Using the original “undiluted” sample from Question 1 (see details below), 10µL

Question

Using the original “undiluted” sample from Question 1 (see details below), 10µL of a 5-to-1 dilution were used to measure protein concentration. With the use of a standard curve, this is found to be 140µg. What is the specific activity of the original sample?

Here is the information for Question 1:

Assayed for LDH activity were 5µL of a sample that was diluted 6 to 1. The activity in the reaction vessel, which has a volume of 3mL, is 0.30U. What is the A/min observed? What is the relative activity of the original sample?

U=(Abs/min)/((6220 M-1cm-1)(1cm)) x 106µM/M x (3x10-3L)

U=(Abs/min) x 0.482µmol

0.30U= (Abs/min) x 0.482µmol

0.622= Abs/min

0.30U/.005mL x 6 = 360U/mL (Relative activity)

Explanation / Answer

Specific activity = activity of enzyme/mL / concentration of protein in mg .

Here 0.3 Units of activity of enzyme in 3 ml solution.

hence 1ml solution contains 0.1 units .

Specific activity =0.1/0.140mg of prtn = 0.7142 units

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