Isoelectric point: Difference between revisions
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The isoelectric point, or pI, is the pH at which a protein has zero [[Net charge|net charge]]. When the pH is higher than the isoelectric point, the protein has negative charge, and when lower, positive charge. You can calculate the isoelectric point of your protein easily using on-line resources: | The isoelectric point, or pI, is the pH at which a protein has zero [[Net charge|net charge]]. When the pH is higher than the isoelectric point, the protein has negative charge, and when lower, positive charge. You can calculate the isoelectric point of your protein easily using on-line resources: | ||
==Calculating Isolelectric Point Using EMBL WWW Gateway to Isoelectric Point Service== | ==Calculating Isolelectric Point Using EMBL WWW Gateway to Isoelectric Point Service== | ||
<font color='red'>The EMBL Gateway to pI appears to be out of service in May, 2013. Use the alternative below.</font> | |||
*First, get the one-letter amino acid sequence of your protein of interest. | *First, get the one-letter amino acid sequence of your protein of interest. | ||
**An easy way to do this for a protein that has a solved structure: get to the page for the PDB ID at [http://www.pdb.org the RCSB Protein Data Bank]. There in the upper right under 'Dsiplay files', click the 'FASTA Sequence' link and download all chains in FASTA format. Open the text file and block the sequence of the chain of interest (excluding the comment line beginning >) and copy it to the clipboard. | **An easy way to do this for a protein that has a solved structure: get to the page for the PDB ID at [http://www.pdb.org the RCSB Protein Data Bank]. There in the upper right under 'Dsiplay files', click the 'FASTA Sequence' link and download all chains in FASTA format. Open the text file and block the sequence of the chain of interest (excluding the comment line beginning >) and copy it to the clipboard. | ||