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1.
目的 对玉米七肽(Ser-Ser-Asn-Cys-Gln-Pro-Phe,SSNCQPF)进行糖基化制备和分离纯化,并对其进行乙醇脱氢酶(alcohol dehydrogenase,ADH)激活活性验证。方法 通过谷氨酰胺转氨酶(transglutaminase,TGase)介导,以玉米七肽作为酰基供体,D-氨基葡萄糖(D-glucosamine,GlcN)为酰基受体的糖基化反应,并分离纯化玉米糖肽单体——SSNCQ(GlcN)PF。使用超高效液相色谱-静电场轨道阱质谱仪(ultra performance liquid chromatography-quadrupole-exactive orbitrap mass spectrometry,UPLC-QE Orbitrap MS)进行面积归一化法测定糖肽纯度,采用核磁共振波谱仪(nuclear magnetic resonance,NMR)测定糖肽的氢谱(1H NMR)和碳谱(13C NMR),并结合二级质谱进行结构定性分析。最后用酶标仪(microplate reader spectrometry,MRS)对比测定玉米七肽及其糖肽的ADH激活活性,以验证玉米七肽糖基化修饰对其ADH激活活性的影响。结果 玉米糖肽经过分离、纯化和冻干后,使用液质联用仪测定其纯度达到99.11%,并且通过二级质谱、核磁氢谱和碳谱的分析,确定氨基葡萄糖连接在玉米七肽谷氨酰胺残基的氨基上。在摩尔浓度为2.5 mM时,糖肽的ADH激活率比玉米七肽高9.89%。结论 与玉米肽相比,采用TGase酶介导玉米七肽和氨基葡萄糖合成的糖肽,具有更高的促酒精代谢生物活性,为玉米肽糖基化在食品工业中的应用提供参考。  相似文献   

2.
采用气相色谱法分析酶法合成MCT中脂肪酸和甘油酯的组成及含量。结果表明:辛酸(FFA)、辛酸甘油一酯(MG)、辛酸甘油二酯(DG)、辛酸甘油三酯(MCT)分离效果较好;4种标准物质的色谱峰面积与质量浓度呈良好的线性关系,线性相关系数达0.994 7~0.999 8,方法的精密度实验中相对标准偏差(RSD)为0.261%~2.527%;加标回收率为95.732%~102.703%,RSD为0.728%~3.028%,检测时间为18 min。该方法可以完成对合成反应中间产物MG、DG及终产品MCT的快速准确分析。  相似文献   

3.
广式香肠烘烤过程中游离脂肪酸的变化研究   总被引:2,自引:1,他引:1  
利用气相色谱对广式香肠中游离脂肪酸 (freefattyacid ,FFA)组分进行色谱分析。广式香肠游离脂肪酸中主要是十六碳和十八碳的脂肪酸 ,其中 ,不饱和脂肪酸占的比例较大。烘烤过程中广式香肠FFA组成发生变化 ,不饱和脂肪酸的质量分数由 53%升至 6 0 % ,饱和脂肪酸的质量分数则由 4 7%降为 4 0 % ;烘烤过程中FFA含量逐渐增加 ,由未烘时的 7 12 9mg/g干重上升为 52h时的 13 74 6mg/ g(干重 ) ,成品中FFA含量达干重质量的 1%以上。各游离脂肪酸组分含量增加的程度不同 ,增加的速率为 :亚油酸 >油酸 >棕榈油酸 >硬脂酸 >棕榈酸  相似文献   

