基质固相分散萃取-高效液相色谱-串联质谱法分析拟南芥中的赤霉素

建立了基质固相分散萃取-高效液相色谱-串联质谱法(MSPD-HPLC-MS/MS)同时测定拟南芥中3种赤霉素GA1, GA3和GA4的分析方法。将拟南芥样品与C18填料混合研磨制成MSPD柱,并采用80%冷甲醇洗脱。采用反相C18色谱柱进行分离,以0.05%甲酸水溶液和乙腈为流动相进行梯度洗脱,采用电喷雾离子源负离子模式(ESI~)电离,多反应监测模式检测。对样品前处理条件、色谱分离条件和质谱检测条件进行了优化,结果表明,在最优条件下,3种赤霉素在10～300 ng/g范围内均呈良好线性关系,相关系数(r2)均大于0.98,检出限在1.1～4.1 ng/g之间。在10～50 ng/g添加水平下,平均回收率范围为54.7%～102.6%,相对标准偏差（RSD,n=3)为3.2%～12.8%。该方法操作简单、灵敏度高、选择性好、回收率高,适合拟南芥中GA1、GA3、GA4含量的测定。     

Inhibitory effects of glycyrrhetic acid derivatives on 11 beta- and 3 alpha-hydroxysteroid dehydrogenases of rat liver.

Glycyrrhetic acid (GA), an aglycone of glycyrrhizin (GL), is a potent inhibitor of 11 beta- and 3 alpha-hydroxysteroid dehydrogenases. 11 beta-Hydroxysteroid dehydrogenase activity of rat liver microsomes was potently inhibited by GA, 3-deoxyglycyrrhetic acid (3-deoxyGA), 3-ketoglycyrrhetic acid (3-ketoGA), 3-epiglycyrrhetic acid (3-epiGA) and 11-deoxoglycyrrhetic acid (11-deoxoGA), with I50 values of 2-4 x 10(-7) M. However, 18 alpha-stereoisomers (I50 = 3-7 x 10(-6) M) of GA, 3-deoxyGA and 11-deoxoGA were one tenth less inhibitory on the enzyme activity than the corresponding 18 beta-isomers. On the other hand, 18 alpha-stereoisomers of GA, 3-deoxyGA and 11-deoxoGA inhibited 3 alpha-hydroxysteroid dehydrogenase activity of rat liver cytosol more potently than the corresponding 18 beta-isomers. I50 values of 18 alpha- and 18 beta-isomers were 2 and 7 x 10(-6) M, respectively, in the case of GA, 8 and 20 x 10(-6) M in 3-deoxyGA, 3 and 20 x 10(-6) M in 11-deoxoGA. These results indicate that the 18 beta-conformation of oleanane is important for the inhibition of 11 beta-hydroxysteroid dehydrogenase but on the contrary the 18 alpha-conformation is important for the inhibition of 3 alpha-hydroxysteroid dehydrogenase.     

Synthesis and anti-HIV activity of triterpene 3-<Emphasis Type="Italic">O</Emphasis>-galactopyranosides,analogs of glycyrrhizic acid

A new method for synthesizing triterpene 3-O-galactosides, analogs of glycyrrhizic acid (GA) based on 18βglycyrrhetic acid (GLA) methyl esters and 18,19-dehydro-GLA, using 2,3,4,6-tetra-O-acetyl-a-Dgalactopyranosyl bromide as the glycosyl donor, I–Br promoter, and 4-? molecular sieves was developed. The method could produce primarily 3-O-α-D- or β-D-galactopyranosides depending on the reaction conditions. The 3-O-α-D-galactopyranoside of GLA exhibited an index of selectivity (IS) 2.9 times greater than that of GA for inhibition of accumulation of virus-specific protein p24 of HIV-1. β-D-Galactopyranoside of GLA was more cytotoxic for MT-4 cells and exhibited weak anti-HIV-1 activity.     

