[RASMB] AUC of RNA and RNA-proteins complexes

[Arthur Rowe]

Dear Pascal -

I would give a slightly different emphasis from Jo Butler in replying to
your question. Under two headings:

(1) value of vbar to be used

The value of vbar of RNA as its sodium salt is indeed less than the 0.55
ml/g often used for DNA. But although it is doubtless a bit variable (e.g.
may depend on which RNA, precise amount of salt, etc), I think that 0.50
ml/g may be too low a value. For 16S rRNA we long ago measured the value in
200 mM NaCl to be 0.524 ± 0.08 / 0.521 ± 0.007 ml/g for two separate
preparations. One of the same samples however, in 200 mM KCl gave a vbar =
0.580 ± 0.004 ml/g ! (the latter value has been found by others).  See
Pearce, Rowe & Turnock (1975) J Mol Biol 97 193-205***.

(2) is life hell working with RNA ?

As Jo says, no, it need not be, if you take reasonable precautions. I have
always found however that 'reasonable precautions' had to go beyond what Jo
recommends. RNAse is ubiquitous - your fingertips have it on them, its over
your bench, its probably in your glassware and cells, as the wretched stuff
recovers even from boiling. The way to keep it at bay is to treat every
reagent used with DEPC (freshly added from alcoholic solution,  it does not
retain activity once in aqueous solution) and to soak/rinse all cells and
glassware with distilled water to which DEPC has been freshly added. If all
else fails - and on occasion it can do - then adding the (horribly expensive
!) 'RNAsein' (a specific pancreatic inhibitor) is called for.

What Jo says about the likely range of s value etc I totally agree with. It
is probable, by the way, that compact, folded RNA is more resistant to the
dreaded RNAse.

Good luck !

Arthur Rowe

***pdf available to be mailed, on request.

--
*******************************************************
Arthur J Rowe
Professor of Biomolecular Technology
NCMH Business Centre
University of Nottingham
School of Biosciences
Sutton Bonington
Leicestershire LE12 5RD   UK

Tel:        +44 (0)115 951 6156
            +44 (0)116 271 4502
Fax:        +44 (0)115 951 6157
email:      arthur.rowe at nottingham.ac.uk
            arthur.rowe at connectfree.co.uk (home)
Web:        www.nottingham.ac.uk/ncmh/business
*******************************************************


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