生姜蛋白酶的大分子结合修饰

采用单甲氧基聚乙二醇(mPEG)和右旋糖苷对生姜蛋白酶进行大分子结合修饰。在酶液质量浓度为2.0mg/mL的硼酸缓冲液中,加入三聚氯氰活化的mPEG 或高碘酸钠活化的右旋糖苷,于40℃修饰反应1h,对修饰剂与酶蛋白的质量比和pH 值条件进行优化：mPEG 与酶的质量比为17.5:1.0、pH9.0,mPEG 修饰酶的修饰率为52.6%,相对酶活力(修饰酶活力/ 天然酶活力)为54.0%;右旋糖苷与酶的质量比为42:1、pH6.0,右旋糖苷修饰酶的修饰率为51.6%,其相对酶活力为原天然酶的3.3 倍。两种修饰酶的热稳定性均比天然酶显著增强,且右旋糖苷修饰酶的热稳定性明显高于mPEG 修饰酶。结果表明：右旋糖苷对生姜蛋白酶的修饰效果优于聚乙二醇,适用于酶蛋白的化学修饰与新型酶制剂的开发利用。     

单甲氧基聚乙二醇修饰中性蛋白酶的制备及特性研究

采用氰脲酰氯活化的单甲氧基聚乙二醇(mPEG5000)对中性蛋白酶进行化学修饰,研究其酶学性质及在非水相中的稳定性。结果表明,中性蛋白酶经mPEG5000修饰后,最适温度仍为50℃,与游离酶一致;其相对活性呈现出修饰率依赖性;修饰酶的热稳定性、底物亲和力均较游离酶有较大改善,且在多种有机溶剂体系中表现出更强的稳定性。表明mPEG5000修饰后的中性蛋白酶在多种不利条件下的耐受性得到提高,为其在非水相催化领域的应用提供了研究基础。     

单甲氧基聚乙二醇-醛对草酸脱羧酶的修饰

草酸脱羧酶(Oxdc)可用于预防、治疗草酸钙结石症,为了改善其使用性能,该文采用单甲氧基聚乙二醇(mPEG)对Oxdc进行修饰,并对修饰反应条件进行了初步优化,在mPEG-醛/Oxdc摩尔比50∶1,pH 5.0,37℃反应12h条件下,Oxdc修饰率为50.69%,酶活保持率67.52%。经SDS-PAGE和红外光谱(IR)分析,证明mPEG共价结合于酶蛋白分子上。酶学特性分析发现,热处理后修饰草酸脱羧酶(mPEG-Oxdc)的酶活保持21.6%,而野生草酸脱羧酶(Oxdc)酶活完全丧失;在pH 2.0^pH 6.0酸性环境下mPEG-Oxdc的酶活相对高于Oxdc;经胰蛋白酶处理,Oxdc相对酶活仅为20.6%,而mPEG-Oxdc保持47.1%。结果表明:mPEG-Oxdc相对于Oxdc,其热稳定性、pH适应性及对胰蛋白酶的耐受性都有所增强。     

硫酸化修饰对小球藻胞内多糖抗氧化及抗肿瘤活性的影响

为探究小球藻多糖硫酸化修饰对生物活性影响,本研究采用小球藻(Chlorella sp.22)为实验材料,提取胞内多糖经DEAE-52纤维素阴离子交换柱分离纯化得到纯化多糖HDB-1,对纯化多糖HDB-1进行硫酸化修饰得SHDB-1,对硫酸化修饰前后多糖进行抗氧化活性和抗肿瘤活性研究。结果表明,纯化组分HDB-1以α-呋喃糖为主。用三氧化硫-吡啶法对HDB-1进行硫酸化修饰得到SHDB-1,其取代度为1.046。抗氧化活性结果表明,HDB-1与SHDB-1的DPPH自由基清除率IC₅₀(半抑制浓度)值分别为29.28 mg/mL和14.49 mg/mL,羟自由基清除率IC₅₀值分别为36.75 mg/mL和28.59 mg/mL,可知SHDB-1抗氧化效果优于HDB-1。抗肿瘤结果表明,HDB-1及SHDB-1在1 mg/mL浓度下对细胞无毒性,HDB-1与SHDB-1的IC₅₀值分别为960.16μg/mL及658.19μg/mL,可知SHDB-1抑制宫颈癌细胞Hela增殖效果优于HDB-1。以上结果表明,硫酸化修饰的小...     

