Similarity and Specificity of Chlorophyll b Triplet State in Comparison to Chlorophyll a as Revealed by EPR/ENDOR and DFT Calculations

2019 ◽  
Vol 123 (39) ◽  
pp. 8232-8239 ◽  
Author(s):  
Alessandro Agostini ◽  
Maria Giulia Dal Farra ◽  
Harald Paulsen ◽  
Antonino Polimeno ◽  
Laura Orian ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Triplet State ◽  
Chlorophyll A ◽  
Chlorophyll B

Triplet-State Electron Spin Resonance of Chlorophyll a and b Molecules and Complexes in PMMA and MTHF. I: Experimental Determination of Fine-Structure and Rate Constants

1978 ◽  
Vol 33 (1) ◽  
pp. 83-93 ◽  
Author(s):  
W. Hagele ◽  
D. Schmid ◽  
H. C. Wolf
Keyword(s):  
Triplet State ◽  
Chlorophyll A ◽  
Rate Constants ◽  
Resonance Field ◽  
Zero Field ◽  
Chlorophyll B ◽  
Low Concentrations ◽  
Spin Resonance ◽  
Chlorophyll A And B

The triplet state zero-field splittings and the rate constants for the population and depopulation of the triplet spin sublevels have been investigated for chlorophyll a and chlorophyll b in polymethylmethacrylate (PMMA) and methyltetrahydrofurane (MTHF) as a function of the concentration. In PMMA both chlorophyll a and chlorophyll b yielded only one ESR spectrum in the entire range of concentration which could be covered (1.5 × 10-5 - 1 × 10-3 mole/1). In MTHF the results were more complicated. At low concentrations (up to 103 mole/1) only one spectrum was observed, at higher concentrations additional spectra were detectable (all together two for chlorophyll a and five for chlorophyll b at 10-1 mole/1). The assignment of these spectra was facilitated by observing the "triplet resonance-field identity" which connects the resonancefield strengths for the canonical orientations of one particular species. Furthermore, the rate constants for some of these species could be determined.

Etude sur la teneur en pigment de frênes qui croissent dans des conditions différentes

1973 ◽  
Vol 37 ◽  
Author(s):  
N. Lust
Keyword(s):  
Chlorophyll A ◽  
Strong Influence ◽  
The Other ◽  
Pigment Content ◽  
Chlorophyll B ◽  
Light Quantity ◽  
Yellow Pigments ◽  
The One ◽  
Green Pigments

Pigment content of ashes grown up under different circumstances - The pigment content (chlorophyll a, chlorophyll b,  xanthophyll and carotene) has been researched with ashes grown up under  different light circumstances and varying in age and height.     The results prove that the general laws concerning the influence of light  on the pigment content, don’t always work.     The phenomen is very complex. The light quantity is very important in some  cases, but insignificant in others. It seems origin and height of plants have  a strong influence. The results prove also the influence of the environment  is much higher on small plants as on big ones.     The research indicates finally the correlation between the green pigments,  the yellow pigments, and between the green pigments on the one side and the  yellow ones on the other side.

scholarly journals Shading Effects on Leaf Gas Exchange, Leaf Pigments and Secondary Metabolites of Polygonum minus Huds., an Aromatic Medicinal Herb

Plants ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 608
Author(s):  
Fairuz Fatini Mohd Yusof ◽  
Jamilah Syafawati Yaacob ◽  
Normaniza Osman ◽  
Mohd Hafiz Ibrahim ◽  
Wan Abd Al Qadr Imad Wan-Mohtar ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Secondary Metabolites ◽  
Chlorophyll A ◽  
Leaf Gas Exchange ◽  
Photosynthesis Rate ◽  
Total Phenolic ◽  
Chlorophyll B ◽  
Low Light ◽  
Total Anthocyanin ◽  
Polygonum Minus

