Question

List the proteins detection techniques in increasing order of sensitivity: A. Bradford, B. Biuret, C. Lowry Choose the correct answer from the options given below:

• A. A, B, C \
• B. B, C, A \
• C. A, C, B \
• D. C, B, A

Hint:

Biuret is always the least sensitive (needs mg amounts). Bradford is very sensitive and super common in biochemistry labs for small yields. Order: Biuret $<$ Lowry $<$ Bradford.

Answer 1

The Correct Option is B

Step 1: Concept Protein quantification assays possess distinct lower limits of detection based on their chemical mechanics and colorimetric reagents. Higher sensitivity means the assay can detect smaller quantities of protein.

Step 2: Meaning * Biuret assay: Relies on copper ions coordinating with peptide bonds; requires milligram levels of protein (least sensitive). * Lowry assay: Combines biuret chemistry with Folin-Ciocalteu reagent oxidation of aromatic residues; detects microgram amounts. * Bradford assay: Relies on the direct binding of Coomassie Brilliant Blue G-250 dye to basic/aromatic residues; highly rapid and highly sensitive.

Step 3: Analysis Sorting the techniques from least sensitive to most sensitive: 1. Biuret method (B) - operating range is broad, usually 1-10 mg/mL. 2. Lowry method (C) - operating range is lower, down to around 10-100 $\mu$g/mL. 3. Bradford method (A) - highly sensitive, able to measure concentrations down to 1-10 $\mu$g/mL. Thus, the increasing sequence is B $\rightarrow$ C $\rightarrow$ A.

Step 4: Conclusion The sequence B, C, A corresponds to option B. Final Answer: (B)