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The influence of wine polymers on the spontaneous precipitation of calcium tartrate in a model wine system has been examined. Rhamnogalacturonan-I was identified as the most effective inhibitor (precipitation induction time of 180 min compared with 7 min for the standard model). It is argued that this is a consequence of rhamnogalacturonan-I's ability to participate in the 'egg-box' type sequestration of calcium ions. The more structurally complex rhamnogalacturonan- II had only a minor influence on the induction time (22 min). Arabinogalactan proteins and mannoproteins also have little influence with induction times ranging from 12 to 15 min. An ultra-filtration study of four Chardonnay wines, prepared with and without the use of pectolytic enzymes, was performed in a search for conditions that might maximise the concentration of rhamnogalacturonan-I. However, rhamnogalacturonan-I could not be identified in any of the four wines. Implications of these observations, specifically the need to understand the inhibition exerted by specific uronic acids, for winemaking and calcium tartrate precipitation are discussed. [ABSTRACT FROM AUTHOR]

The rhamnogalacturonan-II dimer (dRG-II) forms strong complexes in vitro with lead (Pb) and other selected cations. We examined the in vivo bioavailability of Pb complexed with dRG-II and the effect of unleaded dRG-II on the intestinal absorption and tissue retention of Pb in rats. Forty male Wistar rats were divided into four groups. Each group consumed a purified control diet for 3 wk or the same diet supplemented with: i) 3 mg of Pb/kg, ii) 0.5 g of leaded dRG-II/kg, or iii) 0.5 g of leaded dRG-II/kg and 4.5 g of unleaded dRG-II/kg. The leaded dRG-II provided approximately 3 mg of Pb/kg of diet. A chemical balance study was conducted during the last 5 d of the 3-wk study, and blood and organs were sampled for Pb and mineral analyses. The apparent intestinal absorptions of Pb were 62.3, 15.2, 11.8 and -0.1%, and Pb balances were 1.9, 9.6, 5.6 and -0.2 microg/d for the control and the three experimental groups, respectively. The Pb complexed with dRG-II was less available than Pb acetate, as reflected by significantly lower blood and tissue Pb levels. The addition of unleaded dRG-II decreased the intestinal absorption and the tissue retention of Pb significantly. We further found that the apparent absorption and status of magnesium, zinc and iron were unaffected by Pb treatment or dRG-II addition. We conclude that dRG-II may be useful in decreasing toxicity related to chronic Pb exposure. Human studies will be necessary however, to further evaluate the clinical utility of this beneficial effect. [ABSTRACT FROM AUTHOR]

Rhamnogalacturonan II (RG-II) is a structurally complex pectic mega-oligosaccharide that is released enzymatically from the primary cell wall of higher plants. It contains roughly 30 monosaccharide units (MW ∼5 kDa) including very unusual residues such as Kdo, Dha, aceric acid and apiose. Previous studies have demonstrated that these monomers are arranged into four structurally well-defined oligosaccharide side chains (A–D), linked to a homogalacturonan mainchain, but the specific attachment sites of these branches on the pectic backbone have not yet been elucidated. In the present work, fairly complete assignments of the 750 MHz 1 H NMR spectra and partial assignments of the 13 C NMR spectra of the sodium-borohydride-reduced RG-II monomer were obtained for a 5 mM sample isolated from red wine. On the whole, these data corroborate the primary structures of the sidechains previously established by methylation analysis, partial hydrolysis and FAB-MS spectrometry but some heterogeneity has been demonstrated (partial substitution at B5, B6, and A5). The preferred orientations of the majority of the sidechain glycosidic linkages in the RG-II monomer have been determined from the sequential nOe data and the solution structure is generally in good agreement with the stable conformers previously obtained by molecular modeling (MM3) of the disaccharide and sidechain oligosaccharide building blocks. All of a two-residue, a three-residue, and a four-residue segment of the backbone have been tentatively identified from long range interactions between sidechain protons as well as in the mainchain. Taking into account the length of the 9-mer galacturonan mainchain described in prior work, these building blocks constitute almost the complete structure of RG-II (Scheme 2). [ABSTRACT FROM AUTHOR]

This study describes the identification of aqueous-soluble antigens in Leishmania promastigotes immunologically and biochemically closely related to the major surface antigen. Proteins from surface-iodinated L. braziliensis braziliensis and L. donovani chagasi promastigotes, extracted and separated by partitioning in the detergent Triton X-114, were analyzed. Immunoblotting of the extracted proteins, using homologous antisera, showed recognition of a 72-kDa labeled, amphiphilic antigen of L. b. braziliensis and a 65-kDa surface antigen of L. d. chagasi. The respective homologous sera also recognized non-labeled hydrophilic antigens, similar in their apparent molecular weights to the major surface antigens. The amphiphilic and hydrophilic antigens of each species were found to share common antigenic determinants, inasmuch as monospecific antibodies that recognized the amphiphilic protein reacted with the hydrophilic antigen. Structural homology was also obtained in the peptide-digestion profiles of the amphiphilic and the respective hydrophilic major antigens. Zymogram assay showed that both amphibilic and hydrophilic fractions displayed proteolytic activity that could be directly attributed to the major L. b. braziliensis and L. d. chagasi antigens. The hydrophilic antigens found in this study are probably not hydrolytic products of the surface antigens and occur in large quantities in the promastigote cytosol. [ABSTRACT FROM AUTHOR]