To begin, prepare a 10x stock of HsADA1 in 1x PBS at pH 7.4 to achieve a final concentration of 10 micromolar. Prewarm a thawed 15-milliliter aliquot of pooled human serum to 37 degrees Celsius. Then add 100 microliters of the 10x HsADA1 stock to both 900 microliters of pooled human serum and PBS taken in two separate low-bind microcentrifuge tubes.
Dilute 100 microliters of each enzyme and non-enzyme mixture one to one with 30%glycerol made in 1x PBS. Flash-freeze the tubes with liquid nitrogen and store at minus 80 degrees Celsius. Seal all the tubes with transparent film and place them in a 37 degrees Celsius incubator.
