大豆蛋白酶解肽的分子量分布及抑制ACE活性关系研究

研究不同蛋白酶作用的酶解肽表现在血管紧张素转化酶(ACE)活性抑制差异,酶解产物的水解度、分子量分布与ACE抑制率的相互关系。用胰蛋白酶、胃蛋白酶、中性蛋白酶、木瓜蛋白酶、碱性蛋白酶等五种蛋白酶对大豆分离蛋白酶解,进行了多肽增量、水解度、超滤膜分离及其ACE抑制率对比等实验。结果表明,碱性蛋白酶的多肽增量最大,胃蛋白酶次之,依次为木瓜蛋白酶和中性蛋白酶,胰蛋白酶则出现反常;水解度随着酶解的时间而增加,碱性蛋白酶的最大水解度可达到21%,依次为胃蛋白酶、木瓜蛋白酶和中性蛋白酶,最低为胰蛋白酶仅为9%左右;与此对应的碱性蛋白酶的酶解物的ACE活性抑制率为最高(44.9%),胃蛋白酶次之(43.5%)。分子量范围在1000Da以下组分对ACE的抑制效果最高,碱性蛋白酶作用获得的小分子肽组成为71.25%,胃蛋白酶的为69.35%,但其对应的ACE抑制率却为64.57%和78.49%。中性蛋白酶、木瓜蛋白酶和胰蛋白酶作用获得的小分子肽的ACE抑制率分别为45.7%、47.3%和29.6%。胃蛋白酶的降压肽制备效果为最好,其次为碱性蛋白酶、木瓜蛋白酶、中性蛋白酶和胰蛋白酶。     

酶解鲢肉制取ACE抑制肽工艺条件的优化

采用复合风味酶水解鲢(Hypophthalmichthys molitrix)肉制取血管紧张素转化酶(ACE)抑制肽,通过正交试验对水解工艺进行优化,并用SephadexG-15凝胶柱对酶解产物进行分离。结果表明:复合风味酶在温度50℃、pH8.0、料液比1:6、加酶量5000U/g.pr、水解12h的条件下,酶解产物的水解程度及对ACE的抑制率最高,其水解度为34.40%,氮利用率为92.01%,抑制率为66.52%;该酶解产物中相对分子质量较大和较小部分的ACE抑制活性偏低,只有相对分子量在一定范围内的短肽才对ACE具有较好的抑制作用,其中在第3洗脱峰处得到的ACE抑制肽活性最高,其ACE抑制率为63.04%。     

一种新型绵羊乳酪蛋白ACE抑制肽结构鉴定及分子结合机制分析

本研究旨在利用蛋白酶水解绵羊乳酪蛋白,制备新型血管紧张素转化酶（Angiotensin-I-Converting Enzyme,ACE）抑制肽并对其分子抑制机制进行分析,为功能性绵羊乳多肽乳制品开发提供技术支持。试验以绵羊乳酪蛋白为原料,以水解度、ACE抑制率和分子量分布为评价指标,从四种蛋白酶中筛选最适蛋白酶,选择<3 kDa的组分通过LTQ Orbitrap Velos质谱仪进行肽鉴定,筛选潜在的ACE抑制肽进行人工合成并测定其半抑制浓度（IC₅₀）,采用Linewaver-Burk作图确定酶抑制动力学,结合分子对接进一步解释肽段的抑制机制。结果表明:碱性蛋白酶为最佳水解蛋白酶;从κ-酪蛋白中筛选出一种新的ACE抑制肽KYIPIQY,半抑制浓度（IC₅₀）为5.73 μmol/L;Linewaver-Burk图表明该肽对ACE为混合型抑制模式;分子对接显示,KYIPIQY通过与ACE的S1和S2活性口袋形成氢键和疏水作用力发生紧密结合并且可以扭曲ACE的Zn2+四面体,抑制ACE催化活性的失活而发挥高效的ACE抑制活性。     

