合成阿斯巴甜菌种的筛选

为了探索酶法合成阿斯巴甜的新思路和新方法,从富含蛋白的土样中筛选出能够分解二肽阿斯巴甜的菌种。利用其可逆性的特点,以L-天门冬氨酸和L-苯丙氨酸甲酯为主要合成原料,以菌体酶作为催化剂进行合成实验。经高效液相色谱检测,结果表明筛选到一株菌(ASPD1)能够合成阿斯巴甜;通过单因素实验法探讨了反应时间、温度、pH值等诸因素对产物形成的影响。     

黑玉米中黑色素的提取工艺及组分研究

以黑玉米为原料，对黑玉米中的黑色素的提取工艺进行了研究，通过正交实验得出了提取黑玉米中黑色素的最佳提取条件：95％的乙醇溶液、料液比1：30、pH=1、浸提时间45min；并利用液质联用技术（LC—MS）对山东和山西两种黑玉米中黑色素的种类进行了探讨。结果表明，山东中主要含有两种花青素，分别是矢车菊和天竺葵花色素；山西中主要含有三种花青素，分别是矢车菊、天竺葵和芍药花色素。     

忍冬属植物开花过程中绿原酸类化合物含量的变化

忍冬是中国传统中药材金银花的药源植物。采用高效液相色谱—光电二极管阵列检测器联用技术(HPLC-PAD)和高效液相色谱—电喷雾离子化—多级质谱联用技术(HPLC-ESI-MSn)对忍冬和4种同属植物在开花不同阶段中绿原酸类化合物进行了定性和定量分析,以明确忍冬属植物花的利用价值及其最佳采收期。结果发现:4种忍冬属植物花蕾及开放花朵中均含有新绿原酸、绿原酸、绿原酸甲酯、异绿原酸A和一种异绿原酸的异构体;绿原酸和总绿原酸在花蕾中的含量高于开放花朵,但贯月忍冬变化不显著;火焰忍冬、贯月忍冬、台尔曼忍冬中绿原酸和总绿原酸的含量在花蕾膨大期(大白期)和初花期(银花期)都高于忍冬,而格雷姆忍冬和忍冬差异不显著,研究表明,4种忍冬属植物花及花蕾都具有较高的开发利用价值。     

耐寒睡莲花瓣中花青素苷组成及其与花色的关系

睡莲(Nymphaea spp.)为多年生水生观赏花卉。以耐寒睡莲不同花色的119个栽培品种为材料, 利用高效液相色谱(HPLC-DAD)和液质联用技术(HPLC-ESI-MSⁿ)测定了其花瓣中的花青素苷成分。采用英国皇家园艺学会比色卡(RHSCC)和国际照明委员会(CIE)制定的CIEL^*a^*b^*表色系统测量了57个品种的花色, 运用多元线性回归方法分析花色与花青素苷组成之间的关系。结果表明: 耐寒睡莲花瓣中含有14种花青素苷, 其中飞燕草素-3-半乳糖-5-乙酰-半乳糖苷(Dp3Ga5acetylGa)、飞燕草素-3-鼠李糖-(1→2)-半乳糖苷(Dp3Rh(1→2)Ga)、矢车菊素-3-半乳糖-(1→2)-半乳糖苷(Cy3Ga(1→2)Ga)、矢车菊素-3-乙酰-半乳糖-(1→2)-半乳糖苷(Cy3acetylGa(1→2)Ga)、矢车菊素-3-没食子酰-半乳糖苷(Cy3galloylGa)、飞燕草素-3-乙酰-葡萄糖苷(Dp3acetylG)、飞燕草素-3-葡萄糖苷(Dp3G)和矢车菊素-3-半乳糖-半乳糖-半乳糖苷(Cy3GaGaGa)8个组分在耐寒睡莲中为首次报道。Dp3Ga、Dp3galloylGa、Cy3Ga(1→2)Ga和Cy3galloylGa是决定耐寒睡莲呈色的关键花青素苷。     

石榴皮抗氧化活性成分的提取及其组分的研究

以DPPH抑制率为指标,研究石榴皮中抗氧化活性成分。采用超声波法进行提取,通过正交实验确定了最佳提取工艺为:乙醇浓度60%、pH3、料液比(m/v)1∶15、提取3次,每次40 min。石榴皮粗提物依次用石油醚、氯仿、乙酸乙酯、正丁醇、水萃取,经D101大孔吸附树脂纯化,并采用液相色谱-质谱联用法(LC-MS)对石榴皮抗氧化成分进行鉴定。结果表明,石榴皮粗提物中,正丁醇部位对DPPH的抑制率最高,达62.68%,液-质联用鉴定出安石榴苷的两种异构体为石榴皮中最主要的抗氧化成分。     