Delivering Transmembrane Peptide Complexes to the Gas Phase Using Nanodiscs and Electrospray Ionization

The gas-phase conformations of dimers of the channel-forming membrane peptide gramicidin A (GA), produced from isobutanol or aqueous solutions of GA-containing nanodiscs (NDs), are investigated using electrospray ionization-ion mobility separation-mass spectrometry (ESI-IMS-MS) and molecular dynamics (MD) simulations. The IMS arrival times measured for (2GA + 2Na)²⁺ ions from isobutanol reveal three different conformations, with collision cross-sections (Ω) of 683 Å² (conformation 1, C1), 708 Å² (C2), and 737 Å² (C3). The addition of NH₄CH₃CO₂ produced (2GA + 2Na)²⁺ and (2GA + H + Na)²⁺ ions, with Ω similar to those of C1, C2, and C3, as well as (2GA + 2H)²⁺, (2GA + 2NH₄)²⁺, and (2GA + H + NH₄)²⁺ ions, which adopt a single conformation with a Ω similar to that of C2. These results suggest that the nature of the charging agents, imparted by the ESI process, can influence dimer conformation in the gas phase. Notably, the POPC NDs produced exclusively (2GA + 2NH₄)²⁺ dimer ions; the DMPC NDs produced both (2GA + 2H)²⁺ and (2GA + 2NH₄)²⁺ dimer ions. While the Ω of (2GA + 2H)²⁺ is similar to that of C2, the (2GA + 2NH₄)²⁺ ions from NDs adopt a more compact structure, with a Ω of 656 Å². It is proposed that this compact structure corresponds to the ion conducting single stranded head-to-head helical GA dimer. These findings highlight the potential of NDs, combined with ESI, for transferring transmembrane peptide complexes directly from lipid bilayers to the gas phase.

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Graphical Abstract ?

     

Synthesis and confirmation of structure for the gibberellin GA131 (18-hydroxy-GA4)

A general method for the hydroxylation of the 18-methyl group in gibberellins has been developed, as demonstrated by the successful synthesis of 18-hydroxy GA(4) (GA(131)) by means of a tandem process involving the conjugate addition of alkoxides to the alpha-methylene lactone moiety of a ring A-seco-gibberellin followed by an intramolecular aldol reaction.     

高效液相色谱-串联质谱法测定葡萄中的吡效隆和赤霉素

采用高效液相色谱-串联质谱法（HPLC-MS/MS）建立了葡萄果实中吡效隆（CPPU）和赤霉素（GA3）两种植物生长调节剂残留量的定性定量分析方法。样品用0.5%甲酸水溶液和乙腈（体积比4:1）混合溶剂提取,经Strata-X固相萃取净化,使用Agilent SB-C18 色谱柱（50mm×2.1mm,1.8μm）,以0.5%甲酸水溶液-乙腈为流动相,流量0.3mL/min,采用电喷雾离子化源（ESI）多反应监测（MRM）模式下HPLC-MS/MS检测。在最佳检测条件下,得到吡效隆和赤霉素在2.0～100.0μg/L检测范围内线性关系良好,相关系数大于0.999;检出限(LOD)分别为0.3μg/L、0.5μg/L,定量限(LOQ)分别为1.0μg/L、2.0μg/L,回收率和精密度均能达到要求,表明该法准确,可用于葡萄中吡效隆和赤霉素残留量测定。     

Use of 2,4-dinitrophenylhydrazone of glyoxylic acid for the determination of glyoxylic acid by the chromatographic-spectrophotometric method and by differential pulse polarography

Two different methods (one based on chromatography and spectrophotometry and the other on polarography) have been developed for the determination of glyoxylic acid in the form of a derivative with 2,4-dinitrophenylhydrazine (DNPH. GA). The TLC method allows the separation of two DNPH. GA isomers ("trans" and "cis"). Spectrophotometric measurements of the eluents of the separated compounds (lambda=360 nm) allow the determination of GA within the range from 4 to 30 microg. Using differential pulse polarography, the conditions of DNPH. GA formation were examined. The reduction peak of this derivative (E(P)=-0.430 V), observed by dpp, was used to develop a polarographic determination of GA within the concentration range from 1.10(-4) to 7.10(-4) mol/l.     

