Acyclic tautomers in crystalline carbohydrates: the keto forms of 1-deoxy-1-carboxymethylamino-D-2-pentuloses (pentulose-glycines).

NMR and X-ray diffraction studies on acyclic carbohydrate keto tautomers of N-(1-deoxy-d-erythro-2-pentulos-1-yl)- and N-(1-deoxy-d-threo-2-pentulos-1-yl)glycines (ribulose-glycine, 1 and xylulose-glycine, 2), are reported. In aqueous solutions, both 1 and 2 exist as a tautomeric mixture, with the beta-furanose as a major form, followed by the alpha-furanose and the acyclic keto tautomer. Both 1 and 2 crystallize as zwitterions in the acyclic keto form.

Gestational age standardized nuchal thickness values for estimating mid-trimester Down's syndrome risk.

Objective: Our aim was to develop gestational age standardized indices of fetal nuchal thickening. In addition, we wanted to develop a method for combining nuchal thickness data with maternal age for calculating individual Down's syndrome risk.

Methods: Nuchal thickness was measured prospectively in pregnancies undergoing genetic amniocentesis.

Superoxide free radical generation by Amadori compounds: the role of acyclic forms and metal ions.

Generation of oxygen free radicals by glycated proteins is widely believed to be one of the causes of oxidative stress in diabetes and aging. Metal ion catalysis is regarded as an essential part of the oxidative mechanism. In this work, we also considered an alternative "metal-free" superoxide radical formation by a number of fructose-amino acids (Amadori compounds) derived from glycine and lysine, which represent the simplest models for early glycated proteins.

A blue encrustation found on skeletal remains of Americans missing in action in Vietnam.

A blue encrustation was found on the repatriated remains of three U.S. Servicemen listed as missing in action (MIA) from Vietnam after 28 years.

Inhibition of colony formation in agarose of metastatic human breast carcinoma and melanoma cells by synthetic glycoamine analogs.

We studied the influence of 10 synthetic glycoamine analogs on colony formation in 0.3 and 0.9% agarose by metastatic human breast carcinoma (MDA-MB-435) and melanoma (TXM-13) cells.

Molecular and crystal structure of N-(2-deoxy-D-aldohexos-2-yl)-glycines (Heyns compounds).

Heyns compounds, 2-carboxymethylamino-2-deoxy-D-glucose (1), -mannose (2), and -galactose (3), were prepared by N-carboxymethylation of the corresponding hexosamines and 1 was also prepared via the reaction of D-fructose with glycine. Both 1 and 3 crystallize from aqueous solutions as zwitterions in the alpha-pyranose form and in the 4C1 conformation. Crystalline 1 is nearly isostructural to N-acetylglucosamine, forming stacks of molecules with infinite chains of homodromic hydrogen bonds along the stacks.

Catalysis of reduction of carbohydrate 2-oxoaldehydes (osones) by mammalian aldose reductase and aldehyde reductase.

In mammalian tissues, carbohydrate 2-oxoaldehydes, or 'osones', formed by cleavage of carbohydrate residues from glycated proteins, cause damage to cells and tissues by cross-linking of proteins. In the substrate specificity study reported here, we show that several osones are relatively good substrates for the reduced, unactivated form of aldose reductase (EC 1.1.

The reaction of D-glucose with aminoguanidine.

The reaction of D-glucose with aminoguanidine was examined at pH 7.0 and 37 degrees C (phosphate buffer). Under these conditions, the reaction requires ca.

Crystal structure of an Amadori compound, N-(1-deoxy-beta-D-fructopyranos-1-yl)-glycine ("D-fructose-glycine").

The first crystal structure data on an Amadori compound, N-(1-deoxy-beta-D-fructopyranos-1-yl)-glycine, are reported. The space group is P2(1) with Z = 2 and cell parameters a = 7.246(1), b = 10.

The preparation and characterization of some Amadori compounds (1-amino-1-deoxy-D-fructose derivatives) derived from a series of aliphatic omega-amino acids.

Amadori compounds (1-amino-1-deoxy-D-fructose derivatives) were prepared by reacting D-glucose with a series of aliphatic amino acids. These include Amadori compounds derived from glycine (1), beta-alanine (2), gamma-amino butyric acid (3), delta-aminovaleric acid (4), epsilon-amino-caproic acid (5) and N alpha-formyl-L-lysine (6). In the FAB mass spectra, molecular-ion clusters as well as fragment ions corresponding to loss of water or CO2 molecules were observed.

3-Deoxyfructose concentrations are increased in human plasma and urine in diabetes.

3-Deoxyglucosone (3-DG) is a reactive dicarbonyl sugar thought to be a key intermediate in the nonenzymatic polymerization and browning of proteins by glucose. 3-DG may be formed in vivo from fructose, fructose 3-phosphate, or Amadori adducts to protein, such as N epsilon-fructoselysine (FL), all of which are known to be elevated in body fluids or tissues in diabetes. Modification of proteins by 3-DG formed in vivo is thought to be limited by enzymatic reduction of 3-DG to less reactive species, such as 3-deoxyfructose (3-DF).

Ascorbic acid glycation: the reactions of L-threose in lens tissue.

