Apurinic sites?

[Brian Smith-White]

In Article <2mjg7v$h9e at mserv1.dl.ac.uk> "marodriguez at mvax.cbm.uam.es (marodriguez)" says:
> Dear netters,
>     I'm posting this for a friend. He wants to know how to depurinate 
> supercoiled DNA, and HOW to detect the amount of this depurination. The method 
> he is doing now is the next:
> 
>      o Incubation of the supercoiled plasmid in Tris-HCL 0.01M (pH=5.2); NaCl 
> 0.1M; Sodium citrate 0.01M, during 15-20 minutes, at 70 C.
>      o Aliquots of this incubations are denaturalized by 2 hours incubation at 
> room temperature, in K2HPO4-KOH 0.3M (pH=12.3). 
>      o Neutralization using KH2PO4-HCl 1M (pH=4.0).
>      o This samples are loaded in agarose gels, stained with ethium bromide to 
> detect the amount of supercoiled or relaxed plasmid.
> 
>      If you have any other method that works, please let me know about it.
	Use alkaline sucrose gradients collected through a UV monitor. The 
protocols are preserved in some papers by F. Studier and his coworkers from 
the 1960s. The agarose gel is much to insensitive.
> 
>      Thanks in advance.
> 
>      Miguel Angel RODRIGUEZ-GABRIEL
>      Centro de Biologia Molecular
>      Universidad Autonoma de Madrid
>      Cantoblanco. 28049 Madrid. SPAIN.
> 
>      FAX: 34-1-3974799
>      e-mail: marodriguez at mvax.cbm.uam.es
> 
>