瑞士乳杆菌对契达干酪成熟期间所产ACE抑制肽的影响及其消化稳定性

为明确瑞士乳杆菌对契达干酪中血管紧张素转换酶（angiotensin-converting enzyme,ACE）抑制肽活性的影响,以蛋白质水解度和ACE抑制率为指标,与干酪乳杆菌组、鼠李糖乳杆菌组和空白组干酪进行对照,研究瑞士乳杆菌对干酪成熟期间蛋白质水解及ACE抑制活性的影响,并对ACE抑制活性最高时期的干酪进行消化稳定性研究。结果表明：成熟期间,3 组益生菌干酪的活菌数无明显差异（P＞0.05）,但均高于空白组;益生菌干酪的蛋白质水解程度和ACE抑制活性显著高于空白组（P＜0.05）,其中瑞士乳杆菌干酪的蛋白质水解程度最强,活性最高（79.71%）。模拟消化后,瑞士乳杆菌干酪活菌数降低14.30%,ACE抑制活性显著增加（P＜0.05）,达到86.06%,多肽质量浓度增加至2.81 mg/mL;研究不同分子质量超滤组分消化后的ACE抑制活性发现,其中大于10 kDa的多肽活性升高,小于10 kDa的活性下降。此外,添加瑞士乳杆菌不影响干酪的整体可接受性。因此,瑞士乳杆菌能促进干酪ACE抑制肽的产生并提高其活性,消化后活性的升高主要与大分子肽的降解有关。     

挤压和发酵对小米多肽ACE抑制活性及抗氧化作用的影响

以小米为原料,制备具有血管紧张素转换酶(ACE)抑制作用的食源性活性多肽。采用挤压和发酵的方法对小米粉进行处理,研究其对小米蛋白消化率的影响,同时对在胃蛋白酶-胰酶水解条件下得到的小米多肽进行ACE抑制活性和抗氧化能力分析。结果表明,相比于原粉,挤压和发酵对小米多肽的ACE抑制活性和抗氧化能力都有显著的影响(P<0.01);挤压对小米蛋白消化率的影响较大(53.11%);挤压小米蛋白水解肽具有较强的ACE抑制活性(IC50=0.057 mg肽/mL)、DPPH自由基清除能力(10.99μmol/g肽)和铁离子还原能力(82.92μmol/g肽)。     

鲍鱼内脏胶原ACE抑制肽纯化及结构初探

以超滤所得鲍鱼内脏胶原血管紧张素转化酶(Angioemin-I Converting Enzyme,ACE)抑制肽(分子量小于3000 u)为研究对象,通过DEAE-52纤维素柱层析分离后用葡聚糖凝胶G-25柱层析对鲍鱼内脏胶原ACE抑制肽进行纯化,得到ACE抑制活性较高的肽。采用红外光谱技术对所得组分的二级结构进行了初步的研究。结果表明:鲍鱼内脏胶原ACE抑制肽经DEAE-52纤维素阴离子交换层析分离,Na Cl溶液(0.1、0.3、0.6 mol/L)单一浓度和梯度洗脱均得到一个组分,梯度洗脱的多肽得率为82.7%,该组分的ACE抑制率为81.23%;再过葡聚糖凝胶G-25分子筛柱,用蒸馏水洗脱,所得的洗脱曲线为单一对称峰,ACE抑制率为82.12%。通过傅里叶红外光谱分析得出胶原ACE抑制肽中具有β-折叠和α-螺旋结构。初步认为,β-折叠和α-螺旋结构对鲍鱼内脏胶原多肽的ACE抑制活性起到重要作用。     

