Modified molecular interactions of the pheophytin and plastoquinone electron acceptors in photosystem II of chlorophyll D-containing Acaryochloris marina as revealed by FTIR spectroscopy

Triplet Delocalization over the Reaction Center Chlorophylls in Photosystem II

The triplet state of chlorophyll formed by charge recombination in photosystem II (PSII) is a precursor of harmful singlet oxygen. Although main localization of the triplet state on the monomeric chlorophyll, Chl_D1, at cryogenic temperatures has been suggested, how the triplet state is delocalized on other chlorophylls remains unclear. Here, we investigated the distribution of the triplet state of chlorophyll in PSII using light-induced Fourier transform infrared (FTIR) difference spectroscopy. Measurements of triplet-minus-singlet FTIR difference spectra with PSII core complexes from cyanobacterial mutants, D1-V157H, D2-V156H, D2-H197A, and D1-H198A, in which the interactions of the 13¹-keto C═O groups of the reaction center chlorophylls, P_D1, P_D2, Chl_D1, and Chl_D2, respectively, were perturbed, identified the 13¹-keto C═O bands of the individual chlorophylls and showed that the triplet state is delocalized over all of these chlorophylls. It is suggested that the triplet delocalization plays important roles in the photoprotection and photodamage mechanisms in PSII.

The Influence of Lactic Acid Fermentation on Selected Properties of Pickled Red, Yellow, and Green Bell Peppers

Red, yellow, and green peppers are vegetables rich in natural pigments. However, they belong to seasonal vegetables and need to be treated to prolong their shelf life. One new approach to processing vegetables is to pickle them using lactic acid bacteria. The use of such a process creates a new product with high health value, thanks to the active ingredients and lactic acid bacteria. Therefore, this study aimed to evaluate the effect of the applied strain of lactic acid bacteria (LAB) on the chemical properties, including the content of active compounds (pigments) and the physical properties of the peppers. Levilactobacillus brevis, Limosilactobacillus fermentum, and Lactoplantibacillus plantarum were used for fermentation and spontaneous fermentation. The pigments, polyphenols content, and antioxidant properties were determined in the pickled peppers, as well as sugar content, color, dry matter, texture properties, and the count of lactic acid bacteria. In all samples, similar growth of LAB was observed. Significant degradation of chlorophylls into pheophytins was observed after the fermentation process. No significant differences were observed in the parameters tested, depending on the addition of dedicated LAB strains. After the fermentation process, the vitamin C and total polyphenols content is what influenced the antioxidant activity of the samples. It can be stated that the fermentation process changed the red bell pepper samples in the smallest way and the green ones in the highest way.

Identification of major carotenoids from green alga Tetraspora sp. CU2551: partial purification and characterization of lutein, canthaxanthin, neochrome, and β-carotene

The green algae Tetraspora sp. CU2551 was previously identified as a strain with high potential for biohydrogen production; however, its algal biomass characteristics changed from green to reddish orange within 43 days of biohydrogen production. The crude pigments were extracted, partially purified, and characterized by chemical determination. The present study focused on elucidating the carotenoid composition of the selected green alga Tetraspora sp. CU2551. The pigment extract was partially purified and fractionated using thin layer chromatography, and yielded two major and two minor carotenoid bands. The fractions were confirmed by high-performance liquid chromatography with a diode array detector (HPLC-DAD) before being identified and confirmed using Liquid Chromatograph-Quadrupole Time of Flight-Mass Spectrometry (LC-QTOF-MS). The spectral data of these fractions revealed four sub-fractions of interest that were lutein, canthaxanthin, neochrome, and β-carotene, which had percentages in the crude extracts of 30.57%, 25.47%, 7.89%, and 0.71%, respectively. Lutein and canthaxanthin were found to be the major carotenoid pigments present. Our findings in this present study are the first reporting of Tetraspora sp. CU2551 as a potential alternate source for carotenoid pigment production.

Formulation of Ethyl Cellulose Microparticles Incorporated Pheophytin A Isolated from Suaeda vermiculata for Antioxidant and Cytotoxic Activities

BACKGROUND

This study is designed to discover a method for delivering an efficient potent pheophytin a (pheo-a) into more absorbed and small polymeric ethyl cellulose (EC) microparticles.

METHODS

Silica gel and Sephadex LH-20 columns were used to isolate pheo-a from the chloroform extract of the edible plant, Suaeda vermiculata. Pheo-a was incorporated into EC microparticles using emulsion-solvent techniques. The antioxidant activity of pheo-a microparticles was confirmed by the level of superoxide radical (SOD), nitric oxide (NO), and reducing power (RP) methods. Meanwhile, the cytotoxic effect of the product was investigated on MCF-7 cells using MTT assay.

