[AMBER] Suspicious pKas from CpHMD

From: Matthew Guberman-Pfeffer via AMBER <amber.ambermd.org>
Date: Thu, 9 Feb 2023 05:08:35 +0000

Dear AMBER Community,

I’m getting some really strange pKas for CpHMD simulations performed at pHs from 5 to 10. For example,

LYS 8: pKa = 564.07106 (+- 9292.89711 ) ; Hill coefficient = 0.004 (+- 0.060 )
AS4 114: pKa = -52.65171 (+- 144.03991 ) ; Hill coefficient = 0.046 (+- 0.112 )

Each simulation was propagated for 40 ns. My CpH-relevant settings were icnstph=2, ntcnstph=100, ntrelax=100, and solvph = 5, 6, 7, 8, 9, or 10.

Is there anything besides running the simulations for longer that I should try? Should I expand the range of considered pHs? What else can I try to get more reasonable pKas for these residues? Or, what should I inspect to see if something is going wrong?

Best,
Matthew

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Received on Wed Feb 08 2023 - 21:30:02 PST
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