DMSO in CaCl2 Competent Cells

[Dima Klenchin]

In article 
<gddavis-1907951835120001 at ppp206.modems.uoknor.edu>,
   gddavis at essex.ecn.uoknor.edu (Greg Davis) wrote:
>Can anyone tell me what the function of DMSO is in the 
preservation of
>frozen competent CaCl2 competent cells?
>
>Thanks,
>Greg
>
My understanding is that it's not for preservation but for 
the competence. As nobody knows what how E.coli 
uptakes DNA, I guess it's a mistery what DMSO does here. 
(For that matter: what CaCl2 does and how???)

-dima