The growing demand for high value aromatic herb Polygonum minus-based products have increased in recent years, for its antioxidant, anticancer, antimicrobial, and anti-inflammatory potentials. Although few reports have indicated the chemical profiles and antioxidative effects of Polygonum minus, no study has been conducted to assess the benefits of micro-environmental manipulation (different shading levels) on the growth, leaf gas exchange and secondary metabolites in Polygonum minus. Therefore, two shading levels (50%:T2 and 70%:T3) and one absolute control (0%:T1) were studied under eight weeks and 16 weeks of exposures on Polygonum minus after two weeks. It was found that P. minus under T2 obtained the highest photosynthesis rate (14.892 µmol CO2 m−2 s−1), followed by T3 = T1. The increase in photosynthesis rate was contributed by the enhancement of the leaf pigments content (chlorophyll a and chlorophyll b). This was shown by the positive significant correlations observed between photosynthesis rate with chlorophyll a (r2 = 0.536; p ≤ 0.05) and chlorophyll b (r2 = 0.540; p ≤ 0.05). As the shading levels and time interval increased, the production of total anthocyanin content (TAC) and antioxidant properties of Ferric Reducing Antioxidant Power (FRAP) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) also increased. The total phenolic content (TPC) and total flavonoid content (TFC) were also significantly enhanced under T2 and T3. The current study suggested that P.minus induce the production of more leaf pigments and secondary metabolites as their special adaptation mechanism under low light condition. Although the biomass was affected under low light, the purpose of conducting the study to boost the bioactive properties in Polygonum minus has been fulfilled by 50% shading under 16 weeks’ exposure.

scholarly journals A study of the low-lying singlet and triplet electronic states of chlorophyll A and B

2013 ◽  
Vol 78 (11) ◽  
pp. 1775-1787 ◽  
Author(s):  
Mihajlo Etinski ◽  
Milena Petkovic ◽  
Miroslav Ristic
Keyword(s):  
Chlorophyll A ◽  
Density Functional ◽  
Chlorophyll B ◽  
Fluorescence Lifetimes ◽  
Functional Theory ◽  
Chlorophyll A And B ◽  
Vertical Ionization Potentials ◽  
Density Functional Theory Optimization ◽  
Triplet Formation ◽  
Good Agreement

Chlorophylls have been extensively investigated both experimentally and theoretically owing to the fact that they are essential for photosynthesis. We have studied two forms of chlorophyll, chlorophyll a and chlorophyll b, by means of density functional theory. Optimization of S0, S1 and T1 states was performed with the B3-LYP functional. The computed fluorescence lifetimes show good agreement with the available experimental data. The electronic adiabatic energies of S1 and T1 states are 2.09/2.12 and 1.19/1.29 eV for chlorophyll a and chlorophyll b respectively. We discussed the implications of this results on the triplet formation. Also, the calculated vertical ionization potentials shows good agreement with the experimental results.

DFT Calculations on Group 5 Mixed Metal Tetramers: TaxNbyVz (x + y + z = 4)

2004 ◽  
Vol 57 (12) ◽  
pp. 1197 ◽  
Author(s):  
Magdalene A. Addicoat ◽  
Mark A. Buntine ◽  
Gregory F. Metha
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Triplet State ◽  
Density Functional ◽  
Metal Cluster ◽  
Functional Theory ◽  
Mixed Metal ◽  
Mixed Metal Cluster ◽  
Group 5

We report Density Functional Theory (DFT) calculations on mixed-metal tetramers comprised of the Group 5 (Vb) elements V, Nb, and Ta. Our results show that the lowest energy structures for Nb4 and Ta4 are regular tetrahedra with Td symmetry and singlet multiplicity whereas V4 is a triplet state with C2v symmetry. The monosubstituted isomers, A3B, all have C3v symmetry but several higher energy Cs structures have been found that are approximately 100 kJ mol−1 higher in energy. The disubstituted isomers all posses arachno-butterfly structures; the A2B2 types with C2v symmetry and the A2BC types with Cs symmetry. However, the relative openness of the arachno structures is found to be specific to the composition of the mixed-metal cluster.

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