Plasmid Info:
Plasmid Information
Product Name: pSF-OXB20-NH2-Flag-3C
Product Code: OG2788
Size (bp): 3902 bp
Bacterial Antibiotic Selection: KanR
Origin and Compatibility: pUC high copy derived from pBR322
Bacterial Copy Number: 500-700 per cell
Promoter: OXB20 strong constitutive bacterial promoter
Plasmid Purpose:
This plasmid is designed to express tagged proteins in E.coli. The plasmid contains a constitutive promoter (OXB20) derived from the region upstream of the E.coli RecA gene. It does not require induction or any additional components for activity. It is the strongest of the bacterial promoters that we provide and this high level of expression can cause expression problems with some proteins with poor solubility. For this reason we sell a range of bacterial promoters with different expression levels (OXB1(low)>OXB20(high)) that can be provided with the peptide tags in this plasmid on request.
About the Cleavage Tag:This plasmid also encodes a protease cleavage site that is designed to be positioned between your gene of interest and the tag to allow the removal of the tag following protein purification or isolation. This plasmid contains a 3C cleavage tag. The protein sequence of the cleavage tag is: LEVLFQ?GP. Human Rhinovirus (HRV) 3C Protease is a highly specific protease that cleaves between the Glu and Gly residues of its recognition site. It is often produced with the trademname 'PreScission protease'.
For more information on which cleavage tag to use see our cleavage tag guide.
Promoter Expression Level:This plasmid contains a constitutive bacterial promoter that does not require induction. It is the strongest bacterial promoter we sell and this can cause solubility and expression problems with some proteins. We also offer a range of other bacterial promoters that are compatible with this plasmid and are available on request.
FLAG is a registered trademark of the Sigma Aldrich Corporation.
About the Peptide Tag:This plasmid contains an n-terminal Flag epitope tag that can be fused to a gene of interest to allow protein detection and/or purification. The sequence of the tag is: DYKDDDDK
For more information on the methods that can be used to purify proteins please see our protein tag guide.
Sequence and Map:
Other Info:
Transcription Termination:This plasmid contains three alternative transcription terminators for mammalian bacterial and bacteriophage (T7) expression. This means that only the promoter needs to be changed to alter the expression system you are using. We sell multiple promoters that can be used in each of these systems. The presence of each terminator does not reduce expression in the alternative systems.
Cloning:
Making Protein Fusions:This plasmid has been designed to allow three types of cloning into the main MCS to join a coding sequence with the tag.
1: SnapFusion Cloning:If you would like to fuse your coding sequence to the tag with minimal additional bases you can use our SnapFusion technology. This process involves amplifying your gene by PCR to add specific restriction sites onto the ends. When these sites are cut they produce an overhang that is compatible with this plasmid cut with BseRI or BsgI.
To insert your gene:
1: Amplify your gene with primers designed using this spreadsheet
2: Cut the plasmid with either BseRI or BsgI.*
3: Cut your gene with the enzyme you added using the spreadsheet (any of AcuI BpmI BpuEI BseRI BsgI EciI).
4: Clone the gene into the plasmid using DNA ligase.
Using this method with an N-terminal tag plasmid will result in the tag coding sequence immediately followed by your genes ATG start codon at the join. This results in a seamless fusion of the two sequences with no extra bases being added. Using this method on C-terminal tag plasmids will convert your genes stop codon into a TAC (Tyr Y) codon followed by the plasmid tag coding sequence. This results in no extra bases between your gene and the tag. See the diagram below for more information.
*Please note that insect expression plasmids cannot be cut with BsgI only BseRI because of unavoidable conflicting sites in the backbone. Also Yeast plasmids cannot be cut with BseRI because of unavoidable restriction sites in the backbone.
Using this technique will create a gene fragment that can be ligated into any or our >1500 peptide and reporter tag plasmids. If you use one of the other techniques below (Gibson InFusion Seamless or LIC) you will need new primers for every vector you clone into because the arms of homology will change according to the tag plasmid you are cloning into.
If you find that your gene sequence has sites in it that make using this cloning strategy difficult you can still use one of the alternative methods below (e.g. standard cloning or Gibson cloning).
Open the Primer Design Tool to help you design primers for cloning your gene in our SnapFusion technique.
2: Standard Enzymes:If you are not concerned about leaving a few extra bases between the tag coding sequence and your gene you can clone your gene into the vector using standard cloning restriction enzymes. This strategy will require you to choose which enzymes you want to use to clone your gene.
Open the Primer Design Tool which provides primers with different enzyme choices positioning your gene as close to the tag as possible in each case. Please note that standard enzymes will always leave additional nucleotides between your gene and the tag but using the spreadsheet will ensure the tag and gene are in frame.
3: Gibson cloning/InfusionHD/GeneArt Seamless/Ligase Independent Cloning (LIC) Methods:
These cloning techniques use reagents sold by other companies and allow you to fuse sequences together using enzymes that chew back the DNA to leave overlapping ends/overhangs. The subsequent method of joining the DNA depends on the kit used. To use one of these techniques you can either design your own primers or you can use the spreadsheet below to help with the design.
Open the Primer Design Tool to help you design primers for cloning your gene using Gibson assembly InfusionHD GeneArt Seamless cloning or Ligase Independent Cloning (LIC) techniques.
IP Status:
Intellectual Property StatusThis product is part of our SnapFast plasmid range, for more information on the Intellectual property status of this plasmid please click here
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1.标准曲线的标准品是否一定要梯度稀释，为什么？我试过非梯度稀释的，也可以达到线性R2=0.99.
2.我用了CurveExpert做标曲，自动搜索后发现有10种提供的方程，各种形式的，其中一个十分适合我的实验结果（LogisticModel），而其他的感觉又不适合，因为结果常常为负值。这又是为啥捏？
3.实验的酶标仪最大OD值可以测到4，如果我的测量结果在1.3，是否像其他人所说的＞1了就不准确了。
4.利用夹心法进行定量分析是否一定要使用线性方程？
不好意思啊，一下问了这么多问题，最近做了一个月的ELISA，完全摸不清头脑啊。谢谢各位了
在这种测定方法中有3种必要的试剂：①固相的抗原或抗体（免疫吸附剂） ②酶标记的抗原或抗体（标记物）③酶作用的底物（显色剂）
测量时，抗原（抗体）先结合在固相载体上，但仍保留其免疫活性，然后加一种抗体（抗原）与酶结合成的偶联物（标记物），此偶联物仍保留其原免疫活性与酶活性，当偶联物与固相载体上的抗原（抗体）反应结合后，再加上酶的相应底物，即起催化水解或氧化还原反应而呈颜色。
其所生成的颜色深浅与欲测的抗原（抗体）含量成正比。 这种有色产物可用肉眼、光学显微镜、电子显微镜观察，也可以用分光光度计（酶标仪）加以测定。其方法简单，方便迅速，特异性强。向左转|向右转
ELISA双抗体夹心法(enzyme linked immunosorbent assay——sandwich technique)的原理是将特异性抗体结合到固相载体上形成固相抗体，然后和待检血清中的相应抗原结合形成免疫复合物，洗涤后再加酶标记抗体，与免疫复合物中抗原结合形成酶标抗体-抗原-固相抗体复合物，加底物显色，判断抗原含量。
生物帮有相关介绍。编码RNA http://doc.bio1000.com/show-3399.html
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