Quantification of Protein

There are two major principles to quantify concentration of proteins. タンパク質の定量法には、大きくわけて二つの方法がある。

  1. Spectrophotometric method
  2. Colorimetric method - relative quantification using some standard substances such as BSA or casein.
Type Detection wavelength (nm) Approx. sensitivity
ABS (near-UV) Spectr. 280 nm 20-3000 µg
Lowry method Color. 770 nm 5-100 µg
ABS (near-UV) Spectr. 205 nm 1-100 µg
Bradford method Color. 595 nm 1-50 µg
BCA method Color. 562 nm 0.2-50µg

Spectrophotometric method


Extinction coefficient

ε280nm (M-1cm-1) = 5500NTyr+1490NTrp+125NCys

[protein] = A280nm x ε280nm M-1

NTyr,NTrp,NCys:Amino acids' count