Figure 4.

Circular dichroism spectra of L-3,4-dihydroxyphenylalanine (L-DOPA; 0.5 mM) alone in phosphate buffered saline (PBS) buffer (pH = 7.4, 298K) as prepared (dotted black curve) and after 24 h, 3, 7, and 15 days (red, green, wine, and blue curves, respectively).