[gmx-users] number of gauche <-> trans transitions with CHARMM36 and AMBER force fields

[ABEL Stephane 175950]

Dear all, 

I would like to compute the number of CCCC gauche <--> trans transitions (per ns) for for several alkanes. I know that I can use g_angle with -ot flag. But in the manual it is stated that this command works only for dihedrals with multiplicity 3. 

In CHARMM36 force field, for example,  the CCCC dihedrals parameters have the following form:  

CTL2    CTL2    CTL2    CTL3    9       0.00    0.677808        2       ; New
CTL2    CTL2    CTL2    CTL3    9       180.00  0.196648        3       ; New
CTL2    CTL2    CTL2    CTL3    9       0.00    0.43932 4       ; New
CTL2    CTL2    CTL2    CTL3    9       0.00    0.740568        5       ; New
CTL2    CTL2    CTL2    CTL2    9       0.00    0.422584        2       ; New
CTL2    CTL2    CTL2    CTL2    9       180.00  0.594128        3       ; New
CTL2    CTL2    CTL2    CTL2    9       0.00    0.309616        4       ; New
CTL2    CTL2    CTL2    CTL2    9       0.00    0.405848        5       ; New

So it is possible to use the g_angle functionality with this force field ? Probably I can comment the lines where the angle multiplicity is not equal tp 3 and regenerate a  tpr file and use it with g_angle, right ?  

Stephane