Radicals in Cellular Structures
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BIOPHYSICS
Radicals in Cellular Structures Yu. A. Shapovalova, *, P. P. Gladyshevb, S. T. Tuleukhanova, E. V. Shvetsovaa, and Zh. T. Abdrasulovaa aal-Farabi
Kazakh National University, Almaty, 050040 Republic of Kazakhstan Dubna State University, Dubna, Moscow oblast, 141982 Russia *e-mail: [email protected]
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Received December 5, 2019; revised February 18, 2020; accepted May 25, 2020
Abstract—The involvement of natural radicals in single-electron processes of cell activity is considered. It was shown that coenzymes that have intermediate free radical quinoid and semichinoid forms can interact with carotenoids to form complexes with a charge transfer with an absorption band of 1030 nm. Moreover, the complex can perform an active light-harvesting function during photosynthesis up to 1100 nm, with the energy transfer from chlorophylls a and b to the complex. Studies of the sorption of the alcoholdehydrogenase–nicotinamide adenine dinucleotide enzyme–cofactor system on a hydrophobic electrically conductive carrier showed that the activity of the enzyme–cofactor system is at its maximum for sequential sorption of the coenzyme and then the apoenzyme. The orientation of the biocatalytic system on the immobilization matrix is of great importance. Keywords: radicals, coenzymes, carotenoids, charge-transfer complexes, sorption, immobilization DOI: 10.1134/S000635092004020X
INTRODUCTION Radicals are atoms or molecules with an unpaired electron, which determines their high instability and activity associated with the tendency of radicals to accept or donate an extra electron. In biological objects, natural and foreign radicals are distinguished. It is known that foreign oxygen-based radicals are formed as a result of physical or chemical effects on the cells of living organisms. Radicals damage amino acids and proteins and disorganize cellular structures and biological membranes. The role of foreign free radicals in the development of cancer, atherosclerosis, myocardial infarction, stroke, and ischemia, as well as diseases of the nervous and immune systems, lungs, liver, kidneys, blood, and skin has been proven. In addition, they cause premature aging [1, 2]. Biological objects have specialized enzyme systems to reduce the aggressive effect of radicals on humans and animals, as well as natural bioorganic compounds and synthetic compounds that provide antioxidant defense to neutralize radicals. The role of antioxidant protection is performed by biocatalysts such as superoxide dismutase, catalase, glutathione-dependent peroxidase, and transferase, which reduce the detrimental effects of radicals by removing peroxide compounds. A large number of phenolics that exhibit antioxidant properties have been isolated, for example, vitamins E (α-tocopherol), K1 (phylloquinone), and Abbreviations: ADH, alcohol dehydrogenase, LDH, lactate dehydrogenase.
K2 (menaquinone), ubiquinones, tryptophan, phenylalanine, as well as a significant number of plant and animal pigments (carotenoids , flavonoids, and phenolcarboxylic acids) [3].
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