Hello all, I had the worst time the other day finding an online tool to calculate charge versus pH values for an input protein sequence. There are many programs for calculating the isoelectric point (pI), put not many that output a complete titration curve.
Because such information is often useful in protein purification and crystallization, I coded up a quick perl program I would like to share with the CCP4 community. The code is attached. It is pretty self-explanatory. Input a FASTA file as a command line arguement and the program outputs charge vs. pH value pairs (unsorted). The constants defined in the program header can be used to alter the pKa values used, titration starting and ending points, and grid sampling. Please feel free to use, distribute, and modify freely. Also attached is a ASCII plotting tool that takes paired values from a file or STDIN and plots them to STDOUT in ascii using automatically determining ranges and binning values. These two programs work well like so: "./titrate.pl FASTA.seq | ./plot.pl" to produce a nice ascii plot of charge vs. pH. I hope these are helpful to someone. Best, Paul Smith Paladin Scientific paladinscientific.com
titrate.pl
Description: Perl program
plot.pl
Description: Perl program
