The ultrafast photochemistry of vitamin D – Towards understanding the quantum biology of a self-regulating system
Molecular Physics seminar
Monday 04 July 2016
to 12:00 at
Enrico Tapavicza (California State University)
The main source of vitamin D for humans is its generation by the sun’s ultraviolet (UV) light.
Oral administration of large vitamin D quantities can lead to vitamin D overdose, which affects
negatively many regulation cycles in our body. In contrast, overproduction of vitamin D due to
extended sun exposure has never been observed . It has been found that a complex network
of vitamin D photo isomers that are connected by reversible chemical and photochemical
reactions in our skin prevents vitamin D overproduction. The mechanism of the self-regulation
is not well understood . An important feature of the self-regulating cycle is its characteristic
wavelength dependent photochemistry: UV light with longer wavelengths induces different
photochemical reactions than UV light with short wavelengths. Thus, the distribution of
photochemical isomers is a function of the spectral composition of the sun and varies with day
time and time of the year. Furthermore, large absorption coefficients of some vitamin D
isomers lead to an intrinsic sun protection upon extended UV light exposure, which reduces
vitamin D production.
In this talk, I will present new theoretical and experimental results that can explain several
aspects of this self-regulating cycle. We combine ab initio molecular dynamics simulations
based on quantum chemistry [3, 4, 6] with time-resolved femtosecond resolved experiments [5,
6, 7, 8, 9], to understand the photo dynamics of several vitamin D related photochemical
reactions. In particular we are interested in how the specific geometry of vitamin D affects its
photochemical reactivity. Furthermore, we want to understand the role of each individual
vitamin D photo isomer in the self-regulating cycle.
We acknowledge support by the California State University (CSU), Long Beach start-up fund
and the CSU Program for Education and Research in Biotechnology (CSUPERB) fund.
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 E. Tapavicza, A. M. Meyer, and F. Furche. Unravelling the details of vitamin D photosynthesis by non- adiabatic
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Geng, Travis Thompson, Noel Baluyot, Richard D. Thomas, Enrico Tapavicza, Tony Hansson
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