RESULTS

Pheo-a was isolated from S. vermiculata in a 12% concentration of the total chloroform extract. The structures were confirmed by NMR and IR spectroscopic analysis. The formulated microparticles were uniform, completely dispersed in the aqueous media, compatible as ingredients, and had a mean diameter of 139 ± 1.56 µm as measured by a particle size analyzer. Pheo-a demonstrated a valuable antioxidant activity when compared with ascorbic acid. The IC₅₀ values of pheo-a microparticles were 200.5 and 137.7 µg/mL for SOD, and NO respectively. The reducing power of pheo-a microparticles was more potent than ascorbic acid and had a 4.2 µg/mL for IC₅₀ value. Pheo-a microparticles did not show notable cytotoxicity on the MCF-7 cell line (IC₅₀ = 35.9 µg/mL) compared with doxorubicin (IC₅₀ = 3.2 µg/mL).

CONCLUSIONS

the results showed that water-soluble pheo-a microparticles were prepared with a valuable antioxidant activity in a wide range of concentrations with a noteworthy cytotoxic effect.

Rapid Determination of Chlorophyll and Pheophytin in Green Tea Using Fourier Transform Infrared Spectroscopy

The chlorophyll, pheophytin, and their proportions are critical factors to evaluate the sensory quality of green tea. This research aims to establish an effective method to determine the quantification of chlorophyll and pheophytin in green tea, based on Fourier transform infrared (FT–IR) spectroscopy. First, five brands of tea were collected for spectral acquisition, and the chlorophyll and pheophytin were measured using the reference method. Then, a relation between these two pigments and FT–IR spectroscopy were developed based on chemometrics. Additionally, the characteristic IR wavenumbers of these pigments were extracted and proved to be effective for a quantitative determination. Successively, non-linear models were also built based on these characteristic wavenumbers, obtaining coefficients of determination of 0.87, 0.80, 0.85 and 0.89; and relative predictive deviations of 2.77, 2.62, 2.26 and 3.07 for the four pigments, respectively. These results demonstrate the feasibility of FT–IR spectroscopy for the determination of chlorophyll and pheophytin.

Photosynthesis at the far-red region of the spectrum in Acaryochloris marina

Acaryochloris marina is an oxygenic cyanobacterium that utilizes far-red light for photosynthesis. It has an expanded genome, which helps in its adaptability to the environment, where it can survive on low energy photons. Its major light absorbing pigment is chlorophyll d and it has α-carotene as a major carotenoid. Light harvesting antenna includes the external phycobilin binding proteins, which are hexameric rods made of phycocyanin and allophycocyanins, while the small integral membrane bound chlorophyll binding proteins are also present. There is specific chlorophyll a molecule in both the reaction center of Photosystem I (PSI) and PSII, but majority of the reaction center consists of chlorophyll d. The composition of the PSII reaction center is debatable especially the role and position of chlorophyll a in it. Here we discuss the photosystems of this bacterium and its related biology.

Analysis of the Physiological and Molecular Responses of Dunaliella salina to Macronutrient Deprivation

The halotolerant chlorophyte Dunaliella salina can accumulate up to 10% of its dry weight as β-carotene in chloroplasts when subjected to adverse conditions, including nutrient deprivation. However, the mechanisms of carotenoid biosynthesis are poorly understood. Here, the physiological and molecular responses to the deprivation of nitrogen (-N), sulfur (-S), phosphorus (-P) and different combinations of those nutrients (-N-P, -N-S, -P-S and -N-P-S) were compared to gain insights into the underlying regulatory mechanisms of carotenoid biosynthesis. The results showed that both the growth and photosynthetic rates of cells were decreased during nutrient deprivation, accompanied by lipid globule accumulation and reduced chlorophyll levels. The SOD and CAT activities of the cells were altered during nutrient deprivation, but their responses were different. The total carotenoid contents of cells subjected to multiple nutrient deprivation were higher than those of cells subjected to single nutrient deprivation and non-stressed cells. The β-carotene contents of cells subjected to -N-P, -N-S and -N-P-S were higher than those of cells subjected to single nutrient deprivation. Cells subjected to sulfur deprivation accumulated more lutein than cells subjected to nitrogen and phosphorous deprivation. In contrast, no cumulative effects of nutrient deprivation on the transcription of genes in the carotenogenic pathway were observed because MEP and carotenogenic pathway genes were up-regulated during single nutrient deprivation but were downregulated during multiple nutrient deprivation. Therefore, we proposed that the carotenoid biosynthesis pathway of D. salina is regulated at both the transcriptional and posttranscriptional levels and that a complex crosstalk occurs at the physiological and molecular levels in response to the deprivation of different nutrients.