Bromophenol blue (
3',3",5',5"-tetrabromophenolsulfonphthalein) is used as an acid-base
indicatorA pH indicator is a halochromic chemical compound that is added in small amounts to a solution so that the pH of the solution can be determined visually. Hence a pH indicator is a chemical detector for hydronium ions...
, a
color markerA Color marker is used to monitor the processes of agarose gel electrophoresis and polyacrylamide gel electrophoresis. Commonly used color markers include Bromophenol blue, Cresol Red, Orange G and Xylene cyanol....
and a dye.
As an acid-base
indicatorA pH indicator is a halochromic chemical compound that is added in small amounts to a solution so that the pH of the solution can be determined visually. Hence a pH indicator is a chemical detector for hydronium ions...
its useful range lies between
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
3.0 and 4.6. It changes from yellow at pH 3.0 to purple at pH 4.6; this reaction is reversible.
Bromophenol blue is also used as a color marker to monitor the process of
agarose gel electrophoresisAgarose gel electrophoresis is a method used in biochemistry and molecular biology to separate DNA, or RNA molecules by size. This is achieved by moving negatively charged nucleic acid molecules through an agarose matrix with an electric field...
and polyacrylamide gel electrophoresis.
Bromophenol blue (
3',3",5',5"-tetrabromophenolsulfonphthalein) is used as an acid-base
indicatorA pH indicator is a halochromic chemical compound that is added in small amounts to a solution so that the pH of the solution can be determined visually. Hence a pH indicator is a chemical detector for hydronium ions...
, a
color markerA Color marker is used to monitor the processes of agarose gel electrophoresis and polyacrylamide gel electrophoresis. Commonly used color markers include Bromophenol blue, Cresol Red, Orange G and Xylene cyanol....
and a dye.
Acid-base indicator
As an acid-base
indicatorA pH indicator is a halochromic chemical compound that is added in small amounts to a solution so that the pH of the solution can be determined visually. Hence a pH indicator is a chemical detector for hydronium ions...
its useful range lies between
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
3.0 and 4.6. It changes from yellow at pH 3.0 to purple at pH 4.6; this reaction is reversible.
Color marker
Bromophenol blue is also used as a color marker to monitor the process of
agarose gel electrophoresisAgarose gel electrophoresis is a method used in biochemistry and molecular biology to separate DNA, or RNA molecules by size. This is achieved by moving negatively charged nucleic acid molecules through an agarose matrix with an electric field...
and polyacrylamide gel electrophoresis. Since bromophenol blue carries a slight negative charge at moderate pH, it will migrate in the same direction as
DNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information...
or
proteinProteins are organic compounds made of amino acids arranged in a linear chain and folded into a globular form. The amino acids in a polymer chain are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues...
in a gel; the rate at which it migrates varies according to gel density and
bufferA buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. It has the property that the pH of the solution changes very little when a small amount of acid or base is added to it. Buffer solutions are used as a means...
composition, but in a typical 1% agarose gel in
TAE bufferTAE buffer is a buffer solution containing a mixture of Tris base, acetic acid and EDTA.In molecular biology it is used in agarose electrophoresis typically for the separation of nucleic acids such as DNA and RNA. It is made up of Tris-acetate buffer, usually at pH 8.0, and EDTA, which sequesters...
or
TBE bufferTBE or Tris/Borate/EDTA, is a buffer solution containing a mixture of Tris base, boric acid and EDTA.In molecular biology, TBE and TAE buffers are often used in procedures involving nucleic acids, the most common being electrophoresis. Tris-acid solutions are effective buffers for slightly basic...
, bromophenol blue migrates at the same rate as a DNA fragment of approximately 500
base pairIn molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair . In the canonical Watson-Crick base pairing, adenine forms a base pair with thymine , as does guanine with cytosine in DNA. In RNA, thymine is replaced...
s.
Xylene cyanolXylene cyanol can be used as a colour marker to monitor the process of agarose gel electrophoresis and polyacrylamide gel electrophoresis. Bromophenol blue and orange G can also be used for this purpose.-Migration speed:...
and
Orange GOrange G is a synthetic azo dye used in histology in many staining formulations. It usually comes as a disodium salt. It has the appearance of orange crystals or powder...
may also be used for this purpose.
Dye
Bromophenol blue is also used as a dye. At neutral pH, the dye absorbs red light most strongly and transmits blue light. Solutions of the dye therefore are blue. At low pH, the dye absorbs ultraviolet and blue light most strongly and appears yellow in solution.
In solution at pH 3.6 (in the middle of the transition range of this pH indicator) obtained by dissolution in water without any pH adjustment, bromophenol blue has a characteristic green red color. This phenomenon is called
dichromatic colourDichromatism is a phenomenon where the hue of the colour in materials or solutions are dependent on both the concentration of the absorbing substance and the depth or thickness of the medium traversed...
. Bromphenol blue is the substance with the highest known value of
Kreft's dichromaticity indexKreft's dichromaticity index is a measure for quantification of dichromatism. It is defined as the difference in hue angle between the color of the sample at the dilution, where the chroma is maximal and the color of four times more diluted and four times more concentrated sample...
. This means that it has the largest change in color
hueHue is one of the main properties of a color, defined technically , as “the degree to which a stimulus can be describedas similar to or different from stimuli that are described as red, green, blue, and yellow,”...
, when the thickness or concentration of observed sample increases or decreases.
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