Spectroscopic Study and Simulation from Recent Structural Models for Eumelanin:  I. Monomer, Dimers

Stark, K.; Gallas, James M.; Zając, G.; Eisner, M.; Golab, Joseph T.

doi:10.1021/jp0266594

Cited by 78 publications

(107 citation statements)

References 35 publications

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“…Our results are in good agreement with those calculated by Bolivar-Marinez et al [20] and Stark et al [5]. All three molecules are planar to within numerical accuracy (c.f., [5,22]). …”

Section: Resultssupporting

confidence: 92%

A first-principles density-functional calculation of the electronic and vibrational structure of the key melanin monomers

Powell

Baruah

Bernstein

et al. 2004

The Journal of Chemical Physics

156

127

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We report first principles density functional calculations for hydroquinone (HQ), indolequinone (IQ) and semiquinone (SQ). These molecules are believed to be the basic building blocks of the eumelanins, a class of bio-macromolecules with important biological functions (including photoprotection) and with potential for certain bioengineering applications. We have used the ∆SCF (difference of self consistent fields) method to study the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), ∆HL. We show that ∆HL is similar in IQ and SQ but approximately twice as large in HQ. This may have important implications for our understanding of the observed broad band optical absorption of the eumelanins. The possibility of using this difference in ∆HL to molecularly engineer the electronic properties of eumelanins is discussed. We calculate the infrared and Raman spectra of the three redox forms from first principles. Each of the molecules have significantly different infrared and Raman signatures, and so these spectra could be used in situ to non-destructively identify the monomeric content of macromolecules. It is hoped that this may be a helpful analytical tool in determining the structure of eumelanin macromolecules and hence in helping to determine the structure-property-function relationships that control the behaviour of the eumelanins.

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“…Our results are in good agreement with those calculated by Bolivar-Marinez et al [20] and Stark et al [5]. All three molecules are planar to within numerical accuracy (c.f., [5,22]). …”

Section: Resultssupporting

confidence: 92%

A first-principles density-functional calculation of the electronic and vibrational structure of the key melanin monomers

Powell

Baruah

Bernstein

et al. 2004

The Journal of Chemical Physics

156

127

View full text Add to dashboard Cite

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“…[29] However, it has been reported that the spectrum is affected by interactions among eumelanin protomolecules. [30] Recently, Buehler and co-workers, considering excitonic couplings between eumelanin oligomers (tetramers, pentamers, and octamers), found that the computational spectra with geometric (packing) disorder of a single species of DHI oligomers ( Fig. 3) agree with experiments, and that excitonic couplings among eumelanin protomolecules have a considerable role in the increase of the probability of absorption toward the higher energy end of the spectrum.…”

Section: Introductionmentioning

confidence: 68%

Natural melanin pigments and their interfaces with metal ions and oxides: emerging concepts and technologies

Mauro

Soliveri

et al. 2017

MRS Communications

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Melanin (from the Greek μέλας, mélas, black) is a biopigment ubiquitous in flora and fauna, featuring broadband optical absorption, hydration-dependent electrical response, ion-binding affinity as well as antioxidative and radical-scavenging properties. In the human body, photoprotection in the skin and ion flux regulation in the brain are some biofunctional roles played by melanin. Here we discuss the progress in melanin research that underpins emerging technologies in energy storage/conversion, ion separation/water treatment, sunscreens, and bioelectronics. The melanin research aims at developing approaches to explore natural materials, well beyond melanin, which might serve as a prototype benign material for sustainable technologies.

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“…Melanin absorbs strongly in the visible and UV. Spectra in the visible region should indicate relative melanin concentrations among samples (45,46). According to that premise, D40-P7, D43-P5, and D42-P5 had more concentrated melanin than D41-P6, D37-P8, and D39-P8.…”

Section: Cwepr Of Synthetic Melaninmentioning

confidence: 96%

Melanin photoprotection in the human retinal pigment epithelium and its correlation with light-induced cell apoptosis

Seagle

Rezai

Kobori

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

104

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Time-resolved electron paramagnetic resonance (TREPR) spectroscopy was used to study melanin free radicals in human retinal pigment epithelium (RPE) cells and tyrosine-derived synthetic melanin. TREPR signal traces from RPE cells reveal in vivo light-induced melanin free radical photochemistry in more detail than previously known. Electron spin polarization reflecting a non-Boltzmann population within the energy levels of the spin system is observed in RPE cells as the result of the triplet state photoproduction and subsequent disappearance of free radicals in the melanin polymer. In a set of RPE cells cultured from individual sources, differences in optical absorption, continuous wave EPR spectra, and TREPR signals were correlated with apoptosis assays performed by flow cytometry. Continuous wave EPR spectra of RPE cells and TREPR of acidified synthetic melanin suggest that increased melanin aggregation provides an increase in photoprotection in the RPE cells that are relatively less susceptible to blue light-induced apoptosis.continuous wave EPR ͉ electron spin polarization ͉ time-resolved EPR I n the eye, retinal pigment epithelium (RPE) is a monolayer of cuboidal cells between the photoreceptors and choriocapillaris of the eye and is specialized to uptake, phagocytize, and recycle the outer segment of photoreceptors and retinaldehyde, the chromophore of rhodopsin (1). RPE cell death plays a major role in the pathogenesis of age-related macular degeneration, the leading cause of blindness in the population Ͼ60 years of age in the developed world (2). Possible reasons given for the degeneration of RPE cells are their exposure to high oxidative stress and damaging irradiation (2-6).The pigment melanin, found in RPE cells, is a heterogeneous polymer consisting of various monomers believed to be oxidation products of dopa (dihydroxyphenylalinine) derived from tyrosine (7). Melanin contains intrinsic, indolesemiquinone-like doublet-state radicals (8, 9). Extrinsic indolesemiquinone-like radicals are reversibly photogenerated under visible or UV irradiation (9). RPE melanin serves a photoprotective role by absorbing radiation and scavenging free radicals and reactive oxygen species (ROS) (8-11). Evidence also exists for a phototoxic role for melanin in RPE cells, especially in aged cells, including measurable ROS photoproduction (8,(12)(13)(14)(15)(16)(17)(18). Electron paramagnetic resonance (EPR) spectroscopy enables a sensitive and nondestructive analysis and differentiation of natural melanin (9,19,20). The photophysical, redox, and aggregation properties of melanin as well as its ability to bind metals, proteins, and drugs have stimulated numerous studies in chemical, physical, and medical research (8, 9). The diversity and interrelations of its properties and the lack of chemical structures have hampered a clear understanding of the roles of melanin in RPE cells (8,9). Nanosecond time-resolved (TR) EPR studies have not been reported despite the relevance of TREPR to the study of melanin photochemistry (9). El...

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Spectroscopic Study and Simulation from Recent Structural Models for Eumelanin: I. Monomer, Dimers

Cited by 78 publications

References 35 publications

A first-principles density-functional calculation of the electronic and vibrational structure of the key melanin monomers

A first-principles density-functional calculation of the electronic and vibrational structure of the key melanin monomers

Natural melanin pigments and their interfaces with metal ions and oxides: emerging concepts and technologies

Melanin photoprotection in the human retinal pigment epithelium and its correlation with light-induced cell apoptosis

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