Ultrafast Triplet Generation and its Sensitization Drives Efficient Photoisomerization of Tetra-cis-lycopene to All-trans-lycopene

Abstract

Lycopene biosynthesis in photosynthetic organisms controls the metabolic flux of reaction center carotenoids like β-carotene and lutein through the geometric four-step isomerization of 7,9,9',7'-tetra-cis-lycopene (prolycopene) to its all-trans form. In plants and cyanobacteria, a redox-controlled flavoenzyme carotenoid isomerase catalyzes the prolycopene isomerization although its functional loss inside the chloroplast can be rescued by light. In order to address the chloroplast-specificity and efficiency of the light-induced isomerization reaction, we need to critically understand the excited state dynamics of prolycopene and the nature of electronic states that lead to the isomerization. Using broadband femtosecond transient absorption spectroscopy, we observe ∼610 fs rise of the long-lived triplet state from the photoexcited S2 with a quantum yield of ∼0.19. The triplet state eventually triggers the first C═C bond isomerization at the symmetric 9 or 9' position on the tetra-cis backbone to yield the tri-cis product with 15% quantum efficiency. However, direct sensitization of the photoreactive triplet state via meso-tetraphenyl porphyrin sensitizer under steady state illumination leads to an efficient production of all-trans-lycopene with 58% quantum yield. Our work implies that chlorophyll-enriched chloroplasts should form an optimized photoreaction vessel for prolycopene isomerization, and synthetic utilization of such cis-carotenoids can lead to efficient triplet harvesting photon-conversion devices.

High-Throughput Phenotyping Approach for Screening Major Carotenoids of Tomato by Handheld Raman Spectroscopy Using Chemometric Methods

“…The low carotenoid samples did not show any significant carotenoid band in the Raman spectrum ( Figure 2 b). The position of the C=C stretching Raman band was inversely related to the length of the conjugated polyene chain, isomerization ( trans vs. cis ), the side groups of polyene chain and the presence of other constituents bonded to carotenoids in the plant material [ 13 , 40 , 41 , 42 ].…”

Acis-carotene derived apocarotenoid regulates etioplast and chloroplast development

“…In the dark, the isomerisation of tri- cis -ζ-carotene to di- cis -ζ-carotene and tetra- cis -lycopene to all- trans -lycopene has a strict requirement for ZISO and CRTISO activity respectively (Park et al, 2002; Chen et al, 2010). However, light-mediated photoisomerisation in the presence of a photosensitiser can substitute for a lack of isomerase activity (Giuliano et al, 2002; Vijayalakshmi et al, 2015; Alagoz et al, 2018).…”

Raman and Infrared Spectra for All-trans-astaxanthin in Dimethyl Sulfoxide Solvent

“…It is well known that configurations and environments have significant effects on the properties of carotenoids [10,11,16,19], especially with respect to the structure of the conjugated double C=C bond chain, but also the chemical structure of the whole molecule. In both theory [10,11] and experiment [16,27,32], Raman spectra have been proven useful for investigation of the molecular structures of carotenoids under different conditions.…”

“…For example, in experimental Raman spectra, the ν 1 band arising from the C=C stretching modes of AXT is found at 1512 cm −1 in standard samples but at 1520 cm −1 in the highest-concentration samples [16], and this discrepancy is caused by the differences between the environments. The frequency of the ν 1 Raman bands of various carotenoids and polyenesis linearly related to the S 0 →S 2 electronic transition, and this relationship has been shown to depend on the effective conjugation length of the carotenoid conformers and on the methyl groups connected to the conjugated chain [10,19]. Regarding the split of ν 1 mode of alltrans β-carotene Raman spectrum, Hildebrandt's group has made a detailed study both experimentally and theoretically.…”

“…Carotenoids, which have a significant role in biological systems, have been intensively investigated because of their rich photochemistry [1,2], photophysics [3,4], and photobiology properties [5]. Accordingly, numerous theoretical [6][7][8][9][10][11][12] and experimental [3,[12][13][14][15][16][17][18][19][20] studies have investigated the excited electronic structures, molecular configurations, and environmental effects for different carotenoids. Astaxanthin (AXT), which exists in the all-trans configuration, is a member of the carotenoid family containing C=O, O−H, and terminal β-ionone ring groups [13].…”