Chapter 4
Concluding Remarks and Future
Perspectives
Abstract Summarizing our findings, we give concluding remarks and future
perspectives. One of next challenges will be to unveil quantum effects of atomic
nuclei in melanogenesis. While the classical description of atomic nuclei is sufficient
for most scenarios, certain phenomena require quantum mechanical description of
both atomic nuclei and electrons.
Keywords Computational materials design (CMD
® ) · Quantum effects
In this book, we introduced melanin chemistry studies with the emphasis of computational approach. With the aid of quantum chemical calculation, we aimed to understand branched reactions involved in melanogenesis, namely dopachrome conversion and cyclization/thiol binding of dopaquinone analogues. The former reaction,
dopachrome conversion produces eumelanin monomers DHI and DHICA, whereas
the latter reaction cyclization/thiol binding of dopaquinone analogs results in the
switching between eumelanogenesis and pheomelanogenesis.
As described in Chap. 2, the computational studies of dopachrome conversion
found important factors affecting the selective formation of DHI and DHICA. The
branch into DHI and DHICA formation, respectively, results from decarboxylation and deprotonation from α-carbon of dopachrome. These reaction modes are
controlled by the protonated/deprotonated state of the quinonoid group that is located
distant from α-carbon. This is the result that the characteristics of π-conjugated
system are clearly exhibited. Integrating the obtained results, the catalytic effects of
basic pH and Cu(II) experimentally observed can be explained based on two aspects:
promotion of the rate-determining step and protection of quinonoid group from protonation. Thus, the computational approach provides the atomic-scale understanding
of dopachrome conversion. It is expected that these findings are used to predict the
relation between the synthetic condition and the eumelanin composition, namely the
DHI/DHICA ratio.
As described in Chap. 3, the computational studies of cyclization and thiol
binding for dopaquinone and structurally similar o-quinones revealed key factors
affecting the reactivity toward the two reaction modes. Cyclization and thiol binding
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
R. Kishida et al., Melanin Chemistry Explored by Quantum Mechanics,
https://doi.org/10.1007/978-981-16-1315-9_4
81
Concluding Remarks and Future
Perspectives
Abstract Summarizing our findings, we give concluding remarks and future
perspectives. One of next challenges will be to unveil quantum effects of atomic
nuclei in melanogenesis. While the classical description of atomic nuclei is sufficient
for most scenarios, certain phenomena require quantum mechanical description of
both atomic nuclei and electrons.
Keywords Computational materials design (CMD
® ) · Quantum effects
In this book, we introduced melanin chemistry studies with the emphasis of computational approach. With the aid of quantum chemical calculation, we aimed to understand branched reactions involved in melanogenesis, namely dopachrome conversion and cyclization/thiol binding of dopaquinone analogues. The former reaction,
dopachrome conversion produces eumelanin monomers DHI and DHICA, whereas
the latter reaction cyclization/thiol binding of dopaquinone analogs results in the
switching between eumelanogenesis and pheomelanogenesis.
As described in Chap. 2, the computational studies of dopachrome conversion
found important factors affecting the selective formation of DHI and DHICA. The
branch into DHI and DHICA formation, respectively, results from decarboxylation and deprotonation from α-carbon of dopachrome. These reaction modes are
controlled by the protonated/deprotonated state of the quinonoid group that is located
distant from α-carbon. This is the result that the characteristics of π-conjugated
system are clearly exhibited. Integrating the obtained results, the catalytic effects of
basic pH and Cu(II) experimentally observed can be explained based on two aspects:
promotion of the rate-determining step and protection of quinonoid group from protonation. Thus, the computational approach provides the atomic-scale understanding
of dopachrome conversion. It is expected that these findings are used to predict the
relation between the synthetic condition and the eumelanin composition, namely the
DHI/DHICA ratio.
As described in Chap. 3, the computational studies of cyclization and thiol
binding for dopaquinone and structurally similar o-quinones revealed key factors
affecting the reactivity toward the two reaction modes. Cyclization and thiol binding
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
R. Kishida et al., Melanin Chemistry Explored by Quantum Mechanics,
https://doi.org/10.1007/978-981-16-1315-9_4
81