Figure 1

Enzyme degradation due to storage on filter papers. a) 150 filter papers with control blood spots with normal activity, moderate deficiency, severe deficiency, and no enzyme (100%, 30%, 10%, and 0%) were stored for up to 10 days at 4°C, and their activity measured at days 1,2,4,6,9, and 10. b) Samples were stored at room temperature, in the dark, for days 1–5, and the activity measured daily.