1.7 Summary of This Chapter and Scope of This Book
25
when decarboxylation from dopachrome occurred, while the formation of DHICA
proceeds by tautomerization with the retained carboxyl group. These branched reactions determine the chemical composition of melanin, namely the ratio of eumelanin/pheomelanin and the ratio of DHI/DHICA of eumelanin. So far, factors that
influence these competitive reactions at the branch points have been investigated,
although the mechanisms by which the branching occurs have not been clarified yet.
Furthermore, chemistry of melanogenesis-like reactions initiated by tyrosine/dopa
analogs is still an unexplored region. Therefore, it is a great challenge to establish a
theoretical basis for understanding the whole picture of melanogenesis-like reactions
that enables us to predict the reactivity for various cases of molecules.
In this book, we focus on two types of reactions in melanogenesis, which are
thought to determine the properties of melanin. One is dopachrome conversion,
which is responsible for the production of two types of monomers that build eumelanin. The other is dopaquinone conversion, which is responsible for eumelanin or
pheomelanin production. The main objective is to give an explanation from a general
point of view of how these reactions proceed at the atomic level as well as discussing
chemical factors affecting the reaction pathway branching. Furthermore, we also
aimed to understand melanogenesis-like reactions based on comparative investigation for various o-quinones. Throughout the investigation introduced in this book,
first principles calculation based on density functional theory was employed for simulating the reactions. Moreover, as a model of the reaction environment in aqueous
solutions, a continuous dielectric model that stabilizes polarized electronic states of
molecules by means of dielectric response of solvent was used.
Chapter 2 introduces theoretical works performed on dopachrome conversion
[123, 124], and Chap. 3 introduces theoretical studies regarding reactions of
dopaquinone and o-quinones [125–127]. Chapter 4 summarizes the contents of this
book and discusses future prospect.
References
1. M. d’Ischia, K. Wakamatsu, A. Napolitano, S. Briganti, J.C. García-Borrón, D. Kovacs, P.
Meredith, A. Pezzella, M. Picardo, T. Sarna, J.D. Simon, S. Ito, Melanins and melanogenesis:
methods standards protocols. Pigment Cell Melanoma Res. 26, 616–633 (2013)
2. S. Ito, K. Wakamatsu, Chemistry of mixed melanogenesis-pivotal roles of dopaquinone.
Photochem. Photobiol. 84, 582–592 (2008)
3. S. Ito, K. Wakamatsu, Human hair melanins: what we have learned and have not learned from
mouse coat color pigmentation. Pigment Cell Melanoma Res. 24, 63–74 (2010)
4. M. Seiji, T.B. Fitzpatrick, R.T. Simpson, M.S.C. Birbeck, Chemical composition and
terminology of specialized organelles (melanosomes and melanin granules) in mammalian
melanocytes. Nature 197, 1082–1084 (1963)
5. J.Y. Lin, D.E. Fisher, Melanocyte biology and skin pigmentation. Nature 445, 843–850 (2007)
6. T.P. Dryja, M. O’Neil-Dryja, J.M. Pawelek, D.M. Albert, Demonstration of tyrosinase in the
adult bovine uveal tract and retinal pigment epithelium. Invest. Ophthalmol. Visual Sci. 17,
511–514 (1978)
25
when decarboxylation from dopachrome occurred, while the formation of DHICA
proceeds by tautomerization with the retained carboxyl group. These branched reactions determine the chemical composition of melanin, namely the ratio of eumelanin/pheomelanin and the ratio of DHI/DHICA of eumelanin. So far, factors that
influence these competitive reactions at the branch points have been investigated,
although the mechanisms by which the branching occurs have not been clarified yet.
Furthermore, chemistry of melanogenesis-like reactions initiated by tyrosine/dopa
analogs is still an unexplored region. Therefore, it is a great challenge to establish a
theoretical basis for understanding the whole picture of melanogenesis-like reactions
that enables us to predict the reactivity for various cases of molecules.
In this book, we focus on two types of reactions in melanogenesis, which are
thought to determine the properties of melanin. One is dopachrome conversion,
which is responsible for the production of two types of monomers that build eumelanin. The other is dopaquinone conversion, which is responsible for eumelanin or
pheomelanin production. The main objective is to give an explanation from a general
point of view of how these reactions proceed at the atomic level as well as discussing
chemical factors affecting the reaction pathway branching. Furthermore, we also
aimed to understand melanogenesis-like reactions based on comparative investigation for various o-quinones. Throughout the investigation introduced in this book,
first principles calculation based on density functional theory was employed for simulating the reactions. Moreover, as a model of the reaction environment in aqueous
solutions, a continuous dielectric model that stabilizes polarized electronic states of
molecules by means of dielectric response of solvent was used.
Chapter 2 introduces theoretical works performed on dopachrome conversion
[123, 124], and Chap. 3 introduces theoretical studies regarding reactions of
dopaquinone and o-quinones [125–127]. Chapter 4 summarizes the contents of this
book and discusses future prospect.
References
1. M. d’Ischia, K. Wakamatsu, A. Napolitano, S. Briganti, J.C. García-Borrón, D. Kovacs, P.
Meredith, A. Pezzella, M. Picardo, T. Sarna, J.D. Simon, S. Ito, Melanins and melanogenesis:
methods standards protocols. Pigment Cell Melanoma Res. 26, 616–633 (2013)
2. S. Ito, K. Wakamatsu, Chemistry of mixed melanogenesis-pivotal roles of dopaquinone.
Photochem. Photobiol. 84, 582–592 (2008)
3. S. Ito, K. Wakamatsu, Human hair melanins: what we have learned and have not learned from
mouse coat color pigmentation. Pigment Cell Melanoma Res. 24, 63–74 (2010)
4. M. Seiji, T.B. Fitzpatrick, R.T. Simpson, M.S.C. Birbeck, Chemical composition and
terminology of specialized organelles (melanosomes and melanin granules) in mammalian
melanocytes. Nature 197, 1082–1084 (1963)
5. J.Y. Lin, D.E. Fisher, Melanocyte biology and skin pigmentation. Nature 445, 843–850 (2007)
6. T.P. Dryja, M. O’Neil-Dryja, J.M. Pawelek, D.M. Albert, Demonstration of tyrosinase in the
adult bovine uveal tract and retinal pigment epithelium. Invest. Ophthalmol. Visual Sci. 17,
511–514 (1978)