金华火腿中生物活性肽的血管紧张素转化酶调节功能及其分离纯化

为了探究干腌火腿中生物活性肽的降血压功能,以金华火腿为原料,提取其生物活性肽成分,并通过分离纯化鉴定具有血管紧张素转化酶(ACE)调节功能的生物活性肽。结果表明:经Sephadex G-25分子排阻色谱分离后,金华火腿生物活性肽可分为A、B、C、D共4个组分,其中组分C的ACE抑制活性最强,达到31.8%。将组分C经离子交换柱分离后,金华火腿多肽可分为C1、C2、C3、C4共4个组分,其中C2组分的ACE抑制活性显著高于其它组分,活性高达49.0%(P＜0.05)。经Nano-LC-ESI-MS/MS鉴定得到C2中含有8条多肽,经ACE活性测定,序列IESDLERAEE在8条多肽中活性最强,ACE抑制活性达到59.1%。结论:金华火腿多肽具有良好的体外调节ACE活性的功能,为进一步开展其体内血压调节功能研究奠定了基础。     

菜籽蛋白水解物及其膜分离组分的降血压相关活性

应用商业化蛋白酶Alcalase水解菜籽分离蛋白(RPI),并通过膜分离技术将水解物分离成4种不同分子质量大小的多肽组分(<1kD、1～3kD、3～5kD和5～10kD);评价水解物(RPH)和多肽组分的血管紧张素转化酶-Ⅰ(ACE)、肾素抑制活性和氧自由基吸收能力(ORAC)。结果表明:分子质量大小与菜籽肽的氧自由基吸附能力成负相关;<1kD的组分具有最大的ACE抑制活性(抑制率为(83.42±0.35)%)和氧自由基吸附能力;与膜分离组分相比,Alcalase水解物具有最高的肾素抑制活性。研究认为,菜籽蛋白Alcalase水解物及其<1kD的膜分离组分可能作为功能性成分用于降血压相关的功能食品和保健品的开发。     

酶解米糠蛋白分离提取ACE抑制肽及其结构研究

研究酶解米糠蛋白中具有ACE抑制活性短肽组分及其序列,本实验采用等电点沉淀法提取米糠蛋白,经胃蛋白酶、胰蛋白酶、木瓜蛋白酶等单独或联合水解米糠蛋白,并采用Sephadex G-15凝胶层析和SP-Sephadex C-25离子交换层析分离各酶解组分。ACE抑制活性检测结果显示:酶解组分中含有较高抑制活性成分,其相对分子量在500单位以内。各组中活性最高的组分进行HPLC-MS分析,其中活性最高的胃蛋白酶联合胰蛋白酶酶解活性组分主要为Arg-Tyr、Met-Trp、Gly-Val-Tyr或Gly-Asp-Phe,其共同特征是C端具有苯环样结构,提示:这种环结构可能是ACE抑制剂的重要结构特征。     

大豆生理活性肽的研究(Ⅱ)--抗氧化性和ACE抑制活性的初步研究

采用AS1.398和Alcalase两种蛋白酶,制备了水解度为10%～24%的大豆多肽,对其抗氧化性、ACE抑制活性和相对分子质量的分布进行了研究,结果表明采用AS1.398酶水解的DH为12%的产品抗氧化活性最高,添加量为6 mg/mL时使亚油酸的氧化诱导期延长2.92倍,其相对分子质量分布在1 000以上的组分较多;采用Alcalase酶水解的DH为14%的大豆多肽产品,ACE抑制活性最高,IC50为0.144 mg/mL,其相对分子质量分布大多在200～600之间.     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the     

Chinese CTP Market

According to Printing and Printing Equipment Industries Association of China（PEIAC）＇s statistics to the plate manufucturer in China, in 2013, the actual offset plate production has reached 346 million square meters in China. Among them, the CTP production volume was 245 million square meters, up by 11% than that of last year; the total sales of the CTP plate was 239 million square meters, up by 13%.     

Preparatory Work of Print China 2015 is Going Smoothly

正Held at Guangdong Modern International Exhibition Center,Print China 2015 will cover 7exhibition halls,besides the original Hall No.3,4,5,6,7,the newly built F zone of Hall 3 will be used too.The total area will be140,000 square meters.Hall 3:Offset and large printing equipment,package printing equipment,post press