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).

Thanks.

-mangopango-

chill on ice. gently vortex. quick spin and pipett carefully.

-fred_33-

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.

-timjim-

QUOTE (fred_33 @ Mar 20 2007, 01:24 AM)

chill on ice. gently vortex. quick spin and pipett carefully.

so after the quick spin, do I draw from the bottom? or draw from the middle of solution or does it even matteR?

thanks

-mangopango-

QUOTE (mangopango @ Mar 20 2007, 10:19 AM)

so after the quick spin, do I draw from the bottom? or draw from the middle of solution or does it even matteR?

thanks

from the middle to top of the solution. you want to avoid any pellet.

-mdfenko-