Browsing by Subject "Chlorophyll"

Now showing 1 - 4 of 4

Open Access
Differential effects of nitrogen and sulfur deprivation on growth and biodiesel feedstock production of Chlamydomonas reinhardtii
(2012) Cakmak, T.; Angun P.; Demiray, Y.E.; Ozkan, A.D.; Elibol, Z.; Tekinay, T.
Biodiesel production from microalgae is a promising approach for energy production; however, high cost of its process limits the use of microalgal biodiesel. Increasing the levels of triacylglycerol (TAG) levels, which is used as a biodiesel feedstock, in microalgae has been achieved mainly by nitrogen starvation. In this study, we compared effects of sulfur (S) and nitrogen (N) starvation on TAG accumulation and related parameters in wild-type Chlamydomonas reinhardtii CC-124 mt(-) and CC-125 mt(+) strains. Cell division was interrupted, protein and chlorophyll levels rapidly declined while cell volume, total neutral lipid, carotenoid, and carbohydrate content increased in response to nutrient starvation. Cytosolic lipid droplets in microalgae under nutrient starvation were monitored by three-dimensional confocal laser imaging of live cells. Infrared spectroscopy results showed that relative TAG, oligosaccharide and polysaccharide levels increased rapidly in response to nutrient starvation, especially S starvation. Both strains exhibited similar levels of regulation responses under mineral deficiency, however, the degree of their responses were significantly different, which emphasizes the importance of mating type on the physiological response of algae. Neutral lipid, TAG, and carbohydrate levels reached their peak values following 4 days of N or S starvation. Therefore, 4 days of N or S starvation provides an excellent way of increasing TAG content. Although increase in these parameters was followed by a subsequent decline in N-starved strains after 4 days, this decline was not observed in S-starved ones, which shows that S starvation is a better way of increasing TAG production of C. reinhardtii than N starvation. © 2012 Wiley Periodicals, Inc.
Open Access
Electronic excited states of the CP29 antenna complex of green plants: a model based on exciton calculations
(Springer / Kluwer Academic Publishers, 2000) İşerı, E. İ.; Albayrak, D.; Gülen, D.
We have suggested a model for the electronic excited states of the minor plant antenna, CP29, by incorporating a considerable part of the current information offered by structure determination, site-directed mutagenesis, and spectroscopy in the modeling. We have assumed that the electronic excited states of the complex have been decided by the chlorophyll-chlorophyll (Chl) and Chl-protein interactions and have modeled the Coulombic interaction between a pair of Chls in the point-dipole approximation and the Chl-protein interactions are treated as empirical fit parameters. We have suggested the Qy dipole moment orientations and the site energies for all the chlorophylls in the complex through a simultaneous simulation of the absorption and linear dichroism spectra. The assignments proposed have been discussed to yield a satisfactory reproduction of all prominent features of the absorption, linear and circular dichroism spectra as well as the key spectral and temporal characteristics of the energy transfer processes among the chlorophylls. The orientations and the spectral assignments obtained by relatively simple exciton calculations have been necessary to provide a good point of departure for more detailed treatments of structure-function relationship in CP29. Moreover, it has been discussed that the CP29 model suggested can guide the studies for a better understanding of the structure-function relationship in the major plant antenna, LHCII.
Open Access
Glycosylated conjugated oligomer and chlorophyll based nanoparticles for photodynamic therapy
(2023-01) Oduncu, Ezgi
Nanomaterial-based therapeutic agents are drawing a lot of attention because numerous capabilities, including drugs, targeting groups, and photoactive units, can be combined on one platform to treat infectious diseases and cancer. In this regard, two different nanomaterials and their nanomedicine applications were re-ported. Firstly, red-emitting glycosylated conjugated oligomer (COL) nanopar-ticle was prepared and hybrid conjugation with gold nanoparticles was prepared by the nanoprecipitation method in order to examine photothermal applications. Due to their authentic electronic and optical characteristics, showing high sin-glet oxygen production ability, enabling control of the sizes of nanoparticles by acetyl groups in the side chains, enhancing their stability, and improving cell permeability via the hydrophobic effect they are promoting photosensitizers for photodynamic therapy. Secondly, chlorophyll, a natural photo absorbent, was ex-tracted from spinach leaves, and chlorophyll nanoparticles were prepared by nano-precipitation method because of their promoting properties which are high bio-compatibility, low production cost, and natural reductive chemical atmosphere, containing plenty of hydrogen atoms and being environmentally friendly. Then, hybrid conjugation with gold nanoparticles was prepared to investigate photother-mal therapy application. Both of the nanoparticles showed a high generation ability of reactive oxygen species (ROS) even at low light intensities and short exposure times which makes nanoparticles an ideal photosensitizer. From the antibacterial experiment, when Gram-negative (Escherichia coli, E. coli) bacteria were incubated with chlorophyll-based nanoparticles, a reduction up to 2.8-log and 2.33-log in colony-forming units (CFUs) was obtained under light irradiation for Chl-Au and Chl nanoparticles, respectively. Also, these nanoparticles showed minimal dark cytotoxicity (0.32-log and 0.15-log). On the other hand, conjugated oligomer-based nanoparticles precipitated in bacterial suspension and were un-able to pass across the cell wall of bacteria which was proved by SEM images and 4 mm and 5 mm inhibition zone were recorded for COL and COL-Au nanopar-ticles which are highly lower than ampicillin (7 mm). Along with these results, it is deduced that conjugated oligomer nanoparticles are not proper for antibac-terial photodynamic applications although the interaction between the bacterial cell wall and nanoparticle was promoted with gold conjugation. For anticancer photodynamic therapy applications, MCF-7 breast cancer cells were treated with these nanoparticles in the dark and under white light illumination for 20 min-utes, and the decline in cell viability was recorded at 50 %, 60 %, and 58 %, 72 %reduction for Chl, Chl-Au, and COL, Chl-Au nanoparticles, respectively. Also, they demonstrated dark cytotoxicity with the increment of concentration. Ad-ditionally, they also demonstrated the capacity for cellular imaging due to their inherent fluorescent properties, which might be used for image-guided PDT ap-plications. Along with this, the cytotoxicity results were supported by displaying the cellular uptake of nanoparticles and their surrounding the nucleus of breast cancer cells.
Open Access
Nitrogen and sulfur deprivation differentiate lipid accumulation targets of chlamydomonas reinhardtii
(2012) Cakmak, T.; Angun P.; Ozkan, A.D.; Cakmak, Z.; Olmez, T.T.; Tekinay, T.
Nitrogen (N) and sulfur (S) have inter-related and distinct impacts on microalgal metabolism; with N starvation having previously been reported to induce elevated levels of the biodiesel feedstock material triacylglycerol (TAG), while S deprivation is extensively studied for its effects on biohydrogen production in microalgae.1,2 We have previously demonstrated that N- and S-starved cells of Chlamydomonas reinhardtii display different metabolic trends, suggesting that different response mechanisms exist to compensate for the absence of those two elements.3 We used C. reinhardtii CC-124 mt(-) and CC-125 mt(+) strains to test possible metabolic changes related to TAG accumulation in response to N and S deprivation, considering that gamete differentiation in this organism is mainly regulated by N.4 Our findings contribute to the understanding of microalgal response to element deprivation and potential use of element deprivation for biodiesel feedstock production using microalgae, but much remains to be elucidated on the precise contribution of both N and S starvation on microalgal metabolism. © 2012 Landes Bioscience.