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Figure 9:
A comparison graph of binding scores in the DBD (red) and the LBD (blue).
Analysis of the results for the LBD shows that DHT, the positive control bounds with the highest
affinity. This is important to note because it is also the ligand which, when the AR is mutated,
causes the cell line to become oncogenic. However, further analysis of the results shows the ca58
bonded with better affinity than ca27, the molecule of interest, and
had a comparable level of
binding to DHT. This indicates that ca58 is the most favorable molecule to bind to the human AR
LBD possibly due to the chemical effects of its meta-positioned hydroxyl groups. The negative
control of docetaxel had very positive results indicating that the scale of the binding is accurate,
and the results are reliable.
Analysis of the results of the DBD binding demonstrates that the positive control (PP) was not the
most effective binding ligand. Instead, 4 different ligands had binding more preferable than the
positive control and of those, ca58 had the highest binding affinity
as well as having binding
affinity near twice as strong as the positive control. The reason ca58 might have the highest affinity
is because of its meta-positioned hydroxyl groups. In each of the images for ca58 (both the LBD
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and the DBD) the red orbs representing the hydroxyl groups can be seen protruding out of the
binding pockets. It is reasonable to hypothesize that because of the hydroxyl groups outside the
binding pocket, that favorable interactions between these polar molecules and the AR are occurring
which account for the increase in bond affinity. Also, it is important to note that the ca27 analogs
without the Michaels acceptors did not have very favorable binding in comparison to the other
analogs which further strengthens the previously held notions that the reason ca27 was down
regulating the expression of the AR is because of the alpha-beta unsaturated carbon bonds.
Upon further analysis of the DBD images, the four ligands, which have binding affinity higher
than the positive control, are bounded to the opposite side of the DNA from the AR whereas the
positive control bound to the same side as the AR. This might attribute to why these four ligands
had higher binding affinity than the positive control, as the binding location to the DNA might be
independent of the presence of the AR. Further research and experimentation will need to be done
to corroborate this. Other docking models are necessary to test whether a more limited DBD would
produce more accurate results.
Analysis of the graph comparing the LBD to the DBD binding affinities (figure 9) sees an overall
preference to the DBD. It is important to note however that the negative control for the DBD was
not nearly as unfavorable as the
negative control for the LBD, however it was still overall
unfavorable with a moderately high positive value. Other negative controls were also used for both
LBD and DBD modeling that were not displayed but showed similar if not the same results as
docetaxel. Since this negative control is still unfavorable, the results should be considered to be
valid and as such, the DBD is the preferred binding site for ca27 and its analogs. This corroborates
previous studies as, even in the presence of DHT, ca27 down regulated the expression of the AR
but these models indicate that DHT will bind over ca27 or any of its analogs to the LBD, leaving
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the DBD the only alternative for the binding of ca27 or its analogs. These results will either be
corroborated by this research or disproven.
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