pI's of 2 proteins

[biology_06er]

Hi there,

We did an experiemnt the other day where we had to sep. out two proteins via a colum containing CM beads. It had a pH of 6 and both proteins bound to this. So to sep them out we used a pH of 7.6 and collected a sample and then used a pH and of 9 and collected sample 2. So now I have to comment on the charge properties and likely pI's of (cytochrome C and haemoglobin)..

CM contains a negative charge right? So that means in order for those 2 proteins to bind to it they both proteins must contain a positive charge?...and it says "for a given protein it is necessary to carry out ion-exchange chrom at a pH aboive or below its pI. Above its pI a protein will be -ve charged and above its pI it will carry a +ve charge"...

so if i was to say that both proteins carried a positive charge would this be correct? How would I work out what the pI is of each protein?

Thanks,
b_06er