From Wikipedia,
the free encyclopedia
A standard curve is a
quantitative research tool, a
method of plotting assay data that
is used to determine the
concentration of a substance,
particularly
proteins and
DNA.
The assay is first performed
with various known concentrations
of a substance similar to that
being measured. For example a
standard curve for protein
concentration is often created
using known concentrations of
bovine serum albumin. The
assay procedure may measure
absorbance,
optical density,
luminescence,
fluorescence,
radioactivity, or something
else. The assay for protein is
called the Bradford assay; it is a
colourimetric assay. The reagent
coomassie brilliant blue turns
blue when it binds to arginine and
aromatic
amino acids present in
protein. The intensity of the
colour is best measured at 595 nm,
which is the maximum absorbance (Amax)
frequency of the blue dye, using a
spectrophotometer. In this
case the greater the absorbance,
the higher the protein
concentration.
This data is used to make the
standard curve, plotting
concentration on the X axis, and
assay measurement on the Y axis.
The same assay is then performed
with samples of unknown
concentration. To analyze the
data, one locates the measurement
on the Y-axis that corresponds to
the assay measurement of the
unknown substance and follows a
line to intersect the standard
curve. The corresponding value on
the X-axis is the concentration of
substance in the unknown sample.
See also
References
(pdf format)
Bradford Protein Assay.
Bio-Rad Quick Starttm
Bradford Protein Assay
Instructional Manual. URL
accessed on
May 31,
2005.
