ss DNA purification

[Andrew Taylor]

>Does anyone out there have a method for isolationg ss M13 phage DNA on a
>cesium chloride gradient instead of a potassium iodide gradient?  What I
>am doing is in vivo excision from a Lambda ZapII library but the ss DNA I
>isolate has a huge contamination of ds DNA (concluded from S1 nuclease
>digestion).  Any help is appreciated.  Thanks in advance.

Is the M13 packaged in this system?  Purifying M13 phage (on a CsCl gradient) 
is a very good way to get it away from just about everything (except perhaps 
ribosomes) because the DNA-protein complex has a density very different from 
proteins or DNA.

Andrew