ThermoFisher Scientific NanoDrop Eight, User Manual

Page: 54 / 152

5 Protein Applications
Measure Protein A280
54 NanoDrop Eight User Guide Thermo Scientific
Calculated protein concentrations are
based on the absorbance value at 280 nm,
the selected (or entered) extinction
coefficient and the sample pathlength. A
single-point baseline correction (or analysis
correction) may be applied.
Concentration is reported in mass units.
Calculators are available on the Internet to
convert concentration from mass to molar
units based on sample sequence.
Absorbance values at 260 nm and 280 nm
are used to calculate purity ratios for the
measured protein samples.
Purity ratios are sensitive to the presence of
contaminants in the sample, such as
residual solvents and reagents typically
used during sample purification.
Measured Values
A280 absorbance
Note : For micro-volume absorbance measurements, the
spectra are normalized to a 10 mm pathlength equivalent.
• Protein absorbance values are measured at 280 nm
using the normalized spectrum. If Baseline Correction is
not selected, this is the reported A280 value and the
value used to calculate protein concentration.
• If Baseline Correction is selected, the normalized and
baseline-corrected absorbance value at 280 nm is
reported and used to calculate protein concentration.
Sample Pathlength
• For micro-volume measurements, the software selects
the optimal pathlength (between 1.0 mm and 0.1 mm)
based on sample absorbance at the analysis wavelength.
• Displayed spectra and absorbance values are normalized
to a 10 mm pathlength equivalent.