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PubMed1989

Structural analysis of glycosyl-phosphatidylinositol antigens of Leishmania major.

Three glycosyl-phosphatidylinositol glycolipids recognized by antibodies from patients with cutaneous leishmaniasis were extracted from Leishmania major promastigotes by hexane:isopropanol and then purified by thin layer chromatography and LH-20 gel chromatography. Structural analysis was carried out using chemical analyses, fast atom bombardment mass spectrometry, and 1H NMR. The major structures deduced can be summarized as follows: (formula: see text) where n = 0, 1, 2; R1 = (CH2)23-CH3; R2 = (CH2)14-CH3 or (CH2)16-CH3. Alkyl-acyl substitutions in the glycerol backbone showed considerable heterogeneity. These three glycolipids belong to a relatively new class of compounds and may represent sequential steps in the biosynthesis of glycosyl-phosphatidylinositols which anchor proteins or other glycoconjugates to Leishmania cell membranes.

Animals↗
PubMed1991

Structural analysis of a glycosylphosphatidylinositol glycolipid of Leishmania donovani.

A glycosylphosphatidylinositol (GPI) glycolipid antigen recognized by sera from patients with visceral leishmaniasis was isolated from Leishmania donovani promastigotes. The carbohydrate moiety was cleaved from the lipid part by digestion with specific phosphatidylinositol phospholipase C. After separation, structural analysis was carried out on the phosphorylated inositol oligosaccharide and the alkylacyl glycerol. The following major structures were found: [formula: see text] The presence of the conserved sequence Man alpha 1-2Man alpha 1-6Man alpha 1-4GlcN-PI of glycosyl phosphatidylinositol protein anchors in this antigen may be consistent with a precursor role of Leishmania glycosyl phosphatidylinositol anchored proteins for this glycolipid.

Animals↗
PubMed1995

Structural analysis of alkaline-soluble polysaccharide, P-1, from the kernels of Prunus mume Sieb. et Zucc.

A polysaccharide fraction extracted with cold 0.5 M NaOH from the kernels of Prunus mume exhibited some biological activities. A polysaccharide, P-1, was purified from the 0.5M NaOH extract by ion-exchange chromatography and gel-filtration. The results of the structural analysis of P-1 to determine the relationship between the activities and the structure are described in this paper. In the mild acid hydrolysis of P-1, the nondialyzable hydrolysate (I-3) believed to be its core portion was obtained. The yield of I-3 was 26.0% and contained 59.8% uronic acid as galacturonic acid (GalA). The neutral sugars of I-3 were composed of rhamnose, xylose and galactose in a molar ratio of 1.0:3.4:0.3 following analysis by gas-liquid chromatography. The molecular weight of I-3 was estimated to be ca. 14000 by gel-filtration on Toyopearl HW55F. I-3 exhibited the mitogenic activity toward spleen cells as well as P-1. These facts appeared to confirm that I-3 was the core part of P-1 and important for its biological activity. I-3 was successfully reduced by the Taylor and Conrad method to avoid so much repetition. Methylation analysis of the reduced hydrolysate by gas-liquid chromatography and gas chromatography-mass spectroscopy showed that the ratio of 1,4-linked galactopyranosyl and 1,3,4-linked galactopyranosyl residues were significantly increased in comparison with native I-3. These results suggested that I-3 was composed of 1,4- and 1,3,4-linked galacturonic acid residues in the main chain.

Animals↗
PubMed1979

Isolation and structural analysis by mass analysed ion kinetic energy spectroscopy of diverse sidechains from steroids of similar tetracyclic carbon skeletons.

The technique of mass analysed ion kinetic energy spectroscopy has been applied to the structural determination of five different substituent sidechains from five steroids of similar ring anatomy. A mass spectrometer of reversed geometry, which permits ion selection according to its mass-to-charge ratio before the ions enter the electric sector, was used to isolate the ion corresponding to the mass of each particular sidechain. Subsequent mass analysed ion kinetic energy spectra of the selected ion demonstrated daughter ions whose compositions were compatible with the structures of the model compounds. This ability to determine the structure of a specific portion of a large molecule and to permit differentiation of minor structural features in a series of compounds, whose major framework is similar, adds a new dimension to the powerful mass analysed ion kinetic energy spectroscopy technique for structural analysis of complex biological molecules.

