1,7-二氧杂螺[5.5]十一烷异头效应的量子化学研究

用量子化学密度泛函理论B3LYP方法结合6-311G(d,p)基组和自洽反应场(SCRG)极化连续介质模型(PCM)对1,7-二氧杂螺[5.5]十一烷的异头效应进行了理论研究.结果表明,1,7-二氧杂螺[5.5]十一烷的3种异构体中,A表现为双异头效应,B表现为单异头效应,C没有明显的异头效应.在气相条件下,A和B的异头效应能分别为36.0和19.7 kJ/mol.在水溶液中,A和B的异头效应能分别为26.4和14.0 kJ/mol.溶剂的介电常数和偶极矩越大,A和B的异头效应能越大.     

Anomeric specificity of glucose-stimulated insulin release: evidence for a glucoreceptor?

The effects on insulin secretion of alpha and beta anomers of D-glucose were studied in the in vitro perfused rat pancreas. Both phases of insulin release showed consistent stereospecificity for alpha-glucose; this specificity indicates an action of glucose independent of intracellular glucose metabolism.     

Dialysis of certain sugars through cellophane

Of several sugars examined, alkali most affects the rate of dialysis through cellophane of alpha-beta-D-mannose and alpha-beta-maltose. The rates of dialysis of these two sugars are influenced by 0.01 and 0.1N solutions of sodium and potassium hydroxide. The rate of dialysis of sucrose is not influenced by the solutions employed.     

Effect of sugars on transport of alanine in intestine

The eflect of glucose and galactose on transport of alanine by rabbit ileum has been investigated. Transmural transport and cellular ac cumulation of the amino acid were in hibited by the sugars, but alanine in flux across the mucosal border of the cells was unaltered.     

Metal chlorides in ionic liquid solvents convert sugars to 5-hydroxymethylfurfural

Replacing petroleum feedstocks by biomass requires efficient methods to convert carbohydrates to a variety of chemical compounds. We report the catalytic conversion of sugars giving high yield to 5-hydroxymethylfurfural (HMF), a versatile intermediate. Metal halides in 1-alkyl-3-methylimidazolium chloride are catalysts, among which chromium (II) chloride is found to be uniquely effective, leading to the conversion of glucose to HMF with a yield near 70%. A wide range of metal halides is found to catalyze the conversion of fructose to HMF. Only a negligible amount of levulinic acid is formed in these reactions.     

混接茂谷橘橙对芦柑叶片和果实淀粉酶活性的影响

为探讨混合嫁接对柑橘果实物质代谢等生理过程的影响,对混合嫁接后的芦柑和茂谷橘橙淀粉酶活力进行测定。结果表明：茂谷橘橙淀粉酶活力显著高于芦柑;混合嫁接茂谷橘橙后的芦柑比未嫁接的淀粉酶活性显著增强,且变化趋势也与茂谷橘橙相似。     

甘薯生长发育过程中可溶性糖含量与淀粉积累的关系

以甘薯品种徐薯１８为材料，测定了甘薯各生育阶段块根的淀粉积累量和叶片、块根的游离糖含量．结果表明，薯叶总糖含量范围为１．２—７．７ｍｇ／ｇＦＷ．当总糖水平呈上升趋势（还原糖约占总糖的９５％，蔗糖占非还原糖９５％以上）时，块根淀粉积累快；在雨季和收获期，总糖水平下降，还原糖和蔗糖所占比例亦降低，块根淀粉积累速率低．甘薯块根总糖含量在２０．３—３７．０ｍｇ／ｇＦＷ时淀粉积累率高，总糖水平低．在生育前期，随着甘薯的生长，还原糖含量下降而蔗糖含量增加并保持占非还原糖的１００％；在生育后期，还原糖增加而蔗糖含量下降（但仍保持占非还原糖９０％以上）．淀粉积累率低时，块根总糖水平急剧升高．     

