乳铁蛋白和乳铁素的抗菌活性比较

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。     

锌、铁饱和乳铁蛋白体外抗HBsAg分泌的研究

目的:探讨锌饱和乳铁蛋白(Zn2+-BLF)、铁饱和乳铁蛋白(Fe2+-BLF)体外抑制乙型肝炎表面抗原分泌作用,为锌、铁乳铁蛋白应用于临床治疗乙型肝炎病毒(HBV)感染提供理论和试验依据。方法:以天然HBV感染HepG2细胞为模型,通过应用ELISA法测定细胞上清中的HBsAg水平来检测Zn2+-BLF、Fe2+-BLF的抗HBsAg分泌效果,并用MTT法对Zn2+-BLF、Fe2+-BLF对HepG2细胞的毒性进行研究。结果:Zn2+-BLF、Fe2+-BLF对细胞的最大无毒剂量(TD0)分别为1.5g/L、3.0g/L;先用HBV对HepG2细胞进行感染,再分别加入Zn2+-BLF、Fe2+-BLF,各浓度组Zn2+-BLF均对HBsAg分泌有一定抑制作用,Zn2+-BLF浓度1.0g/L时对HBsAg的抑制率达60.49%;浓度为1.0g/L、0.5g/L的Fe2+-BLF能显著抑制HBsAg的分泌,但0.1g/L的Fe2+-BLF不能显著抑制HBsAg的分泌。结论:当HepG2细胞感染HBV后,Zn2+-BLF、Fe2+-BLF可以显著抑制HBsAg的分泌,Zn2+-BLF对HBsAg的抑制作用强于Fe2+-BLF,但其作用机理有待深入研究。     

茶多酚抑制人膀胱癌细胞生长的研究

研究不同浓度茶多酚对人膀胱癌EJ细胞的抑制和杀灭的作用。用细胞生长曲线观察不同剂量的茶多酚对EJ细胞增殖的影响，用琼脂糖凝胶电泳来检测细胞凋亡还是死亡。结果表明：细胞生长曲线证实茶多酚对EJ细胞生长有明显的抑制作用，抑制强度与茶多酚浓度呈正相关；125－500μg/ml浓度茶多酚琼脂糖凝胶电泳呈典型的“梯状电泳（DNA ladder)带；茶多酚在浓度1000μg/ml时，人膀胱癌EJ细胞被杀灭。     

不同来源Lfcin诱导Jurkat细胞凋亡的对比研究

本文以牛乳铁蛋白素LfcinB和人乳铁蛋白素LfcinH为研究对象,研究其通过降低线粒体膜电位抑制Jurkat细胞增殖效果及两者的差异性。采用MTT法检测LfcinB和LfcinH对Jurkat细胞增殖影响;Hoechst33258染色法荧光显微镜观察Jurkat细胞核的变化;运用Annexin V-FITC/PI双标记流式细胞术将LfcinB和LfcinH促进Jurkat细胞凋亡的阶段进行区分;JC-1染色激光共聚焦显微镜观察细胞线粒体膜电位的改变。结果显示:LfcinH和LfcinB对Jurkat细胞有显著的抑制作用(P0.05),呈剂量依赖性;经LfcinB和LfcinH处理后的Jurkat细胞在荧光显微镜下均可见细胞核皱缩、碎裂呈凋亡特征;激光共聚焦显微镜观察到Jurkat细胞线粒体膜电位下降;流式细胞术检测发现Jurkat细胞经LfcinB和LfcinH处理48 h时主要发生早期凋亡。研究结果表明:Jurkat细胞凋亡的机制可能是通过影响线粒体膜电位导致Jurkat细胞凋亡并抑制细胞增殖;当两者浓度小于250μg/mL时LfcinH对Jurkat细胞抑制效果较强,浓度大于250μg/mL时两者对Jurkat细胞抑制效果相近。     

