Towards structure-property-function relationships for eumelanin.

We discuss recent progress towards the establishment of important structure-property-function relationships in eumelanins-key functional bio-macromolecular systems responsible for photo-protection and immune response in humans, and implicated in the development of melanoma skin cancer. We focus on the link between eumelanin's secondary structure and optical properties such as broad band UV-visible absorption and strong non-radiative relaxation; both key features of the photo-protective function. We emphasise the insights gained through a holistic approach combining optical spectroscopy with first principles quantum chemical calculations, and advance the hypothesis that the robust functionality characteristic of eumelanin is related to extreme chemical and structural disorder at the secondary level. This inherent disorder is a low cost natural resource, and it is interesting to speculate as to whether it may play a role in other functional bio-macromolecular systems.

[1]  J. Flammer,et al.  Absolute Rate Constants for the Quenching of Reactive Excited States by Melanin and Related 5,6-Dihydroxyindole Metabolites: Implications for Their Antioxidant Activity , 2000, Photochemistry and photobiology.

[2]  B. Pullman,et al.  The band structure of melanins. , 1961, Biochimica et biophysica acta.

[3]  F. Galluzzi,et al.  Photoelectronic properties of synthetic melanins , 1996 .

[4]  H. Stubb,et al.  Electrical conductivity of synthetic DOPA-melanin polymer for different hydration states and temperatures. , 1995, Journal of biomaterials science. Polymer edition.

[5]  G. Zajac,et al.  Tunneling microscopy verification of an x‐ray scattering‐derived molecular model of tyrosine‐based melanin , 1994 .

[6]  J. Simon,et al.  Radiative Relaxation of Sepia Eumelanin is Affected by Aggregation¶ , 2001 .

[7]  J. Simon,et al.  Ultrastructural organization of eumelanin from Sepia officinalis measured by atomic force microscopy. , 2001, Biochemistry.

[8]  Gregor Jung,et al.  The photophysics of green fluorescent protein: influence of the key amino acids at positions 65, 203, and 222. , 2005, Biophysical journal.

[9]  A. Young,et al.  The Soluble Eumelanin Precursor 5,6‐Dihydroxyindole‐2‐carboxylic Acid Enhances Oxidative Damage in Human Keratinocyte DNA after UVA Irradiation ‡ , 1999, Photochemistry and photobiology.

[10]  J. Simon,et al.  Wavelength‐dependent Photoacoustic Calorimetry Study of Melanin , 1998, Photochemistry and photobiology.

[11]  J. Simon,et al.  Building Blocks of Eumelanin: Relative Stability and Excitation Energies of Tautomers of 5,6-Dihydroxyindole and 5,6-Indolequinone , 2003 .

[12]  Rinaldo Cubeddu,et al.  Age-related changes in the morphology, absorption and fluorescence of melanosomes and lipofuscin granules of the retinal pigment epithelium , 1990, Vision Research.

[13]  G. Prota,et al.  Melanins and melanogenesis , 1992 .

[14]  R. Alfano,et al.  Fluorescence spectroscopy of eumelanins , 1984 .

[15]  Joel Gilmore,et al.  A quantum yield map for synthetic eumelanin. , 2005, The Journal of chemical physics.

[16]  E. Land,et al.  Interaction of radicals from water radiolysis with melanin. , 1986, Biochimica et biophysica acta.

[17]  D. Galvão,et al.  Polymerization of 5,6‐indolequinone: A view into the band structure of melanins , 1988 .

[18]  L. E. Bolivar-Marinez,et al.  GEOMETRIC AND SPECTROSCOPIC STUDY OF SOME MOLECULES RELATED TO EUMELANINS.1. MONOMERS , 1999 .

[19]  T. McIntire,et al.  Effect of stacking and redox state on optical absorption spectra of melanins -- comparison of theoretical and experimental results. , 2005, The journal of physical chemistry. B.

[20]  J. Gallas,et al.  FLUORESCENCE OF MELANIN‐DEPENDENCE UPON EXCITATION WAVELENGTH AND CONCENTRATION , 1987 .

[21]  P. Fromme,et al.  Chlorophyll Excitations in Photosystem I of Synechococcus elongatus , 2002 .

[22]  J. R. Tata.  Biochimica et biophysica acta, vol. 1000 , 1990 .

[23]  J McGinness,et al.  Amorphous Semiconductor Switching in Melanins , 1974, Science.

[24]  J Bernsdorf,et al.  Engineered metal binding sites on green fluorescence protein. , 2000, Biochemical and biophysical research communications.

[25]  Paul Meredith,et al.  Radiative Relaxation Quantum Yields for Synthetic Eumelanin¶ , 2003, Photochemistry and photobiology.

[26]  C. Burkhart,et al.  The mole theory: primary function of melanocytes and melanin may be antimicrobial defense and immunomodulation (not solar protection) , 2005, International journal of dermatology.

[27]  Alberto Albertini,et al.  The neuromelanin of human substantia nigra: physiological and pathogenic aspects. , 2004, Pigment cell research.

[28]  P. Crippa,et al.  A band model for melanin deducted from optical absorption and photoconductivity experiments. , 1978, Biochimica et biophysica acta.

[29]  B. Powell.  5,6-Dihydroxyindole-2-carboxylic acid: a first principles density functional study , 2004, q-bio/0408018.

[30]  J. Simon,et al.  Ultrafast Nonradiative Relaxation Dynamics of Eumelanin , 2001 .

[31]  Christa Critchley,et al.  Artificial photosynthesis : from basic biology to industrial application , 2005 .

[32]  J. Lakowicz.  Principles of fluorescence spectroscopy , 1983 .

[33]  G. Zajac,et al.  Spectroscopic Study and Simulation from Recent Structural Models for Eumelanin: II. Oligomers , 2003 .

[34]  Klaus Hoffmann,et al.  Fluorescence Studies of Melanin by Stepwise Two-Photon Femtosecond Laser Excitation , 2000, Journal of Fluorescence.

[35]  G. Zajac,et al.  Spectroscopic Study and Simulation from Recent Structural Models for Eumelanin: I. Monomer, Dimers , 2003 .

[36]  H. C. Longuet-Higgins.  On the origin of the free radical property of melanins. , 1960, Archives of biochemistry and biophysics.

[37]  M L Wolbarsht,et al.  Melanin, a unique biological absorber. , 1981, Applied optics.

[38]  B. Powell,et al.  A first-principles density-functional calculation of the electronic and vibrational structure of the key melanin monomers. , 2004, The Journal of chemical physics.

[39]  Carlos Frederico de Oliveira Graeff,et al.  Synthetic melanin thin films: Structural and electrical properties , 2004 .

[40]  B. Powell,et al.  DHICA Paper Revised Final Version Publish Ahead of Print , 2022 .