David L. Chandler | MIT News Office
May 22, 2014
Melanin — and specifically, the form called eumelanin — is the primary pigment that gives humans the coloring of their skin, hair, and eyes. It protects the body from the hazards of ultraviolet and other radiation that can damage cells and lead to skin cancer, but the exact reason why the compound is so effective at blocking such a broad spectrum of sunlight has remained something of a mystery.
Now researchers at MIT and other institutions have solved that mystery, potentially opening the way for the development of synthetic materials that could have similar light-blocking properties. The findings are published this week in the journal Nature Communications by graduate students Chun-Teh Chen and Chern Chuang, professor of civil and environmental engineering Markus Buehler, and three others.
Although eumelanin has been known for decades, pinning down its molecular structure, and identifying the reasons for its broadband light absorption, have been daunting tasks. This is, in part, because of the very characteristics that make it so interesting: Typically, the constituents of a chemical compound can be determined through spectroscopy, among other tools, but in the case of eumelanin the spectrographs don’t show the sharp peaks that are ordinarily useful in identification. So indirect means of analysis were needed.
The team used a combination of computation and experimental analysis to derive the structure of the material, finding that a major source of the broadband absorption was the physical arrangement of the constituents, not their chemical characteristics. Specifically, the combination of disorder and order in the physical arrangement produces a “smearing” of the material’s spectral absorption, and providing its crucial broadband blocking ability.
“You can’t do traditional analytical chemistry on this particular system,” Chuang, a graduate student in chemistry, says, “where you isolate each component. Only indirect ways of probing” can be used, he says.
The disorder that turned out to be key, the team says — a physical disorder called “geometric disorder” — is different from the chemical disorder that other researchers have studied. It turns out that both kinds of disorder may play a complementary role in producing eumelanin’s broadband absorption.
The material forms tiny crystals — a chemically ordered state — but with intrinsic randomness, such that the orientations of the stacked molecules can be arbitrary and the sizes of the crystals different, forming aggregate structures that are highly disordered. That combination of order and disorder contributes to eumelanin’s broadband absorption, the team found.
“It’s a naturally existing nanocomposite,” Buehler says, “that has very critical macroscopic properties as a result of the nanostructure.”
While eumelanin molecules all share a basic chemistry, more than 100 variations of that composition exist; the slight variations from one molecule to another may contribute to the disorder that broadens the ability to absorb light, Buehler says. “The jury is still out on which is more important,” he says.
Understanding the origins of eumelanin’s optical properties could help guide the creation of new synthetic materials, Buehler says. These insights may be useful in developing materials for applications such as pigments, he says, or in improving the efficiency of solar cells.
While this analysis still leaves open questions about the precise structure of eumelanin molecules, Buehler says, “Building an accurate structural model is one of our big aims.”
A similar combination of computational modeling based on quantum mechanics, molecular dynamics, and direct observation using electron microscopy “can probably be applied to many systems,” Buehler says. “It’s a methodological advance that is validated because this system has such unique optical properties, which we can reproduce. It shows the method can be useful.”
Sergei Tretiak, a researcher in the theoretical division at Los Alamos National Laboratory who was not involved in this research, says that understanding eumelanin’s structure was “a scientific puzzle for a long time.” The new work, he says, “provides a somewhat unexpected answer to this conundrum.” The researchers’ approach, he says, “exemplifies a multidisciplinary approach to [a] complex problem, where a single method is unable to provide a satisfying answer.”
The research team also included Jianshu Cao, a professor of chemistry at MIT, Vincent Ball at the University of Strasbourg in France, and David Ruch at the Centre de Recherche Public Henri Tudor in Luxembourg. The work was partly funded by the U.S. Department of Energy through the Center for Excitonics at MIT.
The brain of humans consists of Gray matter, White matter, and Black matter.
The white matter of the brain comprises nerve fibers that connect the gray matter. It is composed of nerve fibers and myelin. The nerve fibers form the connections between the nerve cells. Myelin is a fatty sheath wrapped around nerve fibers. The myelin sheath has two functions: insulation and acceleration of impulse conduction. Insulation is important for the prevention of short-circuits. Through its special construction, myelin accelerates the propagation of impulses along nerve fibers.
Myelin is an essential part of the white matter. When the myelin sheath is damaged or disappears, the conduction of impulses along nerve fibers slows down or fails completely. Consequently, brain functions become hampered or be lost.
