Melanin ( ; from Ancient Greek μέλας (mélas) 'black, dark') refers to a family of biomolecules structured as oligomers or polymers, which primarily function as pigments in various organisms. These melanin pigments are synthesized within specialized cells known as melanocytes.
Melanin ( ; from Ancient Greek μέλας (mélas) 'black, dark') is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes.
Five fundamental categories of melanin have been identified: eumelanin, pheomelanin, neuromelanin, allomelanin, and pyomelanin. Melanin synthesis occurs via melanogenesis, a multistage chemical process involving the oxidation of the amino acid tyrosine, subsequently followed by polymerization. Pheomelanin, a cysteinated variant, incorporates polybenzothiazine moieties, which are predominantly responsible for imparting red or yellow hues to certain skin and hair types. Neuromelanin is localized within the brain; investigations have explored its potential therapeutic utility in addressing neurodegenerative conditions, including Parkinson's disease. Allomelanin and pyomelanin represent two distinct forms of nitrogen-free melanin.
Phenotypic color variations in mammalian epidermis and hair are predominantly governed by the concentrations of eumelanin and pheomelanin within the respective tissues. In typical human subjects, eumelanin exhibits higher concentrations in tissues necessitating photoprotection, including the epidermis and the retinal pigment epithelium. Among healthy individuals, epidermal melanin levels correlate with UV exposure. Conversely, retinal melanin concentrations demonstrate an age-dependent decline, decreasing 2.5-fold from the first to the ninth decade of life, a phenomenon ascribed to oxidative degradation facilitated by reactive oxygen species originating from lipofuscin-dependent pathways. Excluding cases of albinism or hyperpigmentation, the human epidermis typically comprises approximately 74% eumelanin and 26% pheomelanin, largely independent of skin tone. Specifically, eumelanin content ranges from 71.8% to 78.9%, while pheomelanin varies between 21.1% and 28.2%. The total melanin concentration in the epidermis spans from approximately 0 μg/mg in albino epidermal tissue to over 10 μg/mg in darker pigmented tissue.
In human skin, melanogenesis is triggered by exposure to ultraviolet (UV) radiation, leading to dermal darkening. Eumelanin functions as an efficient light absorbent, capable of dissipating more than 99.9% of absorbed UV radiation. This characteristic property suggests that eumelanin safeguards skin cells against damage from UVA and UVB radiation, thereby mitigating the risk of folate depletion and dermal degradation. However, UV radiation exposure is correlated with an elevated risk of melanoma, a malignancy originating from melanocytes (melanin-producing cells). Research indicates a reduced incidence of skin cancer among individuals possessing higher melanin concentrations, corresponding to darker skin tones.
Types of Melanin
Eumelanin
Eumelanin (lit.'true melanin') exists in two distinct forms, associated with 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). DHI-derived eumelanin presents as dark brown or black and is insoluble, whereas DHICA-derived eumelanin is lighter in color and soluble in alkaline solutions. Both eumelanin types originate from the oxidation of tyrosine within specialized organelles known as melanosomes. This enzymatic reaction is catalyzed by tyrosinase. The initial product, dopaquinone, can subsequently convert into either 5,6-dihydroxyindole (DHI) or 5,6-dihydroxyindole-2-carboxylic acid (DHICA). Both DHI and DHICA undergo oxidation and subsequent polymerization to yield the two forms of eumelanin.
Under physiological conditions, DHI and DHICA frequently co-polymerize, generating a diverse array of eumelanin polymers. These polymeric structures contribute to the spectrum of melanin components found in human skin and hair, encompassing light yellow/red pheomelanin, light brown DHICA-enriched eumelanin, and dark brown or black DHI-enriched eumelanin. The resulting polymers exhibit variations in both solubility and color.
Examination of highly pigmented skin (Fitzpatrick types V and VI) reveals that DHI-eumelanin constitutes the predominant fraction, accounting for approximately 60–70%, succeeded by DHICA-eumelanin at 25–35%, with pheomelanin representing a minor component of only 2–8%. Significantly, although DHI-eumelanin enrichment is observed during sun tanning, this process is concurrently associated with a reduction in both DHICA-eumelanin and pheomelanin levels. The presence of a minimal quantity of black eumelanin, without other pigments, results in grey hair. Similarly, a sparse amount of eumelanin, in the absence of other pigments, leads to blond hair. Eumelanin is found in various tissues, including skin and hair.
