 of porcine pancreatic secretory trypsin inhibitor II (Kazal).

The synthesis by fragment condensation of protected peptides corresponding to the amino acid sequences 15-35, 25-52 and 15-52 of porcine pancreatic secretory trypsin inhibitor II (Kazal type) is described. The Rudinger modification of the azide procedure was used in the fragment coupling steps. The tert-butyloxycarbonylheptapeptide hydrazide (sequence 22-28) was reacted with the heptapeptide methyl ester free base (sequence 29-35) and the resulting tert-butyloxycarbonyltetradecapeptide methyl ester after selective deprotection, coupled with the benzyloxycarbonylheptapeptide hydrazide (sequence 15-21) to give the protected peptide methyl ester corresponding to the 15-35 sequence which was then converted to the corresponding hydrazide. The synthesis of the 25-52 sequence was achieved by assembling the protected peptide hydrazide corresponding to the amino acid residues 25-35, with the C-terminal heptadecapeptide 36-52. The resulting protected octaeicosapeptide (sequence 25-52) was selectively deblocked with trifluoroacetic acid and acylated with the benzyloxycarbonyldecapeptide hydrazide 15-24 to give the desired octatriacontapeptide corresponding to sequence 15-52 of the inhibitor. An attempt to prepare the 15-52 sequence through the condensation of fragments corresponding to 15-35 and 36-52 sequences was unsuccessful. The identity and purity of the synthetized peptide derivatives wre established by elemental analysis (in some cases), amino acid analysis, optical rotation, and thin-layer chromatography in two solvent systems. The final products were also evaluated, after partial deprotection with anhydrous hydrogen fluoride or aqueous 90% trifluoroacetic acid, by paper electrophoresis at different pH values.

Amino Acid Sequence↗
PubMedDate not supplied

Metabolism of butalbital, 5-allyl-5-isobutylbarbituric acid, in the dog.

Butalbital, 5-allyl-5-isobutylbarbituric acid, labeled in the 2-position with 14C, was administered to dogs. Ninety-two percent of the radioactivity of the dose was excreted in the urine. The drug and three major urinary metabolites were identified in the urinary excretion of the dog. The major metabolite was 5-isobutyl-5-(2,3-dihydroxypropyl)barbituric acid, which accounted for 50.2% of the dose. Smaller amounts of the unchanged drug (2.6% of the dose) and urea (8.6% of the dose) were present. 5-Allyl-5-(3-hydroxy-2-methyl-1-propyl)barbituric acid, formed by omega-hydroxylation, accounted for 10.1% of the dose; the optical rotation of the 1,3-diethyl derivative was [alpha]D20 = +10.5. Five minor and unidentified metabolities accounted for an additional 10.7% of the dose. A total of 82.2% of the dose was accounted for.

Animals↗
PubMedDate not supplied

Stereochemical aspects of the metabolism of 5-ethyl-5-phenylhydantoin (Nirvanol) in the dog.

Enantiomers of 5-ethyl-5-phenylhydantoin (EPH) were administered to dogs, and urinary metabolites were quantitated. After administration of (R)-EPH, the urinary products included unchanged drug, 5-ethyl-5-(4-hydroxyphenyl)hydantoin (p-EHPH), 5-ethyl-5-(3-hydroxyphenyl)hydantoin (m-EHPH), and an N-glucuronide of EPH. Administration of (S)-EPH gave urinary products consisting of unchanged drug, p-EHPH, m-EHPH, an N-glucuronide of EPH, and a dihydrodiol metabolite, which has been isolated and identified as (5 S)-5-[(3R,4R)-3,4-dihydroxy-1,5-cyclohexadien-1-yl]-5-ethylhydantoin. The levorotatory isomers of p- and m-EHPH have been assigned the (R)-configuration. An unidentified metabolite of EPH has been detected through its reactivity under basic conditions to yield 2-ethyl-2-phenylhydantoic acid, which can be cyclized with acid to EPH. Quantitative studies of the disposition of single oral doses of (R)-, (S)-, and (RS)-EPH by these metabolic routes suggest that the metabolism of one enantiomer is unaffected by the presence of the other enantiomer. Stereoselectivities of metabolic pathways are discussed in relation to stereoselectivities observed for phenytoin metabolism in the dog.

Animals↗
PubMed1978

[Study of the antibiotic parvulomycin. The isolation of alpha,alpha-trehalose and L-glutamic acid].

A non-reducing disugar and amino acid were isolated in the studies on the structure of parvulomycin. The acid hydrolysis of the disugar revealed the presence of 2 moles of D-glucose. Acetylation of the disugar resulted in formation of octa-O-acetyl-alpha,alpha-tregalose, saponification of which resulted in formation of alpha,alpha-tregalose. Its physical parameters, i.e. melting point of the mixed sample, optical rotation, IR-spectrum coincided with those of the authentic alpha,alpha-tregalose. The isolated amino acid proved to be L-glutamic acid on thin-layer chromatography with witness and comparison of the physico-chemical properties of their hydrochlorides.

Acetylation↗
PubMed1983

Beta-thiomaltosides as active site probes for alpha-amylase.

A series of substituted 1-thio-beta-D-maltopyranosides was synthesized and confirmed by elemental analysis, optical rotation, NMR, and liquid chromatography. These compounds were shown by several biochemical techniques to bind to the active site of alpha-amylase. Steady-state kinetic studies showed the compounds to be competitive inhibitors, with affinities lying within the range of the natural ligands, maltose and maltotriose. Affinity chromatography employing p-aminophenyl-1-thio-beta-D-maltopyranoside linked to Sepharose provides a relatively simple procedure for alpha-amylase purification. The binding of p-bromphenyl-1-thio-beta-D-maltoside was observed in crystals of alpha-amylase using X-ray crystallography, and through the use of difference Fourier analysis its interaction at 5.0-A resolution with the active site of the enzyme has been visualized. The inhibitor binds in a long, deep cleft that divides the two major domains of the enzyme. These studies are believed to provide a first step toward the rational design of ligands for the physiological regulation of starch breakdown and utilization through modulation of alpha-amylase activity.

Animals↗