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.
Nutrition for health and sports performance
Nick Draper, Helen Marshall in Exercise Physiology, 2014
Figure 2.7 illustrates the bonding for the three nutritionally important hexoses: fructose, glucose and galactose. Often monosaccharides bond in a three dimensional structure and so can be represented more correctly using a ring notation (Figure 2.8) rather than as shown in Figure 2.7 as this is closer to their structure in reality. The differences between the simple sugars in this group come from the distribution of the hydrogen and oxygen atoms. Glucose (sometimes referred to as dextrose) is a building block for more complex sugars such as cellulose (found in plants) and is perhaps the most plentiful organic substance on earth. Glucose forms naturally in plants and animals break down (catabolise) carbohydrates to glucose through digestion. Fructose, another common simple sugar is found in fruits and honey. Galactose is most commonly found as a building block for the milk sugar lactose but is also present in peas. Ribose and deoxyribose are important pentoses for humans as they form part of the structure for DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), the blueprint and genetic coding for the development of each cell in our bodies.
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 pharmacokinetic 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
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).
Chromosome aberration in typical biological systems under exposure to low- and high-intensity magnetic fields
Published in Electromagnetic Biology and Medicine, 2020
Emanuele Calabrò, Hit Kishore Goswami, Salvatore Magazù
Chromosomes are molecules composed of the deoxyribonucleic acid (DNA) that represents the genetic material of a living being. In human beings, there are 22 pairs of chromosomes and 2 sex chromosomes for a total of 46. DNA is an organic polymer composed of monomers that are called nucleotides. They consist of a phosphate group and a nitrogenous base linked to deoxyribose by the so-called N-glycoside bond. The nitrogenous bases that can be used in nucleotide formation are adenine, cytosine, guanine and thymine disposed in base pairs of adenine-thymine (A-T) and guanine-cytosine (G-C) that in aqueous solutions are linked one each other by hydrogen bonds forming a double helix structure because of the repulsions between the negative charge of phosphate groups. This double helix structure is bound to proteins (the histones) that have positively charged amino acids in order to bind the DNA which is negatively charged and is wrapped around the core of histone of eight protein subunits forming the nucleosome. About 200 base pairs of DNA are coiled around each histone. This coil is untwisted generating a negative superturn per nucleosome that is the active chromatin.
Related Knowledge Centers
- Arabinose
- DNA
- Enantiomer
- Monosaccharide
- Nucleic Acid
- Deoxy Sugar
- Sugar
- Hydroxy Group
- Fischer Projection
- L-Deoxyribose