Lactadherin is a widely distributed glycoprotein (~ 50 kDa), which was originally characterized due to its association with milk fat/lipid globule membranes. Synonymous names are PAS-6/7, bovine-associated mucoprotein, BA-46, P47, and MFG-E8. Structural hallmarks of lactadherin are the presence of two epidermal growth factor (EGF) homology domains (with an RGD peptide motif in the second EGF domain), and two C domains sharing homology with the discoidin family of lectin domains including the phospholipid-binding domains of blood clotting factors V and VIII. Lactadherin shows preferential binding to phosphatidylserine (L-form) in a calcium independent manner, and binds more specifically than Annexin V.
Purified lactadherin functions as an anticoagulant by blocking phosphatidylserine-containing membrane sites for blood coagulation proteins (10). Fluoresence-labeled lactadherin functions as a sensitive probe for exposed phosphatidylserine on nucleated cells and on stimulated platelets (8, 9) . Lactadherin will bind to membranes that have phosphatidylserine content below the threshold for annexin V binding.
Lactadherin is purified from un-pasteurized bovine milk (11).
Illustrated Applications
Above: K562 cells (top) and HL60 cells (bottom) co-stained with both FITC-conjugated lactadherin (green) and Alexa-647 conjugated annexin V (red) early in apoptosis. The annexin is internalized in granules and is not detectably staining the cells. Reference: Shi, J., Y. Shi, L. N. Waehrens, J. T. Rasmussen, C. W. Heegaard and G. E. Gilbert (2006). "Lactadherin detects early phosphatidylserine exposure on immortalized leukemia cells undergoing programmed cell death." Cytometry A 69(12): 1193-201. Copyright 2006. John Wiley & Sons, Inc. Reprinted with permission of John Wiley & Sons, Inc.
Above: HeLa cells stained with FITC-conjugated lactadherin 2 hours (top) and 3 hours (bottom) after treatment with staurosporine. Early in apoptosis the cells have small vesicles and long, thin appendages that stain avidly for lactadherin. Reference: Waehrens LN, Heeghaard, CW, Gilbert GE, Rasmussen JT. Bovine Lactadherin as a Calcium-independent Imaging Agent of Phosphatidylserine Expressed on the Surface of Apoptotic HeLa Cells 2009 J. Histochem. Cytochem. (ePub June 2009).
Above: Phosphatidylserine exposure in mouse mesenteric venous thrombosis. Mice were given 1 µg each of lactadherin and annexin V by tail vein immediately prior to externalization of the mesentery. The mesentary was exposed to ferric chloride and then the animals were perfused with saline/paraformaldehyde. Serial sections of the mesentary were stained with anti-fibrinogen/fibrin (left), anti-platelet (middle), and anti-lactadherin antibodies (right) developed with the alkaline phosphatase Vector Red substrate. A layer of fibrinogen/fibrin (left, closed arrows) overlaid a mural hemorrhage (open star). Platelets (middle) were scattered along the luminal surface of the thrombus (open triangles) as well as upon fibrinogen/fibrin strands extending into the lumen. Lactadherin staining (right) was strongest along the raised endothelium surface (closed arrow), including adherent platelets close to the wall. Platelets on fibrin strands did not stain detectably (open arrow). (Shi J, Pipe SW, Rasmussen JT, Heegaard CW, Gilbert GE. Lactadherin blocks thrombosis and hemostasis in vivo: correlation with platelet phosphatidylserine exposure. J Thromb Haemost. Jul 2008;6(7):1167-1174).
Guidelines for using BLAC-FITC:
FITC-conjugated bovine lactadherin (BLAC-FITC) is supplied as a 100X stock solution (1.6 micromolar) in a buffer of 20mM Tris, 150mM NaCl, pH 7.4 containing 1% (w/v) bovine serum albumin and 0.02% sodium azide. Assuming that most labeling reaction volumes will be approximately 0.5ml, a 1 ml vial of the 100X stock material will be sufficient for 200 labeling reactions. Additionally, as this product is fluorescently labeled it should be protected from light.
For a typical cell staining experiment, apoptotic cells are collected by centrifugation and resuspended in a physiologic buffer such as TBS (20mM Tris, 150mM NaCl, pH 7.4), HBS (20mM Hepes, 150mM NaCl, pH 7.4) or PBS (4.3mM Na2HPO4, 1.47mM KH2PO4, 137mM NaCl, 2.7 mM KCL, pH 7.4) to a final cell count of approximately 1 x 106 cells/ml. Adherent cells may be harvested by trypsinization, but should be washed at least once in either media or buffer prior to making the final suspension in buffer. Stock 100X FITC-conjugated lactadherin is added to the cell suspension at the rate of 5 microliters for every 0.5ml of the cell suspension. At this point, optional staining with propidium iodide (PI) may be initiated by adding PI to a final concentration of 0.5 to 1 µg/ml. Incubate the reaction mixture at room temperature (protected from light) for a period of 5 to 10 minutes.