缺铁乳铁蛋白体外抗HBsAg分泌的研究

研究缺铁乳铁蛋白体外抑制HBsAg作用,为乳铁蛋白应用于临床治疗乙肝病毒感染提供理论和实验依据。以天然HBV感染HepG2细胞为模型,通过应用ELISA法测定细胞上清中的HBsAg水平来检测缺铁乳铁蛋白抗HBsAg分泌效果,并用MTT法进行缺铁乳铁蛋白对HepG2细胞毒性研究。结果表明,缺铁乳铁蛋白对细胞的半数中毒剂量（TD50）L为8.312g／L,最大无毒剂量（TD0）为1．5g／L;用乙肝病毒对HepG2细胞进行感染,分别加入不同浓度的缺铁乳铁蛋白,24,36,48h测定HBsAg水平,各实验组蛋白对HBsAg分泌几乎没有抑制作用。当HepG2细胞感染乙肝病毒后,缺铁乳铁蛋白不能抑制HBsAg分泌,乳铁蛋白GHBsAg分泌与其铁饱和度有关,但其机理有待进一步深入研究。     

桂花多酚对TNF-α诱导下HUVEC炎症反应保护作用的研究

通过建立体外肿瘤坏死因子(TNF-α)诱导人脐静脉血管内皮细胞(HUVEC)炎症损伤反应模型,研究桂花多酚纯化组分1、2、3对炎症细胞的活性(MTT)、活性氧(ROS)含量、超氧化物歧化酶(SOD)和黄嘌呤氧化酶(XOD)活性影响;以10μg/L TNF-α诱导HUVEC产生炎症反应,加入6000μg/L、3000μg/L、300μg/L和30μg/L桂花多酚纯化组分1、2、3,研究桂花多酚纯化组分1、2、3的浓度及其组成对炎症细胞保护作用的影响。结果表明,当桂花多酚纯化组分2、3浓度为300~3000μg/L、组分1浓度为3000μg/L时,可显著提高由TNF-α诱导的HUVEC细胞活力和SOD酶活性(p0.05),显著抑制炎症细胞中活性氧(ROS)含量和XOD酶活性(p0.05),具有显著抗炎效果。     

甘薯糖蛋白功能研究--体外抗肿瘤与Ames实验

对两个品种的甘薯糖蛋白提取物的功能进行了研究,Ames实验结果表明两个实验样品均具有显著的抗突变作用,在实验剂量0～5000μg/皿的范围内,抑制强度与剂量呈相关趋势;体外抗肿瘤实验揭示,实验样品对COS-1、SHG-44、SKOV3细胞的抑制作用呈现剂量依赖性,最小抑制量为1.5μg/ml。     

乳铁蛋白及其多肽对淋巴细胞增殖活性的影响

乳铁蛋白及其多肽具有很多生物活性,但不同来源的乳铁蛋白及其多肽在很多活性方面表现很大的差异。实验比较研究了4种乳铁蛋白及其胃蛋白酶水解产物对小鼠脾淋巴细胞增殖作用的影响,为乳铁蛋白及其多肽的开发应用提供科学依据。实验结果表明:4种乳铁蛋白对Con A诱导的脾淋巴细胞增殖均有抑制作用,其中驼乳铁蛋白抑制作用最强;而4种乳铁蛋白多肽对Con A诱导的脾淋巴细胞增殖在一定浓度范围内具有促进作用,而超出这个浓度范围,就起到抑制作用,但4种乳铁蛋白多肽对Con A诱导的脾淋巴细胞增殖的影响组间比较没有显著差异。     

菲律宾蛤仔多糖提取物抑制蚕豆根尖细胞微核形成的研究

以菲律宾蛤仔全脏器为原料,经酶解、离心去蛋白、乙醇沉淀、分离、洗涤、干燥得多糖粗制品.通过添加不同浓度的菲律宾蛤仔多糖提取物,研究其对丝裂霉素诱发的蚕豆根尖细胞微核形成的抑制作用.结果表明,浓度为50、100、150μg/ml的多糖对丝裂霉素诱发的微核均有显著抑制作用,并且随多糖浓度的升高,微核率降低,即抑制效果增强.     

酶解牛乳铁蛋白制备乳铁素 B的酶解条件研究

乳铁素B是牛乳铁蛋白经胃蛋白酶酶解后所得到的最重要的抗菌肽，乳铁蛋白酶解生成乳铁素后抗菌活性大大增强。通过正交试验确立了牛乳铁蛋白酶解制备乳铁素B的最佳条件，指出在底物质量浓度为50g／L，酶与底物质量浓度比为1：30(质量比)，酶解时间为60min时所得的乳铁素质量浓度及活性较好。     

Heat-induced aggregation of bovine lactoferrin at neutral pH: Effect of iron saturation

