L-Histidine Modulates the Catalytic Activity and Conformational Changes of the HD3 Deoxyribozyme.

: Riboswitches are functional nucleic acids that regulate biological processes by interacting with small molecules, such as metabolites, influencing gene expression. Artificial functional nucleic acids, including deoxyribozymes, have been developed through in vitro selection for various catalytic functions. In a previous study, an l-histidine-dependent deoxyribozyme was identified, exhibiting RNA cleavage activity in the presence of l-histidine resembling ribonuclease catalytic mechanisms.

Separation of the diastereomers of phosphorothioated siRNAs by anion-exchange chromatography under non-denaturing conditions.

In recent years, several small interfering RNA (siRNA) therapeutics have been approved, and most of them are phosphorothioate (PS)-modified for improving nuclease resistance. This chemical modification induces chirality in the phosphorus atom, leading to the formation of diastereomers. Recent studies have revealed that Sp and Rp configurations of PS modifications of siRNAs have different biological properties, such as nuclease resistance and RNA-induced silencing complex (RISC) loading.

Not all 2',4'-bridged modifications stabilize DNA/RNA duplexes.

2',4'-Bridged modifications such as 2'-,4'--methylene-bridged nucleotides (LNAs) and 2'-,4'--ethylene-bridged nucleotides (ENAs) provide high binding affinity for duplex formation. Stabilization by the introduction of the bridged nucleic acids is considered to be due to pre-organization. In this study, we found that the introduction of 2',4'--bridged 2'-deoxynucleotides (CRNs; Conformationally Restricted Nucleotides) into DNA/RNA duplexes leads to destabilization, as opposed to the previously accepted notion that 2',4'-bridged modifications always lead to stabilization.

An improved synthesis of 2'-,4'--ethylene nucleic acid (ENA) and thermodynamic studies of duplex formation containing the guanosine ENA unit.

Oligonucleotides containing 2'-,4'--ethylene nucleic acids (ENA) have been proven highly effective for antisense therapeutics. 2'-,4'--Ethyleneguanosine and its phosphoramidite were previously obtained from 3,5-di--benzy1-4--(-tolulenesulfonyloxyethyl)-1,2-di--acetyl-α-D-erythropentofuranose by glycosylation, but with limited efficiency. Using 3,5-di--benzy1-4--(2--butyldiphenylsilyloxyethyl)-1,2-di--acetyl-α-D-erythropentofuranose as an alternative substrate, we developed several methods to obtain 2'-,4'--ethyleneguanosine derivatives with much higher yields than previously reported.