# CalcShift

NAME

    CalcShift - calculate ring current shifts

SYNOPSIS

    CalcShift ( 1 | 0 ) ( 1 | 0) string expr expr

DESCRIPTION

Calculate ring current and bond polarization shifts of all selected atoms, taking into account all rings/atoms of the same molecule.

The first argument selects whether ring current shifts should be calculated, the second one whether bond polarization shifts should be calculated. At least one of the two should be selected, a warning is issued otherwise.

The third argument gives the name of the model for the calculation. The description of the models is read from the file:

        $MOLMOLHOME/setup/RingShift

The fourth argument selects a cutoff, contributions to the ring current shifts above this value are listed individually *before* the sum.

The fifth argument gives a maximal distance for the atoms considered for the calculation of bond polarization shifts. Larger values will lead to longer calculation times.

The results are listed for each molecule separately, a summary with average, minimal and maximal values is given at the end.

For all protons but HN, a ring belonging to the same residue as the proton is not considered for the calculation of the ring current shift.

The same is the case for the bond polarization: atoms of the same residue are not considred for the field calculation, except for HN atoms. A more elaborate strategy would have to be used to make the calculated numbers more useful as expected difference to random coil shift, especially for HN atoms.

EXAMPLE

    CalcShift 1 0 Heigh-Mallion 0.5 5.0

REFERENCE

Case, DA. Calibration of ring-current effects in proteins and nucleic acids. Journal of Biomolecular NMR, 6 (1995) 341-346

WARNING

The results for bond polarization shifts were not compared to the results of other programs, so there is no guarantee given on their correctness and usefulness.

SEE ALSO

`SelectAtom`, `PathNames`

DATE

960621