{"id":1075,"date":"2018-02-19T14:53:00","date_gmt":"2018-02-19T19:53:00","guid":{"rendered":"https:\/\/research.cbc.osu.edu\/kohler.40\/?page_id=1075"},"modified":"2023-07-10T14:10:31","modified_gmt":"2023-07-10T18:10:31","slug":"melanin-photophysics","status":"publish","type":"page","link":"https:\/\/research.cbc.osu.edu\/kohler.40\/research\/melanin-photophysics\/","title":{"rendered":"Melanin Photophysics and Photochemistry"},"content":{"rendered":"\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-28f84493 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:33.33%\">\n<div class=\"wp-block-jetpack-slideshow aligncenter\" data-autoplay=\"true\" data-delay=\"5\" data-effect=\"fade\"><div class=\"wp-block-jetpack-slideshow_container swiper-container\"><ul class=\"wp-block-jetpack-slideshow_swiper-wrapper swiper-wrapper\"><li class=\"wp-block-jetpack-slideshow_slide swiper-slide\"><figure><img loading=\"lazy\" decoding=\"async\" width=\"270\" height=\"152\" alt=\"\" class=\"wp-block-jetpack-slideshow_image wp-image-1487\" data-id=\"1487\" src=\"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/Picture1.jpg\"\/><figcaption class=\"wp-block-jetpack-slideshow_caption gallery-caption\">Even in the deep ocean, melanin&#8217;s presence is seen.<\/figcaption><\/figure><\/li><li class=\"wp-block-jetpack-slideshow_slide swiper-slide\"><figure><img loading=\"lazy\" decoding=\"async\" width=\"567\" height=\"523\" alt=\"\" class=\"wp-block-jetpack-slideshow_image wp-image-1485\" data-id=\"1485\" src=\"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/Melanin-Photoluminescence.jpg\" srcset=\"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/Melanin-Photoluminescence.jpg 567w, https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/Melanin-Photoluminescence-300x277.jpg 300w\" sizes=\"(max-width: 567px) 100vw, 567px\" \/><figcaption class=\"wp-block-jetpack-slideshow_caption gallery-caption\">Melanin can exhibit fluorescence, a surprising result.<\/figcaption><\/figure><\/li><li class=\"wp-block-jetpack-slideshow_slide swiper-slide\"><figure><img loading=\"lazy\" decoding=\"async\" width=\"304\" height=\"697\" alt=\"\" class=\"wp-block-jetpack-slideshow_image wp-image-1484\" data-id=\"1484\" src=\"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/Tyndall-effect-in-PDA-dispersion.jpg\" srcset=\"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/Tyndall-effect-in-PDA-dispersion.jpg 304w, https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/Tyndall-effect-in-PDA-dispersion-131x300.jpg 131w\" sizes=\"(max-width: 304px) 100vw, 304px\" \/><figcaption class=\"wp-block-jetpack-slideshow_caption gallery-caption\">Particle-like melanins scatter light via the Tyndall effect!<\/figcaption><\/figure><\/li><li class=\"wp-block-jetpack-slideshow_slide swiper-slide\"><figure><img loading=\"lazy\" decoding=\"async\" width=\"670\" height=\"692\" alt=\"\" class=\"wp-block-jetpack-slideshow_image wp-image-1483\" data-id=\"1483\" src=\"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/MelaninCat.jpg\" srcset=\"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/MelaninCat.jpg 670w, https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/MelaninCat-290x300.jpg 290w\" sizes=\"(max-width: 670px) 100vw, 670px\" \/><figcaption class=\"wp-block-jetpack-slideshow_caption gallery-caption\">Melanin TEM displays its stacking behavior, and sometimes looks like a cat&#8230;..<\/figcaption><\/figure><\/li><li class=\"wp-block-jetpack-slideshow_slide swiper-slide\"><figure><img loading=\"lazy\" decoding=\"async\" width=\"323\" height=\"225\" alt=\"\" class=\"wp-block-jetpack-slideshow_image wp-image-1481\" data-id=\"1481\" src=\"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/image.png\" srcset=\"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/image.png 323w, https:\/\/research.cbc.osu.edu\/kohler.40\/wp-content\/uploads\/2021\/02\/image-300x209.png 300w\" sizes=\"(max-width: 323px) 100vw, 323px\" \/><figcaption class=\"wp-block-jetpack-slideshow_caption gallery-caption\">These shiny &#8220;stones&#8221; are actually melanin solids!<\/figcaption><\/figure><\/li><\/ul><a class=\"wp-block-jetpack-slideshow_button-prev swiper-button-prev swiper-button-white\" role=\"button\"><\/a><a class=\"wp-block-jetpack-slideshow_button-next swiper-button-next swiper-button-white\" role=\"button\"><\/a><a aria-label=\"Pause Slideshow\" class=\"wp-block-jetpack-slideshow_button-pause\" role=\"button\"><\/a><div class=\"wp-block-jetpack-slideshow_pagination swiper-pagination swiper-pagination-white\"><\/div><\/div><\/div>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:66.66%\">\n<p class=\"has-black-color has-pale-cyan-blue-background-color has-text-color has-background\" style=\"font-size:18px\"><strong>Eumelanins are all around us, responsible for the brown-black color of hair and the ink from a cuttlefish. <\/strong>These unknown, heterogeneous structures have challenged experiments aiming to uncover structure-function relationships that explain their sunscreening functions for decades. In human skin, melanin is a natural sunscreen, which absorbs UV and visible photons, forming excited electronic states that decay on ultrafast timescales. In contrast to DNA, nonradiative decay mechanisms for melanin are not understood in large measure because of its uncertain structure.