Research Topics
| John SimonSummaryAffiliation: Duke University Medical Center Country: USA Publications
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Publications
A2E: a component of ocular lipofuscinLaura E Lamb
Department of Chemistry, Duke University, Durham, NC 27708-0346, USA
Photochem Photobiol 79:127-36. 2004..This article presents the current understanding of the photochemistry of A2E and its involvement as a phototoxic agent in RPE cells...
The red and the blackJohn D Simon
Department of Chemistry, Duke University, Durham, North Carolina 27705, USA
Acc Chem Res 43:1452-60. 2010..These results suggest that the epidemiological data may simply result from an increased exposure of the underlying tissues to UV light...- Spectroscopy and photoreactivity of trichochromes: molecular components of pheomelaninsJohn D Simon
Department of Chemistry, Duke University, Durham, NC 27708 0346, USA
Photochem Photobiol 82:318-23. 2006..Both trichochromes are efficient quenchers of 1O2, exhibiting a bimolecular rate constant comparable with vitamin C. These results suggest that trichochromes could serve a protective role in pheomelanin pigments... - Introduction to the Symposium-in-Print on MelaninsJohn D Simon
Department of Chemistry, Duke University, Durham, NC, USA
Photochem Photobiol 84:537-8. 2008 - Current challenges in understanding melanogenesis: bridging chemistry, biological control, morphology, and functionJohn D Simon
Department of Chemistry, Duke University, Durham, NC, USA
Pigment Cell Melanoma Res 22:563-79. 2009.... - Insights into the thermodynamics of copper association with amyloid-β, α-synuclein and prion proteinsLian Hong
Department of Chemistry, Duke University, Durham, NC 27708, USA
Metallomics 3:262-6. 2011..This current review reconciles the disparate models presented in the literature... 
Quantification of the binding properties of Cu2+ to the amyloid beta peptide: coordination spheres for human and rat peptides and implication on Cu2+-induced aggregationLian Hong
Department of Chemistry, Duke University, Durham, North Carolina 27708, USA
J Phys Chem B 114:11261-71. 2010..The differences in the coordination geometries for Cu(2+) by the human and rat Abeta are proposed to contribute to the variation in the ability of Cu(2+) to induce aggregation of Abeta peptides...- Comparisons of the structural and chemical properties of melanosomes isolated from retinal pigment epithelium, iris and choroid of newborn and mature bovine eyesYan Liu
Department of Chemistry, Duke University, Durham, NC 27708-0346, USA
Photochem Photobiol 81:510-6. 2005.... - Human iridal stroma melanosomes of varying pheomelanin contents possess a common eumelanic outer surfaceDana N Peles
Department of Chemistry, Duke University, Durham, North Carolina 27708, USA
J Phys Chem B 113:11346-51. 2009..This provides new insights into the potential contribution of iridal stroma melanosomes both to inducing oxidative stress and to accounting for the observed iris-color-dependent epidemiology of uveal melanoma... - Insight into the binding of divalent cations to Sepia eumelanin from IR absorption spectroscopyLian Hong
Department of Chemistry, Duke University, Durham, NC, USA
Photochem Photobiol 82:1265-9. 2006.... - Quantification of the binding constant of copper(II) to the amyloid-beta peptideLanying Q Hatcher
Department of Chemistry, Duke University, Durham, NC 27708, USA
J Phys Chem B 112:8160-4. 2008..Several previously reported values can be reconciled with the current measurement by careful consideration of thermodynamics associated with the presence of competing ligands used to solubilize copper... - Ultra-low temperature oxidation of 5,6-dihydroxyindole: a novel approach to study synthetic melanogenesisLanying Q Hatcher
Department of Chemistry, Duke University, Durham, NC, USA
Photochem Photobiol 84:608-12. 2008..MS analysis of the reaction mixture reveals the DHI dimer as well as other extensively oxidized DHI units... - Interaction of ochratoxin A with human serum albumin. Binding sites localized by competitive interactions with the native protein and its recombinant fragmentsJennifer L Perry
Department of Chemistry, Duke University, Durham, NC 27708, USA
Chem Biol Interact 141:275-93. 2002..9 x 10(5) M(-1), was smaller than the largest constant for HSA by a factor of approximately 7. The binding constant for OTA with D3, 1.1 x 10(5) M(-1), was very close to that of the secondary binding site for HSA... - Quantification of Ca(2+) binding to melanin supports the hypothesis that melanosomes serve a functional role in regulating calcium homeostasisWilliam D Bush
Department of Chemistry, Duke University, Durham, NC, USA
Pigment Cell Res 20:134-9. 2007..Using this binding constant and the data from a fluorescent Ca(2+) displacement assay, the pK(a) of the carboxyl group coordinated to Ca(2+) is determined to be 3.1 +/- 0.1... - The differing embryonic origins of retinal and uveal (iris/ciliary body and choroid) melanosomes are mirrored by their phospholipid compositionWeslyn C Ward
