Intrinsic Photoprotective Mechanisms in Chlorophylls

Kotkowiak, Michał; Dudkowiak, Alina; Fiedor, Leszek

doi:10.1002/anie.201705357

Cited by 24 publications

(24 citation statements)

References 33 publications

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“…Retinal (vitamin A) is the principal chromophore of the visual photoreceptor in the human eye. Crts participate in solar‐energy conversion in the photosynthetic organelles of phototrophic organisms, in which they act as accessory antenna pigments, but their major function is to protect the photosynthetic apparatus against the harmful triplet states of chlorophylls . The “isoprene rule” of isoprenoid biosynthesis was discovered by nature very early, but its structural rationales remain unexplained since its formulation by Ruzicka .…”

Section: Methodsmentioning

confidence: 99%

Side Methyl Groups Control the Conformation and Contribute to Symmetry Breaking of Isoprenoid Chromophores

Fiedor

Pilch

2018

Angew Chem Int Ed

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Ab initio DFT computations reveal that the essential structural and photophysical features of the conjugated π-electron system of retinal and carotenoids are dictated by "innocent" methyl substituents. These methyl groups shape the conformation and symmetry of the isoprenoid chromophores by causing a sigmoidal distortion of the polyene skeleton and increasing its flexibility, which facilitates fitting to their binding pockets in proteins. Comparison of in vacuo conformations of the chromophores with their native (protein-bound) conformations showed, surprisingly, that the peripheral groups and interactions with the protein environment are much less significant than the methyl side groups in tuning their structural features. The methyl side groups also contribute to a loss of symmetry elements specific to linear polyenes. In effect, the symmetry-imposed restrictions on the chromophore electronic properties are disabled, which is of tremendous relevance to their photophysics. This is evidenced by their non-negligible permanent dipole moments and by the simulated and experimentally measured circular dichroism spectra, which necessarily reflect the chirality of the conjugated π-electron system.

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Section: Methodsmentioning

confidence: 99%

Side Methyl Groups Control the Conformation and Contribute to Symmetry Breaking of Isoprenoid Chromophores

Fiedor

Pilch

2018

Angew Chem Int Ed

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“…Chlorophyll metabolites, derived from plant photosynthetic pigments consumed by herbivores (including humans), are a dangerous group of xenobiotics due to their high phototoxicity (Kotkowiak et al, 2017). Their accumulation in the body may lead to lethal consequences and there must exist an efficient system of elimination of such compounds.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Western blotting analysis for the isolation and detection of membrane xenobiotic transporter ABCG2

et al. 2017

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All organisms are exposed to numerous stress factors, which include harmful xenobiotics. The diversity of these compounds is enormous, thus in the course of evolution diverse biological defense mechanisms at various levels of organization have developed. One of them engages an evolutionarily conserved family of transporters from the ABC superfamily, found in most species - from bacteria to humans. An important example of such a transporter is the breast cancer resistance protein (BCRP/ABCG2), a typical integral membrane protein. It plays a key role in the absorption, distribution and elimination of a wide variety of xenobiotics, including drugs used in chemotherapy, and is involved in multidrug resistance. It also protects against phototoxic chlorophyll derivatives of dietary origin. BCRP is a hemitransporter which consists of one transmembrane domain, made of six alpha-helices forming a characteristic pore structure, and one ATP-binding domain, which provides the energy from ATP hydrolysis, required for active transport of the substrates. The isolation of BCRP is still not an easy task, because its insolubility in water and the presence of membrane rafts pose serious methodological and technical challenges during the purification. The aim of this study was to optimize the methods for detection and isolation of BCRP-enriched fractions obtained from animal tissue samples. In this report we describe an optimization of isolation of a BCRP-enriched membrane fraction, which is suitable for further protein quantitative and qualitative analysis using the molecular biology tools.

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“…Introducing the diarylamino groups at the periphery also shortened the triplet lifetimes. The electron‐donating diarylamino groups would enhance the charge‐transfer characteristics of the excited state, which might intensify the forbidden T 1 –S 0 transition by interstate mixing with the S 1 –S 0 transition …”

Section: Resultsmentioning

confidence: 99%

Effects of the Peripheral Substituents, Central Metal, and Solvent on the Photochemical and Photophysical Properties of 5,15‐Diazaporphyrins

et al. 2019

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Metal complexes of 3,7,13,17‐tetrakis(di(4‐carboxyphenyl)amino)‐5,15‐diazaporphyrin (MDAP‐COOH; M=Pd, Cu) and their ethyl ester precursors (MDAP‐COOEt; M=Pd, Cu) have been synthesized for use as near‐infrared (NIR)‐light‐responsive photosensitizers. Under irradiation with visible or NIR light, PdDAP‐COOEt in toluene generated singlet oxygen (1O2) with an excellent quantum yield (ΦΔ=0.99), whereas CuDAP‐COOEt exhibited a lower efficiency (ΦΔ=0.21). The water‐soluble PdII complex PdDAP‐COOH also behaved as a photosensitizer (ΦΔ=0.20) in a micellar solution. The photophysical properties of these dyes were measured by transient absorption techniques. It was found that the efficiency of the energy transfer from the triplet state of MDAP‐COOR (R=Et, H) to the ground state of dioxygen was highly dependent on the peripheral substituents, the central metal, and the solvent. Furthermore, the phototoxicity of PdDAP‐COOH toward HeLa cells under irradiation of NIR light (720 nm) was evaluated. As expected, PdDAP‐COOH exhibited good photodynamic activity, and control experiments confirmed that 1O2 was generated as the active oxygen species.

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Intrinsic Photoprotective Mechanisms in Chlorophylls

Cited by 24 publications

References 33 publications

Side Methyl Groups Control the Conformation and Contribute to Symmetry Breaking of Isoprenoid Chromophores

Side Methyl Groups Control the Conformation and Contribute to Symmetry Breaking of Isoprenoid Chromophores

Optimization of Western blotting analysis for the isolation and detection of membrane xenobiotic transporter ABCG2

Effects of the Peripheral Substituents, Central Metal, and Solvent on the Photochemical and Photophysical Properties of 5,15‐Diazaporphyrins

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