蓝果忍冬果实中主要糖酸组分的高效液相色谱法测定

为了更好的分析蓝果忍冬的食用价值,为高效利用优异种质资源提供理论依据,采用高效液相色谱法,对42个蓝果忍冬资源的果实中主要糖酸组分及其含量进行了测定。结果表明,供试的42个蓝果忍冬资源果实中主要可溶性糖为葡萄糖,含量在1222~5582.6 mg/100 g,平均值为3412.5 mg/100 g,果糖含量为792.5~3324.7 mg/100g,平均值为2121.1 mg/100 g,还有少量的山梨醇,2种主要的可溶性糖,果糖和葡萄糖比为1:1.61;柠檬酸含量最高,占总酸含量的62.2%,含量每100 g在1029.8~3215.6 mg之间,平均值为1959.6 mg/100 g,苹果酸次之,含量为434.3~1616.6 mg/100 g,平均值为828 mg/100 g,苹果酸占总酸26.2%,其他有机酸含量较低。蓝果忍冬品种间可溶性糖、有机酸含量的变异系数差异较大,为26.11%~106%,其中柠檬酸变异系数最小,草酸最大。     

西方蜜蜂的血糖及其影响因素

蜜蜂对糖的消化和吸收是维持其血糖平衡的基础 .西方蜜蜂血糖主要有 3种 ,即海藻糖、葡萄糖、果糖 ,蛹可能还含有五碳糖 .多种因素影响其血糖平衡 ,内部因素主要包括亚种、发育阶段、级型、血淋巴中的酶、激素等 ;外部因素主要包括食物、饥饿、活动、农药、物理刺激等     

Transport of sugars and amino acids in the intestine: evidence for a common carrier

D-Galactose, L-arginine, and their respective actively transported analogs are partially competitive inhibitors of the active transport of neutral amino acids in the small intestine of hamsters. Since the aforesaid classes of compounds are all transported by similar, sodium-ion-dependent mechanisms and elicit countertransport of each other, all may share a common, polyfunctional carrier in which a series of separate binding sites, namely, one each for sugars, neutral amino acids, basic amino acids, and Na(+) are joined together, as in a mosaic.     

不同采收成熟度对烤烟可溶性糖及品质的影响

设置4种采收成熟度处理,对不同采收成熟度对烤烟可溶性糖及品质的影响进行研究.结果表明:随着采收时间的推迟和成熟度的提高,总糖、还原糖及淀粉的含量逐渐增加,达到某一高点后,随着烟叶的衰老及合成能力的下降,总糖、还原糖及淀粉的含量又降低.烟碱含量也是随着采收时间的推迟和成熟度的提高而逐渐增加,特别是当烟叶生长时间过长,成熟度过高时,烟碱有较大幅度增高.在4种水溶性糖分中,葡萄糖占比最大、为33％～40％,果糖次之、占32％～38％,蔗糖较低、占20％～27％,麦芽糖最低、占5％～8％.综合分析烟叶的外观质量、内在化学成分及感官评吸质量,可作出如下结论:下部叶栽后70(±3)d,中部叶栽后90(±4)d,上部叶移栽后125(±5)d采收的处理为优;上部5～6片烟叶一次性成熟采收的成熟特征是,顶部l～3片叶面绿黄至淡黄,叶面落黄6～8成,主脉变白2/3以上,叶面黄色程度接近顶4～6叶,栽后120～130 d.     

Hemagglutination by fava bean extract inhibited by simple sugars

Hemagglutination by extract of fava bean was inhibited by 5-percent d-glucose, d-fructose, or maltose, but not by 5-percent d-galactose or lactose. Failure to inhibit seems to reflect the presence of a hydroxyl group at the carbon No. 4 position. Hemagglutination was enhanced by dextran of high molecular weight, but not by dextran of low molecular weight. The finding supports the hypothesis that large molecular size explains the enhancement by gum acacia of hemagglutination by fava bean.     

糖对稻米淀粉黏滞性的影响

利用快速粘度分析仪测定葡萄糖、果糖、麦芽糖和蔗糖对稻米淀粉黏滞性的影响,结果显示：随着糖浓度的增加,稻米淀粉峰值粘度下降;随着葡萄糖、果糖、麦芽糖的增加,黏滞谱特征值的最终粘度、热浆粘度和消减值显著降低,而蔗糖对热浆粘度基本没有影响;葡萄糖、果糖使崩解值显著增加,而麦芽糖使崩解值先下降后上升,蔗糖使崩解值显著下降;4种糖都使糊化温度显著增加。     

Cellulose to sugars: new path gives quantitative yield

Cellulosic residues that had been treated with a small amount of chemical solvent under room conditions were quantitatively saccharified on enzyme hydrolysis. This treatment can be used to obtain simple sugars for the production of alcohol and other chemicals.     

