pI {Peptides} | R Documentation |
The isoelectric point (pI), is the pH at which a particular molecule or surface carries no net electrical charge.
pI(seq, pKscale = "EMBOSS")
seq |
An amino-acids sequence |
pKscale |
A character string specifying the pK scale to be used; must be one of |
The isoelectric point (pI) is the pH at which the net charge of the protein is equal to 0. It is a variable that affects the solubility of the peptides under certain conditions of pH. When the pH of the solvent is equal to the pI of the protein, it tends to precipitate and loose its biological function.
# COMPARED TO ExPASy ProtParam # http://web.expasy.org/cgi-bin/protparam/protparam # SEQUENCE: QWGRRCCGWGPGRRYCVRWC # Theoretical pI: 9.88 pI(seq= "QWGRRCCGWGPGRRYCVRWC",pKscale= "Bjellqvist") # [1] 9.881 # COMPARED TO EMBOSS PEPSTATS # http://emboss.bioinformatics.nl/cgi-bin/emboss/pepstats # SEQUENCE: QWGRRCCGWGPGRRYCVRWC # Isoelectric Point = 9.7158 pI(seq= "QWGRRCCGWGPGRRYCVRWC",pKscale= "EMBOSS") # [1] 9.716 # OTHER SCALES pI(seq= "QWGRRCCGWGPGRRYCVRWC",pKscale= "Murray") # [1] 9.818 pI(seq= "QWGRRCCGWGPGRRYCVRWC",pKscale= "Sillero") # [1] 9.891 pI(seq= "QWGRRCCGWGPGRRYCVRWC",pKscale= "Solomon") # [1] 9.582 pI(seq= "QWGRRCCGWGPGRRYCVRWC",pKscale= "Stryer") # [1] 9.623 pI(seq= "QWGRRCCGWGPGRRYCVRWC",pKscale= "Lehninger") # [1] 9.931 pI(seq= "QWGRRCCGWGPGRRYCVRWC",pKscale= "Dawson") # [1] 9.568 pI(seq= "QWGRRCCGWGPGRRYCVRWC",pKscale= "Rodwell") # [1] 9.718