4.
【目的】饮食中氟可影响人体健康与安全,简捷准确检测饮食中氟含量就显得十分重要。【方法】以现有GB/T 5009. 18-2003的氟离子电极电位滴定法为基础,以高倍富集放大反应为获得高灵敏度的突破点,以双点电位滴定法为确保方法准确的手段,探寻出灵敏准确测定谷物中微量氟的新方法。以方法的检测限(LOD)、加标回收率和相对标准偏差(RSD)等为衡量指标,通过单因素试验法对影响富集反应的富集剂种类、用量、温度、时间、反应体系酸度(pH)、搅拌速率和洗涤次数等因素考察后,针对富集反应主要影响因素富集剂用量、反应温度、反应时间和反应体系酸度(pH)等用L9(34)正交试验优化获得最适宜的测定条件。【结果】所得最适宜条件为:含Ca2+复合富集剂用量为(m/m复合剂) = 1:1×105,反应时间200min,反应温度22℃,反应体系酸度pH 5.5,搅拌速率200~300 r/min,沉淀物洗涤4次。该法的LODF = 5.3×10-3 μg/g,且cF在1.0×10-6 mol/L ~ 1.0×10-1 mol/L内呈良好定量函数关系:E = 38.657 lgc - 174.44 (R2 = 0.996)。加标回收率为91.5 %~100.3 %,测定结果较稳定(RSD≤2.7%)。实样氟含量测定值符合GB 2762-2005氟限量要求。【结论】本法集合了富集反应的高倍放大的效果和双点电位滴定法的高精准的特点,测定选择性高,速度快,灵敏度较高,是种实用可靠的微量氟的定量分析方法。且有易于实现自动化和智能化快捷在线检测的潜能。  相似文献   

5.
目的 对茶叶中的百草枯与敌百虫进行定性与定量检测,满足茶叶生产中对这两种农药残留的快速、便携、准确的检测需求。方法 采用表面增强拉曼光谱(surface enhanced Raman spectroscopy SERS)技术对不同浓度的百草枯和敌百虫农药标准溶液进行光谱采集和峰位归属,再对不同茶类茶汤中的梯度农药残留进行检测,建立峰强与农药残留浓度的线性关系。结果 发现在不同茶类中,以茶叶中百草枯在843 cm-1处的拉曼特征峰作为识别峰所建立回归模型预测的百草枯在绿茶、红茶、黑茶茶汤中的最低可检测浓度为1×10-7 moL/L,在乌龙茶茶汤中的最低可检测浓度为1×10-6 moL/L,灵敏度均满足国家规定的茶叶中百草枯最大农药残留限量(0.2 mg/kg);敌百虫的检测中,茶汤中咖啡碱的SERS峰强受敌百虫浓度影响,随敌百虫浓度的增加而减小且呈现显著负线性相关,因此可用茶叶中咖啡碱的拉曼特征峰作为敌百虫浓度的间接识别的依据,所建立的回归模型显示敌百虫在绿茶、红茶、乌龙茶茶汤中的最低可检测浓度为1×10-7 moL/L;在黑茶茶汤中的最低可检测浓度为1×10-6 moL/L,均可达到国家茶叶最大残留限量(2 mg/kg)。结论 使用SERS技术可实现不同茶类茶汤中的百草枯与敌百虫农药残留的简单、快速、准确分析。  相似文献   

6.
目的 制备重金属镉人工抗原并对其进行理化性质和免疫原性鉴定。方法 以乙二胺四乙酸二钠(EDTA.2Na)或二乙基三胺五乙酸(DTPA)为双功能螯合剂,将牛血清白蛋白(BSA)和Cd2+进行螯合,制备镉人工抗原,通过二喹啉甲酸(BCA)法、紫外全波长扫描、聚丙烯酰胺凝胶电泳(SDS-PAGE)、火焰原子吸收法以及动物免疫的方法对人工抗原进行分析鉴定。结果 紫外全波长扫描和SDS-PAGE电泳初步证明人工抗原合成成功;BCA法测定人工抗原BSA-EDTA-Cd2+和BSA-DTPA-Cd2+的蛋白质浓度分别为0.9488、0.5506 mg/mL;火焰原子吸收法测得BSA-EDTA-Cd2+和BSA-DTPA-Cd2+的Cd2+浓度分别为22.8、20.1 μg/mL,说明人工抗原合成成功,且BSA-EDTA-Cd2+和BSA-DTPA-Cd2+的偶联比分别为14.2:1和21.6:1;用BSA-EDTA-Cd2+和BSA-DTPA-Cd2+分别免疫小鼠,四免后血清效价均能达到1:25600,且两组血清敏感性分别达到208.63和98.43 ng。结论 人工抗原BSA-EDTA-Cd2+、BSA-DTPA-Cd2+合成成功,为制备单克隆抗体和建立重金属镉快速免疫分析技术提供研究基础。  相似文献   