Department of Chemistry, Duke University, Durham, NC, USA
Pigment Cell Res 20:61-9. 2007..While the structural and functional roles of melanosomal lipids largely remain to be determined, these different lipid compositions reported herein offer new insights into the roles of melanosomes in the different ocular tissues... - Age-dependent photoionization thresholds of melanosomes and lipofuscin isolated from human retinal pigment epithelium cellsLian Hong
Department of Chemistry, Duke University, Durham, NC, USA
Photochem Photobiol 82:1475-81. 2006..These data suggest that thin deposits of lipofuscin on the surface of retinal pigment epithelium melanosomes are common in the aged eye and that this renders the melanosomes more pro-oxidant... - Insights into melanosomes and melanin from some interesting spatial and temporal propertiesJohn D Simon
Department of Chemistry, Duke University, Durham, NC, USA
J Phys Chem B 112:13201-17. 2008..The article concludes with a brief discussion of important unanswered research questions in this field... - Photoionization thresholds of melanins obtained from free electron laser-photoelectron emission microscopy, femtosecond transient absorption spectroscopy and electron paramagnetic resonance measurements of oxygen photoconsumptionTong Ye
Department of Chemistry, Duke University, Durham, NC, USA
Photochem Photobiol 82:733-7. 2006..The lower ionization potential observed for pheomelanin could be an important part of the explanation for the greater incidence rate of UV-induced skin cancers in red-haired individuals... - Current understanding of the binding sites, capacity, affinity, and biological significance of metals in melaninLian Hong
Department of Chemistry, Duke University, Durham, North Carolina 27708, USA
J Phys Chem B 111:7938-47. 2007..This article examines the current state of understanding of this field... - Physical and chemical characterization of iris and choroid melanosomes isolated from newborn and mature cowsLian Hong
Department of Chemistry, Duke University, Durham, NC 27708-0346, USA
Photochem Photobiol 81:517-23. 2005..These tissue-related and age-related chemical differences between samples affected the optic density and metal binding properties of melanosomes, which are believed to be closely associated with the biological functions of melanins... - Aggregation of eumelanin mitigates photogeneration of reactive oxygen speciesJ Brian Nofsinger
Department of Chemistry, Duke University Medical Center, Durham, NC 27708-0347, USA
Free Radic Biol Med 32:720-30. 2002..The effect of aggregation on the photogeneration of ROS serves to provide a foundation for the understanding of the dichotomy of photoprotective and phototoxic properties of melanin... - Metal-ion interactions and the structural organization of Sepia eumelaninYan Liu
Department of Chemistry, Duke University, Durham, NC, USA
Pigment Cell Res 18:42-8. 2005.... - Establishing structure-function relationships for eumelaninJ Brian Nofsinger
Department of Chemistry, Duke University, Durham, North Carolina 27708, USA
Biopolymers 67:302-5. 2002.... - Binding of Cu(II) to human alpha-synucleins: comparison of wild type and the point mutations associated with the familial Parkinson's diseaseLian Hong
Department of Chemistry, Duke University, Durham, NC 27708, USA
J Phys Chem B 113:9551-61. 2009..g., small oligomeric species, such as dimers and trimers) relative to WT and A53T. Thus, we propose that the high affinity site is attributed to the binding of Cu(II) to those small oligomeric species... - Isolation and biophysical studies of natural eumelanins: applications of imaging technologies and ultrafast spectroscopyYan Liu
Department of Chemistry, Duke University, Durham, NC 27708, USA
Pigment Cell Res 16:606-18. 2003..Ultrafast laser spectroscopy studies of melanins are providing insights into the time scales and mechanisms by which melanin dissipates absorbed light energy... - The ultraviolet absorption coefficient of melanosomes decreases with increasing pheomelanin contentDana N Peles
Department of Chemistry, Duke University, Durham, North Carolina 27708, USA
J Phys Chem B 114:9677-83. 2010..2). On the basis of the reported optical properties of synthetic models, this result suggests that the absorption of pheomelanin is less than eumelanin at wavelengths of biological relevance ( approximately 315-400 nm)... - Ion-exchange and adsorption of Fe(III) by Sepia melaninYan Liu
Department of Chemistry, Duke University, Durham, NC, USA
Pigment Cell Res 17:262-9. 2004..These observations imply the existence of channels within the melanin granules that can serve to transport metal ions... - Binding of metal ions to melanin and their effects on the aerobic reactivityLian Hong
