Problamatic A260/280 ratio of RNA - Problem with qualitative estimation of RNA (Jul/02/2007 )
Hi all,
I am using Rice Seedling (7 days old) to isolate total RNA for microarray analysis using TRi Reagent Sigma.After isolation Readings of Nanodrop is as follows
A260/280 = 1.98
A260/230 = 2.24
After this i purify half of the sample using RNeasy Minelute kit fro Qiagen and the the readings are as follows
A260/280 = 2.12
A260/230 = 1.80 or even worst
Could any body suggest me what could be the possible reason for this?
Many many thanks in Advance
I am using Rice Seedling (7 days old) to isolate total RNA for microarray analysis using TRi Reagent Sigma.After isolation Readings of Nanodrop is as follows
A260/280 = 1.98
A260/230 = 2.24
After this i purify half of the sample using RNeasy Minelute kit fro Qiagen and the the readings are as follows
A260/280 = 2.12
A260/230 = 1.80 or even worst
Could any body suggest me what could be the possible reason for this?
Many many thanks in Advance
What do you want? this ratios (A260/A280) are o.k. all > 1.8 indicates low protein-contaminations. ratios (A260/A230) is more problematic in your RNeasy purification, because it is too low which indicates contamination with guanidinium-thiocyanate (should be above 2.0). Purities with Tri reagent are ok from my point of view.
well your 260/280 ratios are very good 
after your column purification, you have eluted part of the ethanol used to wash the column. It's not a problem when working with formaldehyde or acrylamide gels, but may be tough for RTPCR for ex.
Best advice would be to pellet the RNA with butanol or isopropanol, wash it with 70%etoh and let it dry correctly. Then resuspend in DEPC water or TE, the one of your choice.