Capillary column gas chromatographic identification of sugars in honey as trimethylsilyl derivatives

A method for identifying carbohydrates (mono-, di- and trisaccharides) in honey is presented. It is based on the separate preparation of both trimethylsilyl ethers and oxime trimethylsilyl ethers of the sugars followed by their gas chromatographic separation on a fused-silica capillary column coated with OV-101 using temperature programming. From the two chromatograms, the number of peaks given by each derivatized sugar, their relative retention times and peak-area ratios are used for identification. The identities of two unidentified trisaccharide peaks are considered. Quantitative applications to honey sugar analysis are discussed.

The pH dependence of the hydrolysis of chromogenic substrates of the type, Lys-Pro-Xaa-Yaa-Phe-(NO2)Phe-Arg-Leu, by selected aspartic proteinases: evidence for specific interactions in subsites S3 and S2

Variation in the kinetic parameters, kcat and Km, with pH has been used to obtain evidence for significant acid-dissociation processes in the hydrolysis of octapeptide substrates by three aspartic proteinases. These substrates are all cleaved at the peptide bond between a Phe (P1) and a p-nitroPhe (P1') residue resulting in a shift in absorbance at 300 nm that facilitates kinetic measurements. The substrates differ in the amino-acid residues present in the P3 and the P2 positions. Porcine pepsin, calf chymosin, and the aspartic proteinase from Endothia parasitica all show pH dependencies that imply that favorable or unfavorable interactions can occur with the S3 or S2 areas of the enzyme-active site. Examination of the crystallographically determined structure of the E. parasitica proteinase and consideration of the amino-acid sequence differences between the three enzymes suggests that the origin of the pH effects arises from favorable interactions between Glu-13 (COO-) of pig pepsin and Thr (OH) or His (ImH+) in P3 of a substrate. Similarly, Lys-220 (NH3+) of chymosin and a Glu (COO-) in P2 of a substrate may produce a favorable interaction and Asp-77 (COO-) of E. parasitica proteinase and a Glu (COO-) in P2 of a substrate may produce an unfavorable interaction. These results lead to possible explanations for subtle specificity differences within a family of homologous enzymes, and suggest loci for study by site-directed mutagenesis.

Duodenal ulceration: review of 110 cases

This paper describes 110 cases of childhood duodenal ulcer, which were diagnosed over 26 years: 63 were diagnosed by barium meal examination; 47 by upper gastrointestinal endoscopy. The mean age at diagnosis was 11.2 years, with symptoms reported in 46% before 10 years and in 15% before 6 years of age. There was often a considerable delay in diagnosis, particularly in the younger age group. Nocturnal pain (61%) and a close family history of duodenal ulcer disease (62%) were the most valuable pointers to the diagnosis. Fifteen children had required surgery for persistent symptoms. Thirty four had received treatment with an H2 receptor antagonist, and all but four had had a satisfactory initial response. Seventy per cent relapsed within six months of discontinuing treatment, and long term maintenance treatment may therefore be necessary.

[Anomalous origin of the left coronary artery. The form in infants]

Twenty-four cases of anomalous origin of the left coronary artery from the pulmonary artery are reported. These cases were collected over 27 years divided into three 9-year periods according to the years of the initial studies. The clinical aspects and diagnostic investigations (notably echocardiography, myocardial radioisotope imaging and various angiographic procedures) are reviewed; aortography seems to be, even now, the best exploratory method. Treatment is analyzed according to the periods of observations. From the earliest cases it may be concluded that ligation proved ineffective in infants and medical treatment often failed. Progressively, medical treatment with digitalis (now better controlled), potassium-sparing diuretics and vasodilators has become more effective. On the other hand, direct reimplantation of the left coronary artery onto the aorta has become the preferred surgical procedure. Among the 8 most recent cases (seen between 1977 and 1986), 4 were cured by medical treatment under the age of 3 and subsequent reimplantation. In the other 4 patients asystolia responded to medical treatment, and these children are now awaiting reimplantation.

Kinetic characterization of dopamine as a suicide substrate of tyrosinase

A kinetic study of the inactivation of frog epidermis tyrosinase by a suicide substrate dopamine hydrochloride is described. The kinetic parameters and constants which characterize this reaction have been determined and the effects of pH and the stoichiometric inhibition by chloride have been considered.

A systematic series of synthetic chromophoric substrates for aspartic proteinases

The hydrolysis of the chromogenic peptide Pro-Thr-Glu-Phe-Phe(4-NO2)-Arg-Leu at the Phe-Phe(4-NO2) bond by nine aspartic proteinases of animal origin and seven enzymes from micro-organisms is described [Phe(4-NO2) is p-nitro-L-phenylalanine]. A further series of six peptides was synthesized in which the residue in the P3 position was systematically varied from hydrophobic to hydrophilic. The Phe-Phe(4-NO2) bond was established as the only peptide bond cleaved, and kinetic constants were obtained for the hydrolysis of these peptide substrates by a representative selection of aspartic proteinases of animal and microbial origin. The value of these water-soluble substrates for structure-function investigations is discussed.