Labeled cells may be analyzed by a variety of methods including flow cytometry and fluorescence microscopy. Fluorescence detection may be monitored using the following detector settings:
BLAC-FITC: Ex = 488 nm; Em = 530 nm
PI: Ex = 488 nm; Em = 640 nm
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一、机械裂解法主要有以下两中:
1.热休克(Thermal shock),既反复冻溶法,是一种常用的机械裂解方式比,通常由冷冻和解冻两部分组成(freezing and thawing),.原理:由于细胞内冰粒形成和剩余细胞液的盐浓度增高引起溶胀,使细胞结构破碎.冷冻通常在液氮或-20°C冰上进行,解冻可以在37、50、65 或100℃水浴中进热休克比化学裂解温和,但是很有效,有资料表明用热休克和溶菌酶与SDS的方法获得了90%的细胞裂解率.
2.超声波处理(Ultrasonication)既利用超声加热的方法,把细胞破碎.但这种处理会导致DNA 的断裂,所以加热不宜过剧烈,要设定好超声时间和间隙时间,一般超声时间不超过5秒,间隙时间最好大于超声时间,这些都有利于保护酶的活性.bead-beating 也是常用的机械处理方式,有报道指出bead-beating 比热休克和化学裂解的细胞裂解效果更好 虽然DNA产量较高,但通常得到的DNA片段较小.
二、 化学裂解和酶裂解法(在提核酸时联合使用)
主要是裂解液处理法,细胞裂解液的主要目的有以下几种:(1)利用去污剂破坏脂质双分子层,破裂细胞;(2)溶解蛋白;(3)蛋白变性使其稳定;(4)抑制蛋白酶活性.
主要根据不同的目的,裂解液的组成有所不同,主要有提取核酸和蛋白两中.在提取RNA或DNA时,我们主要是要充分裂解细胞,得到更多的核酸;如果我们的目的是蛋白,那要根据蛋白的位置、特性等因素考虑裂解液,在提取蛋白后,再根据实验需要复性蛋白等.以下是细胞裂解中常用试剂和其作用:
50 mM Tris-HCl pH 7.4(缓冲体系),150 mM NaCl(等渗体系),1 mM PMSF (强大的蛋白酶抑制剂),1 mM EDTA(变性剂和稳定剂),5 μg/ml Aprotinin(蛋白酶抑制剂),5 μg/ml Leupeptin(蛋白酶抑制剂),1% Triton x-100(破坏细胞),1% Sodium deoxycholate(中度变性剂和蛋白溶解剂),0.1% SDS(强变性剂和蛋白溶解剂).7M 尿素,2M硫脲(可以提高膜蛋白的融解),蛋白酶K等.
这样可不可以?
另还有几个问题:1、这样的裂解液裂解线粒体提蛋白可不可以
2、裂解液加多少剂量
3、12000g离心10min和30分钟有没有区别
不知单纯使用冰浴中超声裂解够了吗?还是说要选用裂解液呢?最主要的就是我不知道该怎么赔这个裂解液,使其COX活性不产生影响
一、机械裂解法主要有以下两中:
1.热休克(Thermal shock),既反复冻溶法,是一种常用的机械裂解方式比,通常由冷冻和解冻两部分组成(freezing and thawing),.原理:由于细胞内冰粒形成和剩余细胞液的盐浓度增高引起溶胀,使细胞结构破碎.冷冻通常在液氮或-20°C冰上进行,解冻可以在37、50、65 或100℃水浴中进热休克比化学裂解温和,但是很有效,有资料表明用热休克和溶菌酶与SDS的方法获得了90%的细胞裂解率.
2.超声波处理(Ultrasonication)既利用超声加热的方法,把细胞破碎.但这种处理会导致DNA 的断裂,所以加热不宜过剧烈,要设定好超声时间和间隙时间,一般超声时间不超过5秒,间隙时间最好大于超声时间,这些都有利于保护酶的活性.bead-beating 也是常用的机械处理方式,有报道指出bead-beating 比热休克和化学裂解的细胞裂解效果更好 虽然DNA产量较高,但通常得到的DNA片段较小.
二、 化学裂解和酶裂解法(在提核酸时联合使用)
主要是裂解液处理法,细胞裂解液的主要目的有以下几种:(1)利用去污剂破坏脂质双分子层,破裂细胞;(2)溶解蛋白;(3)蛋白变性使其稳定;(4)抑制蛋白酶活性.
主要根据不同的目的,裂解液的组成有所不同,主要有提取核酸和蛋白两中.在提取RNA或DNA时,我们主要是要充分裂解细胞,得到更多的核酸;如果我们的目的是蛋白,那要根据蛋白的位置、特性等因素考虑裂解液,在提取蛋白后,再根据实验需要复性蛋白等.以下是细胞裂解中常用试剂和其作用:
50 mM Tris-HCl pH 7.4(缓冲体系),150 mM NaCl(等渗体系),1 mM PMSF (强大的蛋白酶抑制剂),1 mM EDTA(变性剂和稳定剂),5 μg/ml Aprotinin(蛋白酶抑制剂),5 μg/ml Leupeptin(蛋白酶抑制剂),1% Triton x-100(破坏细胞),1% Sodium deoxycholate(中度变性剂和蛋白溶解剂),0.1% SDS(强变性剂和蛋白溶解剂).7M 尿素,2M硫脲(可以提高膜蛋白的融解),蛋白酶K等.
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