背景：
白血病抑制因子(Leukemia Inhitory Factor, LIF)是一种通过抑制自发分化而促使胚胎干细胞(ES)长期存活的淋巴因子。去除LIF将引起干细胞的分化，但干细胞仍可保持其增殖潜能和多能性。人LIF对人和小鼠细胞具有相同的生物活性。大肠杆菌(E.coli)表达的重组人LIF由非糖基化的单个肽链组成，含有180个氨基酸，分子量为19,717Da。

bioLEAD LIF的优点：   

1)      对于人和小鼠细胞的活性相同

2)      经ES(胚胎干细胞)培养测试，可长期保持干细胞的未分化状态和种系传递能力

3)      工作浓度与其它公司同为1000U/ml，因此可做无缝隙直接转换

4)      纯度高于95%

5)      价格便宜

6)      保证活性，否则100%退款

 bioLEAD LIF的活性测试：  

 1. 胚胎干细胞(ES)培养测试：

小鼠胚胎干细胞(W4)在添加重组人LIF (1000 Units/mL)的培养基中培养。传代10次(共25天)后，胚胎干细胞仍保持着正常的形态 (图1)。核型分析结果显示，80%的胚胎干细胞含有正常的40条染色体(图2)。

 2. 长期培养的胚胎干细胞(ES)种系传递能力测试： 

小鼠胚胎干细胞(W4)在含有白血病抑制因子(重组人LIF)的培养基中培养，传代10次(共25天)后显微注射入C57/BL6小鼠的囊胚腔中，仍可生成雄性嵌合体小鼠，主要来源于胚胎干细胞(>95%，根据Agouti鼠毛色判断)。将两只雄性嵌合体小鼠与雌性C57BL/6J小鼠杂交，所有的子代(26只，4窝), 均携带W4 胚胎干细胞来源的Agouti鼠毛色基因。结果表明长期培养的胚胎干细胞(ES)具有种系传递能力。

使用该产品的文献：
Rotter et al. Mutant p53 facilitates somatic cell reprogramming and augments the malignant potential of reprogrammed cells. J. Exp. Med.. 2010; 207: 2127-2140.  

bioLEAD LIF的详细信息：
Cat. No.: BL-Z00384

Source: E. coli

MW: 19,717 Da

Description:
Leukemia Inhibitory Factor (LIF) is a lymphoid factor that promotes long-term maintenance of embryonic stem cells by suppressing spontaneous differentiation. LIF has a number of other activities including cholinergic neuron differentiation, stem cell pluripotency control, bone and fat metabolism, mitogenesis of certain factor-dependent cell lines, and the promotion of megakaryocyte production in vivo. Mature human and murine mature LIFs exhibit 78% sequence identity at the amino acid control.Human LIF is equally active on both human and mouse cells. Murine LIF is approximately 1000 times less active on human cells than hLIF. Recombinant Human LIF produced in E. coli is a single, non-glycosylated, polypeptide chain containing 180 amino acids and having a molecular mass of 19,717 Da.

Purity:
Greater than 95% as determined by the following methods:
(a) RP-HPLC analysis
(b) Anion-exchange FPLC
(c) Reducing and non-reducing SDS-PAGE silver-stained gel
analysis

Endotoxin Level:
Less than 0.1 ng/ug (1 IEU/ug) of LIF

Specific Activity:
The ED50 is determined by the M1 cell differentiation assay is < 0.01 ng/ml, corresponding to a specific activity of > 1×10⁸ units/mg.

Storage:
Lyophilized rHuLIF remains stable at room temperature for three weeks, but it is best stored desiccated below -18°C. Upon reconstitution rHuLIF should be stored at 4°C for up to one week and -18°C for longer periods it is recomme nded that a carrier protein (0.1% HSA or BSA) be added. Please avoid repeated freeze-thaw cycles

Formulation:
LIF is lyophilized after extensive dialysis against PBS.

Reconstitution:
We recommend a quick spin followed by reconstitution in water to a concentration of 0.1-1.0 mg/ml. We also recommend that further dilutions be made into buffer or medium to which protein (e.g., 1% BSA) or Tween 20 has been added. This solution can then be stored at 4°C for one week or at -20°C for longer periods.

Sequence analysis:
The sequence of the first five N-terminal amino acids has been found to be Ser-Pro-Leu-Pro-Ile.