Inhibitory effect of cysteine and glutathione on phenoloxidase from kuruma prawn (Penaeus japonicus)

The inhibitory effect of cysteine and glutathione on phenoloxidase (PO) from kuruma prawn were investigated. Cysteine and glutathione inhibited the oxidation of 3-(3,4-dihydroxylphenyl)-l-alanine (l-DOPA) catalyzed by kuruma prawn PO. Those thiol compounds showed competitive inhibition with K_i values of 0.45–0.46 mM. The inactivated PO could be partially recovered by the addition of copper acetate (0.01–0.2 mM). Almost complete restoration of PO activity was achieved with the addition of N-ethylmaleimide (NEM) in the range 0.05–0.2 mM, suggesting the importance of sulfhydryl groups of cysteine and glutathione for their inhibitory activity. Additionally, both cysteine and glutathione prevented the colour development by trapping the colour intermediates or reducing o-quinone to colourless compounds.     

Identification of a cysteine proteinase from Jumbo squid (Dosidicus gigas) hepatopancreas as cathepsin L

A cysteine proteinase from Jumbo squid (Dosidicus gigas) hepatopancreas was partially purified by a two step procedure involving ammonium sulfate precipitation and gel filtration chromatography and further by SDS–PAGE. The molecular weight of the proteinase was 24 kDa determined by SDS–PAGE and 23.7 kDa with mass spectrometry. The activity had an optimum pH of 4.5 and optimum temperature of 55 °C under the assay for cathepsin L specific synthetic substrate Z-PAAFC. The cathepsin B and H specific synthetic substrates Z-AAAFC and H-AMC did not show any hydrolysis with the partially purified enzyme. Peptide mapping of trypsin digests of the 24 kDa band from SDS–PAGE showed the squid cysteine proteinase was homologous to cathepsin L from different animal sources. The activity of the partially purified fraction with the cathepsin L specific substrate Z-PAAFC was inhibited 75–89% by enzyme inhibitors specific for cysteine proteinases but was also significantly inhibited by serine and aspartate proteinase inhibitors.     

The influence of hydrophobic substances on water vapor permeability of fish gelatin films modified with transglutaminase or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)

The effect of different hydrophobic substances on water vapor permeability (WVP) of unmodified fish gelatin films and cross-linked with transglutaminase (TGase) or with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) was determined. Both unmodified and cross-linked films were characterized by very poor water barrier properties. Amaranth oil, rapeseed oil, lanolin, beeswax and ozococerite at concentration of 10% decreased WVP of unmodified gelatin films by 42, 15, 37, 53 and 36%, respectively. Increasing concentration of these substances up to 60% caused further improving of the water barrier properties. Addition of lecithin into film-forming emulsions prevented separation of lipid layer on the film surface. Among unmodified films with lecithin and 60% of lipids the highest decrease of WVP was found in case of amaranth oil and beeswax, by 73 and 87%, respectively, in comparison to only-gelatin films. WVP of chemically modified films in the presence of 60% of beeswax with addition of lecithin was decreased by about 65%. Enzymatically modified films with beeswax were very brittle and broke during analyzes, similarly as those with amaranth oil and lecithin. WVP of enzymatically modified films with lecithin and 60% of rapeseed oil and lanolin was respectively, about 60 and 47% lower than that of films without hydrophobic substances.     

The water vapour permeability,mechanical properties and solubility of fish gelatin–chitosan films modified with transglutaminase or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and plasticized with glycerol

The effect of glycerol on the mechanical and water barrier properties, as well as on the water solubility, of fish gelatin–chitosan films (4:1, w/w) cross-linked with TGase or EDC was determined. The addition of glycerol in concentrations up to 30% (of the substrate mass) to the fish gelatin–chitosan films modified with TGase or EDC did not change their solubility in buffers of pH 3 and 6 at 25 °C or during heating at 100 °C for 60 min. The chemical and enzymatic cross-linking of the components did not increase the water barrier properties of the films. WVP of the films modified with EDC and TGase was not affected by glycerol at concentrations up to 25% of the substrate mass. Tensile strength of the films decreased after modification of the components with TGase or EDC, respectively, by about 25% and 40%. The elongations of the enzymatically modified films containing 20% of glycerol and of chemically modified films containing 15% of glycerol were, respectively, about 8 and 13 times higher than those of unplasticized films; however, the tensile strengths of plasticized films were, respectively, 2.5 and 5 times lower.     

