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Photosynthesis
Published in Thomas M. Nordlund, Peter M. Hoffmann, Quantitative Understanding of Biosystems, 2019
Thomas M. Nordlund, Peter M. Hoffmann
Two other discoveries involving photosynthetic system adjustment to changing light levels should be mentioned. First, a primary role of carotenoids is believed to be photoprotection from high light levels, which can produce potentially damaging amounts of triplet excitations in the chlorophyll arrays. Yellow-colored carotenoid xanthophylls assist in photoprotection of green leaves. The plant and light intensity control enzymatic interconversion of two major xanthophyll forms, violaxanthin and zeaxanthin. Zeaxanthin’s triplet quenching protects lipids and the light-harvesting antennae (next section), and triggers reorganization of PSII antenna pigment-proteins. At high light levels, zeaxanthin production from violaxanthin is stimulated, reducing levels of triplets and excitations that reach the reaction centers, thus protecting the plant. Kromdijk et al. found a potentially important agricultural application of this xanthophyll cycle. The green plant response to changing light levels does not quite match the rate at which variable cloud cover typically changes the light intensity reaching plants in farm areas.14 See Figure 10.10. After production of higher levels of zeaxanthin and array reorganization to suppress high-light photodamage, plant leaves needed minutes to hours to readjust to reduced light caused by cloud cover. During this readjustment period, photosynthetic activity is corresponding reduced. Kromdijk bioengineered an accelerated interconversion and found that tobacco plant biomass production could be increased by about 15% under real field conditions. Though engineered plants would have to be produced in high quantity for this to be economically significant, the potential crop yield increase may justify the effort. The reader should notice the very biochemical/molecular-biological “flavor” of Figure 10.10: enzymes and genetic engineering are the focus; structures and mechanisms are not—a challenge for the next cadre of biophysicists. An issue deserving some thought relates to the genetic approach to this bioengineering of photosynthesis. If the new strain of crops survived, the modification would be a permanent addition to the (local) ecosystem, with its possible benefits and dangers. See miniproject 10.10. A final note on xanthophylls—readers with sensitive or aging eyes may have noticed zeaxanthin featured prominently on the labels of eye-vitamin supplements, where it purportedly supports eye health in humans.
Extraction of lutein/zeaxanthin from Arthrospira Platensis and optimisation of the saponification process using the response surface methodology
Published in Indian Chemical Engineer, 2022
Kevin Joseph Sam, Maya Suresh Nair, Sivasubramanian Velmurugan, Ravikumar Rajarathinam, Loganathan Arumugam
Cyanobacteria are the most primordial creatures that make oxygen through photosynthesis. Lipids, carbohydrates, pigments, antioxidants, and vitamins are rich in these photosynthetic microalgae. Since the ancient period, microalgae have been used for food and energy [1]. Numerous experiments have been conducted since then to extract high-value chemicals from these algae. The use of microalgae ranges from improving the extraction process to obtaining a single-valued chemical such as lipids and even biofuels [2]. Since there are countless possibilities of extraction and optimisation using these cyanobacteria, the studies involving them are expanding and evolving as the technology and techniques evolve [3]. Xanthophylls, such as lutein and zeaxanthin, are carotenoids that are yellow-coloured natural pigments, whereas zeaxanthin is a conjugate of lutein [4]. Lutein and zeaxanthin are naturally found in green vegetables, fruits, egg yolk and dietary supplements [5]. It is an eye tissue constituent that prevents cataracts and improves vision [6]. Lutein and zeaxanthin are widely used as drugs for preventing eye diseases and age-related macular degeneration [7]. Because the human body does not produce lutein or zeaxanthin, it must be obtained through dietary supplements [8]. Marigold flowers are globally utilised as the main source of lutein. They contain large quantities of lutein esters, which constitute about 80% of the carotenoids [9].
Optimization of explosion puffing drying for high-value yellow-fleshed peach crisps using response surface methodology
Published in Drying Technology, 2019
Jiangfeng Song, Gorby Gonzalles, Jun Liu, Zhuqing Dai, Dajing Li, Chunquan Liu, Min Zhang
Carotenoid extraction and analysis procedures were done based on preliminary studies. Briefly, 3 g sample powders were weighed and mixed using 30 mL of hexane-ethanol-acetone-toluene (10:6:7:7) and settled at room temperature in the dark for 4 h. After that, 2 mL 40% KOH-methanol solution was added and placed for complete saponification under nitrogen gas, 30 mL of n-Hexane and 38 mL 10% of sodium sulfate were then added for partitioning of carotenoids. The upper layer containing carotenoids was collected for C30-HPLC-DAD-MS analysis.[21,22] The total carotenoid content was calculated as the sum of major identified carotenoid compounds including β-carotene, α-carotene, lutein, zeaxanthin, and β-cryptoxanthin. The identification of carotenoids was accomplished by comparing retention times, ultraviolet (UV)-visible absorption maxima, electron ionization, and chemical ionization mass spectroscopy fragmentation patterns.
Recent developments in imaging and surgical vision technologies currently available for improving vitreoretinal surgery: a narrative review
Published in Expert Review of Medical Devices, 2023
Elham Sadeghi, Sashwanthi Mohan, Danilo Iannetta, Jay Chhablani
New combination solutions have been introduced that need more studies to be confirmed. Membrane Blue-Dual contains TB, BriB, and polyethyleneglycol (PEG) to make a heavier solution to ease deposition on the retina [156], but it may progress the outer retina and RPE changes [157]. ILM Blue, which contains BriB with PEG for retinal sedimentation, is a safe dye for ILM staining with no short-term toxicity [158]. Lutein (lutein, zeaxanthin, and BriB for vitreous stating), DoubledyneTM (BriB, TB, lutein), and TwinTM (TB, Blulife) are the other examples of new combination dyes [159,160].