Pheomelanin
Pheomelanins (from Greek φαιός phaios 'grey') are responsible for a spectrum of yellowish to reddish hues. These pigments exhibit high concentrations in the lips, nipples, glans of the penis, and vagina. The combination of a modest quantity of eumelanin (which typically produces blond hair) with pheomelanin yields orange hair, commonly referred to as "red" or "ginger" hair. Pheomelanin is also present in the skin, and individuals with red hair frequently exhibit a more pinkish skin tone. While ultraviolet light exposure elevates pheomelanin levels, similar to eumelanin, pheomelanin in hair and skin reflects yellow to red light instead of absorbing it, potentially exacerbating damage from UV radiation.
Pheomelanin production is critically contingent upon the availability of cysteine. This cysteine is transported into the melanosome, where it reacts with dopaquinone to synthesize cys-dopa. Subsequently, cys-dopa undergoes a series of transformations culminating in pheomelanin formation. Chemically, pheomelanins diverge from eumelanins by incorporating benzothiazine and benzothiazole units into their oligomeric structure, which are formed in the presence of the amino acid L-cysteine, rather than DHI and DHICA.
Pheomelanins, unlike eumelanins, are infrequently observed in lower organisms, leading to assertions of their status as an "evolutionary innovation within the tetrapod lineage." However, contemporary research has identified their presence in certain fish species.
Neuromelanin
Neuromelanin (NM) is an insoluble polymeric pigment synthesized within distinct populations of catecholaminergic neurons in the brain. Humans possess the highest quantities of NM, with smaller amounts detected in other primates, and a complete absence in numerous other species. Its precise biological function remains elusive; however, human NM has demonstrated efficient binding capabilities for transition metals like iron and various other potentially toxic molecules. Consequently, it is hypothesized to play pivotal roles in apoptosis and the pathogenesis of Parkinson's disease.
Other forms of melanins
Prior to the 1960s, melanin was categorized exclusively into eumelanin and pheomelanin. However, in 1955, neuromelanin, a melanin associated with neural cells, was identified. Subsequently, in 1972, pyomelanin, a water-soluble variant derived from the oxidation of homogentisic acid, was discovered. By 1976, allomelanin, recognized as the fifth distinct form of melanin, was identified in natural contexts. Its formation results from the oxidation of compounds including 1,8-dihydroxynaphthalene, 1,4,6,7,9,12-hexahydroxyperylene-3,10-quinone, and catechol.
Peptidomelanin
Peptidomelanin is a distinct water-soluble variant of melanin. It has been observed to be secreted into the ambient medium by germinating spores of Aspergillus niger (strain: melanoliber). Peptidomelanin constitutes a copolymer formed between L-DOPA eumelanin and short peptides, which create a 'corona' structure imparting solubility to the substance. These peptide chains are covalently attached to the L-DOPA core polymer through peptide bonds. This observation has informed a proposed biosynthetic pathway involving the hydroxylation of tyrosinylated or cysteinylated peptides, generated by proteases during sporogenesis, which are subsequently incorporated autoxidatively into an expanding L-DOPA core polymer.
Peptidomelanin is synthesized through the action of a broad-spectrum copper oxidase. This enzyme features a type-3 di-copper catalytic center situated within a substantial, solvent-accessible cavity. Research indicates that this enzyme oxidizes the thiol groups of cysteinylated peptides, thereby facilitating their copolymerization with an L-DOPA-derived core polymer.
Selenomelanin
Melanin can be enriched with selenium as an alternative to sulfur. This selenium analog of pheomelanin has been successfully synthesized via both chemical and biosynthetic pathways, utilizing selenocystine as a precursor. Given selenium's elevated atomic number, the resulting selenomelanin is anticipated to offer superior protection against ionizing radiation compared to other established melanin forms. Experimental studies involving human cells and bacteria have validated this protective capacity, suggesting potential applications in space exploration.
Trichochromes
Trichochromes (formerly known as trichosiderins) are pigments synthesized via the same metabolic pathway as eumelanins and pheomelanins; however, they possess a low molecular weight, distinguishing them from the latter. These compounds are found in certain types of red human hair.
Humans
In humans, melanin serves as the principal determinant of skin color. Additionally, it is present in hair, the pigmented tissue beneath the ocular iris, and the stria vascularis of the inner ear. Within the brain, melanin-containing tissues encompass the medulla and pigmented neurons situated in brainstem regions, including the locus coeruleus. Furthermore, its presence is noted in the zona reticularis of the adrenal gland.