膝沟藻毒素GTX 2,3完全抗原的合成与鉴定

膝沟藻毒素GTX 2,3是一类小分子物质,不具备免疫原性,欲制备其免疫血清及抗体,则必须与偶联剂及载体蛋白偶联形成完全抗原。运用乙二醛作为偶联剂,分别与牛血清白蛋白(BSA)、血蓝蛋白(KLH)合成免疫抗原GTX 2,3-glyoxal-BSA和检测抗原GTX 2,3-glyoxal-KLH,并对经超滤纯化浓缩后的偶联产物进行BCA蛋白浓度测定、全波段紫外扫描、变形SDS-PAGE凝胶电泳和抗原免疫原性的鉴定。结果表明,免疫抗原和检测抗原的蛋白质量浓度分别为8.52 mg/m L和5.72 mg/m L;经全波段紫外扫描和变形SDS-PAGE凝胶电泳鉴定,半抗原GTX 2,3-乙二醛与载体蛋白BSA、KLH偶联成功,偶联比约为1︰16和1︰20,并制备出纯度较高的免疫抗原;用制备的人工抗原GTX 2,3-glyoxal-BSA对Balb/C小鼠进行免疫,通过间接ELISA检测6免后小鼠血清效价达到1︰20 000。成功制备了具有较强免疫原性的膝沟藻毒素GTX 2,3人工抗原。     

苄嘧磺隆人工抗原的合成与鉴定

以2-甲酸甲酯苄磺酰胺和琥珀酸酐为原料合成半抗原(hapten),经薄层层析和1H-NMR鉴定后,采用混合酸酐法分别与牛血清蛋白(BSA)和卵清白蛋白(OVA)偶联获得免疫原(hapten-BSA)和包被原(hapten-OVA),紫外光谱分析法计算得其偶联比分别为8:1和13:1,初步说明具有较好免疫原性。通过动物免疫实验获得了效价达1:32000的阳性血清,采用间接酶联免疫吸附检测(ELISA)法检测抗体的IC50和IC10值为0.5032mg/L和0.0024mg/L,表明人工抗原合成成功。     

氯化苦急性经口、经皮、吸入毒性试验

[目的]检测氯化苦经消化道、皮肤和呼吸道3种暴露途径引起动物的中毒症状、死亡率及半数致死剂量,为急性毒性分级和生产使用防护提供科学的资料。[方法]GB 15670—1995《农药登记毒理学试验方法》中急性经口、经皮、吸入染毒方法。[结果]氯化苦急性经口LD50:雌性为369(271~501)mg/kg,雄性为316 mg/kg,经皮LD50雌雄大鼠均为926(636~1 350)mg/kg,吸入LC50(2 h)雌雄大鼠均为316 mg/m3。[结论]该实验室条件下,氯化苦对大鼠急性经口、经皮、吸入毒性均属于中等毒。     

牛毛水解物的生物安全性研究

根据化学品的生物安全性评价程序及检验方法,通过动物试验对牛毛水解物的急性经口毒性、急性经皮毒性、急性吸入毒性和急性皮肤刺激性进行评价。结果表明:牛毛水解物对雌、雄性SD大鼠的急性经口、急性经皮的LD_(50)(半数致死剂量)值均大于5 000mg/kg,急性吸入毒性的LD50值大于5 000mg/m~3,属低毒类化学品,生物安全性较好;急性皮肤刺激试验中,牛毛水解物对家兔皮肤无刺激。     

亚硒酸钠的急性、蓄积性、亚急性毒性研究

目的：对常见的硒强化剂亚硒酸钠的毒性进行研究。方法：以Wistar大鼠为实验动物,分别采用改良寇氏法进行急性毒性实验,剂量递增法进行蓄积毒性实验,以1/20 LD50、1/10 LD50、1/5 LD50剂量连续灌胃30d进行亚急性毒性实验。系统研究亚硒酸钠对大鼠生长状况、组织病理变化、血常规、血液生化指标的影响。结果：大鼠经口灌胃亚硒酸钠的LD50为11.75mg/kg,蓄积系数为3.3,有中等蓄积毒性作用。0.588mg/kg剂量亚硒酸钠对大鼠生长有一定抑制作用,剖检及组织学变化以心、肝、脾、肺、肾等实质器官损伤为主,对主要器官脏器指数、血常规指标、血液生化指标均有不同程度影响。结论：亚硒酸钠属于高毒性物质,可以对大鼠造成急性、蓄积性、亚急性损伤。     

新型绿色溶剂1-庚基-3-甲基咪唑氯盐离子液体对小鼠急性暴露毒性研究

目的 探究烷基咪唑离子液体1-庚基-3-甲基咪唑氯盐(1-heptyl-3-methylimidazolium chloride, C7[MIM]Cl)对小鼠急性暴露的毒性作用。方法 采用上下法, 研究了C7[MIM]Cl对小鼠的急性经口毒性并对死亡小鼠进行解剖病理学观察; 采用最大限量法确定小鼠急性经皮毒性的范围, 并评价其毒性等级; 采用急性眼刺激法, 考察C7[MIM]Cl对小鼠眼和黏膜原发性刺激和腐蚀作用。结果 研究表明C7[MIM]Cl经口暴露对小鼠的肝脏、肾脏表现出明显毒性损伤作用, 其半数致死量(50% lethal dose, LD50)为119.00 mg/(kg·bw), 95%可信区间为87.95~202.00 mg/(kg·bw), 属于中等毒性。同时急性经皮试验表明其LD50在200~1000 mg/(kg·bw)之间。急性眼刺激试验表明, C7[MIM]Cl对小鼠眼部有中度刺激性, 甚至可以导致小鼠死亡。结论 C7[MIM]Cl属于中等毒性化合物, 在食品领域应用的安全性亟待开展更广泛的毒理学评价。     

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.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

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