新型低聚噻吩衍生物的合成及其凝胶化性能研究

设计合成了一系列新型低聚噻吩衍生物N,N'-双十八烷基-5,5"-(2,2:5,2"-三噻吩)二酰胺[N,N'-distearyl-5,5"-(2,2:5,2"-terthiophene) dicarboxamide (DNC₁₈₃T)]、N,N'-双烷烃基-5,5"-(3,3"-双辛烷基-2,2:5,2"-三噻吩)二酰胺[N,N'-dialkyl-5,5"-(3,3"-dioctyl-2,2:5,2"-terthiophene)dicarbox-amide(DNC_nDOc3T,n=5,8,16,18)]及N,N'-双十八烷基-5,5-(3,3-双辛烷基-2,2:5,2":5",2-四噻吩)二酰胺[N,N'-distearyl-5,5-(3,3-dioctyl-2,2:5,2":5",2-tetrathiophene)-dicarboxamide(DNC₁₈DOc4T)].研究结果表明,DNC₁₈₃T和DNC₅DOc3T同有机溶剂不形成凝胶.DNC_nDOc3T(n=8,16,18)和DNC₁₈DOc4T能同几种有机溶剂形成透明、半透明或不透明的凝胶.通过测定凝胶随温度变化的红外光谱(IR)、核磁共振氢谱(¹HNMR)、紫外光谱(UV),揭示出形成有机低分子凝胶的驱动力不仅有分子间氢键,而且π-π相互作用也是一个非常重要的因素.偏光光学显微镜、扫描电子显微镜(SEM)显示出有机低分子凝胶呈三维网络结构.另外,DNC₁₈Doc3T/盐/氰基苯凝胶体系在电场作用下发生可逆的颜色.     

Microwave synthesis of gibberellin acid 3 magnetic molecularly imprinted polymer beads for the trace analysis of gibberellin acids in plant samples by liquid chromatography-mass spectrometry detection

In this study, novel GA3 magnetic molecularly imprinted polymer (mag-MIP) beads were synthesized by a microwave irradiation method, and the beads were applied for the trace analysis of gibberellin acids (GAs) in plant samples including rice and cucumber coupled with high performance liquid chromatography-mass spectrometry (HPLC-MS). The microwave synthetic procedure was optimized in detail. In particular, the interaction between GA3 and functional monomers was further studied for the selection of the optimal functional monomers during synthesis. It can be seen that the interaction between GA3 and acrylamide (AM) finally selected was stronger than that between GA3 and other functional monomers. GA3 mag-MIP beads were characterized by a series of physical tests. GA3 mag-MIP beads had a porous and homogeneous surface morphology with stable chemical, thermal and magnetic properties. Moreover, GA3 mag-MIP beads demonstrated selective and specific absorption behavior for the target compounds during unsaturated extraction, which resulted in a higher extraction capacity (～708.4 pmol for GA3) and selectivity than GA3 mag-non-imprinted polymer beads. Finally, an analytical method of GA3 mag-AM-MIP bead extraction coupled with HPLC-MS detection was established and applied for the determination of trace GA1, GA3, GA4 and GA7 in rice and cucumber samples. It was satisfactory that GA4 could be actually found to be 121.5 ± 1.4 μg kg(-1) in real rice samples by this novel analytical method. The recoveries of spiked rice and cucumber samples were found to be 76.0-109.1% and 79.9-93.6% with RSDs of 2.8-8.8% and 3.1-7.7% (n = 3), respectively. The proposed method is efficient and applicable for the trace analysis of GAs in complicated plant samples.     

Analyses of gibberellins by capillary electrophoresis-mass spectrometry combined with solid-phase extraction

A new, simple and rapid capillary electrophoresis-mass spectrometry (CE-MS) method, using a cationic polymer-coated capillary to reverse electroosmotic flow, is proposed and validated for the separation and simultaneous quantification of 11 gibberellins (GAs). Under optimum conditions, a baseline separation of 11 GAs, including GA1, GA3, GA4, GA5, GA6, GA7, GA13, GA19, GA20, GA24 and GA53 was accomplished within 25 min using 70 mM ammonium formate/formic acid buffer (pH 3.8) and 2% (v/v) acetonitrile with -25 kV as the separation voltage. Satisfactory results were obtained in terms of linearity (R2 between 0.984 and 0.995), precision (RSD of migration time below 0.8%) and sensitivity (LOD between 0.31 and 1.02 microM). Furthermore, a novel solid-phase extraction (SPE) procedure was developed for the pre-concentration and purification of GAs using Oasis MAX cartridges. The combination of SPE and CE-MS approach was applied to screen for endogenous GAs present in coconut (Cocos nucifera L.) water sample. To illustrate the applicability of the method, GA1 and GA3 were successfully detected and quantified in coconut water. Finally, the GA1 and GA3 identities were further unequivocally confirmed by CE-tandem MS experiments operating in the multiple reaction monitoring mode.     

