lowest concentration of RNA - to be visible on gel (Apr/15/2008 )

Hi all,

I have 2 questions:

1. What's the lowest concentration of RNA needed for it to be visible on gel?
I measured my RNA sample on nanodrop and it reads 25ng/uL but it is not very visible on the gel (no smear but very faint tRNA band).
Has it degraded or the concentration of RNA is too low?

2. For leaf RNA extraction, 4 bands were observed on gel in a single lane. Could anyone tell me what is it that I have got
on (?). Dont seem to have the (?) band when i extract RNA from stem. Thanks!

........ (?)
........ (rRNA: 28S)
........ (rRNA: 18S)
........ (tRNA)

do you have a picture of your gel?
the ? band could be DNA contamination. 25 ng/ul should be visible on gel

I'm with our good toejam.
A DNA "blob" can explain your 4° band.
Anyway does it form a real band or is it stuck in the well?
Didn't you use any DNAse treatment?