The goal of our study was to characterize the effect of iron saturation on the thermal aggregation of lactoferrin (Lf). Iron saturation markedly increased the thermal stability of Lf and decreased aggregation. Heating holo-Lf at 80 °C led to soluble polymer formation whereas apo and native Lf associated into large insoluble aggregates. The thermal aggregation of holo-Lf was mainly driven by non-covalent interactions, with intermolecular thiol/disulphide reactions also observed above 80 °C. For apo and native Lf, intermolecular thiol/disulphide reactions increased, suggesting that free thiol residues initiated cross-linking reactions and that iron saturation contributed to maintaining Lf disulphide bond integrity and protecting the protein from aggregation. We demonstrated that apo-Lf in the presence of N-ethylmaleimide (NEM) could undergo large aggregate formation through non-covalent interactions without the participation of intermolecular disulphide links. A mechanism for the thermal aggregation of Lf is proposed, emphasizing the influence of iron saturation.     

Impact of the iron saturation of bovine lactoferrin on adsorption to a strong cation exchanger membrane

Bovine lactoferrin (bLf) is a high-value iron-binding whey protein used for infant nutrition because of several health-promoting activities. The bLf concentration in whey is very low. Most methods for Lf enrichment use ion exchange chromatography since it is highly selective. However, established processes and emerging methods result in a rather low yield, partly due to inhomogeneous adsorption behaviour. To date, reasons for this have not been investigated. In this study, the impact of the state of iron binding on the adsorption of bLf to cation exchangers was investigated as affected by medium conditions. It was found that the iron-depleted apo Lf has a lower adsorption affinity than iron-saturated holo Lf in the acidic pH-range; e.g., at pH 4.8, close to the pH-value of acid whey, less than 70% of apo Lf adsorbed, whereas >85% of holo Lf bound. At physiological pH values, more than 90% of both forms bound.     

Screening of Bifidobacterium spp. based on in vitro growth responses to bovine lactoferrin

In the present study, we investigated the in vitro growth responses of fourteen strains of four Bifidobacterium spp. (Bifidobacterium infantis, B. breve, B. bifidum, B. longum) against bovine lactoferrin (bLf) at various concentrations. Bacterial strains were grown in deMan, Rogosa and Sharpe (MRS) broth with or without bLf, and growth was monitored by measuring absorbance at 660 nm. A dose‐dependent and strain‐dependent growth response was observed. Bifidobacterium spp. were ranked into high, medium and low according to their calculated relative growth response levels against lactoferrin (Lf). Strains showed better growth responses against holo‐type Lf. However, no inhibitory effects at high concentrations (4 mg mL^?1) or with apo‐type Lf were observed. These results strongly suggest that the growth response of Bifidobacterium spp. against bLf may be a selection criterion for their use in fermented products. In addition, use of holo‐type Lf in fermented food products may be more effective for probiotic growth, and could also be used as a source of iron to the host.     

牛初乳中乳铁蛋白的分离及纯化

乳铁蛋白(Lactoferrin,简称Lf)作为一种糖蛋白,主要存在于哺乳动物的各种外分泌物中,如乳汁、眼泪、唾液等,乳汁尤其是初乳中Lf的含量很高犤1犦。本文通过盐析法和有机溶剂沉淀法从牛初乳中分离出乳铁蛋白,并应用酶联免疫法鉴定各步骤中分离的乳铁蛋白,获得的乳铁蛋白的相对分子量为75,000Da。      

Camel milk lactoferrin reduces the proliferation of colorectal cancer cells and exerts antioxidant and DNA damage inhibitory activities

Lactoferrin (Lf), the main iron-binding protein of milk, has biological activities. We have evaluated the potential of camel milk lactoferrin for its ability to inhibit the proliferation of the colon cancer cell line, HCT-116, in vitro, DNA damage and its antioxidant activities for the first time. The antioxidant capacity of Lf was evaluated by different assays, including ferric-reducing/antioxidant power assay (FRAP), free radical-scavenging activity (DPPH), nitric oxide (NO) radical-scavenging assay, total antioxidant activity and DNA damage, compared with vitamin C and rutin.     

