Yep you are right. Looking a bit deeper I found that it was to do with checking if there were any atoms in an unsaturated ring of a certain size. The second one finds there is an unsaturated ring of size 6 (Bit 181) where as the first one does not. 

Thanks,
J

On 14 Dec 2012, at 06:55, Egon Willighagen <egon.willighagen@gmail.com> wrote:

On Thu, Dec 13, 2012 at 7:52 PM, John May <johnmay@ebi.ac.uk> wrote:
Say for example we query the structures for the following fragment

BTW, these two fragments are both present in both structures...

Egon


--
Dr E.L. Willighagen
Postdoctoral Researcher
Department of Bioinformatics - BiGCaT
Maastricht University (http://www.bigcat.unimaas.nl/)
Homepage: http://egonw.github.com/
LinkedIn: http://se.linkedin.com/in/egonw
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