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乳铁蛋白和乳铁素的抗菌活性比较 总被引:2,自引:1,他引:2
牛乳铁蛋白是从牛乳中提取出来的一种铁结合性糖蛋白,牛乳铁素是从牛乳铁蛋白N-端水解下来的25个氨摹酸残荩。它们具有多种乍物学功能,其中的广谱抗菌性尤为引人注目。本实验以牛初乳中提取的乳铁蛋白及其水解产物乳铁素为研究对象,选取大肠杆菌为实验菌株,进行铁饱和乳铁蛋白和缺铁性乳铁蛋白、乳铁素对大肠杆菌生长抑制的比较研究。研究结果表明:铁饱和乳铁蛋白、缺铁性乳铁蛋白和乳铁索的最小抑菌浓度分别为6mg/ml、3mg/ml和15μg/ml,乳铁素的最小杀菌浓度为30μg/ml。乳铁蛋白水解后,经纯化获得的乳铁素,其抗菌能力较缺铁性乳铁蛋白增加200倍,较铁饱和乳铁蛋白增加400倍。 相似文献
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乳铁蛋白抑菌活性及机理研究 总被引:4,自引:0,他引:4
乳铁蛋白对G-和G 都有抑菌效果,乳铁蛋白对G-的作用比较强.铁饱和度越低,抑菌性越强.环境pH值变化对G-影响不大,对G 影响较大,pH为7.5~8.0时抑菌效果最佳.乳铁蛋白经过70℃以下的巴氏杀菌后抑菌活性没有影响.HCO3-浓度增加,有利于增强抑菌性.柠檬酸盐和阳离子浓度增加会使抑菌活性下降.圆二色性分析表明,随着铁饱和度的增加,乳铁蛋白的α-螺旋构象逐步转变为β-折叠构象,蛋白质分子排列更为有序,分子的结构变得更加紧密.DSC研究表明乳铁蛋白的N-叶和C-叶铁结合能力不同造成热稳定性差异,低铁饱和度时较高的抑菌活性主要来自于C-叶. 相似文献
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应用鼠李糖乳杆菌和嗜酸乳杆菌发酵豆腐黄浆水,分析了黄浆水和发酵黄浆水还原三价铁、清除DPPH和ABTS+自由基以及螯合二价铁的能力.结果表明,嗜酸乳杆菌发酵黄浆水的还原力最强,显著高于鼠李糖乳杆菌发酵的黄浆水和未发酵的黄浆水;经过发酵的黄浆水清除DPPH和ABTS+自由基的能力明显大于未发酵黄浆水,但是菌种和发酵时间影响不大;螯合二价铁的能力依次为鼠李糖乳杆菌发酵的黄浆水>嗜酸乳杆菌发酵的黄浆水>未发酵黄浆水,且延长发酵时间能提高其螯合二价铁的能力. 相似文献
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比较了二价铁和三价铁作为标准物质,采用1,10菲啰啉分光光度法测定木质活性炭中铁的含量。使用三价铁作为标准溶液,与国家标准(GB/T 12496.19-1999)使用二价铁作为标准溶液测定木质活性炭中铁含量的检验方法的测定结果具有很高的一致性。方法相对标准偏差为1.41%,准确度较高,适用于木质活性炭中铁含量的分析。 相似文献
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Hosokai S Kasiwaya Y Matsui K Okinaka N Akiyama T 《Environmental science & technology》2011,45(2):821-826
This paper describes the reduction of hematite with ammonia for ironmaking, in which the effect of temperature on the products was examined. The results showed that the reduction process began at 430 °C during heating, and with an increase in temperature, the reduction mechanism changed apparently from a direct reduction of ammonia (Fe(2)O(3) + 2NH(3) → 2Fe + N(2) + 3H(2)O) to an indirect reduction via the thermal decomposition of ammonia (2NH(3) → N(2) + 3H(2), Fe(2)O(3) + 3H(2) → 2Fe + 3H(2)O) at temperatures over 530 °C. The final product obtained at 600 and 700 °C was pure metallic iron, in contrast with that formed at 450 °C, that is, a mixture of metallic iron and iron nitride. The results suggest the possibility of using ammonia as a reducing agent for carbonless ironmaking, which is operated at a much lower temperature than 900 °C in conventional coal-based ironmaking. 相似文献
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Ferrous iron (Fe2+) oxidation by microbial iron mat samples, dominated by helical stalks of Gallionella ferruginea or sheaths of Leptothrix ochracea, was examined. Pseudo-first-order rate constants for the microbial mat samples ranged from 0.029 +/- 0.004 to 0.249 +/- 0.042 min(-1) and correlated well with iron content (R2 = 0.929). Rate constants for Na azide-treated (1 mM) samples estimated autocatalytic oxidation by iron oxide stalks or sheaths, with values ranging from 0.016 +/- 0.008 to 0.062 +/- 0.006 min(-1). Fe2+ oxidation attributable to cellular activities was variable with respect to sampling location and sampling time, with rate constants from 0.013 +/- 0.005 to 0.187 +/- 0.037 min(-1). Rates of oxidation of the same order of magnitude for cellular processes and autocatalysis suggested that bacteria harnessing Fe2+ as an energy source compete with their own byproducts for growth, not chemical oxidation (under conditions where aqueous oxygen concentrations are less than saturating). The use of cyclic voltammetry within this study for the simultaneous measurement of Fe2+ and oxygen allowed the collection of statistically meaningful and reproducible data, two factors that have limited aerobic, circumneutral, Fe2+ -oxidation rate studies. 相似文献
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白酒中黄色的形成、检测及去除 总被引:2,自引:0,他引:2
白酒在长期贮存过程中,金属铁与白酒中有机酸反应,使酒中溶入Fe^2 ,使酒呈黄色;Fe^2 进一步氧化成Fe^3 ,在酒中形成棕色沉淀析出。添加适量植酸处理24h,可除去酒中铁离子,使酒达到无色透明,不会影响白酒中香味物质。(孙悟) 相似文献
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Reductive transformation reactions involving mineral-bound Fe2+ species are of great relevance for the fate of groundwater contaminants. For clay minerals, which are ubiquitously present in soils and sediments, the factors determining the reactivity of structural Fe2+ and surface-bound Fe2+ are not well understood. We investigated the reactivity and availability of Fe2+ species in suspensions of chemically reduced montmorillonite (SAz-1) as well as in suspensions of oxidized and reduced nontronite (SWa-1, ferruginous smectite) using two acetylnitrobenzene isomers as reactive probe compounds. The analyses of the reduction kinetics of the two nitroaromatic compounds (NACs) suggested that Fe2+ bound in the octahedral layer of reduced smectites is the predominant reductant and that electron transfer presumably occurs via basal siloxane planes. In contrast, reduction of NACs by Fe2+ associated with oxidized nontronite is orders of magnitude slower than reduction by octahedral Fe2+. Reductive transformation and reversible, nonreactive electron donor-acceptor (EDA) complexation of NACs at basal smectite surfaces occur simultaneously at reduced montmorillonite exhibiting low structural iron content. In contrast, EDA complexation was not observed in suspensions of reduced iron-rich nontronite. Due to the similar reduction rate constants measured for the two NACs, we propose that the (re)- generation of octahedral Fe2+ sites, e.g., by electron transfer and/or Fe rearrangement within the octahedral nontronite layers, partly limited the rate of contaminant transformation. Since iron in clay minerals is available for microbial reduction, our study suggests that octahedral Fe2+ can contribute to abiotic contaminant transformation in anoxic environments. 相似文献