乳铁蛋白的分离及纯化

乳铁蛋白 (Lactoferrin ,简称Lf)作为一种糖蛋白 ,主要存在于哺乳动物的各种外分泌物中 ,如乳汁、眼泪等 ,乳汁尤其是初乳中Lf的含量很高[1] 。Lf是一种多功能蛋白质 ,不仅具有广谱的抗菌作用 ,而且还能够增强机体的抗病毒、抗感染、抗肿瘤的能力和免疫能力。因此 ,从来源丰富的牛初乳中提取出Lf,把它作为功能性成分应用于食品行业 ,具有广阔的应用和开发前景。本文通过盐析法和层析法从牛初乳中分离出乳铁蛋白 ,并应用酶联免疫法 (ELISA)检测不同分离纯化方法所获得的乳铁蛋白的含量 ,并用电泳分析其纯度。所获得的乳铁蛋白的分子质量为 780 0 0u ,其纯度大约为 92 %。     

牛初乳中主要生物活性物质开发的最新进展

综述了近年来牛初乳资源的开发利用状况 ,重点介绍了几种主要功能性物质如免疫球蛋白 (IgG) ,乳铁蛋白 (Lf)及类胰岛素生长因子 (IGF)的分离纯化技术 ,并对牛初乳的综合利用前景进行展望     

乳铁蛋白生物活性及应用进展

乳铁蛋白是一种铁结合型糖蛋白,由哺乳动物体内腺上皮细胞和中性粒细胞产生,为生物活性剂之一。它具有多种生物活性,包括抑菌、抗病毒、抗癌、抗炎、调节免疫和促骨生长等。它已经被用作一些口腔疾病的治疗、婴幼儿配方奶粉的营养强化剂、天然食品保鲜剂、天然化妆品,也可以作为许多棘手疾病辅助和预防治疗的合成原料或载体,被广泛应用在食品、医药、化妆品、畜牧养殖等领域,本文综述了乳铁蛋白的生物活性功能及其与微生物作用机制,并着重从以上五个领域介绍乳铁蛋白的开发与应用,旨在阐明乳铁蛋白的进一步应用前景。     

Effects of feeding vitamin A and lactoferrin on epithelium of lymphoid tissues of intestine of neonatal calves

Circulating levels of vitamin A (retinol) and lactoferrin (Lf) are low in calves at birth. Bovine colostrum contains relatively high amounts of vitamin A and Lf, and both substances are intestinally absorbed by neonatal calves. There is evidence that these compounds interact with insulin-like growth factor binding proteins and thus influence the status and effects of insulin-like growth factor. The hypothesis was therefore tested that vitamin A and Lf influence epithelial growth, development, and absorptive capacity of the small and large intestine and modulate intestinal immune tissues (Peyer's patches; PP). Four groups of calves (n = 7 per group) were fed a milk-based formula with or without vitamin A and (or) Lf. Group F received formula (F) only; group F(A) was fed F supplemented with vitamin A; group F(L) was fed F supplemented with Lf, and group F(AL) received F plus vitamin A plus Lf. An additional group of calves (group C; n = 7) served as positive control and was fed colostrum (C) from pooled milk obtained on d 1, 2, and 3 of lactation. Amounts of nutritive components in formula and colostrum were similar. Blood samples were taken to measure vitamin A and Lf, and plasma xylose (added on d 4 to feeds) was measured postprandially for 8 h as a marker of intestinal absorptive capacity. Plasma vitamin A was low at birth and further decreased in groups F and F(L), but increased in groups F(A), F(AL), and C. Plasma Lf was low at birth and transiently increased up to 4 h after the first meal in group C. Xylose absorption was higher in group C than in other groups. Incorporation of 5-bromo-2'-deoxyuridine into DNA (as a measure of cell proliferation rate) was enhanced in intestinal crypts in groups F and F(L) at all intestinal sites. Ileum villus heights of groups F and F(L) were smaller than of groups F(A) and F(AL). Villus height to crypt depth ratios were smaller in F-fed groups (especially in groups F and F(L)) than in C-fed calves in the duodenum and jejunum. Incorporation of 5-bromo-2'-deoxyuridine into colon crypt cells of group F was greater than in groups F(L) and F(A). Sizes of follicles of PP in the ileum were greater in group F(A) than in group F. In the ileum, vitamin A and Lf tended to interact with PP size. In conclusion, feed supplementation of vitamin A and Lf influenced growth of the ileum and colon. Interactions were observed between vitamin A and Lf on epithelial cell maturation, villus growth, and size of follicles in PP of neonatal calves.