Nucleic Acids
Danilo D. Lasic in LIPOSOMES in GENE DELIVERY, 2019
Nucleotides are molecules that contain a nitrogenous base, a pentose, and phosphoric acid. Bases can be purines or pyrimidines. The sugar group in DNA is deoxyribose and is ribose in RNA, as shown in Figure 3-2. DNA contains two purines, adenine (A) and guanine (G), and two pyrimidines, cytosine (C) and thymine (T), while RNA contains uracil (U) instead of thymine. DNA is composed of a linear sequence of nucleotides that are joined together through phosphodiester linkages spanning the 5′-hydroxyl group of pentose with the 3′-hydroxyl group of the pentose of the next nucleoside. Alternating phosphate and pentose groups form the covalent backbone on which the bases are attached as side groups. Figure 3-3 shows three different presentations of the chemical structure of DNA. This linear polymer is in the helical conformation and matches with a complementary helix into a double helix, which is bound together via hydrogen bonds between bases: adenine forms two hydrogen bonds with thymine and guanine forms three with cytosine. Figure 3-4 shows the chemical structures of the four bases as well as their pairing via hydrogen bonds. Because different DNA molecules have different proportions of G≡C and A=T pairs, their physical properties differ. For instance, temperature of denaturation can vary from 60 to 95°C and increases with GC content. In pure polynucleotides (polyA, for example) the transition is very sharp (about 1°), while long DNA can exhibit gradual melting, with some parts of molecules being separated and others not.
Bleomycin Assay for Catalytic Iron Salts in Body Fluids
Robert A. Greenwald in CRC Handbook of Methods for Oxygen Radical Research, 2018
Bleomycin is the name given to a mixture of structurally similar antitumor antibiotics. It has a number of clinical applications21 and is readily available commercially (e.g., Sigma Chemical Corp.) as its sulfate. Care should be taken in handling it since inhalation of the powder has the potential to cause lung damage,22 which is one of the side effects of bleomycin therapy. Bleomycin binds a number of metal ions, but only its complex with iron salts is capable of releasing TBA-reactive material from DNA.21,26 During DNA degradation, the deoxyribose sugar is cleaved to give a product that forms a colored adduct with thiobarbituric acid under acidic conditions.23,24 Once the bleomycin-iron complex has bound to the DNA, the degradation cannot be prevented by antioxidants25 and so the assay can be applied directly to body fluids.
Nutritional Ergogenic Aids: Introduction, Definitions and Regulatory Issues
Ira Wolinsky, Judy A. Driskell in Nutritional Ergogenic Aids, 2004
assay in which deoxyribose is used as a detector molecule show that addition of a-lipoic acid to hepatic microsomes spares degradation of deoxyribose.13 The a-lipoic acid apparently chelates Fe+2 and diminishes the amount of hydroxyl radical detectable by deoxyribose. Oxidative stress is induced when vitamin C and iron are incubated together. The vitamin C chelates the iron and reduces it to Fe+2; subsequently Fe+2 transfers one electron to oxygen and promotes ROS generation. If vitamin C is present in a 50-fold excess of iron, a-lipoic acid is unable to compete with vitamin C for chelation, and lipid peroxidation occurs.13 Similarly, complexation of Cu+2 by a-lipoic acid explains the protection in copper-induced lipid peroxidation.14
Clinical pharmacology of siRNA therapeutics: current status and future prospects
Published in Expert Review of Clinical Pharmacology, 2022
Ahmed Khaled Abosalha, Jacqueline Boyajian, Waqar Ahmad, Paromita Islam, Merry Ghebretatios, Sabrina Schaly, Rahul Thareja, Karan Arora, Satya Prakash
Chemical modification acts as a significant strategy to optimize the delivery of naked siRNAs to overcome some delivery obstacles. The negatively charged phosphodiester skeleton of siRNA represents a powerful barrier to its cellular uptake through the anionic lipid bilayers of the cell membrane. Furthermore, the original structure of siRNA candidates makes them highly susceptible to degradation by endonucleases with a poor pharmaco*kinetic profile. Also, hazardous off-target side effects such as the unintended block of expression of other genes have been reported besides triggering the host immune response [48]. Consequently, chemically modified siRNA therapeutics can offer a high degree of cellular uptake and resistance against endonucleases in addition to minimizing the harmful off-target effects and antigenicity. Generally, both DNA and RNA are composed of nucleotides as building blocks. Nucleotides compromise a ribose or 2′-deoxyribose sugar moiety with 1′-nucleobase and 3′-phosphate groups. Four sites of chemical modifications to siRNA molecules were previously proposed, including the ribose sugar, nucleobase, phosphate link, and strand terminus [17].
Liposome-encapsulated glycyrrhizin alleviates hyperglycemia and glycation-induced iron-catalyzed oxidative reactions in streptozotocin-induced diabetic rats
Published in Journal of Liposome Research, 2022
Subhrojit Sen
Table 3 represents the iron-catalyzed free radical-mediated lipid peroxidation in the absence or presence of H2O2. Lipid peroxidation was found to be higher in DC + H2O2 samples in comparison to that of NC + H2O2. Treatment of diabetic rats with liposome-encapsulated glycyrrhizin prevented lipid peroxidation and the degree of inhibition was more prominent in DTbd + H2O2 samples compared to that of DTG + H2O2 (NC + H2O2 vs. DC + H2O2 and DC + H2O2 vs. DTbd + H2O2p < .05). Table 4 represents the iron-catalyzed free radical-mediated deoxyribose degradation in the absence or presence of H2O2. TBA reactivity expressed in terms of fluorescence arbitrary units was found to be significantly higher in DC samples compared to that of controls (NC). Deoxyribose degradation was found to be higher in DC + H2O2 samples in comparison to that of NC + H2O2. Treatment of diabetic rats with free glycyrrhizin or liposome-encapsulated glycyrrhizin prevented deoxyribose degradation though the degree of inhibition was more prominent in DTbd + H2O2 samples compared to that of DTG + H2O2 (NC + H2O2 vs. DC + H2O2 and DC + H2O2 vs. DTbd + H2O2p < .05).
Antioxidant and cytoprotective properties of loganic acid isolated from seeds of Strychnos potatorum L. against heavy metal induced toxicity in PBMC model
Published in Drug and Chemical Toxicology, 2022
Alagarsamy Abirami, Simran Sinsinwar, Perumal Rajalakshmi, Pemaiah Brindha, Yamajala B. R. D. Rajesh, Vellingiri Vadivel
Hydroxyl radical scavenging activity was determined by deoxyribose assay (Samak etal. 2009). Fe (II) is oxidized to Fe (III) spontaneously and releases one electron by Fenton’s reaction and that electron attacks hydrogen peroxide to form hydroxyl radical. The formed hydroxyl radical can degrade deoxyribose and produce malondialdehyde (MDA) which can be measured by thiobarbituric acid reactive substances (TBARS) reaction. Thiobarbituric acid (TBA) can reacts with MDA in acidic condition to form pink chromogen, which has absorption maxima at 532 nm. With 100 µl of different concentrations of isolated compound (400, 40, 0.4, 0.04, 0.004 µg/mL), 500 µl of 10 mM deoxyribose, 500 µl of 10 mM ferrous sulfate, and 400 µl of 10 mM hydrogen peroxide were added and incubated for 5 min at room temperature. Then 500 µl of each TBA and trichloro acetic acid (TCA) were added, incubated for 15 min at 90 °C, cooled and absorbance was measured at 532 nm. The hydroxyl radical scavenging activity was calculated and compared with standard eugenol.