7.
为评价H2O2降解对沙棘多糖(sea buckthorn polysaccharides, SBP)结构和性质的影响,采用H2O2联合Fe2+法降解SBP,研究沙棘降解多糖(sea buckthorn degraded polysaccharides, SBDP)的分子质量、单糖组成、粒径、结构特征和抗氧化能力。结果表明,SBDP分子质量(2.902×104Da) 显著低于SBP(3.016×105Da)。离子色谱分析表明, SBDP和SBP均由相同的单糖(岩藻糖、鼠李糖、阿拉伯糖、半乳糖、葡萄糖、甘露糖和半乳糖醛酸)以不同的物质的量比组成。红外光谱及核磁共振波谱证实,SBDP和SBP具有相似的结构特征。与SBP相比,SBDP溶解度提高20.72%,具有更好的吸湿性和保湿性,表观黏度(5.0mg·mL-1)更低,具有剪切稀化行为。与SBP相比,SBDP表现出较高的抗氧化活性, DPPH·、ABTS+·及羟基自由基清除率分别为89.44%±0.12%、96.09%±0.22%和73.25%±1.16%。 H2O2联合Fe2+处理显著降低了SBP分子质量,增强了SBP的功能特性和抗氧化活性,研究旨在为拓展SBP在食品领域的应用提供理论参考。  相似文献   

8.
目的 为研究仿刺参精、卵多肽体外抗氧化及对H2O2诱导巨噬细胞氧化损伤的保护作用。方法 采用切向流超滤法对多肽进行分级制备,通过测定清除1,1-二苯基-2-苦基苯肼自由基(DPPH.)、羟基自由基(.OH)和超氧阴离子自由基(O2-.)的能力来评价体外抗氧化活性,并对多肽的相对分子质量(Mr)、氨基酸(AA)组成及氧化稳定性进行检测分析,通过构建氧化损伤细胞模型,考察多肽对H2O2诱导RAW 264.7巨噬细胞氧化损伤的保护作用。结果 仿刺参精、卵多肽均具有较强的清除DPPH.、.OH和O2-.能力,并且在一定范围内呈现量效关系,Mr<1×103 Da的多肽AJS1和AJE1抗氧化活性表现更强,两者Mr 95.56%和91.89%在1×103 Da以内,疏水性AA和酸性AA比例均较高,并具有极佳的耐盐性和热稳定性,但在贮存和加工过程中仍要注意过酸环境和金属离子对氧化稳定性的影响。所有多肽组对巨噬细胞不存在毒性影响,并且多肽质量浓度为200、400 μg/mL时均对H2O2损伤的RAW 264.7巨噬细胞体现出显著的保护作用(P<0.05)。结论 仿刺参精、卵多肽具有良好的体外抗氧化和对氧化损伤细胞的保护作用,具有开发为功能性食品、医药和化妆品等的潜力。  相似文献   

9.
目的 建立一种快速、灵敏地测定食品中2, 6-二叔丁基对甲苯酚的新方法。方法 通过探讨聚缬氨酸修饰电极的制备条件,确定了采用循环伏安法制备聚缬氨酸修饰电极的最优聚合条件,研究了2,6-二叔丁基对甲苯酚在此电极上的电化学行为。试验从测定pH、电位、扫描速率等方面进一步探讨了测定2,6-二叔丁基对甲苯酚最佳条件。在最优条件下找出了氧化峰电流与浓度的线性关系,作为工作曲线,进一步对食品中的2,6-二叔丁基对甲苯酚进行了测定。结果 在pH=4.0的磷酸盐缓冲溶液中,2,6-二叔丁基对甲苯酚的氧化峰电流与其浓度在4.0×10-7~4.0×10-5mol/L范围内呈线性关系,线性方程:ipa=1.27×10-7+0.23c(mol/L),相关系数为0.9962,检出限4.0×10-8mol/L。结论 方法简单、快速、灵敏,已运用在食品中2, 6-二叔丁基对甲苯酚的检测,获得了满意的结果。此研究建立了测定食品中2,6-二叔丁基对甲苯酚的新方法。  相似文献   

