QSAR - Rank order of activity data

QSAR Society Colleagues,

        I would like to convert biological activity or molecular property
data to a rank order e.g., convert IC50 or p(IC50) data to a
statistically meaningful rank order.

        This may sound like a problem with a simple answer, but apparently
is not for several reasons:

        1) The trivial approach of simply sorting compounds by p(IC50)
and then assigning a rank leads to artificial rank distinctions among
compounds that given the inherent experimental variability of the data is
probably not justified.

        2 If one had replicates for every IC50, one could attempt to do
T-tests between every IC50, and assign a new rank if the statistic exceeds
the 95% confidence level. However, I do not have replicates for every
measured IC50 value.

        3) If one attempts to normalize the IC50 distribution and then
assign ranks, perhaps, on the basis of mean +/- n*sigma values, this
creates "somewhat" artificial ranks where some compounds may have been
right at the border of the mean + sigma, or mean + 2*sigma, etc.

        If anyone has ideas, experience, or suggestions on this topic, I
welcome your comments !

        Regards,
        Jim Metz

James T. Metz, Ph.D.
Research Investigator Chemist

GPRD R46Y AP10-2
Abbott Laboratories
100 Abbott Park Road
Abbott Park, IL 60064-6100
U.S.A.

Office (847) 936 - 0441
FAX (847) 935 - 0548

james.metz!=!abbott.com
Received on 2003-06-19 - 14:40 GMT