Stoichiometric determination of chlorophyll a-water aggregates and photosynthesis. Symbiotic roles of the magnesium atom and the ring V cyclopentanone group in the structural and photochemical properties of chlorophyll a monohydrate and dihydrate

Brace, John G.; Fong, Francis K.; Karweik, Dale H.; Koester, Vaughn J.; Shepard, A. T.; Winograd, Nicholas

doi:10.1021/ja00484a050

Cited by 42 publications

(5 citation statements)

References 6 publications

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“…Our results are entirely consistent with earlier deductions from solution studies on Chl a dimers and oligomers. The mass spectrometric data show that, contrary to opinions expressed in the literature (24)(25)(26)(27), (i) Chl a free of water can be readily obtained by simple procedures and (ii) the Chl a species absorbing maximally at t-680 nm contain no wateri.e., water is not an integral component of the (Chl a). oligomer structure.…”

Section: Resultscontrasting

confidence: 75%

Self-assembled chlorophyll a systems as studied by californium-252 plasma desorption mass spectroscopy

Hunt

Macfarlane

Katz

et al. 1980

Proc. Natl. Acad. Sci. U.S.A.

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Self-assembled chlorophyll a and pheophytin a systems in thin solid films have been studied by 2'52Cf plasma desorption mass spectrometry (PDMS). The 252Cf-PDMS spectra of these films show monomer cation and anion molecular ions, ions of molecular aggregates, and positive and negative ion fragmentation patterns arising from the loss of various aliphatic side chains from the chlorin ring. Chlorophyll a films cast from dry carbon tetrachloride solution, in which chlorophyll a is known to occur as the dimer, produced an abundant dimer ion. The highest degree of chlorophyll a self-assembly was observed in chlorophyll a films cast from n-octane solutions. Oligomer ions extending upwards in size to the heptamer were detected in this system.It has long been recognized that the optical properties of chlorophyll in vivo are anomalous (1). Relative to a solution of chlorophyll in a polar solvent such as pyridine or diethyl ether, an environment in which chlorophyll is known to exist predominantly as monomer (2), the main red absorption band of chlorophyll in vivo is both red-shifted and broadened. Both the absorption and emission spectra are significantly different (3). The discrepancies are most often attributed (i) to aggregation of the pigment molecules or (ii) to specific chlorophyll-protein interactions. Krasnovskii (4), Brody and Brody (5, 6), and others have suggested that chlorophyll occurs in various states of aggregation in vivo, and that interactions between the chlorophyll molecules in the various aggregates perturb the electronic states of the chromophores and, thus, become the primary source of the spectral anomalies in vivo. Whether there are specific chlorophyll-protein interactions that can generate spectral shifts in the absence of pigment chromophore-chromophore interactions is still an unresolved question.The nature of the various red-shifted chlorophyll systems that can readily be prepared in the laboratory thus becomes relevant to the state of chlorophyll in vivo. Organic compounds with large delocalized 7r electron systems (e.g., chlorophyll) experience nonspecific 7r-7r intermolecular attractive dispersion forces that result in aggregation. In addition, chlorophyll is now recognized to have coordination properties (7) particularly conducive to the formation both of chlorophyll-chlorophyll (endogamous) adducts (8), and chlorophyll-nucleophile (exogamous) aggregates (9). Nuclear magnetic resonance (10, 11) and infrared (12) spectroscopy show that the central magnesium atom of chlorophyll with coordination number 4 (as shown in Fig. 1) is coordinatively unsaturated. The Mg atom thus has a strong tendency to acquire electrons by filling one or both of its axial positions with nucleophilic ligands that have lone pairs of electrons. At the same time, the keto C=O function in ring V has been shown to be an excellent nucleophile (12, 13). The

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Section: Resultscontrasting

confidence: 75%

Self-assembled chlorophyll a systems as studied by californium-252 plasma desorption mass spectroscopy

Hunt

Macfarlane

Katz

et al. 1980

Proc. Natl. Acad. Sci. U.S.A.

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“…Ether solutions of Chl a were used to check spectrophotometrically the purity and the concentration of the samples. 10 Appropriate amounts of freshly prepared stock solution were evaporate to dryness under a flow of N 2 gas. Then CD aqueous solutions or water were used to dissolve dry chlorophyll.…”

Section: Methodsmentioning

confidence: 99%

Aggregation processes and photophysical properties of chlorophyll a in aqueous solutions modulated by the presence of cyclodextrins

Agostiano

Catucci

Cosma

et al. 2003

Phys. Chem. Chem. Phys.

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“…On the other hand, the presence of Chla in the CH/CD/Chla film induces a remarkable variation of the XPS C1s signal (Figure 2c); in particular the considerable increase of the peak area percentage of the hydrocarbon component at 285.0 eV can be ascribed to Chla and, specifically, to contributions from the phytyl chain, aromatic carbon atoms of the porphyrinic ring, alkyl and alkenyl substituents of the porphyrinic ring. Noticeably the N1s spectrum of the CH/CD/Chla film shows a new component at 398.3 eV attributed to nitrogen atoms in the Chla porphyrin macrocycle (Brace et al, 1978;Karweik & Winograd, 1976;Bekalé, Barazzouk & Hotchandani, 2012a;Bekalé, Barazzouk & Hotchandani, 2012b). Interestingly, the ratio between the peak area percentages of the N3 (NH 3 + ) and N2 (NH 2 /N-C=O) components increases from 0.075, as observed for both CH and CH/CD films (N2 and N3 peak percentages of 93% and 7%, respectively), to about 0.12 in the case of the CH/CD/Chla film (N2 and N3 peak percentages of 78% and 9%, respectively); this confirm, in excellent agreement with the so far discussed hypothesis, a rearrangement of the CH chains induced by Chla incorporation suggesting a novel disposition of the protonated amino groups on the film surface arising from novel coordination as well suggested by Mandal (2015).…”

Section: Xps Analysismentioning

confidence: 99%

Molecular interactions, characterization and photoactivity of Chlorophyll a/chitosan/2-HP-β-cyclodextrin composite films as functional and active surfaces for ROS production

et al. 2016

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Stoichiometric determination of chlorophyll a-water aggregates and photosynthesis. Symbiotic roles of the magnesium atom and the ring V cyclopentanone group in the structural and photochemical properties of chlorophyll a monohydrate and dihydrate

Cited by 42 publications

References 6 publications

Self-assembled chlorophyll a systems as studied by californium-252 plasma desorption mass spectroscopy

Self-assembled chlorophyll a systems as studied by californium-252 plasma desorption mass spectroscopy

Aggregation processes and photophysical properties of chlorophyll a in aqueous solutions modulated by the presence of cyclodextrins

Molecular interactions, characterization and photoactivity of Chlorophyll a/chitosan/2-HP-β-cyclodextrin composite films as functional and active surfaces for ROS production

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