紫萁贯众化学成分研究

紫萁贯众为紫萁科(Osmundaceae)紫萁属植物紫萁(Osmunda japonica Thunb.)带叶柄残基的根茎.本文采用溶剂法及各种色谱方法从紫萁贯众乙酸乙酯部位分离得到6个化合物,通过理化性质和波谱数据分析,分别鉴定为1,7,9,11-四羟基-3-甲基-5,6-二氢-萘骈蒽醌(1),(E)-3,4-二羟基苯亚甲基丙酮(2),原儿茶酸(3),β-谷甾醇(4),β-胡萝卜苷(5)和二十六烷酸(6).化合物1为首次从植物界中得到,化合物2、3和6均为首次从紫萁属植物中分离得到.     

辐照技术应用于茶叶上的研究进展

本文综述了国内外辐照处理对茶叶卫生质量、感官品质、内含物的影响以及农残降解的研究进展,展望了辐照技术在茶叶上的应用前景和发展方向,为辐照技术在茶叶上的产业化应用提供参考依据。     

海草生物活性成分的研究进展

本文综述了海草中生物活性成分的研究进展,其化学成分类型主要是苯酚类、黄酮类和二萜类化合物,生物活性主要包括抗菌、抗氧化、抗病毒、细胞毒性、抑制海藻生长和抗污损等.     

魔芋葡甘露寡糖的制备、化学结构及对胰岛NO自由基释放量的影响

魔芋精粉经 β 甘露聚糖酶酶解成寡糖后 ,用活性炭柱进行分离纯化 ,以不同浓度 (5 % ,10 % ,2 0 % )的乙醇洗脱 .研究不同洗脱组分对链脲佐菌素 (STZ)诱导糖尿病模型的胰岛NO自由基释放量的影响 .发现 1mg ml以 5 %乙醇洗脱的寡糖可以使胰岛培养液中的NO自由基释放量平均下降2 5 4 % (P <0 0 5 ) ,0 1mg ml以 5 %乙醇洗脱的寡糖使NO自由基水平下降 2 0 % (P <0 0 5 ) .结果表明 ,5 %乙醇洗脱的魔芋寡糖对保护胰岛免受链脲佐菌素 (STZ)的破坏有一定的作用 .用凝胶色谱、红外光谱、元素分析、核磁共振光谱、质谱等方法初步分析了 5 %乙醇洗脱的魔芋寡糖的化学结构 .发现该糖是一种四糖 ,分子量为 6 6 6 .其推测性结构式为 :β D Man(1→ 4 ) β D Man(1→ 4 ) β D Glc(1→ 4 )α D Man ,β D Man(1→ 4 ) β D Glc(1→ 4 ) β D Man(1→ 4 )α D Man或 β D Glc(1→ 4 ) β D Man(1→4 ) β D Man(1→ 4 )α D Man .     

Deterred oviposition response of Monochamus alternatus (Coleoptera: Cerambycidae) to oviposition scars occupied by eggs

1 The oviposition behaviour and response of Monochamus alternatus females to oviposition scars were investigated in the laboratory. 2 Prior to oviposition, females gnawed at the bark surface of Pinus densiflora bolts to make a wound. Then females turned their bodies 180° to position their ovipositors over the wounds and inserted them under the bark through the wounds. After an oviposition, a jelly was deposited while the ovipositor was still inserted. The females then withdrew their ovipositors and rubbed the oviposition scars with the tips of their abdomens. 3 When searching females encountered oviposition scars, they stopped walking and drummed the surface and inside of the oviposition scars with their maxillary and labial palpi. 4 Eighty-six percent of females left oviposition scars containing single eggs after the palpation. By contrast, when females encountered oviposition scars containing no eggs, 76% of them began to gnaw at the scars and 64% deposited single eggs. The response to artificial oviposition scars was similar to that to vacant oviposition scars made by the females. 5 The results of various observations and experiments showed that the females could recognize oviposition scars and discriminate the scars occupied by single eggs from vacant ones, and suggested that the palpation of oviposition scars was the critical discrimination behaviour, indicating mediation by chemical cues.     

