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5
Protein Applications
Measure Protein A280
This application offers six options (shown at
right) for selecting an appropriate extinction
coefficient for each measured sample, to
be used in conjunction with Beer's Law to
calculate sample concentration.
If the extinction coefficient of the sample is
known, choose the
+ MW (molar) or
1% (mass) option and enter the value.
Otherwise, calculate the extinction
coefficient or choose the option that best
matches the sample solution.
Tip: Ideally, the extinction coefficient
should be determined empirically using a
solution of the study protein at a known
concentration using the same buffer.
Most sources report extinction coefficients
for proteins measured at or near 280 nm in
phosphate or other physiologic buffer.
These values provide sufficient accuracy for
routine assessments of protein
concentration.
74
NanoDrop One User Guide
Available Options for Extinction Coefficient
• 1 Abs = 1 mg/mL, where sample type and/or ext.
coefficient is unknown (produces rough estimate of
protein concentration)
• BSA (Bovine Serum Albumin, 6.7 L/gm-cm)
• IgG (any mammalian antibody, 13.7 L/gm-cm)
• Lysozyme (egg white lysozyme, 26.4 L/gm-cm)
• Other protein (
coefficient
• Other protein (
coefficient
•
Note: See
Sample Type
Published Extinction Coefficients
Published extinction coefficients for proteins may be reported
as:
• wavelength-dependent molar absorptivity (or extinction)
coefficient (
) with units of M
• percent solution extinction coefficient (
-1
-1
(g/100 mL)
cm
(i.e., 1% or 1 g/100 mL solution
measured in a 1 cm cuvette)
• protein absorbance values for 0.1% (i.e., 1 mg/mL)
solutions
Tip: Assess published values carefully to ensure unit of
measure is applied correctly.
+ MW), user-specified molar ext.
1%), user-specified mass ext.
for details.
-1
-1
cm
1%) with units of
Thermo Scientific
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