calculate_pI() estimates peptide isoelectric points with a bisection
search over the Henderson-Hasselbalch net-charge equation. The calculation
uses hard-coded terminal pKa values of 8.0 for the N-terminus and 3.1
for the C-terminus, plus side-chain pKa values from aa_properties for C,
D, E, H, K, R, Y, and U.
Arguments
- sequence
Peptide sequence supplied as a character vector. Amino-acid codes must be one-letter uppercase or lowercase symbols from the 22 supported residues in aa_properties. If
NULL, raises an error.
Value
A numeric vector of estimated peptide pI values. Names are preserved
from sequence when present.
Limitations
pI estimation uses the Lehninger pKa set. Calculation may be slow for more than 5000 sequences.
See also
Other utils:
calculate_peptide_mass(),
pepvet_preset()
Examples
calculate_pI("PEPTIDE")
#> [1] 3.303286
calculate_pI(c("AAAAAAAR", "ACDEFGHIKLMNPQRSTVWY"))
#> [1] 10.250003 6.905655