沸石对土壤养分生物有效性和土壤化学性质的影响研究

在花岗岩发育的赤红壤上进行的天然沸石混施化肥的盆栽试验研究结果表明,沸石提高了土壤养分的生物有效性,显著促进玉米的生长,增加玉米的生物量和提高了玉米对N,P,K的吸收量,15N示踪技术表明,沸石处理可以显著提高氮肥的利用率,两造玉米最高的氮肥利用率分别比对照提高28．8％和60．0％,土壤的分析结果表明,沸石处理也可提高土壤阳离子交换量,盐基饱和度和土壤pH值。     

Accurate and efficient method for quantification of urinary histamine by gas chromatography negative ion chemical ionization mass spectrometry

Because of the recognized inaccuracy and unreliability of currently available methods for the quantification of histamine in biological fluids, a method for quantification of urinary histamine by stable isotope dilution assay with negative ion chemical ionization mass spectrometry has been developed. Following the addition of [²H₄]histamine to 1 ml of urine, histamine is extracted into butanol, back-extracted into HCl, derivatized to the pentafluorobenzyl derivative (CH₂C₆F₅)₃-histamine, extracted into methylene chloride, and then quantified with negative ion chemical ionization mass spectrometry by selected ion monitoring of the ratio of ions $\text{m}\text{z}$$\text{430}\text{434}$. Twenty samples can be assayed in 2 days. Precision of the assay is ±2.7% and the accuracy is 97.6%. Lower limits of sensitivity are approximately 100–500 fg injected on-column. This assay provides a very sensitive, accurate, and efficient method for the quantification of histamine in human urine.     

Effects of chemical modification of carboxyl groups on the voltage-clamped nerve fiber of the frog

Summary Voltage-clamped single nerve fibers of the frogRana esculenta were treated with the carboxyl group activating reagent N-ethoxy-carbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) in the presence of different primary amines and without added amine. Carboxyl groups form stable amide bonds with primary amines in the presence of EEDQ. EEDQ treatment reduced the sodium current considerably and irreversibly, regardless of the presence of a primary amine in the Ringer's solution. The potassium current was also reduced. After modification the reduced sodium currents inactivated slowly and incompletely. The descending branch of the sodium current-voltage relation,I _Na(E), was shifted along the voltage axis in the depolarizing direction. The size of the shift was strongly dependent on the amine present during modification with EEDQ. The voltage-dependence of sodium inactivation,h _x (E), was shifted to more positive values of membrane potential by EEDQ in the presence of ethylenediamine (11 mV) and glucosamine (3 mV). In contrast, a small shift to more negative potentials occurred in the presence of taurine (–3 mV) or without the addition of an amine (–2 mV). A tenfold increase of the calcium concentration still shifted theI _Na(E) andh _x (E) curves of the chemically modified fibers. However, these shifts were smaller than those observed on untreated fibers. The currents remaining after the modification were completely blocked by tetrodotoxin; no change of the reversal potential occurred.     

静电作用与修饰铜锌超氧化物歧化酶的稳定性

铜锌超氧化物歧化酶(Cu, Zn-SOD)表面的赖氨酸经化学修饰后, 酶的稳定性显著提高. 赖氨酸被修饰后, 酶的电荷结构遂发生变化, 从而影响到酶分子电场. 使用FDPB方法(有限差分法求解Poission-Boltzman方程)计算了酶修饰前后的静电场变化, 以及对维持酶的结构稳定起重要作用的Cu, Zn配位结构的影响.结果表明, Cu, Zn配位体的两级离解常数在酶修饰后分别约下降10³, 10⁶.     

Modification of the gene 5 DNA unwinding protein with ruthenium

A chemical modification of the gene 5 DNA binding protein (G5BP) from bacteriophage fd was investigated using X-ray diffraction and difference Fourier analysis. The crystalline protein was reacted with pentaammineruthenium (III) trichloride, Ru(NH₃)₅Cl₃, a reagent believed specific for histidine residues and useful in NMR and chemical modification studies of proteins. The major ruthenium site was found by difference Fourier analysis to be 4 Å from histidine 64, the only histidine residue in the molecule. A second bipartite site, believed to be a ruthenium-anion pair, appeared to be salt-bridged to glutamic acid 40 and arginine 16. Indications were present in the difference Fourier results to suggest that the loop containing tyrosine 41 had undergone a slight conformational rearrangement to accommodate this interaction.