The key difference between ethidium bromide and bromophenol blue is that ethidium bromide is a fluorescent dye, whereas bromophenol blue is a non-fluorescent dye.
The terms ethidium bromide and bromophenol blue are commonly used in different research areas due to their use as dyes. However, their chemical structures and uses are different from each other, so their outcome is different as well.
CONTENTS
1. Overview and Key Difference
2. What is Ethidium Bromide
3. What is Bromophenol Blue
4. Ethidium Bromide vs Bromophenol Blue in Tabular Form
5. Summary – Ethidium Bromide vs Bromophenol Blue
What is Ethidium Bromide?
Ethidium bromide is an intercalating agent useful as a fluorescent tag in different laboratories and other applications. It is the chloride salt of homidium bromide. It is used mainly as a nucleic acid stain in molecular biology and agarose gel electrophoresis. The abbreviation of this compound is EtBr.
If ethidium bromide is exposed to UV light, it can fluoresce with an orange color to intensify the after-binding state of DNA. It has a high incidence of antimicrobial resistance, which makes its use impractical in some areas. When this happens, isometamidium chloride is used as an alternative to ethidium bromide.
Figure 01: The Absorption Spectrum of Ethidium Bromide
The chemical formula of ethidium bromide is C21H20BrN3. It has a molar mass of 394.29 g/mol. This substance appears as a purple-red solid, and its melting point can range from 260 – 262 degrees Celsius.
What is Bromophenol Blue?
Bromophenol blue is a pH indicator that is useful as an electrophoretic color marker and a dye. It has the chemical name 3’,3”,5’,5”-tetrabromophenolsulfonphthalein, BPB. The chemical formula of this compound is C19H10Br4O5S. The molar mass of this compound is 669.96 g/mol. It is odorless, and its density can be given as 2.2 g/mL. Its melting point is 273 degrees Celsius, and its boiling point is 279 degrees Celsius. We can prepare it by slowly adding excess bromine to a hot solution of phenolsulfonphthalein in glacial acetic acid.
Bromophenol blue is useful as an acid-base indicator in the range between pH 3.0 to 4.6. It is able to change from yellow at pH 3.0 to pH 4.6. Moreover, it is a reversible reaction. Structurally, bromophenol blue is similar to phenolphthalein.
Figure 02: Bromophenol
Besides, we can use it as a color marker to monitor the process of polyacrylamide gel electrophoresis and agarose gel electrophoresis. This substance can carry a negative charge at moderate pH, where it can migrate in the same direction as DNA or protein in a gel. The migration rate can vary according to gel density and buffer composition. However, in a typical 1% agarose gel in 1 time TAE buffer or TBE buffer, this substance migrates at the same rate as a DNA fragment of about 300 base pairs.
What is the Difference Between Ethidium Bromide and Bromophenol Blue?
Although both ethidium bromide and bromophenol blue are dying agents, they have different chemical features as well as outcomes. The key difference between ethidium bromide and bromophenol blue is that ethidium bromide is a fluorescent dye, whereas bromophenol blue is a non-fluorescent dye.
The below infographic presents the differences between ethidium bromide and bromophenol blue in tabular form for side-by-side comparison.
Summary – Ethidium Bromide vs Bromophenol Blue
Ethidium bromide is an intercalating agent useful as a fluorescent tag in different laboratories and other applications. Bromophenol blue is a pH indicator that is useful as an electrophoretic color marker and a dye. The key difference between ethidium bromide and bromophenol blue is that ethidium bromide is a fluorescent dye, whereas bromophenol blue is a non-fluorescent dye.
Reference:
1. “Ethidium Bromide.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Bromophenol blue cyclic 3D skeletal” By Jynto (talk) – This image was created with Discovery Studio Visualizer., (CC0) via Commons Wikimedia
1. “Ethidium-bromide-abs” By mark somoza – Own work (CC BY 2.5) via Commons Wikimedia