Question

1. which of the following can interfere with the bradford assay?

a. glucose
b. detergents such as sds
c. water
d. sodium chloride

1. what should you do if your samples absorbance exceeds the highest standard?

a. add more dye
b. increase incubation time
c. dilute the sample and re - measure
d. change the wavelength

1. which form of coomassie brilliant blue binds to proteins?

a. cationic (red)
b. neutral (green)
c. anionic (blue)
d. zwitterionic (purple)

1. why is the bradford assay considered more sensitive than the biuret assay?

a. it uses a radioactive label
b. it detects lower protein concentrations in the range on micrograms
c. it measures amino acid composition
d. it does not require a spectrophotometer

1. what is the purpose of blanking the spectrophotometer?

a. to measure baseline absorbance of the buffer/reagent
b. to test the calibration curve
c. to remove dye impurities
d. to measure background protein concentration

Explanation:

• Question 9: Detergents like SDS can disrupt protein - dye interactions in Bradford assay. Glucose, water, and sodium chloride have less significant interference.
• Question 10: If absorbance exceeds the highest standard, diluting the sample (to bring it within the linear range of the calibration curve) and re - measuring is the correct approach. Adding more dye or changing wavelength won't fix the out - of - range issue, and increasing incubation time is not relevant.
• Question 11: In the Bradford assay, the anionic form of Coomassie Brilliant Blue binds to proteins.
• Question 12: The Bradford assay is more sensitive as it can detect protein concentrations in the microgram range, while the Biuret assay has a higher detection limit. It does not use a radioactive label, does not measure amino acid composition, and requires a spectrophotometer.
• Question 13: Blanking the spectrophotometer measures the baseline absorbance of the buffer/reagent. It is not for testing the calibration curve (which is done with standards), removing dye impurities (not the main purpose), or measuring background protein concentration (blank should have no protein).

Answer:

1. B. Detergents such as SDS
2. C. Dilute the sample and re - measure
3. C. Anionic (blue)
4. B. It detects lower protein concentrations in the range on micrograms
5. A. To measure baseline absorbance of the buffer/reagent