How to prepare sample before doing a spec? - (Mar/19/2007 )
Hello, as a new student in a lab I have been doing a lot of specs of DNA and RNA samples for a Northern blot.
My question is:
Once I have obtained my "purified" RNA or DNA solution (Ie: DNA pellet dissolved in TE buffer lets say...) and after storage in -20, how do I prepare the sample before I do a spec?
I usually give the ependorf tube a few good flicks and then mix the solution by a pipette...then draw out the amount I need to spec.
Is this a good way? Or should i centrifuge and draw it out from the bottom?
What is a good method to get reproducible results?
In the lab we have the nanodrop and ultraspec 3000 pro (5mm pathlength, 100 factor which requires a dilution and then 7ul to be loaded into cuvette).
chill on ice. gently vortex. quick spin and pipett carefully.
If you have a nanodrop, it will be very easy. Just pipette 1 ul of sample and check the ratio and concentration. That's all. Simple right?
For normal spec, hmm for me, I just dilute into 100 fold and load it in a 500ul of quartz cuvette and check the ratio and absorbance. hope this helps.
so after the quick spin, do I draw from the bottom? or draw from the middle of solution or does it even matteR?
from the middle to top of the solution. you want to avoid any pellet.