Chemical Phenomena↗
PubMed1991

Structural analysis of proteins by laser desorption and electrospray mass spectrometry.

The development of electrospray and matrix-assisted laser desorption mass spectrometry has provided protein chemists with tools for peptide and protein structure analysis with unprecedented sensitivity and molecular weight range. The two technologies can be viewed as competitive with respect to their molecular mass determinations, but complementary with respect to their differences in instrumentation, sample preparation methods, and nature of spectra produced.

Animals↗
PubMed1992

Structural analysis of five new monosialylated oligosaccharides from human milk.

The total monosialylated oligosaccharide fraction from pooled human milk was isolated by gel filtration and ion-exchange chromatography. Further separation by HPLC using a mobile phase containing an ion-pairing reagent of triethylamine gave five new monosialylated oligosaccharides. Structural analysis was carried out by chemical analyses, fast atom bombardment mass spectrometry, and 500-MHz NMR spectroscopy. Combined structural data revealed the following new structures: [formula: see text]

Carbohydrate Conformation↗
PubMed1992

Medical knowledge for clinical problem solving: a structural analysis of clinical questions.

Despite technological advances that support wide-ranging access to and transfer of knowledge, practicing physicians continue to underutilize current biomedical literature. This paper explores the nature of clinically applicable medical knowledge through a structural analysis of clinical questions. The author analyzed a set of sixty questions, based on actual online search requests of practicing physicians, for stated and unstated needs, certainty levels, implicit and explicit assumptions, decision-making processes, and type of answer required. As a result, four states of information valuable in patient care were identified: prediagnostic assessment, diagnosis, treatment choice, and learning. These states are presented in frame-like structures that integrate declarative and procedural components of medical decision making. It is concluded that clinical problem solving requires a blend of declarative and procedural knowledge. The ratio depends, in part, upon the reasoning process underway at the time of the request. Procedural knowledge required for clinical problem solving may be absent from current biomedical journal literature or difficult to identify.

Decision Making↗
PubMed1991

Structural analysis of phospholipase A2 by near-IR Fourier transform Raman spectroscopy.

Venom toxins were isolated from Formosan cobra (Naja naja atra) by cation-exchange chromatography. Most toxin components could be obtained in relatively pure forms by single-step ion-exchange chromatography whereas an extra step of gel permeation was needed for the separation of phospholipase A2 (PLA2) from the major neurotoxic component, i.e. cobrotoxin. The newer near-IR FT-Raman analytical method has been applied to the characterization of PLA2 in their lyophilized forms. Structural analysis of PLA2 and correlation of Raman spectroscopic data with amino acid compositions were made. The results indicate that phospholipase A2 showed the Raman peak at 1659 cm-1 which is characteristic of the alpha-helical structure in this enzyme. It is also found that the relative Raman signal intensities of Tyr, Phe, Trp and Met residues in purified toxins correlate very well with the structural data obtained from amino acid analysis. The application of near-IR FT-Raman techniques in the detection of the microenvironments of the aromatic amino acids such as Tyr and Trp in the native toxins may prove useful in the investigation of the functional properties of various venom toxins.

Amino Acids↗
PubMed1980

Crossed immunoelectrophoresis and chemical structural analysis used for characterization of two varieties of Escherichia coli K2 polysaccharide antigen.

Crossed immunoelectrophoresis has shown that the Escherichia coli polysaccharide K2 antigen exists in two forms, K2ab and K2a. In confirmation of this finding, chemical structural analysis showed that K2ab, in addition to the galactose, glycerol and phosphate groups common to K2ab and K2a, contained 0 acetyl groups. The contrast between the earlier and the present K2 designation is discussed and the superiority of the CIE technique for this type of analysis is underlined.

Escherichia coli↗
PubMed1990

Isolation and structural analysis of three new disialylated oligosaccharides from human milk.

Five disialylated oligosaccharides, of which three were new compounds, were isolated from pooled human milk. The isolation procedure included gel filtration and ion-exchange chromatography and the final purification was accomplished by HPLC using a mobile phase containing triethylamine as an ion-pairing reagent. Structural analysis was carried out by chemical analyses, fast atom bombardment mass spectrometry, and 500-MHz NMR spectroscopy. The following new structures were found: (formula; see text).

