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51.
A loop modeling method, adaptive simulated annealing, for ab initio prediction of protein loop structures, as an optimization problem of searching the global minimum of a given energy function, is proposed. An interface-friendly toolbox--LoopModeller in Windows and Linux systems, VC and OpenGL environments is developed for analysis and visualization. Simulation results of three short-chain neurotoxins modeled by LoopModeller show that the method proposed is fast and efficient. 相似文献
52.
目的 对57件市售婴幼儿配方奶粉、50件婴幼儿米粉进行梭状芽胞菌分离鉴定分析及毒素基因检测,获得梭状芽胞杆菌的污染水平数据,并评估各鉴定方法。方法 通过分离菌株的生长特性、革兰染色、普通显微镜下形态特征等表型特征,应用微生物飞行时间质谱(MALDI-TOF-MS)、16S rRNA基因测序技术、全基因组测序技术对分离菌株进行综合鉴定,通过PCR对分离的梭状芽胞杆菌进行肉毒毒素基因检测,对肉毒毒素基因PCR阳性片段进行测序和比对分析。结果 57份市售婴儿配方奶粉中有26份样品中检出38株梭状芽胞杆菌,其中9份样品中同时检出超过两种细菌。50份市售婴幼儿米粉中有5份样品检出5株梭状芽胞杆菌。奶粉中分离的一株楔形梭菌E型肉毒梭菌毒素基因PCR扩增阳性,扩增片段测序比对结果显示这段序列并不是E型肉毒梭菌毒素基因,全基因组测序结果也证实。43株梭状芽胞杆菌均未检出肉毒梭菌的毒素基因。结论 梭状芽胞杆菌鉴定需要多种方法的综合分析。市售婴幼儿配方奶粉、婴幼儿米粉中存在梭状芽胞杆菌的污染,应加强婴幼儿配方食品中重要梭状芽胞杆菌的监测,为风险评估提供数据支持。 相似文献
53.
54.
Amber Scarlatos Bruce A. Welt Brian Y. Cooper Douglas Archer Thomas DeMarse Khe V. Chau 《Journal of food science》2005,70(8):r121-r130
Seven serologically related, but antigenically different, botulinum toxins (BoNTs) have been identified including types A, B, C, D, E, F, and G. The bacterium Clostridium botulinum along with some strains of Clostridium baratti and Clostridium butyricum are known to produce botulinum toxins responsible for 4 forms of botulism poisoning including food‐borne botulism, inhalation botulism, wound botulism, and infant botulism. Botulism toxins consist of a heavy chain (100 kDa), responsible for binding to target cells, and a light chain (50 kDa) responsible for catalytic protein cleaving activity. Light chain has been identified as a zinc endopeptidase that cleaves proteins forming the synaptic vesicle docking and fusion complex (Simpson 1996; Lacy and Stevens 1997). The standard for detection of BoNT toxins is the mouse bioassay, which is able to detect as little as 0.02 ng of toxin. Strengths of the mouse bioassay include conceptual simplicity and sensitivity. While the non‐selectivity of the mouse bioassay enables it to detect any BoNT serotype, additional neutralization assays are necessary to determine serotype. Other limitations of the mouse bioassay include expense, expertise related to maintaining mouse‐rearing facilities, and time, because as much as 4 d may be required to obtain results (Hallis and others 1996; Witcome and others 1999). Several attempts to replace the mouse bioassay have been made. Methods that have been developed and hold promise for future replacement of the mouse bioassay include mass spectroscopy, immunoassays, polymerase chain reaction (PCR) assays, and assays based upon protease activities of BoNTs. Currently, no single assay appears to be capable of replacing the broadly applicable mouse bioassay. 相似文献
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56.
