Fig. 4.

Tyr oxidation is not affected by the presence of dextran (Mw 35,000–45,000). The initial rate (Ri_Tyr) and the total consumption of Tyr (initial concentration 500 μM) on incubation with 100 mM AAPH at 37 °C were determined from the decay in the intrinsic fluorescence of the amino acid (λ_ex: 274 nm; λ_em: 304 nm), and by HPLC with diode array detector (280 nm) in the absence or presence of dextran, respectively. Panel A: kinetic profiles of Tyr (500 μM) consumption on incubation with AAPH (100 mM) in phosphate buffer in the absence (black), or presence of 30 mg mL⁻¹ dextran (red) or 60 mg mL⁻¹ dextran (blue). Panel B: Total consumption of Tyr after 0 (black) and 30 min of incubation in the presence of 100 mM AAPH at 37 °C under 20% O₂ in phosphate buffer in the absence (red), and presence of 60 mg mL⁻¹ dextran (blue) as determined by HPLC-diode array detection (280 nm). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)