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A poly(vinyl alcohol) (PVA) membrane containing iron (Fe(0)) particles was developed and tested as a model barrier for contaminant containment. Carbon tetrachloride, copper (Cu2+), nitrobenzene, 4-nitroacetophenone, and chromate (Cr04(2-)) were selected as model contaminants. Compared with a pure PVA membrane, the Fe(0)/PVA membrane can increase the breakthrough lag time for Cu2+ and carbon tetrachloride by more than 100-fold. The increase in the lag time was smaller for nitrobenzene and 4-nitroacetophenone, which stoichiometrically require more iron and for which the PVA membrane has a higher permeability. The effect of Fe(0) was even smaller for CrO4(2-) because of its slow reaction. Forty-five percent of the iron, based on the content in the dry membrane prior to hydration, was consumed by reaction with Cu2+ and 15% by reaction with carbon tetrachloride. Similarly, 25%, 17%, and 6% of the iron was consumed by nitrobenzene, 4-nitroacetophenone, and CrO4(2-), respectively. These percentages approximately double when the loss of iron during membrane hydration is considered. The permeability of the Fe(0)/PVA membrane after breakthrough was within a factor of 3 for that of pure PVA, consistent with theory. These results suggest that polymer membranes with embedded Fe(0) have potential as practical contaminant barriers. 相似文献
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Qian Sui Hubert Roginski Roderick P.W. Williams Cornelis Versteeg Jason Wan 《International Dairy Journal》2010,20(10):707-714
Bovine lactoferrin (LF) with different iron saturation levels (i.e., native (N-) LF, Apo-LF and Holo-LF) dissolved in simulated milk ultrafiltrate was treated by pulsed electric fields. Various heat treatments were conducted as comparisons. The concentration of LF, electrophoretic mobility of the proteins, surface hydrophobicity and the release of LF-bound ferric ions to the aqueous phase of the LF preparations after the PEF or thermal treatments were determined. PEF treatments did not affect the physicochemical properties of Apo-LF, N-LF, or Holo-LF at treatment temperatures ≤50, ≤60, ≤65 °C, respectively. Changes in LF properties at higher temperatures were largely or entirely due to concurrent thermal effects during PEF treatments. The thermal stability of LF correlated with the level of iron saturation. These results will be useful when developing a PEF process for microbial inactivation of LF-containing dairy products with the aim of maximising the retention of this heat-sensitive protein. 相似文献
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Rate and extent of aqueous perchlorate removal by iron surfaces 总被引:1,自引:0,他引:1
The rate and extent of perchlorate reduction on several types of iron metal was studied in batch and column reactors. Mass balances performed on the batch experiments indicate that perchlorate is initially sorbed to the iron surface, followed by a reduction to chloride. Perchlorate removal was proportional to the iron dosage in the batch reactors, with up to 66% removal in 336 h in the highest dosage system (1.25 g mL(-1)). Surface-normalized reaction rates among three commercial sources of iron filings were similar for acid-washed samples. The most significant perchlorate removal occurred in solutions with slightly acidic or near-neutral initial pH values. Surface mediation of the reaction is supported by the absence of reduction in batch experiments with soluble Fe2+ and also by the similarity in specific reaction rate constants (kSA) determined for three different iron types. Elevated soluble chloride concentrations significantly inhibited perchlorate reduction, and lower removal rates were observed for iron samples with higher amounts of background chloride contamination. Perchlorate reduction was not observed on electrolytic sources of iron or on a mixed-phase oxide (Fe3O4), suggesting that the reactive iron phase is neither pure zerovalent iron nor the mixed oxide alone. A mixed valence iron hydr(oxide) coating or a sorbed Fe2+ surface complex represent the most likely sites for the reaction. The observed reaction rates are too slow for immediate use in remediation system design, but the findings may provide a basis for future development of cost-effective abiotic perchlorate removal techniques. 相似文献