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The fluorescence properties of four insulin analogs with tryptophane substitutions, [L-Trp]~(A1) insulin, [D-Trp]~(A1) insulin, [L-Trp]~(B1) insulin and desPhe~(B1) [L-Trp]~(B2) insulin, have been studied. The effect of pH on the fluorescence behaviours of the three L-Trp insulin analogs are similar to only one fluorescence intensity peak at pH 9. [D-Trp]~(A1) insulin shows two fluorescence intensity peaks, a main peak at pH 9.8 and a small peak at pH 5.5. The fluorescence quenching on the acid side of the pH～9 peak is caused by protonation of the A1 α-amino group. The difference in A1 α-amino group pK values of these derivatives, the presence of a second pH-fluorescence peak for the D-Trp derivative and other differences reflect differences in molecular conformation of the two Al-insulin analogs which could form the basis of the pronounced differences in their biological activities.
The fluorescence properties of four insulin analogs with tryptophane substitutions, [L-Trp] ~ (A1) insulin, [D-Trp] L-Trp] ~ (B2) insulin, have been studied. The effect of pH on the fluorescence behaviors of the three L-Trp insulin analogs are similar to only one fluorescence intensity peak at pH 9. [D-Trp] ~ (A1 ) insulin shows two fluorescence intensity peaks, a main peak at pH 9.8 and a small peak at pH 5.5. The fluorescence quenching on the acid side of the pH ~ 9 peak was caused by protonation of the A1 α-amino group. The difference in A1 α-amino group pK values of these derivatives, the presence of a second pH-fluorescence peak for the D-Trp derivative and other differences reflect differences in molecular conformation of the two Al-insulin analogs which could form the basis of the pronounced differences in their biological activities.