Structural analysis of water-soluble glucans from the root of Angelica sinensis (Oliv.) Diels

Two water-soluble glucans (designated APS-1cI and APS-1cII) were extracted from the roots of Angelica sinensis (Oliv.) Diels and further purified by anion-exchange and gel-filtration chromatography. Their molecular weights were determined to be 1.7 x 10(5) and 3.9 x 10(4)Da, respectively. The structures of the purified glucans were investigated by a combination of chemical and instrumental analysis, such as methylation analysis, periodate oxidation, GC-MS, as well as FTIR and NMR spectroscopy ((1)H, (13)C, H-H COSY, HSQC, HMBC, TOCSY and NOESY). The data obtained indicated that APS-1cI was a linear alpha-glucan composed of only (1-->6)-alpha-D-Glcp, and APS-1cII had a repeating unit consisting of (1-->4)-alpha-D-Glcp and (1-->6)-alpha-D-Glcp in a molar ratio of 4:1. Such glucans isolated from A. sinensis (Oliv.) Diels have not been previously reported.     

选择性代谢性谷氨酸受体5激动剂CHPG对创伤性神经元损伤的保护作用研究

目的:研究选择性代谢性谷氨酸受体5激动剂2-氯-4羟苯基甘氨酸(CHPG)对创伤性神经元损伤的保护作用,并初步探讨其保护机制。方法:大鼠皮层神经元原代培养10天后,采用机械划伤的方法建立损伤模型,采用乳酸脱氢酶(LDH)测定和Hoechst 33342染色观察CHPG对神经元的保护作用。结果:①CHPG显著降低损伤后LDH的释放和神经元凋亡。②与对照组相比,CHPG增加了ERK与Akt的磷酸化水平。③使用ERK抑制剂PD98059或者Akt抑制剂LY294002都可以部分逆转CHPG的保护作用。结论:CHPG可以减轻创伤性神经元损伤,这种保护作用可能是由ERK和Akt信号通路介导的。     

丝瓜籽中蛋白质生物合成抑制蛋白的分离、纯化及性质研究

丝瓜（Ｌｕｆｆａｃｙｌｉｎｄｒｉｃａ）种籽,经捣碎、抽提、硫酸铵分级沉淀,ＣＭ－５２离子交换层析,Ｓｅｐｈａｃｒｙ１Ｓ－１００分子筛,阳离子交换ＦＰＬＣ等步骤,分离到两种单链蛋白质生物合成抑制蛋白：Ｌｕｆｆｉｎ－Ａ和Ｌｕｆｆｉｎ－Ｂ。它们都是等电点接近１０的碱性蛋白,ＳＤＳ－ＰＡＧＥ测定分子量分别约为２７ｋｄ和２８ｋｄ,氨基酸组成分析表明两者具很大同源性,但免疫双扩散及ＥＬＩＳＡ检测证明两者的免疫原性有差异。Ｌｕｆｆｉｎｓ对兔网织红细胞裂解液的蛋白质生物合成有强烈的抑制作用,ＩＣ５０分别为１．４×１０－１１ｍｏｌ／Ｌ和２．０×１０－１１ｍｏｌ／Ｌ,比ＴＣＳ的２．９×１０－１０ｍｏｌ／Ｌ低得多。因而,Ｌｕｆｆｉｎｓ很有可能成为肿瘤导向药物的高效＂弹头＂。     

Specific stabilization of DNA triple helices by indolo[2,1-b]quinazolin-6,12-dione derivatives

Derivatives of indolo[2,1-b]quinazolinone containing aminoalkylamino side chains were synthesized as specific DNA triplex stabilizing agents. The aminoalkylamino side chains are essential for triplex stabilization. The position-8 fluorine atom or a methyl group to the nitrogen adjacent to the planar core can enhance triplex stability by 6 degrees C and the effect is additive. Conformational analysis reveals that the orientation of the side chain underlies the ability of this compound to stabilize a DNA triplex.     