Department of Chemistry, Duke University, Durham, NC 27708-0346, USA
Photochem Photobiol 80:477-81. 2004..Cu(II)- and Fe(III)-enriched melanins induce the most damage. Hydroxyl radical, *OH, is proposed to be one of the reactive oxygen species responsible... - Surface elastic properties of human retinal pigment epithelium melanosomesSenli Guo
Department of Chemistry, Duke University, Durham, NC, USA
Photochem Photobiol 84:671-8. 2008..This suggestion indicates that part of the difference in photochemical properties between the old and young melanosomes originates from surface lipofuscin... - The effect of preparation procedures on the morphology of melanin from the ink sac of Sepia officinalisYan Liu
Department of Chemistry, Duke University, Durham, NC 27708-0346, USA
Pigment Cell Res 16:72-80. 2003..The implications of these results on quantifying photochemical properties and kinetic reaction rate constants of melanin are discussed... - Ultrafast absorption and photothermal studies of decarboxytrichochrome C in solutionTong Ye
Department of Chemistry, Duke University, Durham, NC 27708, USA
Photochem Photobiol Sci 2:821-3. 2003..The combination of ultrafast absorption and photoacoustic data suggest photoexcitation produces a long-lived intermediate and the energy of this species is at least 133 kJ mol(-1) above the ground state of the dTC molecule... - The surface oxidation potential of melanosomes measured by free electron laser-photoelectron emission microscopyJacob Garguilo
Department of Physics, North Carolina State University, Raleigh, NC, USA
Photochem Photobiol 83:692-7. 2007..This result is discussed in relation to the age-dependent accumulation of iron in human melanosomes in both the eye and brain... - Neuromelanins isolated from different regions of the human brain exhibit a common surface photoionization thresholdWilliam D Bush
Department of Chemistry, Duke University, Durham, NC, USA
Photochem Photobiol 85:387-90. 2009..5 +/- 0.2 eV (-0.1 +/- 0.2 V vs NHE). All neuromelanins exhibit a common low surface oxidation potential, reflecting their eumelanic component and their inability to trigger redox processes with neurotoxic effect... - Neuromelanins in various regions of human brain are associated with native and oxidized isoprenoid lipidsWeslyn C Ward
Department of Chemistry, Duke University, Durham, NC 27708, USA
Arch Biochem Biophys 484:94-9. 2009..Oxidized and reduced dolichol-related species were identified and determined to be region-dependent... - Comparison of the structural and physical properties of human hair eumelanin following enzymatic or acid/base extractionYan Liu
Department of Chemistry, Duke University, Durham, NC 27708, USA
Pigment Cell Res 16:355-65. 2003..The enzymatically extracted hair melanin, on the contrary, retains the morphology of intact melanosomes and is an excellent source of human melanin... - Direct measurement of the ultraviolet absorption coefficient of single retinal melanosomesDana N Peles
Department of Chemistry, Duke University, Durham, NC, USA
Photochem Photobiol 86:279-81. 2010.... - Quantification of naturally occurring pyrrole acids in melanosomesWeslyn C Ward
Department of Chemistry, Duke University, Durham, NC, USA
Photochem Photobiol 84:700-5. 2008..This work also establishes that PTeCA is a naturally occurring pyrrole acid in melanosomes... - Probing skin pigmentation changes with transient absorption imaging of eumelanin and pheomelaninDan Fu
Princeton University, Department of Chemistry, Princeton, New Jersey 08544, USA
J Biomed Opt 13:054036. 2008..This difference should enable us to map out their respective distribution in tissue samples with subcellular resolution. This technique could provide valuable information in diagnosing the malignant transformation of melanocytes... - Spectroscopic and morphological studies of human retinal lipofuscin granulesNicole M Haralampus-Grynaviski
Department of Chemistry, Duke University, Durham, NC 27708, USA
Proc Natl Acad Sci U S A 100:3179-84. 2003.... - Ultrafast energy transfer from bound tetra(4-N,N,N,N-trimethylanilinium)porphyrin to synthetic dopa and cysteinyldopa melaninsTong Ye
Department of Chemistry, Duke University, Durham, NC 27708-0346, USA
Photochem Photobiol 77:1-4. 2003..These results are consistent with previous photoacoustic studies, which revealed that the TAP-melanin complex behaves like a supermolecular system liberating heat as a whole... - The action spectrum for generation of the primary intermediate revealed by ultrafast absorption spectroscopy studies of pheomelaninTong Ye
Department of Chemistry, Duke University, Durham, NC 27708-0346, USA
Photochem Photobiol 77:41-5. 2003.... - Characterization of the Fe(III)-binding site in Sepia eumelanin by resonance Raman confocal microspectroscopyAlexander Samokhvalov
Department of Chemistry, Duke University, Durham, NC 27708-0346, USA