CARS-SPA算法结合高光谱检测马铃薯还原糖含量

以竞争性重加权自适应选择算法(CARS)结合连续投影算法(SPA)选择马铃薯还原糖含量特征波长,共制备238个样本,比色法测定马铃薯还原糖含量,选择190个样本作校正集,48个样本作验证集,与全光谱和经典变量提取方法比较。结果表明,CARS-SPA算法筛选波段效果最佳,相比于全谱建模其参与建模波长点由203个减少到17个,模型验证集决定系数r~2由0.8464提高到0.8965,均方根误差(RMSEP)由0.0758降到0.0490。结果表明,采用CARS-SPA结合高光谱成像技术检测马铃薯还原糖含量结果可行。     

高效液相色谱搭载可变波长检测器测定桃果肉中糖组分

本试验建立了一种无需衍生反应即可实现高效液相色谱搭载可变波长检测器(HPLC-VWD)直接检测桃果肉中蔗糖、葡萄糖、果糖和山梨醇含量的方法,并对该方法进行了评价。对HPLC-VWD和高效液相色谱搭载示差折光检测器(HPLC-RID)测得不同桃品种中糖组分进行比较分析;并利用建立的HPLC-VWD法测定了葡萄、苹果、粉蕉和梨果肉中糖组分。结果显示,本研究建立的HPLC-VWD法可对糖组分进行有效分离和检测,在相应的范围内线性关系良好,相对标准偏差为0.53%~2.71%,回收率为92%~103%;HPLC-VWD和HPLC-RID法测得结果没有显著差异。     

苹果梨果实生长期间山梨糖醇及其它糖的变化规律

对苹果梨果实的山梨糖醇、果糖、葡萄糖、蔗糖进行了测定。结果表明，山梨糖醇含量在8月20日迅速积累达到最高峰，然后下降，9月20日采收时含量较少；果糖自7月中旬开始迅速增加，采收时含量最高；葡萄糖和蔗糖在整个生长期间含量较微；9月初之前果实中主要以山梨糖醇为主，之后果实中主要以果糖为主。     

青椒对外源糖的吸收与分配规律研究

用含有14 C标记的外源糖 (葡萄糖和蔗糖 )点滴青椒叶片 ,示踪试验表明 :外源糖被叶片吸收后可运转到植株的各个部位 ,但集中向果实 ,幼嫩的茎、叶等生长比较旺盛的库性器官分配 ,其分配量与器官干重无关 ;青椒对外源葡萄糖的吸收率高于蔗糖     

底物添加对森林2个不同演替阶段土壤氨基糖动态的影响

以鼎湖山马尾松林和季风林2个演替阶段的土壤为研究对象,采用室内恒温(25 ℃)培养,研究了葡萄糖和不同数量无机氮施入对土壤氨基糖(氨基葡萄糖、氨基半乳糖和胞壁酸)动态的影响,并利用氨基葡萄糖和胞壁酸的比值探讨了真菌和细菌残留物在碳氮固持过程中的相对贡献。结果表明:在整个培养期间,季风林土壤氨基糖总量显著高于马尾松林,尤其在培养初期,增幅远高于马尾松林, 在培养后期,马尾松林土壤氨基糖含量下降幅度高于季风林。底物添加对不同微生物来源的氨基糖单体含量的影响也有所差异,以胞壁酸为代表的细菌细胞壁残留物比真菌更易受到外源物质的影响,但真菌细胞壁残留物对土壤有机质的截获和稳定作用大于细菌。真菌、细菌残留物的积累和转化过程可以通过氨基葡萄糖和胞壁酸的比值反映,细菌在培养前期更容易利用外源物质,但随着培养时间的进行,真菌占据了主导地位。不同碳氮比的外源底物对氨基糖总量和各氨基糖单体含量的动态影响不显著。与马尾松林相比,处在演替顶级的季风林土壤易于利用活性底物,显著促进了碳氮的微生物固持和微生物残留物在土壤中的保留,这说明土壤氨基糖作为微生物残留物可以探讨土壤碳氮的耦合机制,对调节土壤碳氮的养分平衡具有重要意义。