Cutaneous melanin is synthesized by melanocytes, which are located within the epidermal basal layer. While humans generally exhibit comparable melanocyte concentrations in their skin, melanocytes in specific individuals and ethnic populations generate differing quantities of melanin. The epidermal ratio of eumelanin (74%) to pheomelanin (26%) remains consistent, irrespective of the pigmentation level. A condition termed albinism is characterized by minimal or absent melanin synthesis in certain individuals.
Given that melanin constitutes an aggregate of smaller constituent molecules, numerous melanin types exist, distinguished by varying proportions and bonding arrangements of these molecular components. Both pheomelanin and eumelanin are present in human integument and hair; however, eumelanin represents the predominant melanin in humans and is the form most frequently deficient in cases of albinism.
Melanin Across Organisms
Melanins exhibit highly diverse roles and functions across a wide range of organisms. For instance, a melanin variant constitutes the ink employed by numerous cephalopods as a defensive mechanism against predation. Furthermore, melanins safeguard microorganisms, including bacteria and fungi, from cellular damage induced by stressors such as solar UV radiation and reactive oxygen species. Melanin additionally confers protection against harm from elevated temperatures, chemical stressors (e.g., heavy metals and oxidizing agents), and biochemical challenges (e.g., host immune responses to invading microbes). Consequently, in numerous pathogenic microbes (for example, the fungus Cryptococcus neoformans), melanins seem to contribute significantly to virulence and pathogenicity by shielding the microorganism from host immune responses. In invertebrates, melanin constitutes a crucial component of the innate immune defense system against invading pathogens. Minutes post-infection, the microbe undergoes encapsulation within melanin (melanization), and the concomitant generation of free radical byproducts during capsule formation is believed to facilitate microbial eradication. Certain fungal species, known as radiotrophic fungi, seemingly utilize melanin as a photosynthetic pigment, allowing them to capture gamma rays and convert this energy for growth.
In piscine species, melanin is present not only in the integument but also in internal organs, including the eyes. While the majority of fish species employ eumelanin, Stegastes apicalis and Cyprinus carpio utilize pheomelanin.
The darker pigmentation of avian feathers is attributable to melanin, rendering them less susceptible to bacterial degradation compared to unpigmented feathers or those containing carotenoid pigments. Melanin-containing feathers also demonstrate a 39% greater resistance to abrasion than those lacking melanin, as melanin granules contribute to filling the interstitial spaces between the keratin strands comprising the feathers. Avian pheomelanin synthesis necessitates the intake of cysteine, a semi-essential amino acid crucial for glutathione (GSH) antioxidant synthesis, yet potentially toxic if consumed in excessive dietary amounts. Consequently, numerous carnivorous avian species, characterized by high dietary protein intake, display pheomelanin-derived coloration.
Melanin also plays a significant role in mammalian pigmentation. Mammalian coat patterns are dictated by the agouti gene, which governs melanin distribution. The gene's underlying mechanisms have been thoroughly investigated in mice, offering insights into the broad spectrum of mammalian coat patterns.
In arthropods, melanin deposition in layered structures has been observed, forming a Bragg reflector characterized by an alternating refractive index. When the periodicity of this pattern corresponds to the wavelength of visible light, structural coloration emerges, imparting an iridescent hue to various species.
Arachnids represent one of the few taxonomic groups where melanin has not been readily identified, although research data indicates that spiders do, in fact, synthesize melanin.
Certain moth species, such as the wood tiger moth, utilize melanin synthesis from available resources to improve thermoregulatory capabilities. Across the extensive latitudinal distribution of the wood tiger moth, a correlation has been observed where populations situated further north exhibit elevated melanization levels. Among both yellow and white male phenotypes of this species, individuals possessing greater melanin content demonstrated an enhanced capacity for heat retention; however, this advantage was counterbalanced by an elevated predation risk, attributed to a diminished and less potent aposematic signaling.
Melanin potentially confers protection to Drosophila flies and murine models against DNA damage induced by non-ultraviolet radiation.