高效液相色谱法测定谷子幼苗中的GA_1和GA_3

建立了同时测定谷子幼苗中赤霉素Ａ１（ＧＡ１）和赤霉素Ａ３（ＧＡ３）的高效液相色谱（ＨＰＬＣ）方法。采用ＯＤＳ Ｃ１８色谱柱,以磷酸盐缓冲液和甲醇为流动相,ＧＡ１和ＧＡ３在１０ｍｉｎ内获得良好分离。利用该方法对谷子的两个正常栽培品种及其矮秆突变体的幼苗进行了测定。测定结果表明,谷子幼苗中同时含有ＧＡ１和ＧＡ３两种活性赤霉素,它们各自的质量比是影响谷子株高的重要因素。     

Host–guest complexation in the β-glycyrrhizic acid–2,8-dimethyl-5-[2´-(6″-methylpyridin-3″-yl)ethyl]-2,3,4,5-tetrahydro-1<Emphasis Type="Italic">H</Emphasis>-pyrido[4,3-<Emphasis Type="Italic">b</Emphasis>]indole system

Electronic, IR, and NMR spectroscopy methods were used to study the interaction in the β-glycyrrhizic acid (GA)–2,8-dimethyl-5-[2´-(6″-methylpyridin-3″-yl)ethyl]-2,3,4,5-tetra-hydro-1H-pyrido[4,3-b]indole (Dim) system in an alcoholic medium. The complete assignment of signals in the ¹H and ¹³C NMR spectra of Dim and GA in CD₃OD was made for the individual components and for thier mixtures at different ratios. These data suggest the formation of a host–guest complex in this system. It is hypothesized that associates of GA molecules interact with Dim through Δ^12,13–carbonyl group conjugated bonds in the triterpene moiety of GA that interact with the aromatic systems of the indole and pyridine moieties of Dim, as well as via an acid-base mechanism involving mainly the carboxy groups of glucuronic acid residues in the carbohydrate part of GA and the nitrogen atom of the tetrahydropyridine ring of Dim.     

Determination and survey of ochratoxin A in wheat, barley, and coffee--1997

Ochratoxin A (OA) is a nephrotoxic and nephrocarcinogenic mycotoxin produced by Aspergillus and Penicillium species. It has been found mainly in cereal grains and coffee beans. The purpose of this study was to investigate the occurrence of OA in cereal grains and in coffee imported to the United States. A modified liquid chromatographic (LC) method for determining OA in green coffee was applied to wheat, barley, green coffee, and roasted coffee. The test sample was extracted with methanol-1% NaHCO3 (7 + 3), and the extract was filtered. The filtrate was diluted with phosphate-buffered saline (PBS), filtered, and passed through an immunoaffinity column. After the column was washed with PBS and then with water, OA was eluted with methanol. The eluate was evaporated to dryness, and the residue was dissolved in acetonitrile-water (1 + 1). OA was separated on a reversed-phase C18 LC column with acetonitrile-water-acetic acid (55 + 45 + 1) as eluant and quantitated with a fluorescence detector. Recoveries of OA from the 4 commodities spiked over the range 1-4 ng/g were 71-96%. The limit of detection was about 0.03 ng/g. OA contamination at > 0.03 ng/g was found in 56 of 383 wheat samples, 11 of 103 barley samples, 9 of 19 green coffee samples, and 9 of 13 roasted coffee samples. None of the coffee samples contained OA at > 5 ng/g; only 4 samples of wheat and 1 sample of barley were contaminated above this level.     