巴巴拉百合花的天然香气成分研究

采用水蒸气蒸馏法对巴巴拉百合花挥发油进行了提取．通过毛细管气相色谱-质谱联用法分离并鉴定了其化学成分．并用气相色谱面积归一化法测定了各成分的相对百分含量。共分离出62个峰,确定了其中60种化合物,所鉴定化合物的含量占全油的99．71％．主要化学成分为：萜二烯(59．43％);3,7-二甲基-1．6-辛二烯-3-醇(20．10％);(R)-4-甲基-1-(1-甲基乙基)-3-环己烯1醇(11．32％);3异丙烯基-5,5-二甲基环已烯(4．05％);2-氨基苯甲酸-3,7-二甲基-1,6-辛二烯-3-酯(3．52％);( )-α-萜品醇(p-薄荷-1-酮-8-醇)(2．22%);β-月桂烯(1．08％)。以上7种化合物占总挥发油的94．72％。     

火麻仁挥发油的化学成分研究

本文采用水蒸气蒸馏法提取传统中药火麻仁中的挥发油,用GC毛细管柱进行分析,面积归一化法测定其相对含量,并用GC-MS鉴定其化学成分.共检出90个色谱峰,鉴定其中62个化合物,占挥发油总量的89 25%.鉴定的成分包括44种烃类化合物、7种芳香族化合物和11种脂肪族化合物及其衍生物.烃类化合物中以萜类为主,占挥发油总量的32.01%,相对含量较高的单萜及其衍生物包括β-芳樟醇(1.66%)、β-顺式-罗勒烯(1.30%)、樟脑(0.93%)、冰片和薄荷醇(0.44%);相对含量较高的倍半萜及其衍生物包括大牦牛儿烯 D(8.20%)、α-芹子烯(5.23%)、β-丁香烯(3.65%)、氧化石竹烯(2.22%)、δ-愈创木烯(1.55%)和α-丁香烯(1.19%).     

利用超微量技术分析粘虫单腺体性信息素的化学组成

通过选择提取溶剂、改进提取方法以及毛细柱气相色谱检测条件,摸索出粘虫 Mythimna separata Walker单腺体提取和分析方法;并且确定了单个求偶雌蛾腺体提取物的化学组成、含量和相对比例。讨论了粘虫求偶雌蛾性信息素腺体提取物中各组分含量的个体差异。     

古墓中胡杨心材的挥发性化学成分

利用GC-MS联用技术分析了古墓中2000多年前胡杨(Populus euphratica)心材的挥发性化学成分,并应用色谱峰面积归一化法计算了各成分的相对含量。共分析确认了31种挥发性成分,主要为倍半萜类化合物和酯类化合物。     

进口薯片中脂肪酸成分的检测与分析

目的：对11个进口品牌薯片中的脂肪酸进行测定比较,为消费者选购薯片提供营养学参考。方法：采集多个批次的薯片进行混合缩分,利用气相色谱-质谱联用技术（GC-MS）对薯片中的脂肪酸进行定性定量分析,对薯片中的主要脂肪酸的百分含量进行对比分析。结果：11个薯片样品的总脂肪含量为204~344mg/g,薯片中含有丁酸、辛酸、癸酸等24种脂肪酸,以棕榈油为原料加工的薯片,其棕榈酸、油酸、亚油酸百分含量均值为39.6%、39.5%、9.3%,而以葵花籽油为原料加工的薯片,其相应脂肪酸百分含量均值为7.0%、23.4%、59.5%。结论：薯片中的脂肪酸组成主要受加工所用油料影响。同时加工过程中油料使用时间过长或加热温度过高也会使其不饱和脂肪酸含量减少。     

Blood-Brain Barrier Carrier-Mediated Transport and Brain Metabolism of Amino Acids

