The intensity of the color depends upon the amount of reduced hemoglobin in the blood.

Indeed, in almost all living creatures, hemoglobin is encapsulated in red blood cells, which protect the body from the protein s negative effects (and, in turn, protect hemoglobin from the body s digestive enzymes).

For example, haptoglobin tightly binds to hemoglobin subunits, while hemopexin captures the heme when the hemoglobin releases it.

But free hemoglobin can wreak havoc in the human body, causing hypertension, cardiac arrest, or even death.

Hemoglobin contains hemes, chemical compounds that contain iron a transition metal that can undergo oxidation, or rusting processes.

When released into a person s circulatory system, hemoglobin in these higher oxidation states eventually self destructs, damaging molecules in surrounding tissue.

In the early twentieth century, researchers began to examine hemoglobin the protein responsible for carrying oxygen from the respiratory organs to the rest of the body in red blood cells.

Experts nonetheless believe that hemoglobin based products can be used to save the lives of trauma patients, as well as to treat patients who object to donated blood on religious grounds (for example, Jehovah s Witnesses).

Outside of red blood cells, good ferrous iron the only oxygen carrying form is oxidized uncontrollably to form the bad ferric and ugly ferryl forms of hemoglobin.

They have found that the body s first line of defense against hemoglobin oxidation is a process of reduction, in which molecules like uric acid or ascorbic acid (vitamin C) impede oxidation by reducing the iron to a less oxidizing species.

Researchers (including at my laboratory) have investigated how the body naturally handles the occasional release of hemoglobin from aging red blood cells and from cells affected by blood diseases, such as hemolytic anemia.