GA and AG sequences of DNA react with cisplatin at comparable rates

The sequence selectivity of the antitumor drug cisplatin (cis-[PtCl(2)(NH(3))(2)] (1)) between the 5'-AG-3' and 5'-GA-3' sites of DNA has been a matter of discussion for more than twenty years. In this work, we compared the reactivity of GA and AG sequences of DNA towards the aquated forms of cisplatin (cis-[PtCl(NH(3))(2)(H(2)O)](+) (2), cis-[Pt(NH(3))(2)(H(2)O)(2)](2+) (3), and cis-[Pt(OH)(NH(3))(2)(H(2)O)](+) (4)) using two sets of experiments. In the first, we investigated a DNA hairpin, whose duplex stem contained a TGAT sequence as the single reactive site, and determined the individual rate constants of platination with 2 and 3 for G and A in acidic solution. The rate constants at 20 degrees C in 0.1M NaClO(4) at pH 4.5+/-0.1 were 0.09(4) M(-1)s(-1) (G) and 0.11(3) M(-1)s(-1) (A) for 2, and 9.6(1) M(-1)s(-1) (G) and 1.7(1) M(-1)s(-1) (A) for 3. These values are similar to those obtained previously for an analogous hairpin that contained a TAGT sequence. The monoadducts formed with 2 by both GA purines are extremely long-lived, partly as a result of the slow hydrolysis of the chloro monoadduct at A, and partly because of the very low chelation rate (1.4 x 10(-5)s(-1) at 20 degrees C) of the aqua monoadduct on the guanine. In the second set of experiments, we incubated pure or enriched samples of 1, 2, 3, or 4 for 18-64 h at 25 degrees C with a 19 base pair (bp) DNA duplex, whose radiolabeled top strand contained one GA and one AG sequence as the only reactive sites. Quantification of the number of GA and AG cross-links afforded a ratio of about two in favor of AG, irrespective of the nature of the leaving ligands. These results disagree with a previous NMR spectroscopy study, and indicate that GA sequences of DNA are substantially more susceptible to attack by cisplatin than previously thought.     

Creation of Functional Organic Gels Based on Oligothiophenes

Polymer gels have received a great deal of attention not only from scientific interest but also for their practical applications. Recently, low molecular-weight organic gels have also been receiving growing attention. However, their have been few studies of low molecular-weight organic gels in contrast to extensive studies of polymer gels. In order to develop a novel class of low-molecular-weight organic gels and to gain an insight into the relationship between molecular structures of gel-form…     

Modification of chitosan for construction of efficient antioxidant biodegradable macromolecular systems

The chitosan derivatives containing antiradical fragments in the polymer side chain have been synthesized by interaction of the partially quaternized chitosan(QCH) with gallic acid (GA). The antioxidative activity of the chitosan derivatives — QCH-GA was investigated by thiobarbituric method. Introduction of GA fragment in amount of 2. 0 mass % in the structure of QCH resulted in appearance of pronounced antioxidative activity of the polymeric system contrary to initial chitosan for which this activity was equal to zero. It was found that QCH-GA was a markedly higher effective inhibitor in a peroxidase — catalyzed oxidation of the model amine than the low-molecular antioxidant — GA. Targetted chitosan modification resulted in a substantial raize of the polymeric antimutagenic (at γ-irradiation) efficiency, which for QCH-GA was equal to 92% in comparison with the protective effect of the initial chitosan — 42% (plant test-system, barley seeds, γ = 15 Gr).     

分散固相萃取-超高压液相色谱-串联质谱法测定茶叶中赤霉酸和α-萘乙酸

建立了分散固相萃取-超高压液相色谱-串联质谱分析茶叶中两种植物激素赤霉酸(GA3)与α-萘乙酸(NAA)含量的方法。样品经甲醇均质提取,采用弗罗里硅土、石墨化炭黑(GCB)、丙基乙二胺(PSA)和C18混合吸附剂分散萃取净化。采用HSS C18色谱柱(100mm×2.0mm,1.8μm),电喷雾电离(-),多反应监测模式扫描(MRM),UPLC-ESI(-)-MS/MS检测,外标法定量分析。GA3和NAA分别在0.05～5.0mg/kg与0.10～5.0mg/kg范围内线性关系良好,相关系数r≥0.9990,定量限分别为0.05与0.10mg/kg。GA3和NAA在0.1,0.5和1.0mg/kg水平上的添加回收率分别在85.0%～86.8%和82.9%～84.4%之间,精密度(RSD)≤4.5%。本方法操作简单、准确,适用于测定茶叶中GA3和NAA残留量。     