Abstract: Consumer demand for food safety and quality improvements, combined with new regulations, requires determining the processor's confidence level that processes lowering safety risks while retaining quality will meet consumer expectations and regulatory requirements. Monte Carlo calculation procedures incorporate input data variability to obtain the statistical distribution of the output of prediction models. This advantage was used to analyze the survival risk of Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) and Clostridium botulinum spores in high‐temperature short‐time (HTST) milk and canned mushrooms, respectively. The results showed an estimated 68.4% probability that the 15 sec HTST process would not achieve at least 5 decimal reductions in M. paratuberculosis counts. Although estimates of the raw milk load of this pathogen are not available to estimate the probability of finding it in pasteurized milk, the wide range of the estimated decimal reductions, reflecting the variability of the experimental data available, should be a concern to dairy processors. Knowledge of the C. botulinum initial load and decimal thermal time variability was used to estimate an 8.5 min thermal process time at 110 °C for canned mushrooms reducing the risk to 10?9 spores/container with a 95% confidence. This value was substantially higher than the one estimated using average values (6.0 min) with an unacceptable 68.6% probability of missing the desired processing objective. Finally, the benefit of reducing the variability in initial load and decimal thermal time was confirmed, achieving a 26.3% reduction in processing time when standard deviation values were lowered by 90%. Practical Application: In spite of novel technologies, commercialized or under development, thermal processing continues to be the most reliable and cost‐effective alternative to deliver safe foods. However, the severity of the process should be assessed to avoid under‐ and over‐processing and determine opportunities for improvement. This should include a systematic approach to consider variability in the parameters for the models used by food process engineers when designing a thermal process. The Monte Carlo procedure here presented is a tool to facilitate this task for the determination of process time at a constant lethal temperature. 相似文献
57.
Sankar Marichamy Yirgalem Yigzaw Lo Gorton Bo Mattiasson 《Journal of the science of food and agriculture》2005,85(12):2027-2032
Six pure strains of obligate anaerobes capable of degrading the toxin β‐N‐oxalyl‐L ‐α, β‐diaminopropionic acid (β‐ODAP) contained in grass pea (Lathyrus sativus) have been isolated from cow rumen. The new isolates were identified as Megasphaera elsdenii (five different genotypes) and Clostridium bifermentans using 16S rDNA analysis. The β‐ODAP degrading efficiency of the isolates was evaluated by measuring the amount of β‐ODAP in the growth medium, which contained β‐ODAP as the only carbon source, before and after incubation with the microbes. The method of analysis was liquid chromatography employing bioelectrochemical detection. The biosensor is based on co‐immobilising two enzymes, glutamate oxidase (GlOx) and horseradish peroxidase (HRP), on the end of a spectrographic graphite electrode. β‐ODAP is oxidised by GlOx to form H2O2, which in turn is bioelectrocatalytically reduced by HRP through a mediated reaction using a polymeric mediator incorporating Os2 + /3+ functionalities rapidly shuttling electrons with the electrode_giving rise to the analytical signal. On the basis of this analysis system, the new isolates are capable of utilising β‐ODAP as sole carbon source to a maximum of 90–95% within 5 days with concomitant increase in cell protein. Copyright © 2005 Society of Chemical Industry 相似文献
58.