Carbohydrate Conformation↗
PubMed1976

Structural analysis of phosphatidylcholines of Yoshida ascites hepatoma and liver cells from host rats fed a control and an essential fatty acid-deficient diet.

In order to study the effect of a dietetic manipulation on the phospholipid molecular structure of a poorly differentiated tumor, the phosphatidylcholines from Yoshida hepatoma cells (AH130) grown either in essential fatty acid deficient or control rats were analyzed comparatively to those from the host livers. Due to essential fatty acid deficiency, the host rat liver exhibited an increased level of mono-unsaturated 1,2-diacyl-sn-glycero-3-phosphocholines, a reduced level of the species contained linoleic acid, and the substitution of tetra- and polyunsaturated-1,2-diacyl-sn-glycero-3-phosphocholines with equivalent amounts of species containing eicosatrienoic acid. The structural analysis of the phosphatidylcholines from Yoshida hepatoma cells grown either in control or essential fatty acid deficient rats revealed the occurrence of 1-alkyl-2-acyl- together with 1,2-diacyl-sn-glycero-3-phosphocholines. The alkyl chains of ether-linked phosphatidylcholines were mainly constituted by 18 : 1, while the acyl chains were characterized by a high level of linoleic and arachidonic or eicosatrienoic acids. The 1,2-diacyl-sn-glycero-3-phosphocholines of the Yoshida hepatoma cells grown in control rats, when compared to those of the liver, showed a higher level of 1,2-disaturated, an increased proportion of mono-unsaturated and a lower proportion of tetra- and polyunsaturated species. In addition, the hepatoma cells showed the occurrence of high proportions of reverse isomeric and random species, such as 1-oleoyl-2-palmitoyl-, 1,2-dioleoyl-, 1-oleoyl-2-linoleoyl- and 1-linoleoyl-2-oleoyl-sn-glycero-3-phosphocholines, scarcely represented in the liver. Growth of Yoshida hepatoma cells in essential fatty acid deficient rats resulted in :(i) the disappearence of 1,2-diacyl-sn-glycero-3-phosphocholines containing linoleic acid; (ii) the substitution of tetra- and and polyunsaturated 1,2-diacyl-sn-glycero-3-phosphocholines with small quantities of species containing eicosatrienoic acid; (iii) an increase of of monounsaturated species, mainly 1-stearoyl-2-oleoyl- and 1-palmitoyl-2-palmitoleoyl-sn-glycero-3-phosphocholines; (iv) a remarkable increase of 1,2-dioleoyl-sn-1,2-dioleoyl-sn-glycero-3-phosphocholine.

Animals↗
PubMed1979

The CAN1 locus of Saccharomyces cerevisiae: fine-structure analysis and forward mutation rates.

A system of strains and growth media was developed to allow efficient detection of forward mutation, reversion, complementation, and suppression at the canavanine-resistance (CAN1) locus of Saccharomyces cerevisiae. Genetic fine-structure analysis revealed that the map length is at least 40, and possibly as much as 60 X-ray map units; this is the longest gene map yet reported in S. cerevisiae. Allelic complementation was not observed, despite testing of a large number of allele pairs, and alleles suppressible by the ochre suppressor SUP11 were absent from a sample of 48 spontaneous mutants and occurred infrequently (7%) among a sample of ultraviolet-induced mutants. Infrequent mutant types included canavanine-resistant mutants capable of arginine uptake and alleles thought to represent deletions or inversions. In contrast to previous reports in the literature, the spontaneous forward mutation rate at CAN1 did not increase during meiosis.

Alleles↗
PubMed1981

Structural dimorphism of bile salt/lecithin mixed micelles. A possible regulatory mechanism for cholesterol solubility in bile? X-ray structure analysis.

