Findclash identifies clashes and/or contacts between atoms, based on VDW radii and user-specified criteria. It is the command-line implementation of Find Clashes/Contacts. Coordinates are examined upon each use of the findclash command. To perform continuous monitoring, it is necessary to use the Find Clashes/Contacts graphical interface.
The identified interactions can be shown with selection, coloring, and pseudobonds. Information can be written out, and the largest overlap per atom can be assigned as an attribute named overlap. The command ~findclash removes any pseudobonds that have been drawn to show the interactions.
The overlap between two atoms is defined as the sum of their VDW radii minus the distance between them and minus an allowance for potentially hydrogen-bonded pairs:
overlapij = rVDWi + rVDWj – dij – allowanceij
Option keywords for findclash can be truncated to unique strings and their case does not matter. A vertical bar "|" designates mutually exclusive options, and default values are indicated with bold. Synonyms for true: True, 1. Synonyms for false: False, 0.
interTest true|false
Whether to look for interactions between the specified atoms and other atoms (default), or among the specified atoms.
overlapCutoff cutoff
Pairs of atoms with overlap ≥ cutoff (default 0.6 Å) will be identified. A larger positive cutoff restricts the results to more severe clashes, whereas a negative cutoff can be used to identify favorable contacts. What is reasonable depends on the situation.
hbondAllowance allowance
An allowance > 0 (default 0.4 Å) reflects the observation that atoms sharing a hydrogen bond can favorably approach each other more closely than would be expected from their VDW radii. In the calculation of overlap, the allowance is only subtracted for pairs comprised of a donor (or donor-borne hydrogen) and an acceptor. This is equivalent to using smaller radii to characterize hydrogen-bonding interactions (for example, see Li and Nussinov, Proteins 32:111 (1998)). As in FindHBond, possible donor groups are hydrogen-bearing nitrogen, oxygen, and sulfur atoms, and possible acceptor groups are nitrogen, oxygen, and sulfur atoms with a lone pair.
bondSeparation N
Interactions between atoms that are ≤ N bonds apart will be ignored (N=4 by default).
ignoreIntraRes true|false
Whether to ignore interactions between atoms in the same residue.
selectClashes true|false
Whether to select the identified clash/contact atoms (and deselect all other atoms).
colorClashes true|false
Whether to color the identified clash/contact atoms the clashColor and the remaining atoms the nonclashColor.
clashColor colorname
Color to use for the identified clash/contact atoms when colorClashes is true (default red). Colorname can be none or any color name that specifies a single color.
nonclashColor colorname
Color to use for atoms other than the identified clash/contact atoms when colorClashes is true (default none, which removes per-atom color assignments and reveals the model-level colors). Colorname can be none or any color name that specifies a single color.
makePseudobonds true|false
Whether to create pseudobonds to show the identified interactions.
pbColor colorname
Color to use for the pseudobonds when makePseudobonds is true (default yellow). Colorname can be any color name that can be used with the command color, except byatom or byelement.
lineWidth width
Line width to use for the pseudobonds when makePseudobonds is true (default 2.0 pixels).
setAttrs true|false
Whether to assign the largest overlap per atom as an attribute named overlap.
saveFile file
Whether to write contact/clash information to a file (this option is off unless specified). The information includes atom specifications (see namingStyle), overlaps, and interatomic distances. File is the output file name/pathname; if it includes spaces, it must be enclosed in single or double quote marks. If file is browse or browser, a dialog for saving the file will appear (unless the word is enclosed in quotes, which would generate an output file by that name).
log true|false
Whether to write contact/clash information to the Reply Log. The information includes atom specifications (see namingStyle), overlaps, and interatomic distances.
namingStyle simple|osl
How to specify atoms in contact/clash information written to a file or the log: simple (for example, #0 PHE 16 CD1) or osl (command-line specifier, for example, #0:16@CD1). In the absence of this keyword, the Atomspec display style specified in the General preferences will be used.
See also: distance, hbonds, minimize, Find Clashes/Contacts, the PseudoBond Panel