10.
目的:建立用电感耦合等离子体质谱(ICP-MS)法测定辽宁地区芦荟、人参、五味子、龙胆草中铜、镉、铅、砷、汞5种重金属含量的方法。方法:微波消解法处理样品,采用ICP-MS法测定,射频功率1 500 W,采用碰撞模式,碰撞气为氦气,载气为氩气,载气流速0.7 L.min-1,等离子体气体流速15.0 L.min-1,泵速0.3r.s-1。结果:5种重金属线性关系良好(r>0.999 0);加样回收率为89.8%~96.9%(n=6);检测限为0.0002~0.006mg.kg-1。结论:本方法准确可靠、灵敏简便,可用于芦荟、人参、五味子、龙胆草中多种重金属的质量研究,同时为测定同类中药材中此5种重金属提供参考。S  相似文献   

11.
环糊精葡萄糖基转移酶(Cyclodextrin glycosyltransferase,简称CGT酶)能够通过环化反应生成环糊精,但天然菌株发酵产酶的水平较低,使得环糊精的生产成本居高不下,因此旨在通过异源表达以及发酵优化策略来提高CGT酶的表达量。首先将来源于Bacillus xiaoxiensis STB08的cgt基因插入质粒pET-20b(+)中,在宿主菌Escherichia coli BL21(DE3)中进行分泌表达,在适宜的培养基中发酵96 h后,胞外酶活为34.66 U/mL。然后对发酵条件进行优化,改变溶氧以及添加一定终浓度的Ca2+可使酶活提高到66.86 U/mL及83.15 U/mL,且溶氧与Ca2+协同作用可使酶活提高到105.69 U/mL,相比于优化发酵条件之前提高了204.93%。最后通过蛋白质定位分析及流式细胞分析对溶氧及添加Ca2+影响发酵水平的机理进行了研究。结果表明,较低的溶氧能够减少重组大肠杆菌包涵体的形成,且溶氧较低时细胞活性较高,但溶氧过低时菌体浓度太低,不能满足菌体正常生长及代谢的需求。而添加Ca2+能够减少包涵体的形成,同时Ca2+对细胞有较好的保护作用,因此,在溶氧以及Ca2+的协同作用下,能够保证菌体的高生长浓度,且Ca2+能够增加细胞透性并保护细胞,使得活细胞数目显著增多。该研究提高了CGT酶在大肠杆菌中的可溶性表达量,为该酶的工业化生产提供了新的策略及方法,也可为相关酶的发酵优化提供参考。  相似文献   

12.
基于温度场与热流密度的储粮仓型研究   总被引:1,自引:0,他引:1  
现阶段我国粮仓型式、所用材料多种多样,取得的储粮效果不尽相同.通过建立不同加热方式、不同保温措施的实验模式,研究了粮温和热流量变化规律,并在实仓中进行了测试验证,在采取适合的保温材料、气密性等干预措施下,可改变原有温度场数学模型,消除储粮隐患,为选择适合于粮食安全储存要求的储粮型式、围护材料提供参考.  相似文献   

13.
A major portion of the over expressed yeast mitochondrial aconitase, a large 82 kDa monomeric TCA cycle enzyme, in Escherichia coli led to the formation of inclusion bodies. Bacterial chaperonin GroEL mediated the correct folding of aconitase with the assistance of its co-chaperonin GroES in an ATP dependent manner. Till date the chaperonin assisted folding of aconitase was limited to the shake flask studies with relatively low yields of folded aconitase. No attempt had yet been made to enhance the yield of chaperone mediated folding of aconitase using a bioreactor. The current report deals with the effect of co-expression of GroEL/GroES in the production of soluble, biologically active recombinant aconitase in E. coli by cultivation in a bioreactor at different temperatures under optimized conditions. It revealed that the yield of functional aconitase was enhanced, either in presence of co-expressed GroEL/ES or at low temperature cultivation. However, the outcome from the chaperone assisted folding of aconitase was more pronounced at lower temperature. A 3-fold enhancement in the yield of functional aconitase from the bioreactor based chaperone assisted folding was obtained as compared to the shake flask study. Hence, the present study provides optimized conditions for increasing the yield of functional aconitase by batch cultivation in a bioreactor.  相似文献   