White matter disorders
In many neurological disorders in childhood, the white matter of the brain is predominantly involved. These are called "the white matter disorders". The diagnosis is usually made on the basis of MRI findings. White matter abnormalities on MRI can have different bases on tissue level. It may be that there is a lack of myelin because the myelin was never made in sufficient amounts. It may be that the myelin was formed all right, but is now broken down and lost. It may be that innumerable vacuoles are formed within the myelin sheath. It may be that scar tissue is formed within the white matter. There may be increased amounts of water between the myelinated fibers, etc. Nerve fibers may be lost as well.
It is clear that the term "white matter disorders" comprises many different disorders which all have different consequences for brain function. For instance, loss of myelin is worse for brain function than increase of water content or formation of scar tissue between nerve fibers. It is therefore also clear that the resulting handicap for the child with a white matter disorder is highly variable, depending on what is happening at brain tissue level.
The Black component is called substantia nigra, which is Latin for "black substance." It's black because of neuromelanin, a specialized type of the same pigment that colors skin and hair, and it's a part of the basal ganglia. Finally, we have red -- and that's thanks to the many blood vessels in the brain. So why are preserved brains chalky looking and dull instead of spongy and colorful? It's due to the fixatives, such as formaldehyde, that keep the brain preserved.
The basal ganglia (or basal nuclei) comprise multiple subcortical nuclei, of varied origin, in the brains of vertebrates, which are situated at the base of the forebrain. Basal ganglia nuclei are strongly interconnected with the cerebral cortex, thalamus, and brainstem, as well as several other brain areas. The basal ganglia are associated with a variety of functions including: control of voluntary motor movements, procedural learning, routine behaviors or "habits" such as bruxism, eye movements, cognition and emotion.
Superior athletic ability, superior learning ability, etc. are clearly associated with Neuromelanin (Melanin in the Brain (Black matter)).
The "Common Sense" logic here, would be that "If Albinos can't generate enough Melanin to color their SKIN": then how could they generate enough Melanin to make a healthy "Substantia Nigra" which is almost "Jet Black"?
Melanin theory is a pseudoscientific theory of black supremacy based on the supposed physical properties of melanin, a natural polymer and organic semiconductor.
In humans, melanin is the primary determinant of skin color. People whose ancestors lived for long periods in the regions of the globe near the equator generally have larger quantities of eumelanin in their skins. Melanin theorists assert that the possession of greater quantities of melanin gives black people inherent superiority. Conversely, its lack demonstrates the alleged inhumanity and inferiority of white people.
One of the notions of melanin theory is that white people are mutants, that white skin is an aberration, a form of albinism. Melanin theorist Wade Nobles takes this even further, stating that only Black people are fully human because of their higher levels of skin melanin:
Wade Nobles - That in the evolution of the species, in what some people call the Ontogenetic evolution of humankind, that in the evolution of the species the human family separated in a sense that one branch of the family stopped its evolutionary path and simply depended upon the central nervous system as the total machinery for understanding reality. Whereas, the root of the family continued its path and not only evolved a central nervous system but developed what I called at that time an essential melanic system. And that I even went so far as to try to develop a little formula and suggested that CNS + EMS = HB. CNS (Central Nervous System) + EMS (Essential Melanic System) = HB (Human Being). That the central nervous system combined with the essential melanic system is what makes you human. That, in fact, to be human is to be Black. To be human is to be Black. (Nobles 1989).
Melanin is responsible for the existence of civilization, philosophy, religion, truth, justice, and righteousness. Individuals (whites) containing low levels of Melanin will behave in a barbaric manner. Melanin gives humans the ability to FEEL because it is the absorber of all frequencies of energy. Since whites have the least amount of Melanin, this is why they are perceived by People of Color as generally being rigid, unfeeling (heartless), cold, calculating, mental, and "unspiritual."
This hypothesis is supported by black academic Leonard Jeffries, who was dismissed in 1992 from his post as chairman of the The City College of New York's Black Studies department for having allegedly made antisemitic statements. Jeffries claims that the pigment melanin is the source of intelligence and creativity. He divides humanity into African “sun people” and European “ice people,” the latter being not only melanin-deficient but born cold and greedy, militaristic, authoritarian, and possessed of a host of other racially determined defects.
Welsing also claims that the prevalence of high blood pressure among African Americans is because melanin picks up "energy vibrations" from people who are experiencing stress. Thus people with dark skin will absorb the effects of stress in others resulting in higher blood pressure. In fact, higher rates of hypertension among blacks are linked to norepinephrine, a substance that the body produces under stress and which constricts blood vessels. Studies by Roger Allen at the University of Maryland show that, after being subjected to stress, blacks exhibit elevated blood pressure at least ten times as long as do whites.
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