Carotenoids are an integral part of natural photosynthetic complexes, with tasks ranging from light harvesting to photoprotection. Their underlying energy deactivation network of optically dark and bright excited states is extremely efficient: after excitation of light with up to 2.5 eV of photon energy, the system relaxes back to ground state on a time scale of a few picoseconds. In this article, we summarize how a model based on the vibrational energy relaxation approach (VERA) explains the main characteristics of relaxation dynamics after one-photon excitation with special emphasis on the so-called S* state. Lineshapes after two-photon excitation are beyond the current model of VERA. We outline this future line of research in our article. In terms of experimental method development, we discuss which techniques are needed to better describe energy dissipation effects in carotenoids and within the first solvation shell.

• MeSH
• Photons MeSH
• Photosynthetic Reaction Center Complex Proteins * MeSH
• Carotenoids * MeSH
• Light-Harvesting Protein Complexes MeSH
• Vibration MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Photosynthetic Reaction Center Complex Proteins * MeSH
• Carotenoids * MeSH
• Light-Harvesting Protein Complexes MeSH

Chlorophylls and bacteriochlorophylls, together with carotenoids, serve, noncovalently bound to specific apoproteins, as principal light-harvesting and energy-transforming pigments in photosynthetic organisms. In recent years, enormous progress has been achieved in the elucidation of structures and functions of light-harvesting (antenna) complexes, photosynthetic reaction centers and even entire photosystems. It is becoming increasingly clear that light-harvesting complexes not only serve to enlarge the absorption cross sections of the respective reaction centers but are vitally important in short- and long-term adaptation of the photosynthetic apparatus and regulation of the energy-transforming processes in response to external and internal conditions. Thus, the wide variety of structural diversity in photosynthetic antenna "designs" becomes conceivable. It is, however, common for LHCs to form trimeric (or multiples thereof) structures. We propose a simple, tentative explanation of the trimer issue, based on the 2D world created by photosynthetic membrane systems.

• Keywords
• bacteriochlorophylls, carotenoids, chlorophylls, excitation energy transfer, light-harvesting complexes, photoprotection, photosynthesis, photosystems, pigment-protein complexes,
• MeSH
• Bacterial Proteins chemistry   metabolism   MeSH
• Photosynthesis MeSH
• Protein Conformation MeSH
• Models, Molecular MeSH
• Protein Multimerization MeSH
• Energy Transfer MeSH
• Plant Proteins chemistry   metabolism   MeSH
• Plants metabolism   MeSH
• Cyanobacteria metabolism   MeSH
• Light-Harvesting Protein Complexes chemistry   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Bacterial Proteins MeSH
• Plant Proteins MeSH
• Light-Harvesting Protein Complexes MeSH