Free · Biochemistry calculators 🧫

Enzyme Specific Activity & Required Mass

Find enzyme preparation mass from its specific activity, a target activity per volume and final volume.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

A target of 5 activity units/mL in 20 mL requires 100 units. At 10 units/mg, the required preparation mass is 10 mg.

Preparation mass = target activity per volume × final volume / specific activity per mass

Worked example

Enter these known values and leave the other values blank.

Target activity per solution volume
5 units / mL
Final solution volume
20 mL
Preparation specific activity per mass
10 units / mg
Required enzyme preparation mass
10 mg

Assumptions and limitations

  • Activity, specific activity, mass and volume are positive. Both activity inputs must use the same assay unit and conditions.
  • Specific activity refers to the preparation being weighed. Do not substitute units per mL for units per mg; liquid stock dosing requires its activity per volume.
  • The balance assumes activity is retained during preparation. Temperature, pH, inhibitors, storage losses and changes in assay conditions can affect actual activity.

Common questions

What does an activity unit mean here?

Use the unit definition supplied with your assay or preparation consistently on both sides. The calculator cancels that common unit; it does not convert between different assay definitions.

Is the result pure enzyme protein mass?

It is the mass basis used in the supplied specific activity. For a formulated preparation, that basis may include material other than the enzyme itself.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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