Influence of non‐enzymatic glycosylation (glycation) of pea (Pisum sativum) albumins on their enzymatic hydrolysis

The aim of this study was to investigate the influence of non‐enzymatic glycosylation (glycation) on the susceptibility of pea albumins to pepsin hydrolysis. It was proved that the aqueous albumin extract is de facto a nucleo‐glyco‐metalloprotein complex. The non‐enzymatic glycosylation of pea albumins decreased the content of nucleic acids, hexoses and zinc, which bound to this protein. Glycated pea albumins were more susceptible to hydrolysis by pepsin than non‐glycated ones. Copyright © 2005 Society of Chemical Industry     

松香基阴离子交换树脂的制备及其对己糖碱性降解色素的吸附作用

蔗糖在生产过程中产生的己糖碱性降解色素（Alkaline degradation products of hexoses,HADPs）会导致成品糖色值增加,从而降低成品糖品质。采用悬浮聚合法制备新型松香基阴离子交换树脂（Rosin-based anionic exchange resin,RAER）,用于除去糖汁HADPs。采用扫描电子显微镜、氮气吸附-脱附比表面积及孔径分布测试仪、同步热分析仪等对RAER进行表征,结果表明树脂孔隙结构丰富且热稳定性好。研究了RAER对HADPs的吸附性能,在树脂投加量为0.05 g/mL,吸附温度为70 ℃,接触时间为10 h,pH值为7及HADPs浓度为100 mg/L,RAER对HADPs的脱色率可达到100%,再生20次后脱色率仍有92.2%,RAER具有良好的重复使用性能。Zeta电位分析表明,RAER吸附HADPs行为存在静电吸引作用（离子交换）。RAER吸附HADPs动力学符合准二级动力学模型（R2≥0.99）,等温线符合Freundlich模型（R2≥0.98）,热力学参数ΔH=62.32 kJ/mol,吸附机理是以化学吸附为主的多层吸热过程。     

Transport of hexoses in yeast. Re-examination of the sugar phosphorylation hypothesis with a new experimental approach

The constitutive transport of hexoses in yeast has been re-examined with a new radioactive experimental approach devised to distinguish between association or independence of the transport step with phosphorylation of the sugar substrate. The approach takes advantage of the fact that the label of [2-³H]mannose disappears once it has been phosphorylated by the yeast, due to its conversion to fructose-6-phosphate. Our results with wild-type yeast and this fermentable sugar support the view that the transport of hexoses in yeast does not involve phosphorylation of the substrate. Other features of the transport process have been examined using this experimental procedure and are also reported.     

Templateless Synthesis of Polygonal Gold Nanoparticles: An Unsupported and Reusable Catalyst with Superior Activity

We report the synthesis of polygonal gold nanoparticles (GNPs) by an in situ reduction technique using ferric ammonium citrate as reducing agent in absence of any surfactant or polymeric template. Transmission electron microscopic analysis and selected area electron diffraction patterns confirmed the formation of well‐crystalline polygonal GNPs grown preferentially along the (111) direction, which is consistent with the results of X‐ray diffractometry analysis. The results of control experiments of HAuCl₄ with tri‐ammonium citrate in presence of different externally added metal ions like Fe³⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Al³⁺ suggested the ion‐induced growth mechanism in the formation of polygonal GNPs. The purified polygonal GNPs were then successfully used as catalyst in the borohydride reduction of three isomeric nitrophenols and also in the aerobic oxidation of different D ‐hexoses (e.g., D ‐glucose, D ‐mannose, D ‐fructose). The catalytic activity of these polygonal GNPs is higher by a factor of 300–1000, depending on the GNP's sample type, in nitrophenol reduction compared to that of spherical GNPs. Similar activity enhancement was also observed in the aerobic oxidation of different D ‐hexoses. These polygonal GNPs catalyst are very stable and could be reused several times in the borohydride reduction of nitrophenols without much losing in their virgin catalytic activity.     

Sugars in Mediterranean Floral Nectars: An Ecological and Evolutionary Approach

High-pressure liquid chromatography analyses of 73 plant species showed that the nectars of phrygana (East Mediterranean garrigue) mainly contain sucrose, glucose, and fructose, and traces of 10 minor sugars. Although the sucrose/hexose ratio was not related to plant life habit, ecological constraints had a detectable effect in shaping sugar composition. This was detected by distinguishing the phryganic plant species into spring–summer and winter flowering, with the distinction made on the basis of the water deficit in the study area. Plants flowering in spring–summer had a higher rate of high sucrose (i.e., sucrose/hexose ratio 0.5; 60.8% of the plant species) vs. low hexose nectars (i.e., ratio <0.5; 39.2%). The ratio was reversed in winter flowering species (36.4% vs. 63.6% with high sucrose and high hexose, respectively). Sucrose/hexose ratios were associated with plant family. The highest values were those of Lamiaceae, which differed significantly from the low sucrose Liliaceae and Apiaceae. Based on recorded plant–pollinator interactions in the community, the present data provide evidence of a partitioning of nectar resources by the existing pollinator guilds within the community, based on the sugar profiles of nectar (all sucrose/hexose ratios for all interactions). Among all major groups, bees and wasps (aculeates) preferred high sucrose nectars, which differed significantly from syrphids, anthomyid a.o. flies, and beetles that visited low sucrose nectars. Similarly, butterflies visited lower sucrose nectars compared to bees. Within families, only Megachilidae could be clearly characterized as high sucrose consumers, differing in this respect from all the remaining insect groups including most other bee families. This confirms previous findings that Megachilidae have a key position in Mediterranean communities where they probably constitute a selective factor for high sucrose nectars.