Plants
Plant-synthesized melanins are occasionally designated as 'catechol melanins' due to their capacity to produce catechol upon alkali fusion. This type of melanin is frequently observed during the enzymatic browning process in fruits, exemplified by bananas. Melanin extracted from chestnut shells demonstrates utility as both an antioxidant and a natural coloring agent. Its biosynthesis entails the oxidation of indole-5,6-quinone, catalyzed by tyrosinase-type polyphenol oxidase, originating from tyrosine and catecholamines, which culminates in catechol melanin formation. Notwithstanding this, numerous plant species possess compounds that actively suppress melanin production.
Interpretation as a Single Monomer
Contemporary understanding acknowledges that melanins lack a singular, defined structure or stoichiometric composition. Despite this, various chemical databases, including PubChem, list specific structural and empirical formulae; a common example is 3,8-Dimethyl-2,7-dihydrobenzo[1,2,3-cd:4,5,6-c′d′]diindole-4,5,9,10-tetrone, with the empirical formula C18H§1112§N§1314§O§1516§. This representation can be conceptualized as a hypothetical monomer that aligns with the measured elemental composition and certain characteristics of melanin, though its natural occurrence is improbable. Solano posits that this potentially misleading convention originated from a 1948 report detailing an empirical formula, yet offers no further historical context.
Biosynthetic Pathways
The initial stage in the biosynthetic routes for both eumelanins and pheomelanins is mediated by the enzyme tyrosinase.
- Tyrosine → DOPA → dopaquinone
Dopaquinone is capable of reacting with cysteine via two distinct pathways, leading to the formation of benzothiazines and subsequently pheomelanins.
- dopaquinone + cysteine → 5-S-cysteinyldopa → benzothiazine intermediate → pheomelanin
- dopaquinone + cysteine → 2-S-cysteinyldopa → benzothiazine intermediate → pheomelanin
Furthermore, dopaquinone can undergo conversion to leucodopachrome, subsequently proceeding through two additional pathways to yield eumelanins.
- dopaquinone → leucodopachrome → dopachrome → 5,6-dihydroxyindole-2-carboxylic acid → quinone → eumelanin
- dopaquinone → leucodopachrome → dopachrome → 5,6-dihydroxyindole → quinone → eumelanin
Comprehensive metabolic pathways are accessible within the KEGG database.
Microscopic Appearance
Melanin presents microscopically as a brown, non-refractile, finely granular substance, with individual granules typically measuring less than 800 nanometers in diameter. This characteristic morphology distinguishes melanin from common blood breakdown pigments, which are generally larger, more irregular, refractile, and exhibit a color spectrum from green to yellow or reddish-brown. Within lesions characterized by substantial pigmentation, concentrated melanin aggregates may impede the clarity of histological examination. A diluted solution of potassium permanganate serves as an efficacious bleaching agent for melanin.
Genetic Disorders and Disease States
Oculocutaneous albinism (OCA) encompasses approximately nine distinct types, predominantly manifesting as an autosomal recessive disorder. The prevalence of specific OCA forms varies significantly across different ethnic populations. For instance, oculocutaneous albinism type 2 (OCA2), the most prevalent form, exhibits a notably higher frequency among individuals of Black African descent and White European ancestry. Individuals with OCA2 typically present with fair skin, though generally less pallid than those affected by OCA1. These individuals often exhibit hair colors ranging from pale blonde to golden, strawberry blonde, or even brown, most frequently accompanied by blue eyes. A substantial majority, 98.7–100%, of modern Europeans are carriers of the derived SLC24A5 allele, which is a recognized genetic determinant of nonsyndromic oculocutaneous albinism. This condition is an autosomal recessive disorder, characterized by a congenital reduction or complete absence of melanin pigment in the skin, hair, and eyes. The estimated frequency of OCA2 among African Americans is 1 in 10,000, a figure that contrasts sharply with its frequency of 1 in 36,000 among European Americans. In certain African nations, the disorder's frequency is even more elevated, ranging from 1 in 2,000 to 1 in 5,000. Another variant of albinism, termed "yellow oculocutaneous albinism," demonstrates a higher prevalence within the Amish community, whose ancestry is predominantly Swiss and German. Individuals affected by this IB variant typically present with white hair and skin at birth, yet subsequently develop normal skin pigmentation during infancy.
Ocular albinism impacts not only ocular pigmentation but also significantly impairs visual acuity. Individuals with albinism generally exhibit poor visual performance, with acuity measurements typically falling within the 20/60 to 20/400 range. Furthermore, two specific forms of albinism, which are particularly prevalent among individuals of Puerto Rican origin with an approximate incidence of 1 in 2,700, are linked to mortality rates exceeding those attributed to melanoma-related deaths.
