Crystal structure of a novel two domain GH78 family α‐rhamnosidase from Klebsiella oxytoca with rhamnose bound

The crystal structure of the GH78 family α‐rhamnosidase from Klebsiella oxytoca (KoRha) has been determined at 2.7 Å resolution with rhamnose bound in the active site of the catalytic domain. Curiously, the putative catalytic acid, Asp 222, is preceded by an unusual non‐proline cis‐peptide bond which helps to project the carboxyl group into the active centre. This KoRha homodimeric structure is significantly smaller than those of the other previously determined GH78 structures. Nevertheless, the enzyme displays α‐rhamnosidase activity when assayed in vitro, suggesting that the additional structural domains found in the related enzymes are dispensible for function. Proteins 2015; 83:1742–1749. © 2015 The Authors. Proteins: Structure, Function, and Bioinformatics Published by Wiley Periodicals, Inc.     

AtNHX1基因对荞麦的遗传转化及抗盐再生植株的获得

通过农杆菌介导法将拟南芥液泡膜Na⁺/H⁺反向转运蛋白基因AtNHX1转入荞麦中,在2.0mg/L 6-BA、0.1mg/L IAA、1mg/L KT、50mg/L卡那霉素和500mg/L头孢霉素的MS培养基上进行选择培养,从来源于864块外植体的36块抗性愈伤组织中共获得426棵再生植株（转化频率为4.17%）。经PCR、Southern印迹分析、RT-PCR和Northern检测,初步证实AtNHX1基因已整合至荞麦基因组中。用200mmol/L的盐水对转基因植株和对照植株进行胁迫处理6周,转基因植株能够生存,而对照植株死亡。用不同浓度的NaCl溶液处理转基因植株和对照植株,发现Na⁺及脯氨酸含量在转基因植株中的积累水平显著高于对照植株,而K⁺的含量在转基因植株中的积累水平低于对照植株。次生代谢产物黄酮类化合物芦丁在转基因植株根、茎和叶片中的含量也比对照植株明显要高。这些结果表明利用基因工程手段提高作物的耐盐性是可行的。     

芦丁对胃蛋白酶部分性质的影响

采用紫外光谱和荧光光谱研究芦丁与胃蛋白酶的相互作用。实验结果表明,加入芦丁使胃蛋白酶的紫外吸收差谱迅速增强,特征荧光峰产生静态淬灭,并求得芦丁与胃蛋白酶作用的形成常数。     

梯度洗脱高效液相色谱法测定桑叶中3种活性成分的含量

建立同时测定桑叶中绿原酸、芦丁和槲皮素含量的分析方法。色谱柱为NUCLEODUR C18 RP(250 mm×4.6 mm,5μm),光电二极管检测器,流动相为甲醇-质量分数0.5%磷酸水溶液,梯度洗脱程序为0 min(30:70)-15min(30:70)-25min(50:50)-35min(85:15)-40min(30:70);流速0.8 ml.min-1,检测波长为350 nm。绿原酸、芦丁和槲皮素的线性范围分别为0.1144~1.0296μg(r=0.9996)、0.0436~0.3924μg(r=0.9999)和0.0452~0.4068μg(r=0.9997),平均回收率分别为97.7%(RSD=1.7%)、98.4%(RSD=2.2%)和100.6%(RSD=1.5%)。方法快速简便,专属性强,重复性好,可作为桑叶中绿原酸、芦丁和槲皮素的定量分析方法。     

Inhibition of human low density lipoprotein oxidation by flavonols and their glycosides

Antioxidative effects of the flavonols and their glycosides, i.e., quercetin (Q), quercetin galactopyranoside (QG), quercetin rhamnolpyranoside (QR), rutin (R), morin (MO), myrecetin (MY), kaempferol (K) and kaempferol glucoside (KG), against free radical initiated peroxidation of human low density lipoprotein (LDL) were studied. The peroxidation was initiated either by a water-soluble initiator 2,2'-azobis(2-amidino propane hydrochloride) (AAPH), or by cupric ion (Cu2+). The reaction kinetics were monitored either by the uptake of oxygen and the depletion of alpha-tocopherol (TOH) presented in the native LDL, or by the formation of thiobarbituric acid reactive substances (TBARS). Kinetic analysis of the antioxidation process demonstrates that these flavonols and their glycosides are effective antioxidants against AAPH- and Cu(2+)-initiated LDL peroxidation, the flavonols bearing ortho-dihydroxyl groups possess significantly higher antioxidant activity than those bearing no such functionalities, and the glycosides are less active than their parent aglycones.     

