scholarly journals Carotenoids Do Not Protect Bacteriochlorophylls in Isolated Light-Harvesting LH2 Complexes of Photosynthetic Bacteria from Destructive Interactions with Singlet Oxygen

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5120
Author(s):  
Zoya K. Makhneva ◽  
Maksim A. Bolshakov ◽  
Andrey A. Moskalenko
Keyword(s):  
Singlet Oxygen ◽  
Photosynthetic Bacteria ◽  
Light Harvesting ◽  
Bacterial Photosynthesis ◽  
Ir Absorption ◽  
Absorption Bands ◽  
Sulfur Bacteria ◽  
Ir Absorption Spectra ◽  
Destructive Action

The effect of singlet oxygen on light-harvesting (LH) complexes has been studied for a number of sulfur (S+) and nonsulfur (S−) photosynthetic bacteria. The visible/near-IR absorption spectra of the standard LH2 complexes (B800-850) of Allochromatium (Alc.) vinosum (S+), Rhodobacter (Rba.) sphaeroides (S−), Rhodoblastus (Rbl.) acidophilus (S−), and Rhodopseudomonas (Rps.) palustris (S−), two types LH2/LH3 (B800-850 and B800-830) of Thiorhodospira (T.) sibirica (S+), and an unusual LH2 complex (B800-827) of Marichromatium (Mch.) purpuratum (S+) or the LH1 complex from Rhodospirillum (Rsp.) rubrum (S−) were measured in aqueous buffer suspensions in the presence of singlet oxygen generated by the illumination of the dye Rose Bengal (RB). The content of carotenoids in the samples was determined using HPLC analysis. The LH2 complex of Alc. vinosum and T. sibirica with a reduced content of carotenoids was obtained from cells grown in the presence of diphenylamine (DPA), and LH complexes were obtained from the carotenoidless mutant of Rba. sphaeroides R26.1 and Rps. rubrum G9. We found that LH2 complexes containing a complete set of carotenoids were quite resistant to the destructive action of singlet oxygen in the case of Rba. sphaeroides and Mch. purpuratum. Complexes of other bacteria were much less stable, which can be judged by a strong irreversible decrease in the bacteriochlorophyll (BChl) absorption bands (at 850 or 830 nm, respectively) for sulfur bacteria and absorption bands (at 850 and 800 nm) for nonsulfur bacteria. Simultaneously, we observe the appearance of the oxidized product 3-acetyl-chlorophyll (AcChl) absorbing near 700 nm. Moreover, a decrease in the amount of carotenoids enhanced the spectral stability to the action of singlet oxygen of the LH2 and LH3 complexes from sulfur bacteria and kept it at the same level as in the control samples for carotenoidless mutants of nonsulfur bacteria. These results are discussed in terms of the current hypothesis on the protective functions of carotenoids in bacterial photosynthesis. We suggest that the ability of carotenoids to quench singlet oxygen (well-established in vitro) is not well realized in photosynthetic bacteria. We compared the oxidation of BChl850 in LH2 complexes of sulfur bacteria under the action of singlet oxygen (in the presence of 50 μM RB) or blue light absorbed by carotenoids. These processes are very similar: {[BChl + (RB or carotenoid) + light] + O2} → AcChl. We speculate that carotenoids are capable of generating singlet oxygen when illuminated. The mechanism of this process is not yet clear.

IR spectra of powder hematite: effects of particle size and shape

Clay Minerals ◽  
1981 ◽  
Vol 16 (4) ◽  
pp. 375-382 ◽  
Author(s):  
Jose L. Rendon ◽  
Carlos J. Serna
Keyword(s):  
Particle Size ◽  
Ir Spectra ◽  
Ir Absorption ◽  
Surface Mode ◽  
Absorption Bands ◽  
Size And Shape ◽  
Ir Absorption Spectra ◽  
Theoretical Predictions ◽  
Particle Size And Shape ◽  
Average Size

AbstractHematites obtained by heating goethite gave different IR absorption spectra depending on the temperature of formation. Hematites formed between 250–600°C consisted of lath-like crystals (average size 0.4 ×0.08 µm) and showed, in accordance with theoretical predictions, very similar IR spectra whose absorption bands could all be assigned to surface mode vibrations. However, significantly different IR spectra were given by hematites formed between 700–950°C, the differences being correlated with variations in the size and shape of the particles. Differences observed in the IR spectra of powder hematite do not therefore justify new names for the mineral, as have been proposed in the literature.