The association between albinism and deafness is widely recognized, albeit incompletely elucidated. In his seminal 1859 treatise, On the Origin of Species, Charles Darwin noted the observation that "cats which are entirely white and have blue eyes are generally deaf". In humans, the co-occurrence of hypopigmentation and deafness is characteristic of the rare Waardenburg's syndrome, which is predominantly observed within the Hopi population of North America. The incidence of albinism among Hopi individuals has been estimated at approximately 1 in 200. Analogous patterns of albinism and deafness have been documented in other mammalian species, including canines and rodents. Nevertheless, the absence of melanin per se does not appear to be the direct etiological factor for deafness associated with hypopigmentation, given that most individuals deficient in the enzymes necessary for melanin synthesis exhibit normal auditory function. Instead, cochlear impairment results from the absence of melanocytes within the stria vascularis of the inner ear, although the precise mechanisms underlying this phenomenon remain incompletely understood.
In Parkinson's disease, a neurodegenerative disorder affecting neuromotor functioning, a reduction in neuromelanin levels is observed within the substantia nigra and locus coeruleus, resulting from the selective degeneration of dopaminergic and noradrenergic pigmented neurons. Consequently, this leads to a diminished synthesis of dopamine and norepinephrine. Although no direct correlation between race and neuromelanin levels in the substantia nigra has been established, the notably lower incidence of Parkinson's disease among Black individuals compared to White individuals has "prompt[ed] some to suggest that cutaneous melanin might somehow serve to protect the neuromelanin in substantia nigra from external toxins."
Beyond melanin deficiency, the molecular weight of the melanin polymer can be reduced by several factors, including oxidative stress, light exposure, alterations in its association with melanosomal matrix proteins, shifts in pH, or changes in local concentrations of metal ions. A reduction in the molecular weight or the degree of polymerization of ocular melanin has been hypothesized to transform this normally antioxidant polymer into a pro-oxidant. In its pro-oxidant conformation, melanin has been implicated in the etiology and progression of macular degeneration and melanoma. Rasagiline, a significant monotherapy agent for Parkinson's disease, exhibits both melanin-binding properties and the capacity to reduce melanoma tumors.
Higher eumelanin levels can also present disadvantages, beyond an increased susceptibility to vitamin D deficiency. Furthermore, darker skin tones present a complicating factor in the laser removal of port-wine stains. While generally effective for individuals with lighter skin, laser treatments exhibit reduced efficacy in eradicating port-wine stains in patients of Asian or African descent. Elevated melanin concentrations in individuals with darker complexions tend to diffuse and absorb laser radiation, thereby impeding the absorption of light by the intended target tissue. This phenomenon similarly complicates laser interventions for various other dermatological conditions in individuals possessing darker skin.
Freckles and moles result from localized concentrations of melanin in the skin. These formations are strongly correlated with lighter skin types.
Nicotine exhibits an affinity for melanin-containing tissues, attributed either to its role as a precursor in melanin synthesis or its irreversible binding to melanin. This characteristic is hypothesized to contribute to the elevated nicotine dependence and diminished smoking cessation rates observed among individuals with darker pigmentation.
Human Adaptations
Physiology
Melanocytes introduce melanin granules into specialized cellular vesicles known as melanosomes. Subsequently, these melanosomes are transferred into the keratinocyte cells within the human epidermis. Within each recipient cell, melanosomes aggregate above the cell nucleus, thereby shielding the nuclear DNA from mutations induced by the ionizing ultraviolet radiation emitted by the sun. Populations with ancestral origins in equatorial regions typically exhibit higher concentrations of eumelanin in their skin. This pigmentation confers a brown or black hue and provides protection against intense solar exposure, which more commonly leads to melanomas in individuals with lighter skin.
However, not all effects of pigmentation are inherently advantageous. In hot climates, pigmentation elevates the thermal load, with individuals possessing dark skin absorbing approximately 30% more solar heat compared to those with very light skin; however, this effect may be mitigated by increased perspiration. Conversely, in colder environments, dark skin results in greater heat loss through radiation. Furthermore, pigmentation impedes vitamin D synthesis. Given that pigmentation does not appear to be exclusively beneficial for survival in tropical regions, alternative hypotheses regarding its biological significance have been proposed, such as its potential as a secondary phenomenon resulting from adaptation to parasites and tropical diseases.