Brix degree and sorbitol/xylitol level of authentic pomegranate (Punica granatum) juice

With regard to 45 pomegranate fruits from different regions and several domestic varieties, fruit weight was found to be 137.1–738.2 g, peel share 34.4–73.1%, aril share 26.9–65.6% and fruit juice yield 19.2–48.0%. Brix degree of pomegranate juice samples obtained from the aforementioned fruits changed from 12.2 to 17.8 and was lower than 14.0 in approximately 18% of the samples. Titratable acidity of pomegranate juice samples varied between 2.4 and 30 g/L and the formol number varied between 4.0 and 20.0. The sorbitol/xylitol content ranged between 16 and 423 mg/L, mostly lying between 51 and 200 mg/L with a frequency of 64%. The share of samples containing sorbitol/xylitol higher than 250 g/L is 7%.     

Elimination of aggregates of (1→3) (1→4)-β-D-glucan in dilute solutions for light scattering and size exclusion chromatography study

Methods for eliminating aggregates of cereal (1→3) (1→4)-β-D-glucan in dilute solutions were investigated using dynamic light scattering and size exclusion chromatography. Wheat β-D-glucan samples were selected and dissolved in various solvents under different preparation conditions. The molecular size distribution was monitored by dynamic light scattering measurement. In most of the solutions, there were two well separated species of different average sizes. It appeared that the specie with smaller average size represented the un-aggregated molecules (unimers) and the specie with larger particle size corresponded to the aggregates. The results showed that heat treatment, filtration, ultrasonication, and the use of urea solution (up to 6 M) could not eliminate aggregates completely. However, the percentage of aggregates in aqueous NaOH solution decreased significantly with the increase of NaOH concentration. In 0.5 M NaOH solution, no aggregation was detectable by dynamic light scattering measurement. Both dynamic light scattering and HPSEC data showed that wheat β-D-glucan was stable in 0.5 M NaOH solution without any noticeable degradation when stored at 25 °C for 12 h. The results of present study suggested that 0.5 M NaOH solution is a suitable solvent for cereal β-D-glucans. Using this solvent, the molecular characteristics of wheat β-D-glucan was studied by both dynamic and static light scattering. The weight average molecular weight (M_w), radius of gyration (R_g), hydrodynamic radius (R_h), and the second virial coefficient (A₂) were obtained with the values of 3.29×10⁵ g/mol, 45.6 nm, 26.2 nm, and 1.04×10⁻³ cm³ mol/g² respectively. This study also confirmed that wheat β-glucan in solution exhibited a random coil conformation.     

黑曲霉T3-5-1高活力单宁酶的制备及其性质研究

用黑曲霉T3-5-1生产单宁酶,将粗酶液分别采用硫酸铵沉淀法和透析法初步纯化,结果表明,使用截留分子量12 kDa的透析袋对粗酶液透析后的比活力(3108.58 U/mg),高于硫酸铵沉淀法处理后的比活力(2939.38 U/mg)。然后对透析样品用Sephadex G-100葡聚糖凝胶层析法进一步纯化,得到纯度较高的单宁酶,通过与单宁酶A及单宁酶B进行GPC色谱图比较发现,其分子量基本一致,但黑曲霉T3-5-1单宁酶的比活力(5304.78 U/mg),远高于单宁酶A(1788.15 U/mg)和单宁酶B(935.07 U/mg)的比活力。该单宁酶性质研究表明:其最适pH值为5.0,最适反应温度为40℃,且其酸碱稳定性和热稳定性良好。当底物为没食子酸丙酯时,最大酶促反应速率Vmax为81.96μmol/(L·min),米氏常数Km为0.85 mmol/L。最后考察了该单宁酶的催化合成能力,结果表明,在AOT异辛烷反胶束体系中,该单宁酶可催化没食子酸和丙醇反应合成没食子酸丙酯。     

氯吡苯脲和O3处理‘秦美’猕猴桃采后生理品质与电学特性的关系

为从宏观电学特性方面探究采后O3处理是否可以减轻采前氯吡苯脲（1-(2-chloropyridin-4-yl)-3-phenylurea,CPPU）处理对‘秦美’猕猴桃产生的负面影响,以盛花期后28 d使用20 mg/L CPPU蘸果处理,采后贮藏过程中每隔15 d用70 mg/m3 O3处理2 h的秦美猕猴桃为试材,在（0±1）℃、相对湿度90%～95%条件下贮藏,研究贮藏期间生理指标、品质指标与电学特性之间的关系。结果表明：CPPU＋O3处理组过氧化氢酶活力、VC含量、可滴定酸质量分数整体高于CPPU处理组,呼吸速率、多聚半乳糖醛酸酶、纤维素酶活力低于CPPU处理组,采后O3处理可减轻CPPU对猕猴桃产生的负面影响。在选定的24 个频率中,CPPU处理的猕猴桃特征频率为0.1 kHz,对照组和CPPU＋O3处理的猕猴桃特征频率均为3 980 kHz。通过宏观电学特性判断,采后O3处理能减轻采前CPPU处理对‘秦美’猕猴桃品质和生理方面产生的负面影响。     