Chemical intermediates in dopamine oxidation by tyrosinase, and kinetic studies of the process

A minor pathway for dopamine oxidation to dopaminochrome, by tyrosinase, is proposed. Characterization of intermediates in this oxidative reaction and stoichiometric determination have both been undertaken. After oxidizing dopamine with mushroom tyrosinase or sodium periodate in a pH range from 6.0 to 7.0, it was spectrophotometrically possible to detect o-dopaminoquinone-H+ as the first intermediate in this pathway. The steps for dopamine transformation to dopaminochrome are as follows: dopamine----o-dopaminequinone-H+----o-dopaminequinone---- leukodopaminochrome--- - dopaminochrome. No participation of oxygen was detected in the conversion of leukodopaminochrome to dopaminochrome. Scanning spectroscopy and graphical analysis of the obtained spectra also verified that dopaminequinone-H+ was transformed into aminochrome in a constant ratio. The stoichiometry equation for this conversion is 2 o-dopaminequinone-H+----dopamine + dopaminochrome. The pathway for dopamine oxidation to dopaminochrome by tyrosinase has been studied as a system of various chemical reactions coupled to an enzymatic reaction. A theoretical and experimental kinetic approach is proposed for such a system; this type of mechanism has been named "Enzymatic-chemical-chemical" (EzCC). Rate constants for the implied chemical steps at different pH and temperature values have been evaluated from the measurement of the lag period arising from the accumulation of dopaminochrome that took place when dopamine was oxidized at acid pH. The thermodynamic activation parameters of the chemical steps, the deprotonation of dopaminequinone-H+ to dopaminequinone, and the internal cyclization of dopaminequinone to leukodopaminochrome have been calculated.

Kinetic study and intermediates identification of noradrenaline oxidation by tyrosinase

Characterization of intermediates formed in the noradrenaline oxidation by mushroom tyrosinase and sodium periodate has been performed by rapid scanning spectrophotometry and graphical analysis of obtained spectra. In a pH range from 5.0 to 6.0, it has been possible to detect o-noradrenalinequinone-H+ as the first intermediate in these oxidations. The following steps for noradrenaline transformation into noradrenochrome would be: noradrenaline----o-noradrenalinequinone-H+----o- noradrenalinequinone----leukonoradrenochrome----noradreno chrome. It has been also verified that o-noradrenalinequinone-H+ is transformed into noradrenochrome at a constant ratio. The stoichiometry for this converstion followed the equation: 2-noradrenalinequinone-H+----noradrenaline + noradrenochrome. The pathway between noradrenaline and noradrenochrome has been studied as a system of various chemical reactions coupled to an enzymatic reaction. We have denominated this type of mechanism as an enzymatic-chemical-chemical mechanism, (E2CC). Whole rate constants for the implicated chemical steps at different pH and temperature values have been evaluated from measurement of the lag period arising from the accumulation of noradrenochrome that takes place when noradrenaline was oxidized at pH 5-6. The lag period was independent on enzyme concentration, but was increased when pH and/or temperature were increased. Rate constants pH independent for the deprotonation of noradrenalinequinone-H+ into noradrenalinequinone and for the internal cyclization of noradrenalinequinone into leukonoradrenochrome have been obtained. We conclude that this minor pathway of noradrenaline oxidation by tyrosinase follows a scheme similar to that established for L-dopa.

Colorimetric measurement of glycosylated protein in whole blood, red blood cells, plasma and dried blood

A colorimetric method for the measurement of whole-blood glycosylation (WBG), glycosylated haemoglobin in red blood cells (GHb), glycosylated plasma protein (GPP) and dried-blood glycosylation (DBG) is described which is rapid, inexpensive and precise. GHb correlated well with HbA1 measured by cation-exchange chromatography and was also correlated with WBG, DBG and GPP. DBG, which showed good correlation with GHb, could be measured on several drops of blood dried on filter paper treated with glucose oxidase. Filter papers are posted to the laboratory prior to clinic visits, and by having the DBG result available more rational diabetic management is possible. For DBG, the intra- and inter-assay coefficient of variation at three levels is less than 6%. Reference values in non-diabetic children have been calculated and are compared with values obtained in 'good' clinical diabetic control and in 'fair' control. The filter-paper assay DBG method has a high degree of patient acceptance.

