User 2477d057f2
19-03-2008 19:06:50
Hello ChemAxon
I have been using Marvin 5.0 on my Mac for about 2 months now and I am very satisfied with the product. I have only had a few glitches so far (like difficulty obtaining a good prediction of pKa for NH groups; try the molecules FCCP (exp. pKa = 6.2) and CCCP (exp. pKa = 6.0) and you'll see what I mean). And I wish the GUI was a little better adapted to my Mac (if anyone is listening, Please allow windows to close with apple-C and please make OK the default choice in tool windows so that I can use my keyboard instead of my mouse, and please make the Open and Save file browsers OSX-compliant).
Today's question: Can the pKa plugin be used with user-supplied pKa values instead of structure derived pKa values? This would be a useful little implementation to calculate speciation (distribution of ionized species). Perhaps a little input window with up to 5 or 6 pKa values?
The reason I am asking is that I would like to correct your bulk pKa values to reflect lipid bilayer membrane pKa values.
What would be tremendously useful for me would be the ability to combine the logP plug-in with the pKa plug-in in a novel way: You could include a correction of octonol logP values to membrane log P (logPmem) values (there are solid equations in the literature)(this would be useful to many users), and then use the difference in log Pmem between neutral and ionized species (delta logPmem) to adjust bulk pKa to membrane pKa (pKa mem; pKa mem = pKa - delta logPmem). The delta would have to be calculated for each microspecies of course. Once the new pKa values are obtained, then the speciation calculation is performed to estimate the true ionization behaviour of the ionizable molecule in a biological membrane.
This is very tedious to do by hand. This type of integration between the logP and the pKa plugins would save me countless hours.
Thanks for the support!
Cheers
Louis Martineau
I have been using Marvin 5.0 on my Mac for about 2 months now and I am very satisfied with the product. I have only had a few glitches so far (like difficulty obtaining a good prediction of pKa for NH groups; try the molecules FCCP (exp. pKa = 6.2) and CCCP (exp. pKa = 6.0) and you'll see what I mean). And I wish the GUI was a little better adapted to my Mac (if anyone is listening, Please allow windows to close with apple-C and please make OK the default choice in tool windows so that I can use my keyboard instead of my mouse, and please make the Open and Save file browsers OSX-compliant).
Today's question: Can the pKa plugin be used with user-supplied pKa values instead of structure derived pKa values? This would be a useful little implementation to calculate speciation (distribution of ionized species). Perhaps a little input window with up to 5 or 6 pKa values?
The reason I am asking is that I would like to correct your bulk pKa values to reflect lipid bilayer membrane pKa values.
What would be tremendously useful for me would be the ability to combine the logP plug-in with the pKa plug-in in a novel way: You could include a correction of octonol logP values to membrane log P (logPmem) values (there are solid equations in the literature)(this would be useful to many users), and then use the difference in log Pmem between neutral and ionized species (delta logPmem) to adjust bulk pKa to membrane pKa (pKa mem; pKa mem = pKa - delta logPmem). The delta would have to be calculated for each microspecies of course. Once the new pKa values are obtained, then the speciation calculation is performed to estimate the true ionization behaviour of the ionizable molecule in a biological membrane.
This is very tedious to do by hand. This type of integration between the logP and the pKa plugins would save me countless hours.
Thanks for the support!
Cheers
Louis Martineau