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- Ilagan, R P, et al.
(author)
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Femtosecond time-resolved absorption spectroscopy of astaxanthin in solution and in alpha-crustacyanin
- 2005
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In: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 109:14, s. 3120-3127
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Journal article (peer-reviewed)abstract
- Steady-state absorption and femtosecond time-resolved spectroscopic studies have been carried out on astaxanthin dissolved in CS2, methanol, and acetonitrile, and in purified alpha-crustacyanin. The spectra of the S-0 -> S-2 and S-1 -> S-n transitions were found to be similarly dependent on solvent environment. The dynamics of the excited-state decay processes were analyzed with both single wavelength and global fitting procedures. In solution, the S-1 lifetime of astaxanthin was found to be similar to 5 ps and independent of solvent. In alpha-crustacyanin, the lifetime was noticeably shorter at similar to 1.8 ps. Both fitting procedures led to the conclusion that the lifetime of the S-2 state was either comparable to or shorter than the instrument response time. The data support the idea that dimerization of astaxanthin in alpha-crustacyanin is the primary molecular basis for the bathochromic shift of the S-0 -> S-2 and S-1 - S-n transitions. Planarization of the astaxanthin molecule, which leads to a longer effective pi-electron conjugated chain and a lower S-1 energy, accounts for the shorter tau(1) in the protein.
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