---
name: "g_saltbr"
section: "1"
platform: "linux"
package: "gromacs-data"
version: "5.0.2-1"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/gmx-saltbr"
---

# g\_saltbr(1)

Compute salt bridges

Part of [gmx-saltbr(1)](/gmx-saltbr/1.md).

## NAME

gmx-saltbr - Compute salt bridges

## SYNOPSIS

gmx saltbr \[-f \[\<.xtc/.trr/...\>\]\] \[-s \[\<.tpr/.tpb/...\>\]\]\
            \[-nice \<int\>\] \[-b \<time\>\] \[-e \<time\>\] \[-dt \<time\>\]\
            \[-t \<real\>\] \[-\[no\]sep\]

## DESCRIPTION

**gmx saltbr** plots the distance between all combination of charged groups as a function of time. The groups are combined in different ways. A minimum distance can be given (i.e. a cut-off), such that groups that are never closer than that distance will not be plotted.

Output will be in a number of fixed filenames, **min-min.xvg**, **plus-min.xvg** and **plus-plus.xvg**, or files for every individual ion pair if the **-sep** option is selected. In this case, files are named as **sb-(Resname)(Resnr)-(Atomnr)**. There may be **many** such files.

## OPTIONS

Options to specify input and output files:

**-f** *\[\<.xtc/.trr/...\>\] (traj.xtc) (Input)*\
     Trajectory: xtc trr cpt trj gro g96 pdb tng

**-s** *\[\<.tpr/.tpb/...\>\] (topol.tpr) (Input)*\
     Run input file: tpr tpb tpa

Other options:

**-nice** *\<int\> (19)*\
     Set the nicelevel

**-b** *\<time\> (0)*\
     First frame (ps) to read from trajectory

**-e** *\<time\> (0)*\
     Last frame (ps) to read from trajectory

**-dt** *\<time\> (0)*\
     Only use frame when t MOD dt = first time (ps)

**-t** *\<real\> (1000)*\
     Groups that are never closer than this distance are not plotted

**-\[no\]sep**  *(no)*\
     Use separate files for each interaction (may be MANY)

## SEE ALSO

**[gromacs(7)](/gromacs/7.md)**

More information about **GROMACS** is available at \<*http://www.gromacs.org/*\>.