The density of 70% ethanol allows RNA settlement or say sedimentation in the vial.
"b -mercaptoethanol is used to help to destroy RNases that may be present and will degrade the RNA. b -mercaptoethanol is a reducing agent that will reduce the disulfide bonds of the RNases, thereby destroying the conformation and the functionality of the enzyme". It comes from http://www.norgenbiotek.com/index.php?id=faqs_rnakits
Proteins, RNA, lipids
I do my RNA extractions at pH 5.0. I think it depends on the method that you use. You will have to say what method that you use to do your RNA extractions.
DNA extraction is done by three methods: * Organic extraction * inorganic extraction * solid state method In organic extraction, phenol and chloroform are used to create on organic phase in which cells are lysed and DNA is freed. The DNA remains in the aqueous phase. Ethyl alcohol is used to precipitate the DNA. In the inroganic methos, NaCl and EDTA are used for cell lysis. Following this, an approach similar to the organic method is followed. In solid state extraction, DNA is first precipitated in the presence of high slat and low pH conditions. The precipitated DNA is then adsorbed on to a filter membrane surface.
in RNA extraction we don't need to use a strong lysis solution to the cells like in DNA extraction since we don't need to break the nuclear envelope in case of RNA*. *Be cautious, in some case (ex. hnRNA) the RNA is in the nucleus so you have to break it. Really depend on what you are looking for.
to precipitate protein.
This wash step allows you to centrifuge the sample and collect a "clean" RNA pellet, after discarding the supernatant that contained contaminating salts and proteins. When isolating and purifying RNA, 75% ethanol is used as a wash solution because RNA is a precipitate (solid) in this percentage of ethanol, while most proteins and salts remain in solution (are soluble). At a lower % ethanol, both the RNA and the proteins would be soluble, so you would not be able to separate them. At a higher % ethanol, both the RNA and salts would remain in the pellet, so you would not be able to separate the salts from your RNA. Prior to the wash step, you probably added 100% ethanol to your sample, so the final total concentration of ethanol was 75%. This step is where the RNA precipitates out of solution. You would then centrifuge the sample and discard the supernatant, as above. In the wash step, you are merely using the same solution (75% ethanol) to wash the RNA pellet you created in the previous step.
chloroform is used to denature protein and settle it in the bottom during rna extraction ,also it helps to form organic and inorganic layers in which rna is dissolved in inorganic layer.
"b -mercaptoethanol is used to help to destroy RNases that may be present and will degrade the RNA. b -mercaptoethanol is a reducing agent that will reduce the disulfide bonds of the RNases, thereby destroying the conformation and the functionality of the enzyme". It comes from http://www.norgenbiotek.com/index.php?id=faqs_rnakits
RNAse destroys the RNA and hence RNAse contamination is a problem in RNA extraction as it breaks down RNA. RNAse enzyme is removed by using RNAse inhibitor or precautions like wearing of gloves, autoclaving tips , using RNAse free water/DEPC treated water is done while performing RTPCR
Proteins, RNA, lipids
In a DNA extraction, the purpose of a buffer is to solubilize DNA as well as RNA. Because of this, it prevents the DNA for degrading.
I do my RNA extractions at pH 5.0. I think it depends on the method that you use. You will have to say what method that you use to do your RNA extractions.
You want bands. The bands are ribosmal RNA of various sizes. Bands are good this shows that you did a good job of extracting RNA.
DNA extraction is done by three methods: * Organic extraction * inorganic extraction * solid state method In organic extraction, phenol and chloroform are used to create on organic phase in which cells are lysed and DNA is freed. The DNA remains in the aqueous phase. Ethyl alcohol is used to precipitate the DNA. In the inroganic methos, NaCl and EDTA are used for cell lysis. Following this, an approach similar to the organic method is followed. In solid state extraction, DNA is first precipitated in the presence of high slat and low pH conditions. The precipitated DNA is then adsorbed on to a filter membrane surface.
10-20 % of total cellular rna
in RNA extraction we don't need to use a strong lysis solution to the cells like in DNA extraction since we don't need to break the nuclear envelope in case of RNA*. *Be cautious, in some case (ex. hnRNA) the RNA is in the nucleus so you have to break it. Really depend on what you are looking for.