Effect of bile and bile acids on binding of intrinsic factor to cobalamin and intrinsic factor-cobalamin complex to ileal receptor

Human bile or commercially available bile acids bind [57Co]cobalamin (Cbl) due to the presence of "R"-type binders, which are normally present in the former and present as a contaminant in the latter. The competition of these R proteins for the binding of Cbl by intrinsic factor (IF) could explain the in vivo inhibition attributed previously to the bile acids themselves. R protein seems to be involved in the inhibition of Cbl binding because protease digestion of either bile or bile acid abolishes the Cbl binding ability. Moreover, antibody to R protein abolishes the inhibition. Bile or bile acids do not have a direct effect on either purified IF or the IF-Cbl receptor molecule, even though bile acids increase the attachment of IF-[57Co]Cbl to ileal brush-border membranes. These data demonstrate two steps where components of bile could affect Cbl absorption: the binding of Cbl to IF and of IF-Cbl to its ileal receptor. It is not clear whether these in vitro phenomena are important for the normal absorption of Cbl in vivo.

In vivo evidence that intrinsic factor-cobalamin complex traverses the human intestine intact

Ingested cyano[57Co]cobalamin was recovered as coupled to intrinsic factor from the jejunum of healthy humans. This vitamin-protein complex and the analogous complex from patients having exocrine pancreatic insufficiency were indistinguishable from each other in terms of molecular radius (3.30 nm), ionic nature (eight well-defined isoproteins isoelectric at pH 4.71, 4.84, 4.90, 5.13, 5.23, 5.31, 5.40 and 5.69), and antigenic structure. These findings indicate that the pancreatic proteases do not alter the intrinsic factor cobalamin complex in vivo. Purified R type protein-cyano [57Co]cobalamin complex recovered from patients with exocrine pancreatic insufficiency was similar to the analogous gastric protein in terms of molecular radius (alpha = 4.78 nm) and types of isoproteins (seven well-defined isoproteins isoelectric at pH 2.70, 3.03, 3.38, 3.74, 3.87, 4.05 and 4.20). However, this R protein complex from patients and the intrinsic factor complex from both control subjects and from patients was comprised of more of the acidic type of isoproteins, thereby supporting the notion that carbohydrate-rich isoproteins are more resistant to digestion in the intestine.

A derivative of R-type cyanocobalamin binding proteins in the human intestine. A candidate antibacterial molecule

Human jejunal fluid contains a protein which has a molecular radius of 3.37 nm, an Mr or 60600 and a mean pI of 3.35 and binds cobalamin with a K of 0.1 . 10(9) l/mol. This protein also couples cobalamin analogues lacking the nucleotide moiety, cross-reacts with R-type protein and is resistant to proteolysis in the intestine. These findings refute the hypothesis that cobalamin-analogue binders are present and effectively inhibit the bacterial uptake of analogues in the intestine.

Cobalamin malabsorption due to nondegradation of R proteins in the human intestine. Inhibited cobalamin absorption in exocrine pancreatic dysfunction

In vivo studies demonstrate that the pancreatic enzymes and the ionic environment in the upper gastrointestinal tract are essential determining factors for transport and absorption of cobalamin in man. Jejunal fluid was aspirated from healthy human volunteers after administration of cyano[57Co]cobalamin preparations. Immunochemical analysis of the aspirates demonstrated that all isotopic vitamin was transferred to a protein that is identical to the gastric intrinsic factor in terms of molecular mass (57,500), ionic nature (mean pI, 5.09), and reactivity with anti-intrinsic factor sera. However, in the aspirates from patients with exocrine pancreatic dysfunction the vitamin was found to be coupled > 60% to a protein identical to R proteins in terms of molecular mass (125,000), ionic nature (mean pI, 3.51), and reactivity with anti-R protein and anti-intrinsic factor sera. The preferential transfer of cobalamin to R proteins in the patients and to intrinsic factor in healthy subjects was associated, respectively, with low and normal levels of pancreatic enzymes in the intestine and these in turn were paralleled respectively by impaired and normal ileal absorption of cobalamin. These findings confirm the suggestion that the formation of unabsorbable cobalamin complexes may be the reason of impaired vitamin absorption in exocrine pancreatic insufficiency. Observations made with other selected patients demonstrate: (a) that decreased enzyme activity and nondegradation of R proteins may also be due to nonactivation of pancreatic zymogens in an acidic pH of the intestinal juice the vitamin transported to the jejunum couples to intrinsic factor when pancreatic function is normal, and to intrinsic factor and R protein in exocrine pancreatic insufficiency. The observations made with these selected patients may explain why not all patients with exocrine pancreatic insufficiency develop imparied cobalamin absorption, and also why the malabsorption is corrected by the administration of bicarbonate in certain patients.

Triple X female and Turner's syndrome offspring

A mentally retarded young female having 47 chromosomes with a triple X karotype produced a child with Turner's syndrome associated with mental defeciency. To our knowledge this is the first example of a triple X female giving birth to a child with Turner's syndrome.