14.
The reactivity of octenyl succinic anhydride (OSA) with starch by phase transition catalyst (PTC) was investigated. The effects of two types (quaternary ammonium salt and non-ionic surfactant) and concentrations of PTC on the degree of substitution (DS) and reaction efficiency (RE) of OS-starch were examined. In aqueous medium, the use of a PTC, polyoxyethylene lauryl ether (AEO) produced derivatives with higher DS than others. The DS of OS-starch reached 0.0195 with 0.1% AEO, significantly higher than that (0.0182) without the use of PTC. As the concentration of AEO increased, the DS of OS-starch did not increase. The structural of AEO was investigated by nuclear magnetic resonance (NMR) spectroscopy. Conductivity measurement and Fourier transform infrared (FT-IR) spectroscopy confirmed that AEO could form complexes with Na+. The complex of AEO and Na+ could combine with starch-O, it should be possible to improve the transport of anion starch-O to the hydrophobic reagents.  相似文献   

15.
High-amylose cereal starch has a great benefit on human health. Acid modification is very helpful for application of high-amylose starch in food and non-food industries. In this study, the ordered structure of acid-modified high-amylose rice starch was investigated by GPC, HPAEC, 13C CP/MAS NMR and XRD. Acid preferentially degraded the amylose, then A chain and short B chain of amylopectin. Relative double helix content and crystallinity both initially increased sharply and then progressively with acid hydrolysis. The relative crystallinity of starches obtained from 13C CP/MAS NMR was higher than that from XRD. The onset gelatinisation temperature decreased, while the peak and conclusion temperatures increased with increasing hydrolysis time. The endothermic value initially increased and then decreased with acid hydrolysis. The swelling power decreased while solubility increased after acid hydrolysis. These results add to our understanding of the effect of acid hydrolysis on the high-amylose rice starch.  相似文献   

16.
A new glycosylated biflavonone, morelloflavone-4′″-O-β-d-glycosyl, and the known compounds 1,3,6,7-tetrahydroxyxanthone, morelloflavone (fukugetin) and morelloflavone-7″-O-β-d-glycosyl (fukugeside) were isolated from the epicarp of Garcinia brasiliensis collected in Brazil. The structures of these compounds were established using 1H and 13C NMR, COSY, gHMQC and gHMBC spectroscopy. The compounds exhibited antioxidant activity. The greatest potency was displayed by morelloflavone (2), with IC50 = 49.5 mM against DPPH and absorbance of 0.583 at 400 μg/mL for the reduction of Fe3+. The weakest potency was displayed by 1,3,6,7-tetrahydroxyxanthone (1), with IC50 = 148 mM against DPPH and absorbance of 0.194 at 400 μg/mL for the reduction of Fe3+.  相似文献   

17.
为探究黑曲霉FS10对AFB_1的降解机制,使用黑曲霉FS10的不同组分(菌悬液、发酵液、孢子、菌丝体)对AFB_1进行降解,并研究了AFB_1刺激对黑曲霉FS10降解效果的影响;利用扫描电子显微镜观察降解过程中黑曲霉菌丝体的形态变化;用转录组学技术探究AFB_1可能的降解机理。结果表明:黑曲霉FS10能有效降解AFB_1,72 h时菌悬液的对AFB_1脱除率高达98.65%;黑曲霉FS10孢子对AFB_1无明显脱除作用,但菌丝体对AFB_1有一定的吸附能力,发酵液对AFB_1有明显脱除效果;经过AFB_1诱导刺激后黑曲霉FS10降解效果有明显提升,表明AFB_1处理能显著提升黑曲霉FS10对AFB_1的降解能力。微观结构分析表明AFB_1处理在一定程度上影响黑曲霉FS10的形态,但随着时间的延长这种影响逐渐减小。此外,转录组学分析表明AFB_1处理降低了一些能量代谢基因的水平,这可能是黑曲霉FS10的一种自我保护机制,同时蛋氨酸的合成基因上调,推测AFB_1的降解可能与蛋氨酸的合成有关。  相似文献   

