Spectrophotometric Determination of Protonation Constants of T ry p to ph an at Different Ionic Strengths and Various Ionic Media

The prtnonation constant values of tryptophan were studied at 25 C. different ionic strengths. 0.1-1.0 moldm", and various ionic media of NaCIO, and N4N01, using a combination of spectrophotometrie andpotentiometric techniques. The general vend for the two protonation con Slant Vai net of tryptophan is in theorder of NaC104 > NaNO3 in different ionic media. The dependence of protonation constants on ionicstrength and ionic media were taken into account; using a Debye-Huckel type equation (molarconcentration scale) and the SIT (specific ion interaction theory) approach (udal concentration scale).Differences in protonation constants in thc various supporting electrolytes were also interpreted anddiscussed.