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. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and most viruses). ...

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 (A_max) frequency of the blue dye, using a spectrophotometer. In this case the greater the absorbance, the higher the protein concentration. In spectroscopy, the absorbance A is defined as , where I is the intensity of light at a specified wavelength λ that has passed through a sample (transmitted light intensity) and is the intensity of the light before it enters the sample (or incident light intensity). ... Optical density is the absorbance of an optical element for a given wavelength λ per unit distance: Where: = the distance that light travels through the sample (i. ... Luminescence is light not generated by high temperatures alone. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... Radioactivity may mean: Look up radioactivity in Wiktionary, the free dictionary. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... In physics, spectrophotometry is the quantitative study of spectra. ...

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

• protein
• color
• Logarithmic scale

A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Color is an important part of the visual arts. ... A logarithmic scale is a scale of measurement that uses the logarithm of a physical quantity instead of the quantity itself. ...

References

• Bradford Assay Background

(pdf format) Bradford Protein Assay. Bio-Rad Quick Start^tm Bradford Protein Assay Instructional Manual. URL accessed on May 31, 2005. May 31 is the 151st day of the year in the Gregorian calendar (152nd in leap years), with 214 days remaining. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...