Consider "removed" as a potential state for single-hydrogen rotators

[russell-taylor]

In His 88 for 1dfu, the flipped configuration is preferable. However, there is a rotatable hydrogen attached to O2' in G 75 that has to get pushed aside for the hydrogen coming from His 88. I wonder if this case, or others like it, would benefit from the possibility that a flip causes a good hydrogen bond without adding the rotatable hydrogen.

The O2' is not an acceptor when it has its own hydrogen, but seems like it could accept hydrogen bonds if not.

Consider a command-line option to enable a new potential coarse state for single-hydrogen Movers that has no fine states associated with it and has the hydrogen removed (like happens with Histidine).

Checked with Jane and Dave to see if this makes sense to pursue.

[russell-taylor]

This looks like it could also be useful in 3boy, where HO2* U D 7 clashes with HG1 THR A 56. If one of the two Oxygens these are attached to did not have a hydrogen added, then we would presumably see hydrogen bonding here.

[russell-taylor]

The acceptor status of the O2' (and other single-hydrogen rotator parents) is not changed when a hydrogen is added to it. This differs from the behaviors of the Histidine Nitrogens. This means that the attached hydrogen can rotate out of the way and the atom can still make a hydrogen bond with a neighbor.

Jane reports that we should not add 'removed' as a potential state -- the hydrogens should always be added.