氯吡苯脲处理和质量损失对猕猴桃品质和电学特性的影响

为探明氯吡苯脲（1-(2-chloropyridin-4-yl)-3-phenylurea,CPPU）处理和贮藏过程中质量损失对不同品种 猕猴桃品质和电学特性的影响,以生长期使用20 mg/L CPPU处理幼果的‘秦美’、‘海沃德’猕猴桃为试材,在 室温下贮藏,比较不同质量损失和CPPU处理对‘秦美’、‘海沃德’果实品质指标和电学参数的影响。结果表 明：猕猴桃CPPU处理和贮藏过程中的质量损失都会导致果实品质显著下降,质量损失对‘秦美’猕猴桃品质下降 影响更大,CPPU处理对‘海沃德’猕猴桃品质下降影响更大。在选定的24 个频率中,CPPU处理和未处理的‘秦 美’、‘海沃德’的特征频率分别为3 980、2 510、251、631 kHz,对应的敏感电参数为并联等效电感（Lp）。可 基于果实VC含量与Lp的回归方程实现CPPU处理猕猴桃的无损检测,从而区分猕猴桃是否使用了CPPU。质量损失 率与电学特性无显著相关性,无法建立数学模型实现猕猴桃新鲜度的无损检测。     

Studies on Alkali-Modified Cassava Starch - Changes of Structural and Enzyme (α-Amylase) Susceptibility Properties

Properties of cassava starch could be modified by subjecting to alkalitreatment under controlled experimental conditions. Modified starch samples showed lower amylose content and higher alkali number. Compared to untreated starch samples, alkali modified starches had higher α-amylase (Bacillus sp.) susceptibility. The properties could be advantageously made use of for preparing maltodextrins having DE 20–23.     

Biotransformation of (R)-(+)- and (S)-(−)-limonene to α-terpineol by Penicillium digitatum— investigation of the culture conditions

The biotransformation of (R)-(+)- and (S)-(−)-limonene by Penicillium digitatum was investigated. One strain of P. digitatum was able to convert (R)-(+)-limonene to pure (R)-(+)-α-terpineol in 8 h with a yield of up to 93%. It was found that (R)-(+)-limonene was converted much better into α-terpineol than (S)-(−)-limonene, and that no significant chemical conversion of the substrate occurred in control flasks at pH 3.5. The culture conditions involved such as the type and concentration of co-solvent applied and the sequential addition of substrate were investigated, taking into account some findings on the physical behaviour of the system. The highest bioconversion yields were obtained when the substrate was applied as a diluted solution in EtOH.     

涤纶表面接枝蛋清蛋白改性及其服用性能研究

涤纶是合成纤维中服用性能最突出的纤维,蛋清蛋白具有良好的生物相容性,将蛋清蛋白接枝到涤纶织物上可以开发出服用性能好、生物相容性又好的复合面料。以聚乙烯醇缩水甘油醚(PVAGE)为交联剂,研究了在涤纶织物表面接枝蛋清蛋白的工艺及接枝率对服用性能的影响。采用单因素法得出接枝的最佳工艺条件为:PVAGE浓度1.89%,接枝温度100℃,时间30 min。接枝后涤纶的回潮率有大幅增加,抗静电性能大幅提高,折皱弹性回复性略有下降。     

纳米级La_(1-x)Ba_xCoO_3半导体陶瓷的制备与湿敏性能

采用Sol gel法化学工艺在较低温度下合成纳米级La1 xBaxCoO3(X =0 ,0 .1≤X≤ 0 .2 )湿敏半导体陶瓷 .用XRD、BET比表面吸附、Archimede排水法等技术对所合成陶瓷物相和结构进行了表征和分析 .湿敏特性测试结果表明 ,La1 xBaxCoO3半导体纳米陶瓷有一定的湿敏性能 ,当X =0 ,材料呈负湿 阻特性 ,当 0 .1≤X≤ 0 .2 ,材料呈正湿 阻特性 .从晶界层空穴载流子数角度合理解释了La1 xBaxCoO3纳米陶瓷的正湿 阻特性     

吡咯基丝氨酸乙酯的合成表征及其对大蒜绿变的作用

采用有机合成的方法得到新化合物吡咯基丝氨酸乙酯,验证其是否可以作为大蒜绿变的色素前体,并用核磁共振的方法验证了这种新化合物具有和已报导过的大蒜绿变色素前体-3,4-二甲基吡咯基缬氨酸(PP-Val)和3,4-二甲基吡咯基丙氨酸(PP-Ala)相似的结构,只是R侧链的结构不同.但实验结果表明,吡咯基丝氨酸乙酯不能使新蒜绿变,也不能和丙酮酸发生反应,表明R侧链的结构对这种吡咯基氨基酸是否能作为色素前体起着很重要的作用.     