The structure of the prokaryotic cyclic nucleotide-modulated potassium channel MloK1 at 16 A resolution

The gating ring of cyclic nucleotide-modulated channels is proposed to be either a two-fold symmetric dimer of dimers or a four-fold symmetric tetramer based on high-resolution structure data of soluble cyclic nucleotide-binding domains and functional data on intact channels. We addressed this controversy by obtaining structural data on an intact, full-length, cyclic nucleotide-modulated potassium channel, MloK1, from Mesorhizobium loti, which also features a putative voltage-sensor. We present here the 3D single-particle structure by transmission electron microscopy and the projection map of membrane-reconstituted 2D crystals of MloK1 in the presence of cAMP. Our data show a four-fold symmetric arrangement of the CNBDs, separated by discrete gaps. A homology model for full-length MloK1 suggests a vertical orientation for the CNBDs. The 2D crystal packing in the membrane-embedded state is compatible with the S1-S4 domains in the vertical "up" state.     

Solution structure and dynamics of the lipoic acid-bearing domain of human mitochondrial branched-chain alpha-keto acid dehydrogenase complex

The lipoyl-bearing domain (LBD) of the transacylase (E2) subunit of the branched-chain alpha-keto acid dehydrogenase complex plays a central role in substrate channeling in this mitochondrial multienzyme complex. We have employed multidimensional heteronuclear NMR techniques to determine the structure and dynamics of the LBD of the human branched-chain alpha-keto acid dehydrogenase complex (hbLBD). Similar to LBD from other members of the alpha-keto acid dehydrogenase family, the solution structure of hbLBD is a flattened beta-barrel formed by two four-stranded antiparallel beta-sheets. The lipoyl Lys(44) residue resides at the tip of a beta-hairpin comprising a sharp type I beta-turn and the two connecting beta-strands 4 and 5. A prominent V-shaped groove formed by a surface loop, L1, connecting beta 1- and beta 2-strands and the lipoyl lysine beta-hairpin constitutes the functional pocket. We further applied reduced spectral density functions formalism to extract dynamic information of hbLBD from (15)N-T(1), (15)N-T(2), and ((1)H-(15)N) nuclear Overhauser effect data obtained at 600 MHz. The results showed that residues surrounding the lipoyl lysine region comprising the L1 loop and the Lys(44) beta-turn are highly flexible, whereas beta-sheet S1 appears to display a slow conformational exchange process.     

Moisture excluding efficiency and dimensional stability of wood improved by acylation

The dimensional stability and moisture excluding efficiencies (MEEs) of wood after acetylation, butyrylation, and hexanoylation, were evaluated in this study. After three acylation treatments, an excellent antiswelling efficiency of modified wood specimens was obtained. All the equilibrium moisture contents of acylated wood at three relative humidities (RHs) (33% RH, 65% RH, and 93% RH) were significantly reduced, as compared to those of untreated wood in the same RH, and the MEEs of acylated wood were greatly improved. Acylated wood has consistent MEE at each of the different RHs. With the same percentage of substituted hydroxyl groups, the decreasing order of the MEE of modified wood was hexanoylation > butyrylation > acetylation. This indicates that the molecular volume or hydrophobic property of the substituted acyl groups also has the influence on the MEE of modified wood, in addition to the degree of substitution of the hydroxyl groups.     

An efficient and selective method for preparing glycosyl sulfoxides by oxidizing glycosyl sulfides with OXONE or t-BuOOH on SiO2

Silica gel adsorbed with OXONE or t-BuOOH was used as a mild oxidant to selectively oxidize glycosyl sulfides to corresponding sulfoxides in good yields and without sulfones formation. This method was also found compatible with various other functional groups in the glycosides.     

Bioactivity of selected plant essential oils against the yellow fever mosquito Aedes aegypti larvae

The bioactivity of 14 essential oils from five plants has been studied using the brine shrimp lethality test and the Aedes aegypti larvicidal assay. All essential oils screened had LC50 values smaller than 200 microg/ml, showing significant lethality against brine shrimp. In addition, nine of the 14 essential oils tested showed toxicity against the fourth-instar A. aegypti larvae in 24 h (LC50<100 microg/ml). Of these, the leaf and bark essential oils of Cryptomeria japonica demonstrated high larvicidal activity, the most active being the leaf essential oil of C. japonica, with a LC50=37.6 microg/ml (LC90=71.9 microg/ml), followed by the bark essential oil of C. japonica also showing high activity against A. aegypti larvae, with a LC50=48.1 microg/ml (LC90=130.3 microg/ml). The results obtained from this study suggest that the leaf and bark essential oils of C. japonica are promising as larvicides against A. aegypti larvae and could be useful in the search for new natural larvicidal compounds.