Cobalt(II) complexes of 1,2-(diimino-4′-antipyrinyl)ethane and 4-N-(4′-antipyrylmethylidene)aminoantipyrine

Cobalt(II) complexes of the Schiff bases 1,2-(diimino-4-antipyrinyl)ethane (GA) and 4-N-(4-antipyrylmethylidene)aminoantipyrine (AA) have been prepared and characterised by elemental analysis, electrical conductance in non-aqueous solvents, i.r. and electronic spectra, as well as by magnetic susceptibility measurements. The complexes have the general formulae [Co(GA)X]X (X = ClO^– ₄ or NO₃ ^–), [Co(GA)X₂] (X = Cl^–, Br^– or I^–), [Co(AA)₂]X₂ (X = ClO₄ ^–, NO₃ ^–, Br^– or I^–) and [Co(AA)Cl₂]. GA acts as a neutral tetradentate ligand, coordinating through both carbonyl oxygens and both azomethine nitrogens. In the perchlorate and nitrate complexes of GA one anion is coordinated in a bidentate fashion, whereas in the halide complexes both anions are coordinated to the metal, generating an octahedral geometry around the Co ion. AA acts as a neutral bidentate ligand, coordinating through the carbonyl oxygen derived from the aldehydic moiety and the azomethine nitrogen. Both anions remain ionic in the perchlorate, nitrate, bromide and iodide complexes of AA, whereas both anions are coordinated to the metal ion in the chloride complex, resulting tetrahedral geometry around the Co ion.     

新型低聚噻吩衍生物的设计、合成及其液晶性能的研究

设计、合成了一系列新型低聚噻吩衍生物N,N’-双烷烃基-5,5’-二溴基-2 ,2’：5’,2’-三噻吩-4,4’-二酰胺[N,N’-dialkyl-5,5’-dibromo-2,2’:5 ’,2’-terthiophene-4,4’-dicarboxamide](DNCnDBr3T,n=5,8,6,18)。示差扫描 量热法（DSC）测定的结果及偏光光学显微镜观察的结果显示,DNC18DBr3T, DNC16DBr3T,DNC8DBr3T具有近晶A形液晶性质,DNC5DBr3T不具有液晶性质。为了探 讨分子间氢链对液晶形成的影响,设计、合成了新型低聚噻衍生物4,4“-双烷烃 酯-5,5“-二溴基-2,2’:5’,2’-三噻吩[4,4’-bis(alkyloxycarbonyl)-5,5’ -dibromo-2,2’:5’,2’-terthiophene](DOCnDBr3T,n=5,8,16,18).测定和观察的 结果发现,DOCnDBr3T(n=5,8,16,18）不具有液晶的结果。这个结果表明,酰胺基 的存在于液晶的形成起着重要的作用。测定DNC18DBr3T在结晶状态和液晶状态下的 红外光谱,进一步证实了部分分子间氢键对于液晶的形成起着重要的作用。     

Lentzeacins A-E,New Bacterial-Derived 2,5- and 2,6-Disubstituted Pyrazines from a BGC-Rich Soil Bacterium Lentzea sp. GA3-008

Pyrazines (1,4-diazirines) are an important group of natural products that have tremendous monetary value in the food and fragrance industries and can exhibit a wide range of biological effects including antineoplastic, antidiabetic and antibiotic activities. As part of a project investigating the secondary metabolites present in understudied and chemically rich Actinomycetes, we isolated a series of six pyrazines from a soil-derived Lentzea sp. GA3-008, four of which are new. Here we describe the structures of lentzeacins A-E (1, 3, 5 and 6) along with two known analogues (2 and 4) and the porphyrin zincphyrin. The structures were determined by NMR spectroscopy and HR-ESI-MS. The suite of compounds present in Lentzea sp. includes 2,5-disubstituted pyrazines (compounds 2, 4, and 6) together with the new 2,6-disubstituted isomers (compounds 1, 3 and 5), a chemical class that is uncommon. We used long-read Nanopore sequencing to assemble a draft genome sequence of Lentzea sp. which revealed the presence of 40 biosynthetic gene clusters. Analysis of classical di-modular and single module non-ribosomal peptide synthase genes, and cyclic dipeptide synthases narrows down the possibilities for the biosynthesis of the pyrazines present in this strain.