耦合的非线性反应扩散方程的具有(G'/G)-形式的行波解

运用（G/′G）-展开法,求出了耦合的非线性反应扩散方程的带参数的行波解.这些行波解具有新的结构,当参数取某些特殊值时,可以得到孤波解.     

红曲酯化菌21-3选育及特性研究

以本所分离保藏的9株红曲霉为出发菌株，经紫外线诱变，选育出性能稳定、酯化力强的红曲酯化菌21-3（Monascus pilosus），酯化力约为低温曲和次高温曲的2．1倍，约为高温曲的12．5倍。试验表明：能促进己酸、丁酸及混合酸与乙醇的酯化作用，生成的酯类物质均为己酸乙酯，且酯化能力极强。在培养基中加入适量乙醇，有利于21-3的生长，加入适量乳酸或与乳酸菌共生，有利于酯化酶的合成。     

蓝圆鲹酸/碱等电点沉淀法分离蛋白凝胶特性与消化特性

采用酸/碱等电点沉淀（isoelectric solubilization/precipitation,ISP）法制备蓝圆鲹肌肉分离蛋白（acid/alkaline aided protein isolate,API/KPI）,并对全蛋白（total protein,TP）、肌原纤维蛋白（myofibrillar protein,MP）与分离蛋白的理化特性、凝胶特性以及消化稳定性进行比较研究。结果表明,蓝圆鲹肌肉蛋白在碱性条件下溶解性显著高于酸性条件,经优化后的API与KPI的回收率分别为65.0%与84.6%,显著高于MP（54.0%）。KPI、API与MP的脂肪与灰分含量明显低于TP,其中KPI的粗蛋白含量最高。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳显示KPI与API的蛋白组成与TP相近,但KPI与API的氨基酸组成中甘氨酸与脯氨酸含量显著低于TP。质构与流变学分析结果显示,KPI与API的凝胶强度与储能模量（G’）均明显低于TP与MP,其中TP、MP与KPI的储能模量在50～55 ℃会出现明显的下降趋势,表明发生凝胶劣化现象,而API组无明显变化。扫描电子显微镜结果表明,与90 ℃相比,经55 ℃加热处理的KPI、TP与MP组凝胶结构更加疏松、多孔,这与流变学分析的结果一致。体外模拟胃肠液消化实验表明,MP具有最佳的消化性,API与KPI的消化性相当,且显著高于TP。综上所述,利用ISP制备分离蛋白可显著提高蛋白回收率,且分离蛋白的消化性明显优于TP。由于分离蛋白失去凝胶化能力,故可考虑将其应用于食品蛋白配料领域。     

Improvement on production of (R)-4-chloro-3-hydroxybutyrate and (S)-3-hydroxy-gamma-butyrolactone with recombinant Escherichia coli cells

(R)-4-Chloro-3-hydroxybutyrate (CHB) and (S)-3-hydroxy-gamma-butyrolactone (HL) are used for the synthesis of biologically and pharmacologically important compounds. Enterobacter sp. DS-S-75 was found to have the unique activity to convert (S)-CHB in the racemate to (S)-HL through asymmetric dechlorination, hydrolysis, and lactonization. As a result, the remaining (R)-CHB and formed (S)-HL could be obtained in a one-pot reaction. We purified the CHB degrading enzyme which catalyzing these reactions and isolated the coding gene from the strain DS-S-75 in order to improve the productivity of these compounds using the transformant. Interestingly, the purified enzyme showed not only dechlorinating, but also hydrolyzing activities on CHB and the similar carboxylic esters, it was then designated CHB hydrolase, and appears to be a novel enzyme. The gene had 1101 bp encoding 367 amino acids including a signal peptide composed of 25 residues. The deduced amino acid sequence contained a conserved region generally found in esterases and lipases, but did not have significant similarity. When asymmetric degradation of racemic methyl CHB (CHBM) was performed using a culture broth of Escherichia coli DH5alpha transformed with the isolated gene, the reaction time was shortened 20-fold over that of the strain DS-S-75, and the maximum concentration of the substrate could be increased from 8% to 15% (w/v). Moreover, both of the obtained residual (R)-CHBM and the formed (S)-HL had high optical purities (>99% e.e.).     

丝麻功能新面料的开发(1)

系统阐述了丝麻功能性面料的开发过程,通过应用纳米材料和新型后整理技术,研制具有防缩抗皱、抗菌易去污和抗紫外线等特点的功能性纺织品。探讨了纳米材料在抗皱方面的催化机理,在功能整理上运用了“纤维界面多元复合修饰”概念,以改善天然纤维表面的物理化学属性,从而获得优良的服用性能和目标功能特性。