Photochem Photobiol 80:84-8. 2004..The 580 and 1470 cm(-1) bands are assigned to Fe-OR stretching and ring deformation modes, respectively. These data further substantiate that the Fe(III)-melanin-binding site in melanin is composed of CAT-like structural units... - Oxidation potentials of human eumelanosomes and pheomelanosomesAlexander Samokhvalov
Department of Chemistry, Duke University, Durham, NC 27708, USA
Photochem Photobiol 81:145-8. 2005..The FEL-PEEM experiment offers to be an important new approach for quantifying the effects of age, oxidation and metal accumulation on the oxidation potentials of intact melanosomes... - Comparison of structural and chemical properties of black and red human hair melanosomesYan Liu
Department of Chemistry, Duke University, Durham, NC 27708, USA
Photochem Photobiol 81:135-44. 2005..Excellent agreement is observed between these spectral results and the chemical degradation data... - Molecular aspects of the transport and toxicity of ochratoxin aJian Dai
Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27106, USA
Acc Chem Res 37:874-81. 2004..These studies are beginning to provide a detailed chemical model for the trans-port, accumulation, and genotoxic and carcinogenic effects of OTA... - Binding of warfarin influences the acid-base equilibrium of H242 in sudlow site I of human serum albuminJennifer L Perry
Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
Photochem Photobiol 82:1365-9. 2006..30+/-0.02 protons from the solvent. This measurement suggests that the binding of W- is stabilized by an ion-pair interaction between protonated H242 and the phenoxide group of W-... - The surface oxidation potential of human neuromelanin reveals a spherical architecture with a pheomelanin core and a eumelanin surfaceWilliam D Bush
Department of Chemistry, Duke University, Durham, NC 27708, USA
Proc Natl Acad Sci U S A 103:14785-9. 2006..Such a kinetic model would predict a structural motif with pheomelanin at the core and eumelanin at the surface, which is consistent with the measured surface oxidation potential of the approximately 30-nm constituents of NM granules... - Identification and quantification of dolichol and dolichoic acid in neuromelanin from substantia nigra of the human brainWeslyn C Ward
Department of Chemistry, Duke University, Durham, NC, USA
J Lipid Res 48:1457-62. 2007..The distribution of dol-CA chains lengths in NM also differed from that of dol, suggesting that the enzyme(s) responsible for the conversion of dol to dol-CA prefer a dolichol substrate containing 19 isoprene units... - Mechanistic studies on the photochemical deprotection of 3',5'-dimethoxybenzoin estersMichael C Pirrung
Department of Chemistry, University of California, Riverside, CA 92521 0403 USA
Photochem Photobiol 82:1258-64. 2006..In this multistep reaction, benzofuran formation by a final deprotonation is slower than alpha-ketocation generation... - Perspectives on the structure and function of melaninJohn D Simon
Pigment Cell Melanoma Res 21:346-7. 2008 - Role of ocular melanin in ophthalmic physiology and pathologyDan Ning Hu
Tissue Culture Center, Department of Pathology, The New York Eye and Ear Infirmary and New York Medical College, New York, NY, USA
Photochem Photobiol 84:639-44. 2008.... - Age-related changes in the photoreactivity of retinal lipofuscin granules: role of chloroform-insoluble componentsMałgorzata Rózanowska
Department of Biophysics, Faculty of Biotechnology, Krakow, Poland School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
Invest Ophthalmol Vis Sci 45:1052-60. 2004..As the composition, absorption, and fluorescence of lipofuscin undergo age-related changes, the purpose of this study was to determine whether photoreactivity of lipofuscin granules also changes with the donor age... - Different molecular constituents in pheomelanin are responsible for emission, transient absorption and oxygen photoconsumptionTong Ye
Department of Neurobiology, University of Alabama, Birmingham, AL, USA
Photochem Photobiol 84:437-43. 2008..This raises concern about comparing the results from different photochemical methodologies for melanin, which is a specific case of comparing data on systems where molecular constituents are not well defined... - Effects of photodegradation on the physical and antioxidant properties of melanosomes isolated from retinal pigment epitheliumMariusz Zareba
Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, USA
Photochem Photobiol 82:1024-9. 2006.... - Melanin structure and the potential functions of uveal melanosomesLian Hong
Pigment Cell Res 19:465-6. 2006 - Neuronal pigmented autophagic vacuoles: lipofuscin, neuromelanin, and ceroid as macroautophagic responses during aging and diseaseDavid Sulzer
Department of Neurology, Columbia University, New York, NY 10036, USA
J Neurochem 106:24-36. 2008....
Research Grants
- PHOTODYNAMICS OF ULTRAVIOLET EPIDERMAL CHROMOPHORESJohn Simon; Fiscal Year: 2002....