Determination of peptide dissociation constants and Stokes radius at different protonation stages by capillary electrophoresis.
Peptide electrophoretic mobility measured by capillary zone electrophoresis can be regarded as deriving from the mean of mobilities of different protonated forms, each one participating according to its charge. Stokes radius and relative percentage. The percentage is a function of the peptide dissociation constant and solution pH. Therefore, mobility modifications due to pH variations can be related to peptide dissociation constant, charge, and Stokes radius throughout general binding equations. Thus, not only can peptide dissociation constants be measured, but information about Stokes radius modifications linked to proton loss can also be obtained with picomoles of peptide.
Castagnola
M
M
Istituto di Chimica Biologica, Università di Cagliari, Italy. m.castgnola@uniserv.ccr.rm.cnr.it
Rossetti
D V
DV
Cassiano
L
L
Misiti
F
F
Pennacchietti
L
L
Giardina
B
B
Messana
I
I
D000324:Adrenocorticotropic Hormone / Q000737:chemistry; D000595:Amino Acid Sequence; D001920:Bradykinin / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D019075:Electrophoresis, Capillary / Q000379:methods*; D004743:Enkephalin, Leucine / Q000737:chemistry; D004744:Enkephalin, Methionine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008433:Mathematics; D010446:Peptide Fragments / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D011522:Protons
D010446:Peptide Fragments; D010455:Peptides; D011522:Protons; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D000324:Adrenocorticotropic Hormone; D001920:Bradykinin