Melanin, a unique biological absorber

Wolbarsht, Myron L.; Walsh, A.; George, Graham N.

doi:10.1364/ao.20.002184

Cited by 136 publications

(81 citation statements)

References 5 publications

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“…Eumelanin, which we consider here, is found in much higher levels in black hair and is believed to be a macromolecule of 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and 5,6-dihydroxyindole (DHI) [1,2]. Perhaps the most surprising property of melanins is that, whereas most biomolecules show only well defined absorption peaks around 280 nm (4.5 eV) and little absorption at lower energies [4], the melanins show broad band monotonic absorption in the range 1.5 to 5 eV [3]. Melanins are also efficient free radical scavengers and antioxidants [1].…”

Section: Introductionmentioning

confidence: 99%

5,6-Dihydroxyindole-2-carboxylic acid: a first principles density functional study

Powell

2005

Chemical Physics Letters

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We report first principles density functional calculations for 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and several reduced forms. DHICA and 5,6-dihydroxyindole (DHI) are believed to be the basic building blocks of the eumelanins. Our results show that carboxylation has a significant effect on the physical properties of the molecules. In particular, the relative stabilities and the HOMO-LUMO gaps (calculated with the ∆SCF method) of the various redox forms are strongly affected. We predict that, in contrast to DHI, the density of unpaired electrons, and hence the ESR signal, in DHICA is negligibly small.

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Section: Introductionmentioning

confidence: 99%

5,6-Dihydroxyindole-2-carboxylic acid: a first principles density functional study

Powell

2005

Chemical Physics Letters

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“…After a period of light stress, the amount of reduced ascorbic acid declined in the retina while DHA in the RPE and choroid increased. This pattern was found in guinea pig (30) and in the baboon (26). During the course of this investigation, we identified a possible mechanism for this loss of ascorbic acid, i.e.…”

Section: Photooxidation Of Ascorbic Acid In the Retinal Pigment Epithmentioning

confidence: 62%

“…Under normal conditions, we found that ascorbic acid exists in the reduced form in the neural retina and aqueous humor, but mostly in the oxidized form (dehydroascorbic acid, or DHA) in the RPE and choroid (19,30). After a period of light stress, the amount of reduced ascorbic acid declined in the retina while DHA in the RPE and choroid increased.…”

Section: Photooxidation Of Ascorbic Acid In the Retinal Pigment Epithmentioning

confidence: 96%

Investigation of Laser-Induced Retinal Damage: Wavelength and Pulsewidth Dependent Mechanisms

Glickman¹

1994

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“…At this point, both the color and the thickness of the lesions, as well as total melanin content of the epidermis and papillary dermis, collagen and hemoglobin content affects the infrared image signals that will be eventually produced. 16,17 In our study, we convert the infrared images to mathematical values, based on the surface area of the lesions and pixel intensity. In this way, different values of different wavelengths could be compared.…”

Section: Discussionmentioning

confidence: 99%

Infrared Imaging in Diagnosis of Dysplastic Nevi and Malignant Melanoma

Engın¹,

Keçici²,

Yılmaz³

et al. 2016

Turkiye Klinikleri J Med Sci

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A AB BS ST TR RA AC CT T O Ob bj je ec ct ti iv ve e: : The aim of this study is to handle the subjectivity of clinical observations in the diagnosis of dysplastic nevi and malignant melanoma, by using an alternative spectrophotometric method to simple dermatoscopic examination. M Ma at te er ri ia al l a an nd d M Me et th ho od ds s: : Images taken by CCD (Charge-coupled Device) camera with a 1280x1024 pixel resolution which is capable of taking snapshot images between 400-1000 nm wavelengths were converted to 2048x2560 size data and were subjected to digital image processing. For each lesion, three different images were captured at selected infrared wavelenghts of 770 nm, 810 nm, 850 nm and one image with visible light. Risk score analysis of the digital image processing was carried out on two main parameters. One is surface area risk score (SAR) and the other is pixel intensity risk score (PIR). The same lesions are also evaluated dermatoscopically and ABCD scores of each lesion were calculated. R Re es su ul lt ts s: : Thirty nine patients with 47 pigmented lesions were included in the study. When all the statistical data were put together, positive correlation with ABCD scores is stronger for the images at 770 nm than the ones with 810 nm. Also when we consider all parameters which have been studied separately, the most meaningful correlation with ABCD scores was shown by "total surface area risk score". C Co on nc cl lu u--s si io on n: : Wavelengths of 770 nm and 850 nm seem to be optimal in terms of correlating with ABCD scores of the lesions. Also we need to determine the optimum wavelength range for the accurate diagnosis of melanocytic lesions.K Ke ey y W Wo or rd ds s: : Melanoma; nevus Ö ÖZ ZE ET T A Am ma aç ç: : Bu çalışmanın amacı displastik nevus ve malign melanom tanısında ilk basamak olan rutin dermatoskopinin yerine alternatif spektrofotometrik yöntemler kullanılarak klinik gözlem-lerdeki subjektifliği (öznelliği) azaltmaktır. G Ge er re eç ç v ve e Y Yö ön nt te em ml le er r: : 400-1000 nm arasında görüntü kaydedebilen ve 1280x1024 piksel çözünürlükte çekim yapan CCD (Charge-coupled Device) kamera ile elde edilen görüntüler, 2048x2560 büyüklükte dataya çevrilmiş ve dijital görüntüleme işlemlerine tabi tutulmuştur. Her lezyon için 770 nm, 810 nm ve 850 nm dalga boylarında ve görünür ışıkta olmak üzere dört farklı resim çekilmiştir. Dijital görüntüleme işlemleri sırasında risk skor analizleri iki parametreye göre yapılmıştır; yüzey alanı risk skoru (SAR) ve piksel yoğunluk risk skoru (PIR). Her lezyon için dermatoskopik inceleme de yapılmış ve ABCD skorları hesaplanmıştır. B Bu ul lg gu ul la ar r: : Çalışmaya toplamda 47 pigmente lezyona sahip 39 hasta dahil edilmiştir. İstatistik analizler sonucunda, kızılötesi görüntülerle ABCD skorları arasındaki ilişki 770 nm'de 810 nm'ye göre daha kuvvetli olarak saptanmıştır. Yine çalışılan tüm parametrelere bakıldığında, ABCD skoruyla "total yüzey alan risk skoru" arasındaki ilişki en yüksek bulunmuştur. S So on nu uç ç: : Lezyonların ABCD skorları 7...

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Melanin, a unique biological absorber

Cited by 136 publications

References 5 publications

5,6-Dihydroxyindole-2-carboxylic acid: a first principles density functional study

5,6-Dihydroxyindole-2-carboxylic acid: a first principles density functional study

Investigation of Laser-Induced Retinal Damage: Wavelength and Pulsewidth Dependent Mechanisms

Infrared Imaging in Diagnosis of Dysplastic Nevi and Malignant Melanoma

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