These mainly include purification reactions. Total sample protein can be estimated by A 280. When dealing with an enzyme we often talk about specific activity.
Purification final specific activity initial specific activity.
The percent yield measures the amount of the protein that you have purified in terms of the total amount of that protein that you started with. To calculate the specific activity I divided the enzyme concentration by the protein concentration. The fold purification describes how purified a particular protein is. The responses of the standards are used to plot or calculate a standard curve.