Infrared Spectra of Some Trivalent Earth Metal Cupferrone Complexes

1974 ◽  
Vol 29 (1-2) ◽  
pp. 24-27 ◽  
Author(s):  
A. H. Abou El Ela ◽  
H. H. Afifi
Keyword(s):  
Complex Formation ◽  
Absorption Spectra ◽  
Ammonium Salt ◽  
Infrared Spectra ◽  
Earth Metal ◽  
Ir Absorption ◽  
Absorption Bands ◽  
Ir Absorption Spectra

The IR absorption spectra of the ammonium salt of cupferrone and aluminium, scandium, yttrium and lanthanum trivalent cupferrate complexes are investigated. The IR absorption bands identified in the region 400-4000 cm-1 are given and assigned. It is shown that on complex formation NO stretching frequencies are lowered and new absorption bands are observed and assigned to the M-O band.

Enhanced in vitro photocytotoxicity of water-soluble dendritic pheophorbide-a

2015 ◽  
Vol 19 (07) ◽  
pp. 830-837 ◽  
Author(s):  
Eun Ji Lee ◽  
Hyoung Jun Kong ◽  
Young-Jin Kim ◽  
Jong S. Park ◽  
Myung-Seok Choi
Keyword(s):  
Aqueous Solution ◽  
Cell Death ◽  
Singlet Oxygen ◽  
Death Rate ◽  
Water Soluble ◽  
Pheophorbide A ◽  
Absorption Bands ◽  
Cell Death Rate ◽  
A Cell

Photosensitizers can produce highly reactive singlet oxygen with exposure to visible light and are used in photodynamic therapy to treat a variety of tumors. We report on the synthesis of triethylene glycol dendron-conjugated pheophorbide-a5, a novel photosensitizer. The characteristic absorption bands (Soret and Q-bands, λmax = 405 and 670 nm, respectively) of 5 were appeared clearly in aqueous solution, due to the improved water-solubility of the dendron moiety. The value of singlet oxygen quantum yield of 5 (ΦΔ = 0.22) was higher than free pheophorbide-a (ΦΔ = 0.17) as reference in aqueous solution. Compound 5 also exhibited an enhanced in vitro phototoxicity than pheophorbide-a (PhA) in the concentration range of 1.0–5.0 μg/mL: cell viability in cells treated with 5 was reduced by ~20%, indicating a cell death rate of ~80%, while PhA treatment resulted in a cell death rate of only about 10%. These results indicate that 5 will likely be more efficient in PDT applications. Compared with free PhA, compound 5 showed highly enhanced singlet oxygen generation ability and in vitro photocytotoxicity.

Low Temperature Infrared Absorption Spectra of Cellulosics

1971 ◽  
Vol 25 (2) ◽  
pp. 196-200 ◽  
Author(s):  
Elizabeth R. McCall ◽  
Nancy M. Morris ◽  
Verne W. Tripp ◽  
Robert T. O'Connor
Keyword(s):  
Absorption Spectra ◽  
Hydroxyl Groups ◽  
Ir Absorption ◽  
Absorption Bands ◽  
Striking Increase ◽  
Peak Intensity ◽  
Ir Absorption Spectra ◽  
Infrared Absorption Spectra ◽  
Lower Temperature ◽  
Valonia Ventricosa

The ir absorption spectra of Valonia ventricosa cellulose, hydrocellulose i, and hydrocellulose ii at ambient and liquid nitrogen temperatures have been compared. Some of the bands exhibit a striking increase in peak intensity at the lower temperature. On cooling, changes to lower frequencies occur in the OH stretching region and to higher frequencies in the 1800–300 cir−1 region. The changes which were observed on cooling are undoubtedly associated with hydrogen bonding effects since the positions of absorption bands in the spectra, obtained under the same conditions, of analogous specimens containing no hydroxyl groups are not affected by temperature.

scholarly journals Synthesis, Structural and Electrical Studies of Li-Ni-Cu Nano Ferrites

2018 ◽  
Vol 26 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Shashidhar N. Adarakatti ◽  
Veeresh S. Pattar ◽  
Prashant K. Korishettar ◽  
Bhagyashri V. Grampurohit ◽  
Ravindra G. Kharabe ◽  
...  
Keyword(s):  
Spinel Ferrite ◽  
Unit Cell ◽  
Ir Absorption ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Absorption Bands ◽  
X Ray ◽  
Cell Parameters ◽  
Ir Absorption Spectra ◽  
Vegard’S Law

Abstract Li-Ni ferrite has gained great scientific elicit owing to of its unparalleled properties and applications. The copper doped Li-Ni ferrite has been synthesized by sucrose method. The structure was characterized by X-ray diffraction, which has confirmed the formation of single-phase spinel structure. X-ray diffraction and FTIR data reveals the formation of cubic structure phase. Unit cell parameters vary with copper content; overall variation of the unit cell parameters obeys Vegard’s law. The main absorption bands of spinel ferrite have appeared through IR absorption spectra recorded in the range of 300–700 cm−1. The copper concentration dependence of lattice parameters obeys Vegard’s law. DC electrical resistivity of the prepared samples decreases with increasing in the temperature which shows the semiconducting behaviour of all nano ferrites. The most prominent influence copper doping on the electrical properties of Li-Ni ferrites has been reported.

scholarly journals Bacteriochlorophyll interaction with singlet oxygen in membranes of purple photosynthetic bacteria: does the protective function of carotenoids exist?