<\/p>\n<\/div>\n<\/div>\n\n\n\n<p class=\"has-black-color has-pale-cyan-blue-background-color has-text-color has-background\" style=\"font-size:18px\">While eumelanin is most appreciated for its sunscreening function, the pigment is also known to photogenerate radicals and sensitize reactive oxygen species like singlet oxygen, superoxide anions, and hydroxy radicals. This creates a dichotomy between its photoprotective and photodamaging aspects, making eumelanin a \u201cdouble-edged sword\u201d. We use femtosecond transient absorption spectroscopy to determine the ultrafast excited state relaxation and radical generation pathways underlying these photoprotective and photodamaging functions in natural and synthetic eumelanins.<\/p>\n\n\n\n<p class=\"has-black-color has-pale-cyan-blue-background-color has-text-color has-background\" style=\"font-size:18px\">Natural eumelanin contains pi-stacked chromophores, but the role that aggregation plays on its photochemical properties is poorly understood. As in DNA, excited state decay pathways in melanin likely differ dramatically from ones that operate in simpler building blocks such as DHI. For this reason, we are also studying synthetic melanin films and nanoparticles in a top-down approach. Melanin is highly redox active due to functional groups that can be switched between hydroquinone, semiquinone, and quinone forms. The rich redox chemistry of melanin suggests that it may play a role as either a scavenger or source of reactive oxygen species (ROS) in organisms. Synthetic melanins are also of great interest for a growing number of applications due to their nature as biocompatible, photo- and redox-active materials.<\/p>\n\n\n\n<p class=\"has-black-color has-pale-cyan-blue-background-color has-text-color has-background\" style=\"font-size:18px\">We\nare pursuing bottom-up and top-down studies of melanin excited states. Man-made\nmelanins very similar to natural eumelanin are easily synthesized under mild\nconditions by the oxidative polymerization of dihydroxy-substituted aromatic\ncompounds (catechols) such as the neurotransmitters dopamine and its precursor\nL-DOPA. We are studying small clusters of catechol derivatives that are thought\nto mimic melanin subunits such as 5,6-dihydroxyindole (DHI). Steady-state and\ntime-resolved vibrational spectroscopy provide insight into hydrogen atom\nphotodissociation pathways and how they are affected by intra- vs.\nintermolecular hydrogen bonding. <\/p>\n\n\n\n<p class=\"has-black-color has-pale-cyan-blue-background-color has-text-color has-background\" style=\"font-size:18px\">Chemical and structural disorder profoundly influence the steady-state spectroscopic properties of melanins. We are investigating the consequences of disorder, including redox disorder, on excited state dynamics. Finally, we are exploring parallels between melanin and man-made carbonaceous materials. <\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Eumelanins are all around us, responsible for the brown-black color of hair and the ink from a cuttlefish. These unknown, heterogeneous structures have challenged experiments aiming to uncover structure-function relationships that explain their sunscreening functions for decades. In human skin,<\/p>\n","protected":false},"author":5,"featured_media":0,"parent":13,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1075","page","type-page","status-publish","hentry"],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-json\/wp\/v2\/pages\/1075","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-json\/wp\/v2\/comments?post=1075"}],"version-history":[{"count":12,"href":"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-json\/wp\/v2\/pages\/1075\/revisions"}],"predecessor-version":[{"id":1595,"href":"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-json\/wp\/v2\/pages\/1075\/revisions\/1595"}],"up":[{"embeddable":true,"href":"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-json\/wp\/v2\/pages\/13"}],"wp:attachment":[{"href":"https:\/\/research.cbc.osu.edu\/kohler.40\/wp-json\/wp\/v2\/media?parent=1075"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}