Which reagent can be used to measure protein in cerebrospinal fluid?

Which reagent can be used to measure protein in cerebrospinal fluid?

• A. Biuret
• B. Coomassie brilliant blue
• C. Ponceau S
• D. Bromcresol green

Answer: (B)

The test centers on which dye-based assay gives a reliable, sensitive readout for the relatively small protein amounts found in cerebrospinal fluid. Coomassie brilliant blue is used in the Bradford protein assay, where the dye binds to proteins (especially to arginine and other basic amino acids) and shifts its absorbance, producing a measurable blue color that increases with protein concentration. This makes it highly sensitive and well-suited for CSF, where protein levels are low and small sample volumes are common, so it’s the practical choice for quantifying total protein in CSF. Biuret reagent relies on peptide bonds to measure protein, but it is much less sensitive and needs higher protein concentrations, which isn’t ideal for CSF. Ponceau S is a staining dye used to visualize proteins on membranes rather than to quantify protein dissolved in solution. Bromcresol green typically measures albumin (not total protein) and is less appropriate when a full protein concentration in CSF is required.

The test centers on which dye-based assay gives a reliable, sensitive readout for the relatively small protein amounts found in cerebrospinal fluid. Coomassie brilliant blue is used in the Bradford protein assay, where the dye binds to proteins (especially to arginine and other basic amino acids) and shifts its absorbance, producing a measurable blue color that increases with protein concentration. This makes it highly sensitive and well-suited for CSF, where protein levels are low and small sample volumes are common, so it’s the practical choice for quantifying total protein in CSF.

Biuret reagent relies on peptide bonds to measure protein, but it is much less sensitive and needs higher protein concentrations, which isn’t ideal for CSF. Ponceau S is a staining dye used to visualize proteins on membranes rather than to quantify protein dissolved in solution. Bromcresol green typically measures albumin (not total protein) and is less appropriate when a full protein concentration in CSF is required.