18.
A total of 13 species of microalgae and 14 strains of cyanobacteria, collected directly in the Portuguese coast and lagoons, were characterized for their fatty acid contents, focusing on two with a market potential — i.e. eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA); and another already with alternative (yet somehow more expensive) natural sources — i.e. α-linolenic (ALA) acid. The purpose of this work was their eventual inclusion as additives in food or feed. ALA was the most abundant PUFA in Nannochloropsis sp. (0.616 ± 0.081 mgFA.Lculture− 1.d− 1), and EPA in Phaeodactylum tricornutum (0.148 ± 0.013 mgFA.Lculture− 1.d− 1); Pavlova lutheri was particularly rich in EPA (0.290 ± 0.005 mgFA.Lculture− 1.d− 1) and DHA (0.140 ± 0.037 mgFA.Lculture− 1.d− 1). Despite several previous reports on similar topics and encompassing some of our microalgal species, the wild nature of our strains accounts for the novelty of this work — in addition to the characterization of a few wild cyanobacteria. Eustigmatophyceae class was the best producer of ALA, while Prymnesiophyceae was the best for EPA and ALA. Nodularia harveyana exhibited the highest ALA level (0.611 ± 0.022 mgFA.Lculture− 1.d− 1) and Gloeothece sp. was highest in EPA (0.030 ± 0.004 mgFA.Lculture− 1.d− 1).  相似文献   

19.
Ipomoea aquatica is an aquatic plant that is widely consumed in Southeast Asia as a vegetable. In this study, the influence of various ethanol ratios (0, 20, 50, 80, and 100%) as an extraction solvent and different drying methods including air drying, sun drying, and oven drying on phytochemical constituents of I. aquatica was investigated using a proton nuclear magnetic resonance-based metabolomics approach. The effect on α-glucosidase inhibitory activity and total phenolic content was also examined. Clear discrimination was observed between different ethanol ratios and different drying processes by principal component analysis. The highest α-glucosidase inhibitory activity was observed for absolute ethanol extract from the oven drying method with IC50 value of 204.0 ± 59.0 µg/mL and total phenolic content value of 22.0 ± 0.7 µg gallic acid equivalent/mg extract. Correlation between the α-glucosidase inhibitory activity and the metabolite were analyzed using a partial least square analysis. The metabolites that are responsible for the activity were quercetin derivatives, chlorogenic acid derivatives, sucrose, and fructose. This study highlights the basis for future investigations of I. aquatica as a source of food that has the potential for nutraceutical enhancement and as ingredient in medicinal preparation.  相似文献   

20.
The phenolic composition of the ethanolic extract obtained from the flowers of the medicinal plant Cytisus multiflorus has been elucidated by high performance liquid chromatography, electrospray mass spectrometry and nuclear magnetic resonance analysis. The extract was mainly composed of flavones, including the common chrysin, orientin, luteolin-5-O-glucoside, luteolin-7-O-glucoside, apigenin and apigenin-7-O-glucoside, which appeared as minor components. The major flavone in the extract was chrysin-7-O-β-d-glucopyranoside, and it also contained moderate amounts of a dihydroxyflavone isomer of chrysin, as well as of 2″-O-pentosyl-6-C-hexosyl-luteolin, 2″-O-pentosyl-8-C-hexosyl-luteolin and 6″-O-(3-hydroxy-3-methylglutaroyl)-2″-O-pentosyl-C-hexosyl-apigenin, which are not commonly found in the Fabaceae family. Other novel phenolic compounds found in the ethanolic extract of C. multiflorus comprised the flavones 2″-O-pentosyl-6-C-hexosyl-apigenin, 2″-O-pentosyl-8-C-hexosyl-apigenin and 6″-O-(3-hydroxy-3-methylglutaroyl)-2″-O-pentosyl-C-hexosyl-luteolin. The assessment of the biological activities of the main compounds of this extract are now keen, in order to determine their relevance in the beneficial properties of the plant.  相似文献   

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