G + C rich sequences - blocking agents

David Johnstondaj daj at nhm.ic.ac.uk
Fri Jul 30 04:52:13 EST 1993

On 29 Jul 93 16:42:00 GMT,
  <nishir at ohsu.edu> writes:

>What's the general opinion about blocking agents such as salmon sperm DNA 
>and how it should be treated.

We work on ribosomal DNA sequences where, due to conservation throughout 
the whole of the living world, our probes will bind to DNA from most 
organisms. Hence we cannot use DNA as a blocking agent. We use the 
Boehringer Digoxygenin system and this contains a blocking agent which 
is proteinacious in nature (fraction of dry milk powder - cat 1096 
176 - 50g is approx #36.20 in UK and it goes a long way). If anyone in 
your Dept. is using this system there is always masses left when everything 
else in the kit has run out so you could probably scrounge some from them). 
This appears to work perfectly well on both charged nylon and NC and might 
be woth a try in your system. 

David A. Johnston
Dept of Zoology, The Natural History Museum, Cromwell Road,
South Kensington, London SW7 5DB.
(tel 071 9389297, fax 071 9388754, email daj at nhm.ic.ac.uk)

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