The transport of neutral amino acids through the brain capillary endothelial wall, which makes up the blood-brain barrier (BBB) in vivo, is an important control point for the overall regulation of cerebral metabolism, including protein synthesis and neurotransmitter production. The Michaelis-Menten kinetics of BBB amino acid transport have been investigated in vivo with the brain uptake index (BUI) technique, and in vitro with the isolated human brain capillary preparation. The only amino acid that is albumin-bound is tryptophan, and the majority of albumin-bound tryptophan in the plasma is available for transport through the BBB via an enhanced dissociation mechanism that operates at the surface of the brain capillary endothelium. The availability in brain of amino acids is predicted from the BBB Km values to be sharply influenced by supra-physiological concentrations of phenyalanine in the 200–500 M range. Moreover, the measurement of cerebral protein synthesis with an internal carotid artery perfusion technique and HPLC-based measurements of aminoacyl-transfer RNA specific activities shows an inverse relationship between cerebral protein synthesis and plasma phenyalanine concentrations in the 200–500 M range. These findings indicate the neurotoxicity of hyperphenylalninemia is not restricted to the phenylketonuria range of approximately 2000 M, but is exerted in the supra-physiological range of 200–500 M.     

New Structures of the O-Specific Polysaccharides of Proteus. 4. Polysaccharides Containing Unusual Acidic N-Acyl Derivatives of 4-Amino-4,6-dideoxy-D-glucose

The structures of the O-polysaccharides of the lipopolysaccharides of Proteus mirabilis O7 and O49 were determined by chemical methods, mass spectrometry, including MS/MS, and NMR spectroscopy, including experiments run in an H2O/D2O mixture to reveal correlations for NH protons. The O-polysaccharides were found to contain N-carboxyacetyl (malonyl) and N-(3-carboxypropanoyl) (succinyl) derivatives of 4-amino-4,6-dideoxyglucose (4-amino-4-deoxyquinovose, Qui4N), respectively. The behavior of Qui4N derivatives with the dicarboxylic acids under conditions of acid hydrolysis and methanolysis was studied using GLC-MS.     

Response Surface Methodology-Based Optimized Ultrasonic-Assisted Extraction and Characterization of Selected High-Value Components from Gemlik Olive Fruit

This article presents an optimized ultrasound-assisted ethanolic extraction (UAEE) and characterization of selected high-value components from Gemlik olive fruit (GOF) harvested from Potohar region of Pakistan. Response surface methodology (RSM), involving central composite design (CCD), was applied to optimize the extraction variables i. e., temperature (25–65 °C), extraction time (15–45 min) and aqueous ethanol concentration (60–90 %) for optimal recovery of bioactives extract, total phenolic contents (TPC) and DPPH free radical scavengers. Under the optimized set of conditions such as 43 °C temperature, 32 min extraction time and 80 % aqueous ethanol, the best extract yield (218.82 mg/g), TPC (19.87 mg GAE/g) and DPPH scavenging activity (63.04 %) were recorded. A quadratic polynomial model was found to be reasonably fitted to the observed results for extract yield (p<0.0001 and R²=0.9941), TPC (p<0.0001 and R²=0.9891), and DPPH radical scavenging activity (p<0.0001 and R²=0.9692). Potent phenolic compounds were identified by GC/MS in GOF extract and considerable amount of essential fatty acids were also detected. The current findings support the use of UAEE as an effective green route for optimized recovery of high-value components from GOF and hence its applications can be extended to functional food and nutra-pharmaceutical developments.     

山胡椒果实挥发性物质的化学成分分析

采用SPME-GC/MS联用技术分析山胡椒果实挥发性成分,共分离出57个化学成分,其中匹配度大于等于80%的化合物有45种,占果实挥发性物质含量的78.94%。其中柠檬醛、石竹烯和(Z)-3,7-二甲基-2,6-辛二烯醛是含量最高的三种物质,相对含量为分别为23.09%、22.04%、17.23%,占整个挥发性物质的62.36%。     

Problem of aspartimide formation in Fmoc-based solid-phase peptide synthesis using Dmab group to protect side chain of aspartic acid.

The sequence-dependent, acid- or base-catalysed aspartimide formation is one of the most serious side reactions in solid-phase synthesis of peptides containing aspartic acid. In the present work, we investigated the susceptibility of 4-(N-[1-(4,4-dimethyl-2,6-dioxocyclohexylidene)-3-methylbutyl]amino)benzyl (Dmab), an aspartic acid beta-carboxy side-chain protecting group, for aspartimide formation. As a model, 15-amino acid-residue galanin fragment analogue containing the Asp-Ala motif was used during Fmoc-based solid-phase synthesis. Our study showed a strong tendency of Dmab-protected peptide to form aspartimide with unusual high efficiency. Furthermore, to investigate the susceptibility of Asp-Ala motif for aspartimide formation during the synthesis using Asp(ODmab), a 5-amino acid-residue galanin fragment LGPDA, different types of resin linkers, variety of Fmoc-deprotection conditions and coupling methods were applied.     