The three-dimensional structure of bile salt/lecithin mixed micelles in 0.15 M saline was derived from X-ray small-angle scattering measurements under various conditions. Two essentially different types of micelles were detected. At bile salt:lecithin molar ratios lower than approximately 2:1, lamellar particles similar to a lecithin bilayer arrangement were found. The thickness of the bilayer is 5.1 nm for mixed micelles having a molar ratio of 1:1. The lateral dimensions of the micelle were found strongly dependent upon molar ratio, increasing as lecithin content increases. In addition, it appeared that under certain incompletely defined conditions vesicular particles having diameters in the region of more than 100 nm occur. A molecular model of this type of micelle has been derived by means of a thorough interpretation of the electron density distribution across the plane of the bilayer. This model is generally consistent with the "mixed-disk" model of Mazer et al. [Mazer, N. A., Kwasnick, R. F., Carey, M. C., & Benedek, G. B. (1977) Micellization, Solubilization, Microemulsions, Proc. Int. Symp. 1, 383-402] and thus differs from that proposed by Small [Small, D. M. (1967) Gastroenterology 52,607-610] and Dervichian [Dervichian, D. G. (1968) Adv. Chem. Ser. No. 84, 78-87]. At molar ratios exceeding 2:1, a different type of micelle structure was found. This is a highly isometrical particle of globular shape, probably having a centrosymmetric arrangement of the molecular constituents. At a 3:1 bile salt:lecithin molar ratio, the mean physiological ratio for human gallbladder bile, the diameter of this micelle is 6.2 nm. Provided that other bile constituents have no significant influence on the structure, it may reasonably be expected that native gallbladder bile contains micelles of this latter type. The prevalent balance between the two micellar forms may thus regulate the capacity of bile to transport cholesterol.

Bile Acids and Salts↗
PubMed1982

Virion DNA of ground squirrel hepatitis virus: structural analysis and molecular cloning.

The structure of the encapsidated DNA genome of ground squirrel hepatitis virus (GSHV) has been examined by restriction endonuclease cleavage, nucleic acid hybridization, and molecular cloning. GSHV virion DNA is a relaxed circular molecule of approximately 3,200 bases in length; most molecules harbor an extensive single-stranded region which is largely confined to one-half of the genome. The full-length viral DNA strand is covalently bound to protein. The single-stranded region can be repaired in vitro by the action of the endogenous virion polymerase, exogenously added DNA polymerase from avian myeloblastosis virus, or both. Restriction enzyme cleavage of viral DNA from different isolates demonstrated that multiple variants of GSHV exist in nature. The genomes of two such strains have been cloned in Escherichia coli, and their physical maps have been determined. Nucleic acid hybridization studies revealed that the strains share sequence homology with the DNA of human hepatitis B virus. Regions homologous to the coding regions for the surface and core antigens of human hepatitis B virus have been localized on the GSHV chromosome. Molecular cloning experiments have also led to the identification of a region of the viral genome which is altered in a procaryotic host.

Animals↗
PubMed1991

Evaluating measurement models in clinical research: covariance structure analysis of latent variable models of self-conception.

Indirect measures of psychological constructs are vital to clinical research. On occasion, however, the meaning of indirect measures of psychological constructs is obfuscated by statistical procedures that do not account for the complex relations between items and latent variables and among latent variables. Covariance structure analysis (CSA) is a statistical procedure for testing hypotheses about the relations among items that indirectly measure a psychological construct and relations among psychological constructs. This article introduces clinical researchers to the strengths and limitations of CSA as a statistical procedure for conceiving and testing structural hypotheses that are not tested adequately with other statistical procedures. The article is organized around two empirical examples that illustrate the use of CSA for evaluating measurement models with correlated error terms, higher-order factors, and measured and latent variables.

Analysis of Variance↗
PubMed1986

Nucleotide sequence of the yeast cell division cycle start genes CDC28, CDC36, CDC37, and CDC39, and a structural analysis of the predicted products.

The nucleotide sequences of the yeast cell division cycle start genes CDC36, CDC37, and CDC39 are presented. An open reading frame corresponding in size and mapped position to the mRNA for each gene was revealed. These sequences, as well as that of the CDC28 gene, were analyzed for the presence of consensus sequences postulated to be transcriptional or translational signals, or to be involved in mRNA processing. In addition, the predicted protein products of the four genes were subjected to a number of structural and statistical analyses including codon usage bias analysis, secondary structure analysis and hydropathicity analysis.

Amino Acid Sequence↗