Aparna Dixit Syed Imteyaz Alam Ram Kumar Dhaked Lokendra Singh 《Journal of food science》2005,70(7):m367-m373
A Clostridium sp. RKD isolated from the intestine of decaying fish, showing 99% sequence identity with Clostridium tetani at a 16S rRNA level, produced a neurotoxin that was neutralized by botulinum antitoxin (A+B+E). It also showed an amplification of near‐expected size when polymerase chain reaction (PCR) was performed using group‐ and type‐specific primers for botulinum neurotoxin type B. The isolate exhibited differences with both C. tetani and Clostridium botulinum with respect to phenotypic characteristics and chemotaxo‐nomic markers. Spore production was optimized with respect to media composition and stage of growth. Time‐dependant examination of sporulation revealed 2.6% to 49.0% spores in the late stationary phase culture when grown in different broth media. A simpler method for spore production and isolation from culture grown in tryptose sulfite cycloserine (TSC)/anaerobic agar sandwich resulted in >95% sporulation, which could be purified to near homogeneity by a simple 2‐step procedure. Thermal resistance of spores revealed a biphasic inactivation at lower temperatures with D values for linear inactivation varying from 26.6, 8.0, and 4.3 min at 70 °C, 80 °C, and 90 °C, respectively. The z values of 7.86 °C and 10.47 °C were obtained in the linear and tail regions, respectively. The Weibull parameter b values at 70 °C, 80 °C, and 90 °C were 27.38, 3.55, and 0.99, respectively, with a z’ value of 13.869 °C. The shape parameter n at 70 °C, 80 °C, and 90 °C were 0.63, 0.55, 0.45, respectively. Spores produced on 2 different media (cooked meat medium [CMM] and trypticase peptone yeast‐extract glucose [TPYG] agar) exhibited differences in heat resistance. The addition of lysozyme (50 jj.g/mL) before heat treatment resulted in increased thermal resistance of spores. 相似文献
59.
目的 对从某企业获取的30批次婴儿配方乳粉样品进行肉毒毒素和肉毒梭菌检测,对分离到的1株B型肉毒梭菌进行全基因组测序分析。方法 参照GB 4789.12—2016《食品安全国家标准 食品微生物学检验 肉毒梭菌及肉毒毒素检验》对样品进行肉毒梭菌分离及肉毒毒素分型实验;对分离到的菌株进行全基因组测序,并分析菌株的遗传特征。结果 30批次样品中均未检出肉毒毒素;将增菌液进行小鼠腹腔注射后,4批次乳粉样品出现了典型小鼠肉毒中毒症状,但仅从1批次乳粉样品中分离到肉毒梭菌。基因组测序分析显示,该菌为Ⅰ群B型肉毒梭菌,毒素基因簇为Ha型,毒素基因为B2亚型。结论 针对背景微生物复杂的婴儿配方乳粉中肉毒梭菌检测,不应以菌种分离作为金标准,而应以增菌液小鼠毒性实验结合肉毒抗血清保护实验作为确认方法。全基因组测序可对分离菌种进行精准鉴定和相关遗传特征分析,为中毒事件处理提供可靠的技术支撑。 相似文献
60.
IGF-1 Antibody Prolongs the Effective Duration Time of Botulinum Toxin in Decreasing Muscle Strength
Lingjing Jin Lizhen Pan Wuchao Liu Yan Guo Yuguo Zheng Qiang Guan Zhiyu Nie 《International journal of molecular sciences》2013,14(5):9051-9061
Botulinum toxin type-A (Btx-A), a powerful therapeutic tool in various medical specialties, requires repeated injections to maintain its effect. Therefore, novel methods to prolong the effective duration time of Btx-A are highly needed. Rats were assigned to three major groups: control group (n = 30), Btx-A group (n = 30), and IGF-1 Ab groups. IGF-1 Ab groups were composed by sub-groups A1–A5 (each has 25 rats) for the subsequent IGF-1Ab dose-effect study. Muscle strength was determined by a survey system for rat lower limbs nerve and muscle function. Muscle-specific receptor tyrosine kinase (MuSK), Insulin-like growth factor binding protein-5 (IGFBP5), and growth-associated protein, 43-kDa (GAP43) were determined by real-time polymerase chain reactions (PCRs) and Western blot. We found that Btx-A decreased the muscle strength, with a paralysis maintained for 70 days. IGF-1Ab prolonged the effective duration time of Btx-A. Real-time PCRs and Western blot showed that IGF-1Ab delayed the increase of MuSK and IGFBP5 after Btx-A injection, without affecting GAP43. These results indicate that IGF-1Ab might prolong the effective duration time of Btx-A on muscle strength through delaying the increase of MuSK. It would be interesting to determine whether IGF-1Ab can be used as an auxiliary measure to the Btx-A treatment in the future. 相似文献