Evans blue
Encyclopedia
T-1824 or Evans Blue, often incorrectly rendered as Evan's Blue, is an azo dye which has a very high affinity for serum albumin
. Because of this, it can be useful in physiology
in estimating the proportion of body water
contained in blood plasma
.
Evans blue dye has been used as a viability assay
on the basis of its penetration into non-viable cells, although the method is subject to error because damaged cells may be capable of repair
Evans blue is also used to assess the permeability of the blood-brain barrier
to macromolecules. Because serum albumin cannot cross the barrier, and virtually all Evans Blue is bound to albumin, normally the neural tissue remains unstained. When the BBB has been compromised, albumin-bound Evans blue enters the CNS. It fluoresces with excitation peaks at 470 and 540 nm and an emission peak at 680 nm.
It was named after Herbert McLean Evans
, an American chemist.
Serum albumin
Serum albumin, often referred to simply as albumin is a protein that in humans is encoded by the ALB gene.Serum albumin is the most abundant plasma protein in mammals. Albumin is essential for maintaining the osmotic pressure needed for proper distribution of body fluids between intravascular...
. Because of this, it can be useful in physiology
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
in estimating the proportion of body water
Body water
In medicine, body water is the water content of the human body. A significant fraction of the human body is water. Arthur Guyton 's Textbook of Medical Physiology states that "the total amount of water in a man of average weight is approximately 40 litres, averaging 57 percent of his total body...
contained in blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
.
Evans blue dye has been used as a viability assay
Viability assay
A viability assay is an assay to determine the ability of cells or tissues to maintain or recover its viability. For example, examining the ratio of potassium to sodium in cells indicates viability because if cells do not have high intracellular potassium and low intracellular sodium: the...
on the basis of its penetration into non-viable cells, although the method is subject to error because damaged cells may be capable of repair
Evans blue is also used to assess the permeability of the blood-brain barrier
Blood-brain barrier
The blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...
to macromolecules. Because serum albumin cannot cross the barrier, and virtually all Evans Blue is bound to albumin, normally the neural tissue remains unstained. When the BBB has been compromised, albumin-bound Evans blue enters the CNS. It fluoresces with excitation peaks at 470 and 540 nm and an emission peak at 680 nm.
It was named after Herbert McLean Evans
Herbert McLean Evans
Herbert McLean Evans was a U.S. anatomist and embryologist.He was born in Modesto, California. In 1908, he obtained his medical degree from Johns Hopkins University, eventually becoming its associate professor of anatomy...
, an American chemist.