The effect of kinetin on the level of an indoleacetylaspartic acid like substance in germinating seeds and young plants of Phaseolus vulgaris

Kinetin treatment increased the level of an extractable indoleacetyl conjugate, apparently indoleacetylaspartic acid (IAAsp) in germinating seeds and young plants of Phaseolus vulgaris L. cv. Alabaster. The level of this substance in extracts of treated seeds was always higher than that from water treated seeds irrespective of whether the seeds had been extracted 24, 48 or 72 h after the beginning of the treatment. In all parts of young bean plants treated with kinetin there was more of the substance than in the corresponding parts of water treated plants.     

2-氰基-D,L-苯丙氨酸盐酸盐的合成

合成了非天然氨基酸２－氰基－Ｄ,Ｌ－苯丙氨酸盐以及四个中间体,其结构分别通过红外光谱、核磁共振、元素分析、熔点测试等手段得到确证。     

Synthesis of aspartame precursor with an immobilized thermolysin in tert-amyl alcohol

N-(Benzyloxycarbonyl)-L-aspartyl-L-phenylalanine methyl ester (Z-AspPheOMe), a precursor of the synthetic sweetner asparatame, was synthesized from N-(benzyloxycarbolyl)-L-aspartic acid (Z-Asp) and L-phenylalanine methyl ester (PheOMe) with an immobilized thermolysin in various organic solvents. We found that in tert-amyl alcohol containing a small amount of water the immobilized enzyme showed a high activity comparble to that in ethyl acetate with quite a high stability. The immobilized enzyme was fully stable up to 70 degrees C in tert-amyl alcohol in the absence of the subatrate, and up to 50 degrees C in the presence of the substrate. The high stability in the presence of the substrate was found due to the fact that the release of calcium ions, the stabilizing factor of thermolysin, is suppressed.The substrate concentration dependence of the initial synthetic rate with the immobilized enzyme was quite different from that with the free enzyme in the biphasic system, in contrast to that in ethyl acetate. Finally, Z-AspPheOMe was continuously synthesized in a column reactor using 200 mM PheOMe and 120 mM Z-Asp as the substrate for over 300 h at 45 degrees C and a space velocity of 1 h(-1) without any loss of acivity. (c) 1994 John Wiley & Sons, Inc.     

Synthesis of dipeptide precursors with an immobilized thermolysin in ethyl acetate

N-(Benzyloxycarbonyl)-L-aspartyl-L-phenylalanine methyl ester (Z-AspPheOMe), a precursor of the aspartame, and N-(benzyloxycarbonyl)-L-phenylalanyl-Lphenylalanine methyl ester (Z-PhePheOMe) were synthesized from the respective amino acid derivatives with an immobilized thermolysin (EC 3.4.24.4) in ethyl acetate. Various factors affecting the synthesis of these dipeptide precursors were clarified. The initial synthetic rate was the highest at the water content of 3.5% for both reactions. The substrate concentration dependencies of the initial synthetic rate of Z-AspkPheOMe and Z-PhePheOMe with the immobilized enzyme in ethyl acetate were different from those in an aqueous buffer solution saturated with ethyl acetate but similar to those in the aqueous/organic biphasic system using the free enzyme. Particularly, the initial synthetic rate of Z-AspPhOMe increased in order higher than first order with respect to the concentration of L-phenylalanine methyl ester (PheOMe), whereas it decreased sharply with the concentration of N-(benzyloxycarbonyl)-L-aspartic acid (Z-Asp). Such kinetic behavior could be explained by regarding the inside of the immobilized enzyme as being a biphasic mode composed from the organic phase and aqueous phase where the enzymatic reaction takes place. The reaction in the aqueous/organic biphasic system using the free enzyme could be simulated by taking into consideration the partition of the substrate and the initial rate of synthesis in the aqueous buffer saturated with ethyl acetate. Based on this analysis, the rate of reaction with the immobilized enzyme in ethyl acetate could also be predicted. Z-AsPheOMe and Z-PhePheOMe were synthesized by the fed-batch method where the acid component of the substrate was intermittently added during the course of reaction and by the batch method. In the synthesis of Z-AspPheOMe, the synthetic rate and maximum yield of reaction as well as the stability of the immobilized enzyme were higher in the fed-batch reaction than those in the batch reaction. In the synthesis of Z-PhePheOMe, the results obtained by both methods were similar. (c) 1994 John Wiley & Sons, Inc.