loadProtein: Import a pdb file or fetch it from the Protein Data Bank....
In FedericoComoglio/Rknots: Topological Analysis of Knotted Proteins, Biopolymers and 3D Structures

Description Usage Arguments Details Value Note Author(s) References Examples

Import a pdb file either by fetching the Protein Data Bank or from the file system and return the alpha-Carbon atoms coordinates.

1	loadProtein(pdbID, join.gaps = FALSE, cutoff = 7, ...)

`pdbID`	a single element character vector containing the path to the file in the file system and the name of the PDB file to be read, or the four letter PDB identifier for online file access (fetched from the PDB). For the latter, the `pdbID` is not case sensitive.
`join.gaps`	logical (default FALSE). If TRUE, gaps are joined together with a straight line.
`cutoff`	numeric (in Angstrom), distances between consecutive alpha-Carbon atoms greater than `cutoff` are considered as gaps.
`...`	any other parameter for the `read.pdb` function of bio3d. See the manual for details.

If the selected PDB entry contains more than one polypeptide chain, all the available chains are loaded or downloaded. The PDB atom field is then filtered individually to retain the coordinates of the protein C-alpha trace. If join.gaps is FALSE, additional chains (one for each split) will be produced and labeled according to the following: if C is a chain and C is split in j subchains due to gaps, the resulting subchains will be labeled with C_1, …, C_j.

Notice that any other model or any three-dimensional structure can be directly loaded in R as an N x 3 matrix, where the columns represents the x, y, z coordinates. To this purpose, please see the help pages of read.table, read.delim, read.csv, etc.

A list of length equal to the number of polypeptide chain (if gaps are not present or not considered) or greater (if gaps are present), where each element contains an N x 3 matrix with the x, y, z coordinates of the chain (or subchain) model.

This function makes use of the read.pdb function in the bio3d package. See references for additional details and credits.

Federico Comoglio, federico.comoglio@bsse.ethz.ch

Grant, Rodrigues, ElSawy, McCammon, Caves (2006) Bio3D: An R package for the comparative analysis of protein structures., Bioinformatics 22, 2695-2696

## Not run: 
## Loading from the file system
fn <- system.file("extdata", "1AJC_chainA.pdb", package="Rknots")
protein <- loadProtein(fn)

## Fetching the PDB
protein<- loadProtein('2K0A')
#more than one chain (notice the split)
protein <- loadProtein('1GZ0')
str(protein)

#A protein with two subunits. The first one is split in two subchains.
protein <- loadProtein('1AJC', join.gaps = FALSE, cutoff = 7)
str(protein)

## End(Not run)