2019 ◽  
Vol 486 (4) ◽  
pp. 504-508
Author(s):  
Z. K. Makhneva ◽  
A. A. Ashikhmin ◽  
M. A. Bolshakov ◽  
A. A. Moskalenko
Keyword(s):  
Singlet Oxygen ◽  
Photosynthetic Bacteria ◽  
Light Harvesting ◽  
Direct Action ◽  
Light Harvesting Complexes ◽  
Protective Function ◽  
Classic Work ◽  
Purple Photosynthetic Bacteria ◽  
Apoptosis Process ◽  
Mutant Cells

The direct action of singlet oxygen on the bacteriochlorophyll (BChl) of light-harvesting complexes in the membranes of four types of purple non-sulfur and sulfur photosynthesizing bacteria with and without carotenoids has been studied. It has been found that BChl in carotenoid-less samples is generally more resistant to the action of singlet oxygen compared to the control. It is assumed that carotenoids are not needed to protect BChl of bacterial light-harvesting complexes from singlet oxygen, and in the classic work of Griffith et al. [1] the apoptosis process in carotenoid-less mutant cells, which involves the destruction of complexes, the appearance of monomeric BChl and generation of singlet oxygencaused by BChl, followed by BChl oxidation, was mistakenly attributed to the protective function of carotenoids.

Near-IR Absorption Spectra for the Buckminsterfullerene Anions: An Experimental and Theoretical Study

1992 ◽  
Author(s):  
Del R. Lawson ◽  
Daniel L. Feldheim ◽  
Colby A. Foss ◽  
Peter K. Dorhoug ◽  
C. M. Elliott
Keyword(s):  
Absorption Spectra ◽  
Theoretical Study ◽  
Ir Absorption ◽  
Near Ir ◽  
Ir Absorption Spectra

Synthesis and Biological Evaluations of Organoruthenium Scaffolds: A Comprehensive Update

2018 ◽  
Vol 15 (2) ◽  
pp. 179-207
Author(s):  
Ashaparna Mondal ◽  
Priyankar Paira
Keyword(s):  
Singlet Oxygen ◽  
Anticancer Agents ◽  
Ruthenium Complexes ◽  
Chemotherapeutic Agents ◽  
Quantum Yields ◽  
Ros Generation ◽  
Standard Drug ◽  
Cellular Environment ◽  
Theranostic Agents

Background: Currently ruthenium complexes are immerging as effective anticancer agents due to their less toxicity, better antiproliferative and antimetastatic activity, better stability in cellular environment and most importantly variable oxidation and co-ordination states of ruthenium allows binding this molecule with a variety of ligands. So in past few years researchers have shifted their interest towards organoruthenium complexes having good fluorescent profile that may be applicable for cancer theranostics. Nowadays, photodynamic therapy has become more acceptable because of its easy and effective approach towards killing cancer cells. Objective: Objective of this review article is to shed light on synthesis, characterization, stability and fluorescence studies of various ruthenium [Ru(II) and Ru(III)] complexes and different bioactivity studies conducted with the synthesized compounds to test their candidacy as potent chemotherapeutic agents. Methods: Various heterocyclic ligands containing N,O and S as heteroatom mainly were prepared and subjected to complexation with ruthenium-p-cymene moiety. In most cases [Ru(η6-p-cymene)(µ-Cl)Cl]2 was used as ruthenium precursor and the reactions were conducted in various alcohol medium such as methanol, ethanol or propanol. The synthesized complexes were characterized by 1H NMR and 13C NMR spectroscopy, GC-MS, ESI-MS, elemental analysis and single crystal X-ray crystallography methods. Fluorescence study and stability study were conducted accordingly using water, PBS buffer or DMSO. Stable compounds were considered for cell viability studies. To study the efficacy of the compounds in ROS generation as photosensitizers, in few cases, singlet oxygen quantum yields in presence of light were calculated. Suitable compounds were selected for in vitro & in vivo antiproliferative, anti-invasive activity studies. Result: Many newly synthesized compounds were found to have less IC50 compared to a standard drug cysplatin. Those compounds were also stable preferably in physiological conditions. Good fluorescence profile and ROS generation ability were observed for few compounds. Conclusion: Numerous ruthenium complexes were developed which can be used as cancer theranostic agents. Few molecules were synthesized as photosensitizers which were supposed to generate reactive singlet oxygen species in targeted cellular environment in presence of a particular type of light and thereby ceasing cancer cell growth.

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