OD420 at Time 0	OD420 at Time 30 sec	Rate per sec (OD420 sec-1)
Sample S1	0	0.27	0.009
Sample P2	0	0.18	0.006

Concentration ONP (M)	Absorbance at O/D 420
0	0
2	0.009
4	0.018
6	0.027
8	0.036
10	0.045

could not upload the image for some reason however the standard curve was created using the table above

Calculations

S1 = (0.27-0)/30 = 0.009 OD₄₂₀ sec^-1

P2 = (0.18-0)/30 = 0.006 OD₄₂₀ sec^-1

Use:

your standard curve of ONP concentration,

the concentration of S1 and P2 you calculated earlier &

the fact that the reaction volumes for each assay were 3 mL and contained 0.5 mL of either S1 or P2.

to calculate the of MOLES of ONPG hydrolysed per sec per mg of protein for the S1 and P2 samples.

(Bear in mind that the absorption value reveals the MOLARITY of ONP in the solution but you need to work out the NUMBER OF MOLES released from ONPG by enzymatic hydrolysis in each reaction).