※ 引述《[email protected] (十年後人会在哪里??)》之铭言： : 1.经验上跟cell type有很大的关系..有些cell跑出来的pattern很容易是smear-like, : 不过这在发表时是可以被接受的. : 2.你有测纯度..那应该也同时有测浓度吧..所以你的loading量是多少呢?? : or more information about your running condition..? : 3.H2O2的保存是老问题..它常常因保存不好而不work..有确定H2O2是ok的吗?? : or 能造成DNA ladder的试剂很多,是否可能用其他reagent来induce? 谢谢您的指教，後来我直接寄信问厂商了， 对方说Tri-reagent不适使用於抽取小片段的DNA， 因为小片段DNA会在加了BCP离心分层时，跑到RNA（aqueous phase）那层。 我把往来信件贴在这里给大家参考： To whom it may concern, My lab bought TRI reagent from your company. We isolated RNA of good quality. And currently I also want to isolate DNA by TRI reagent and I did try the method provided in the protocol to see if DNA laddering is generated. But only two bands of molecular weight more than 1200bp were observed. I want to ask, by using this method, if total genomic DNA would be isolated? Are smaller DNA fragments also isolated? And is there any published paper using this method to see DNA laddering? I cannot find any, would you please send me some references? Thank you very much! ----------------------------------------------------------------------------- Hello, XX, Thank you for your email relating to the recovery of DNA from TRI Reagent extracts. When TRI Reagent is used to extract nucleic acids from tissue samples total genomic DNA is recovered. Some of this DNA is full length 100 kb DNA while the remainder will be DNA that has been sheared into smaller fragments during tissue homogenization (e.g. 20-50 kb fragments). If the tissue is undergoing apoptosis, these smaller DNA fragments may also be distributed in the RNA fraction. As the DNA molecule decreases in size it becomes increasingly difficult for the reagent to distinguish between RNA and DNA simply on the basis on the chemistry of the two molecules. After genomic DNA is recovered from TRI Reagent homogenates and cut with appropriate restriction enzymes it can be used for DNA profiling experiments. In order to limit DNA shearing, laboratories that are studying restriction length polymorphism use very gentile enzymatic methods to recovery DNA from their samples. This minimizes shearing artifacts that are typically produced when tissue is homogenized in TRI Reagent. However, these milder techniques would be inappropriate for RNA isolation and this may be why you have not seen DNA recovered with TRI Reagent or TRIzol used in this application? As you know, the “DNA ladders” that are used to quantify PCR products, etc. are prepared commercially and they are not derived from biological material. Thank you for your interest in our products. Please contact me if you have any additional questions relating to this matter. Sincerely yours, Bill Wilfinger, Ph.D. Senior Scientist Product Development and Technical Services Molecular Research Center, Inc. --

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