Protein Concentration Calculator

Calculate protein concentration using Bradford, BCA, Lowry, A280, or Biuret assays

AU
×
y = mx + b (where y = absorbance, x = concentration)

Results

0
mg/mL
0
µg/mL
0
µM

Assay Methods

Bradford: 595 nm, fast, compatible with reducing agents
BCA: 562 nm, linear, compatible with detergents
Lowry: 750 nm, sensitive, time-consuming
A280: Direct UV, no reagents needed
Biuret: 540 nm, simple but less sensitive

Detection Ranges

  • Bradford: 0.1-1.4 mg/mL
  • BCA: 0.02-2 mg/mL
  • Lowry: 0.01-1 mg/mL
  • A280: 0.1-100 mg/mL
  • Biuret: 1-10 mg/mL

Interference Factors

  • Bradford: Detergents (SDS)
  • BCA: Reducing agents, chelators
  • Lowry: Many chemicals interfere
  • A280: Nucleic acids (260 nm)
  • Biuret: Ammonium salts

Standard Proteins

  • BSA: Most common, 66.5 kDa
  • IgG: For antibody work, 150 kDa
  • Lysozyme: Small protein, 14.3 kDa
  • Ovalbumin: Alternative standard, 45 kDa

Tips for Accuracy

  • Use same buffer for standards and samples
  • Prepare fresh reagents
  • Run samples in duplicate/triplicate
  • Include blank controls
  • Stay within linear range

FAQ

Q: Which method is best?
A: Depends on sample composition, required sensitivity, and available equipment.

Q: Why different wavelengths?
A: Each assay uses different chromophores that absorb at specific wavelengths.