Phenolic compounds from Forsythia leaves

Four lignans, four lignan glucosides, one flavonoid and two caffeoyl glycosides of 3,4-dihydroxyphenethyl alcohol were identified variously in leaves of Forsythia suspensa, F. viridissima and F. koreana. The leaf patterns were broadly similar to those reported earlier for the fruits, except that suspensaside and β-hydroxyacteoside were not detected.     

Simultaneous effects of potassium, rutin and temperature on performance ofManduca sexta caterpillars

the simultaneous effects on an insect herbivore (third instar tobacco hornwormManduca sexta (L.): Sphingidae) of temperature (daytime temperatures of 20 °C, 25 °C and 30 °C), a mineral that may play a role in plant defense (potassium) and a common allelochemical (rutin) were examined in a factorial experiment. To manipulate potassium levels, a modified diet with limited plant material was used as the base and KCl and rutin added. Temperature affected efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), time to head-capsule slippage, stadium duration, relative consumption rate (RCR) and relative growth rate (RGR) but not food consumed, biomass gained and approximate digestibility (AD). Potassium concentration influenced all of the variables except AD, time to head-capsule slippage (HCS), duration of the stadium and percent of stadium time to HCS. Rutin impacted negatively on all of the variables except food consumed. Compared to larvae on the non-rutin diets, fewer larvae fed rutin survived through molt initiation to ecdysis and fewer successfully completed ecdysis. Temperature and rutin had interactive effects for AD, ECD, RCR, RGR, time to HCS, and percent of stadium required to reach HCS. Rutin and potassium had interactive effects for biomass gained, RCR, ECI, time to HCS, duration of stadium, and percent of stadium required to reach HCS. Comparison of larval responses on an average potassium concentration (3.1%) versus high concentration (6.1%) showed that at the low daytime temperature increasing potassium concentration depressed biomass gained, but at the warmer temperatures potassium concentration had little effect unless rutin was present. In addition, potassium concentration had little impact on ECI unless rutin was present. These results indicate that significant interactive effects occur among temperature, potassium and rutin, and thus suggest that such interactive effects on larval performance may be common under field conditions, which are characterized by varying temperature and different concentrations of minerals and allelochemicals in hostplants.     

不同提取条件对苦荞籽粒中芦丁降解的影响

本实验研究了不同提取条件对苦荞籽粒中芦丁含量的影响,经HPLC分析,浓度高于40％(v／v)的乙醇对芦丁降解酶有明显的抑制作用,其中90％乙醇的抑制作用最强。苦荞粉与水接触的时间强烈影响芦丁的含量．接触1min芦丁含量迅速由原来的79．72％下降到32．21％,即约60％的芦丁被降解。在pH1．0～11．0范围内．芦丁降解酶具有很强的抗酸碱性。当温度大于60℃时．芦丁降解酶开始缓慢失活,芦丁得以较好保存．高于70℃时芦丁保存率更高;当温度为90℃,芦丁保存率约为对照值的80％。该研究结果对于苦荞芦丁的提取和苦荞食品的加工具有重要的理论意义和实际指导价值。     

The effects of salicylic acid on pigment contents in ultraviolet radiation stressed pepper plants

Pepper (Capsicum annuum L.) plants were sprayed with salicylic acid (SA) and treated with ultraviolet radiation UV-A (320–390 nm), UV-B (312 nm), and UV-C (254 nm) of 6.1, 5.8, and 5.7 W m⁻², respectively. UV significantly reduced contents of chlorophyll (Chl) a and b, and carotenoids (Car). SA treatment moderated Chl and Car reduction in plants treated with UV-B and UV-C. The quantity of antocyanins, flavonoids, rutin, and UV-absorbing compounds in plants that were treated with UV-B, UV-C, and SA were significantly increased. Foliar spray of SA counteracted the UV effects on pepper.