Section 9- Proteins & Labels
9. Proteins & Labels
This software module can be used to determine protein concentration (A280nm) as well as fluorescent dye concentration
(protein array conjugates), or to measure the purity of metalloproteins (such as hemoglobin) using wavelength ratios.
Fluorescent Dye Selection
There are currently nine fluorescent dyes that are hard-coded for use with the Proteins and Labels module (see table
below). Users can also enter & save fluorescent dyes not coded within the ND-1000 software using the ‘Dye/Chromophore
Editor’ button found in the main menu.
Dyes can be selected using the scroll arrows or by highlighting the Dye 1 or Dye 2 box. The respective absorbance
wavelength, extinction coefficient, and 280nm % corrections will be automatically utilized for measurement and
concentration calculation. The default settings from NanoDrop remain Dye 1 set to Cy3. In addition to the fluorescent
dyes available from the drop-down menu, an option entitled ‘None’ is also available. Selecting ‘None’ disables the
respective calculations & numeric displays corresponding to that dye.
Note: Please refer to the dye manufacturer for the appropriate correction factors for user entered dyes.
Sample Volume Requirements
Some proteins are hydrophobic and others hydrophilic giving rise to variable surface tension in the samples to be
measured. Additionally the presence of surfactants or detergents in reagents, such as the Bradford reagent, can
significantly alter surface tension. This occurrence can be overcome without affecting the sample’s absorbance by using a
larger sample volume. A 2 ul sample size is recommended for protein measurements.
Pedestal Reconditioning
Proteins and solutions containing surfactants are known to “un-condition” the measurement pedestal surfaces so that the
liquid column does not form. If this occurs, “buff” the measurement pedestal surfaces by rubbing each measurement
surface aggressively with a dry laboratory wipe 30-40 times. This will “re-condition” the surface allowing the liquid sample
column to form. Alternatively, use the NanoDrop Pedestal Reconditioning Compound (PR-1) as a rapid means of
reconditioning the pedestals when the surface properties have been compromised and liquid columns break during
measurement. Additional information about the PR-1 kit may be found at
www.nanodrop.com.
Measurement Concentration Range
The NanoDrop
®
ND-1000 Spectrophotometer will accurately measure protein samples up to 20 mg/ml (BSA) without
dilution. A table of concentration range and typical reproducibility is listed below.
9-1
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