- Let’s say that you started with an undiluted sample of ß-gal from which you made a 1/100 dilution. You took 10 of the diluted sample and added it to Z buffer to do your assay. After 11 minutes your sample had an A420 of 0.412 versus the blank.
- The A420 in this example equals 0.412. Time in this example equals 11 min. Plugging these values into the formula shown above results in 1.42 x 10-2 units of ß-galactosidase activity:
Units
of ß-gal |
|
0.412 x 0.380 |
= |
---------------------------- |
| |
11 minutes at 37°C |
The answer is 0.0142 units.
- You then use a proportion to determine the number of units of ß-gal in the diluted sample from which you took your 10 µl.
| 1.42 x 10-2 units |
|
? units |
| -------------------- |
= |
--------- |
| 10 µl |
|
1000 µl |
? = 1.42 units/ml
- You have found that you have 1.42 units/ml in the sample you assayed. Now you need to account for your dilution. For the 1/100 dilution you made, you multiply 1.42 units/ml by 100. Therefore you have 142 units/ml of ß-galactosidase in the original undiluted sample.
|
