Fig. 4.

Digestion curves obtained for four distinct peptides showing different combinations of peptide production and decay rates. The results for these peptides are categorized by the production-decay rate combinations (A) rapid-slow, (B) rapid-rapid, (C) slow-slow, and (D) slow-rapid. The circles show the quantitative results obtained when the SIL mixture was added concurrently with the enzyme and the diamonds show the results when it was added post-digestion. Each data point is the mean value calculated with equation 2 from three replicate injections and the error bars represent the 95% confidence interval. Using the proposed mathematical models for each type of SIL introduction strategy, the curves for each peptide were obtained by performing non-linear least square regression analysis on both sets of experimental data simultaneously. The rate constants (k_p and k_d) and coefficients of determination are shown. The dotted line shows the target protein concentration, [S]₀, determined by the regression analysis.