Ribose hydroxyl groups

Look at the "Kekule" resonance structure shown in the center of Eq. 5-4. The two negative charges flanking the dissociable proton are sufficient to hold it firmly to the ring at low pH. The proton is half dissociated only when the pH is raised to 9.2. At still higher values of pH (pfCa -12.4) a proton dissociates from a ribose hydroxyl group. 

Nucleosides form stronger complexes with lanthanides than nucleic bases because of the presence of the ribose hydroxylic group. This is reflected in the intensity of the absorption bands. Cytidine, uridine and thymidine form stronger complexes than adenosine because... 

Perhaps the most definitive structural studies of bound adducts of K-region arene oxides have been done with 7,12-dimethylbenz[a]anthracene 5,6-oxide 3, Reaction of the racemic arene oxide with guanosine in acetone-water resulted in the formation of six products, two of which were characterized as having resulted from attack by the 2 -ribosyl hydroxyl group at positions 5- and 6- of the arene oxide. In addition to the novel but precedented attack on a ribose hydroxyl group, evidence was presented indicating that only the (5R,6S)-enantiomer of the racemic arene oxide participated in the formation of these adducts. In a subsequent study, the remaining four adducts have been characterized. They consist of two... 

The diazaborines were the first class of FabI inhibitors identified. Structural studies with the FabI enzymes from E. coli and B. napus reveal that these compounds form a covalent adduct with the NAD 2 -ribose hydroxyl group and that complex formation leads to ordering of the substrate-binding loop, a loop of amino acids that covers the active site in the ternary complex (Figure 24). The size of this loop is thought to correlate with... 

Amino acids are linked to tRNA molecules by a covalent bond between the carboxyl group of the amino acid and a ribose hydroxyl group of the 3 adenosine of the acceptor stem of the tRNA. A tRNA molecule bonded to it amino acid is said to be "aminoacylated" and the enzymes that catalyze this reaction are called aminoacyl-tRNA synthetases. 

Biittner L, lavadi-Zamaghi F, Hobartner C (2014) Site-specific labeling of RNA at internal ribose hydroxyl groups terbium-assisted deoxyribozymes at work. 1 Am Chem Soc 136(22) 8131-8137. doi 10.102 l/ja503864v... 

Evidence for the structure shown in Fig. 1 was provided by the presence of ir bands in the isolated product for azide (2120 cm" ), acetophenone ketone (1690 cm ), and ribose hydroxyl groups (3300-3400 cjq-i)i8 jjy absence of a thioketone functional group as defined by the iodine-azide spot test of Feigl, which is diagnostic for thiols and thioketones and by the characteristic shift in uv spectrum of upon reaction. " In fact, with PA-Br, it was possible to follow the kinetics of the reaction spectroscopically. In 40 mM potassium phosphate, pH 7.4, at 23°, the pseudo-first-order rate constant was 133 min" M- ... 

CLOGP delivers satisfactory calculations for adenine and ribose and considers the new interaction between N-9 and the ribose oxygen atom when the groups are joined. However, it cannot yet account for any interaction of the ribose hydroxyl groups with N-3. The deoxy and dideoxy analogs are predicted much better. The values for nucleosides calculated using various programs are shown in Table 4. 

The Metal Ion Affinity of Ribose-Hydroxyl Groups Is Small. 199... 

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