computePI | R Documentation |

This function calculates the theoretical isoelectric point of a protein. Isoelectric point is the pH at which the protein has a neutral charge. This estimate does not account for the post-translational modifications.

computePI(seq)

`seq` |
Protein sequence as a vector of single chars in upper case |

The theoretical isoelectric point (pI) as a numerical vector of length one.

Protein pI is calculated using pK values of amino acids described in Bjellqvist et al. See also `SEQINR.UTIL`

for more details.

D. Charif, J.R. Lobry

The algorithm is the same as the one which is implemented at the following url:
https://web.expasy.org/compute_pi/pi_tool-doc.html but with many trials
in case of convergence failure of the non-linear regression procedure.
`citation("seqinr")`

`SEQINR.UTIL`

# # Simple sanity check with all 20 amino-acids in one-letter code alphabetical order: # prot <- s2c("ACDEFGHIKLMNPQRSTVWY") stopifnot(all.equal(computePI(prot), 6.78454)) # # Read a protein sequence in a FASTA file and then compute its pI : # myProts <- read.fasta(file = system.file("sequences/seqAA.fasta", package = "seqinr"), seqtype = "AA") computePI(myProts[[1]]) # Should be 8.534902

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