Competition:Analysis of Data:Sample Experiment:% Specific Bound

Analysis of Percent of Specific Bound versus - Log of Prazosin

On this page you will convert the data to % of Specific Bound and estimate the IC₅₀ value from a plot of % of Specific Bound versus -Log Prazosin.

Matthew has placed your calculations for Log of Prazosin and Average Bound (cpm) from a previous page in the table below.

You now need to calculate % of Specific Bound. This is the same as normalizing the data.

• Specific bound is determined by subtracting nonspecific binding from all of the bound values. Nonspecific values can be taken as the value obtained with the highest concentration of prazosin, the lowest value in the data set, the value obtained using norepinephrine or the bottom of the curve obtained from a nonlinear regression analysis of the Bound vs. Log of Prazosin curve.
• Percent of Specific Bound is determined by dividing the Specific Bound value by either the highest number in the data set, the value obtained in the absence of prazosin or the top of the curve as determined by nonlinear regression analysis of Bound vs. Log of Prazosin curve.

Calculate Specific Bound (cpm) now. In this example we will define nonspecific binding as the amount of [³H]RX821002 bound in the presence of the highest concentration of prazosin. Put your answers in the third column in the table below.

Calculate Percent of Specific Bound using the Bound value obtained in the absence of prazosin. Put your answer in the fourth column.

Prazosin Log (M)	Bound (cpm)	Specific Bound (cpm)	% of Specific Bound
- 12.00	1395
- 9.52	1292
-9.00	1256
-8.52	958
-8.00	730
-7.52	417
-7.00	198
-6.52	126
-6.00	116
-5.52	82
-5.00	81

The plot of % of Specific Bound vs. Log of Prazosin looks like this:

Proceed to the next page to convert the IC₅₀ value to a K_i value.