L-Threose is a significant degradation product of ascorbic acid at pH 7.0 in the presence of oxygen. When compared to several other ascorbate-derived degradation products, it had the greatest ability to glycate and crosslink lens proteins in vitro.

The degradation of L-threose at Maillard reaction conditions.

L-Threose, a comparatively unstable aldose, is produced from L-ascorbic acid in the presence of oxygen and participates vigorously in Maillard reactions, even at comparatively mild conditions. In the present study, the degradation of L-threose at pH 7.0 alone, in the presence of N-alpha-acetyl-L-lysine, and at pH 2.

The extent of N epsilon-(carboxymethyl)lysine formation in lens proteins and polylysine by the autoxidation products of ascorbic acid.

The autoxidation of ascorbic acid (ASA) leads to the formation of compounds which are capable of glycating and crosslinking proteins in vitro. When the soluble crystallins from bovine lens were incubated with ASA in the presence of sodium cyanoborohydride, a single major adduct was observed, whose appearance correlated with the loss of lysine. When polylysine was reacted with equivalent amounts of ASA under the same conditions, this product represented half of the total lysine content after four weeks of incubation at 37 degrees C.

The reaction of some dicarbonyl sugars with aminoguanidine.

The reactions of aminoguanidine (guanylhydrazine) with 3-deoxy-D-erythro-hexos-2-ulose (1a), 3-deoxy-D-glycero-pentose-2-ulose (1b), D-erythro-hexos-2-ulose (1c), and D-glycero-pentose-2-ulose (1d) were examined at 37 degrees at a solution pH of 7.0 (phosphate buffer). For 1a and 1b, two major products were observed and shown respectively to be the 5- and 6-substituted 3-amino-1,2,4-triazine derivatives.

Detection of 3-deoxyfructose and 3-deoxyglucosone in human urine and plasma: evidence for intermediate stages of the Maillard reaction in vivo.

3-Deoxyglucose (3-deoxy-D-erythro-hexos-2-ulose) (3-DG) is a reactive dicarbonyl intermediate involved in the polymerization and browning of proteins by glucose in vitro. Damage to protein by formation of 3-DG in vivo is thought to be limited by enzymes which convert 3-DG to less reactive species, such as 3-deoxyfructose (3-DF). We have developed a sensitive and specific assay for measuring 3-DG and 3-DF in human urine and plasma.

Glycation of lens proteins by the oxidation products of ascorbic acid.

Bovine lens water-soluble proteins were incubated with [I-14C]ascorbic acid (ASA) for 6 days, and the incorporation into protein was measured at daily intervals. Aliquots were also withdrawn to determine the distribution of label among the various ASA oxidation products. A linear incorporation into protein was observed in the presence of NaCNBH3, however, little or no incorporation was seen in its absence.

Detection of Kestoses and Kestose-Related Oligosaccharides in Extracts of Festuca arundinacea, Dactylis glomerata L., and Asparagus officinalis L. Root Cultures and Invertase by C and H Nuclear Magnetic Resonance Spectroscopy.

A previous study (KL Forsythe, MS Feather [1989] Carbohydr Res 185: 315-319) showed that (13)C nuclear magnetic resonance spectroscopy can be used to detect and identify mixtures of 1-kestose and neokestose after conversion to the acetate derivatives. In this study, unequivocal assignments are made for the anomeric carbon and proton signals for the above two trisaccharide acetates as well as for 6-kestose hendecaacetate and for nystose tetradecaacetate (a 1-kestose-derived tetrasaccharide). A number of oligosaccharide fractions were isolated from several plant species, converted to the acetates, and nuclear magnetic resonance spectra obtained.

Modification of galactose and N-acetylgalactosamine residues by oxidation of C-6 hydroxyls to the aldehydes followed by reductive amination: model systems and antifreeze glycoproteins.

Amino acids and peptides have been attached to the C-6 hydroxyls of the galactose and the N-acetylgalactosamine by first oxidizing the C-6 hydroxyls to the aldehydes by galactose oxidase in the presence of small amounts of catalase, followed by reductive amination (alpha-amino group) in the presence of cyanoborohydride. The activity of oxidized antifreeze glycoprotein was greater than 70% of the original, and considerable activity has been retained with some substitutions on reductive amination using cyanoborohydride. The following were some activities retained (as compared with the oxidized antifreeze glycoprotein): Gly, 64; (Gly)2, 88; (Gly)3, 82; (Gly)4, 70; Gly-Gly-NH2, 44; Gly-Glu, 13; Gly-Leu, 40; Gly-Tyr, 57; Gly-Gly-Leu, 50; Gly-Gly-Phe, 30; and Gly-Gly-Val, 35.

The precipitation and cross-linking of lens crystallins by ascorbic acid.

Bovine lens beta-crystallin was incubated with increasing concentrations of sugars and sugar derivatives for a period of 2 weeks in the dark at 37 degrees C. Marked protein precipitation and a browning reaction was observed with both ascorbic acid (ASA) and dehydroascorbic acid (DHA), but little or no reaction was seen with several other sugars and sugar analogs. Similar incubations were carried out with 20 mM ASA, 20 mM DHA and 20 mM glucose, but with increasing amounts of the individual crystallins.