I don't know where to start with it?
A tube is set up for radioimmunoassay containing antibody with a capacity for binding 1ug antigen. Both labelled (50,000 counts per ug) and unlabelled antigen are added to the tube. Work out a formula to calculate the amounts of counts bound to antibody in each case.
Any help will be greatly appreciated!
To calculate the amount of counts bound to the antibody in each case, you'll need to consider the concentrations of labelled and unlabelled antigen, as well as the binding capacity of the antibody.
Let's break down the problem step by step:
Step 1: Determine the concentration of labelled and unlabelled antigen.
- The concentration of labelled antigen (C_l) can be given in counts per microliter (cpm/μL) or per unit of weight (counts per microgram, cpm/μg).
- The concentration of unlabelled antigen (C_u) is typically given in micrograms per milliliter (μg/mL).
Step 2: Calculate the amount of antigen bound to the antibody.
- The amount of labelled antigen (A_l) bound to the antibody can be calculated by multiplying the concentration of labelled antigen (C_l) by the volume of the sample (V).
- Similarly, the amount of unlabelled antigen (A_u) bound to the antibody can be calculated by multiplying the concentration of unlabelled antigen (C_u) by the volume of the sample (V).
Step 3: Convert the amounts of antigen bound to counts.
- Since the labelled antigen is directly measured in counts, the amount of counts bound to the labelled antigen (C_bound_l) is simply equal to the amount of labelled antigen (A_l).
- To determine the amount of counts bound to the unlabelled antigen (C_bound_u), you can use a conversion factor. If the labelled antigen has a specific activity of 50,000 counts per microgram (cpm/μg), then the conversion factor is 50,000 counts/μg. Multiply the amount of unlabelled antigen (A_u) by the conversion factor to obtain the counts bound to the unlabelled antigen.
Step 4: Calculate the total counts bound to the antibody.
- The total counts bound to the antibody (C_total) can be obtained by summing the counts bound to the labelled antigen (C_bound_l) and the counts bound to the unlabelled antigen (C_bound_u): C_total = C_bound_l + C_bound_u.
Now, you can use this formula to calculate the amounts of counts bound to the antibody in each case. Be sure to substitute the appropriate values for the concentrations of labelled (C_l) and unlabelled antigen (C_u), as well as the sample volume (V), to get accurate results.