Evolutionary Origins
Early human populations developed dark skin pigmentation as an adaptive response to the loss of body hair, which subsequently amplified the impact of ultraviolet (UV) radiation. Prior to the evolution of hairlessness, ancestral humans likely possessed lighter skin beneath their fur, akin to that observed in other primate species. Anatomically modern humans originated in Africa approximately 200,000 to 100,000 years ago, subsequently dispersing across the globe through migrations occurring between 80,000 and 50,000 years ago, with evidence of interbreeding with archaic human species (e.g., Neanderthals, Denisovans, and potentially others) in certain regions. The earliest modern humans exhibited darker skin, comparable to that of contemporary indigenous African populations. Subsequent to migrations into Asia and Europe, the selective pressure favoring darker, UV-protective skin diminished. This reduction in selective pressure led to the diverse spectrum of human skin coloration observed today. Among the two prevalent gene variants linked to lighter human skin, Mc1r does not exhibit evidence of positive selection, whereas SLC24A5 has demonstrably undergone positive selection.
Effects
Similar to populations that migrated northward, individuals with lighter skin who relocate towards the equator undergo acclimatization to the significantly more intense solar radiation. Natural selection favors reduced melanin production in environments characterized by weak ultraviolet radiation. The skin of most individuals darkens upon exposure to UV light, thereby providing enhanced protection when required. This process represents the physiological function of sun tanning. Individuals with darker skin, who synthesize higher quantities of skin-protective eumelanin, possess superior defense against sunburn and the onset of melanoma, a potentially lethal form of skin cancer. They also exhibit increased resilience to other health issues associated with intense solar radiation exposure, including the photodegradation of essential vitamins such as riboflavins, carotenoids, tocopherol, and folate.
Melanin within the iris and choroid of the eye offers protection against ultraviolet and high-frequency visible light. Individuals with blue, green, or grey eyes exhibit a heightened susceptibility to ocular issues associated with sun exposure. Concurrently, the ocular lens undergoes age-related yellowing, which confers additional protective benefits. Nevertheless, this age-related stiffening of the lens also results in a significant reduction in its accommodative capacity—the ability to alter its shape for focusing on objects at varying distances—a decline likely attributable to protein crosslinking induced by UV radiation.
Contemporary investigations indicate that melanin may possess protective functions beyond its established role in photoprotection. Melanin demonstrates an effective capacity to chelate metal ions via its carboxylate and phenolic hydroxyl groups, frequently surpassing the efficiency of potent chelating agents such as ethylenediaminetetraacetate (EDTA). Consequently, melanin could function to sequester potentially toxic metal ions, thereby safeguarding cellular integrity. This proposition is substantiated by observations in Parkinson's disease, where the depletion of neuromelanin correlates with elevated iron concentrations within the brain.
Physical Properties and Technological Applications
Empirical data supports the presence of a highly cross-linked heteropolymer covalently bonded to matrix scaffolding melanoproteins. A hypothesis posits that melanin's antioxidant capacity is directly correlated with its degree of polymerization or molecular weight. Inadequate conditions for the efficient polymerization of melanin monomers can result in the formation of lower-molecular-weight, pro-oxidant melanin, which has been implicated in the etiology and advancement of macular degeneration and melanoma. Furthermore, signaling pathways that enhance melanization within the retinal pigment epithelium (RPE) may also contribute to the reduction of rod outer segment phagocytosis by the RPE. This observation has been partially linked to the phenomenon of foveal sparing in macular degeneration.
Role in Melanoma Metastasis
Heavily pigmented melanoma cells exhibit a Young's modulus of approximately 4.93 kPa, significantly higher than the 0.98 kPa observed in non-pigmented cells. The elasticity of melanoma cells is a critical factor influencing metastasis and tumor growth; non-pigmented tumors were found to be larger and disseminate with greater facility than their pigmented counterparts. Given that both pigmented and non-pigmented cells coexist within melanoma tumors, this heterogeneity allows for the simultaneous presence of drug-resistant and metastatic phenotypes.
References
References
"Absorption spectrum of melanin." Department of Computer Science and Technology.
- "Absorption spectrum of melanin". Department of Computer Science and Technology."Tyrosine metabolism—Reference pathway." Kyoto Encyclopedia of Genes and Genomes. Retrieved 13 June 2024."Melanogenesis." Kyoto Encyclopedia of Genes and Genomes. Retrieved 13 June 2024.Source: TORIma Academy Archive