Provided is a labeling method for nucleic acid including a reaction step for hybridizing a nucleic acid probe that has a nucleotide sequence complementary to that of a nucleic acid to be labeled and contains a reactive nucleobase derivative incorporated at a position complementary to that of a target nucleobase as a target of labeling in the nucleic acid to be labeled, to the nucleic acid to be labeled; a transferring step for transferring a transfer group contained in the reactive nucleobase derivative to the nucleotide residue containing the target nucleobase in the nucleic acid to be labeled; and a labeling step for labeling the transfer group transferred to the nucleotide residue with a radioactive material.

Methods and compositions are provided for oligonucleotides that bind targets of interest. The targets include cells and microvesicles, such as those derived from various diseases. The oligonucleotides can be used for diagnostic and therapeutic purposes. The target of the oligonucleotides can be a target such as PARP1, HIST1H1B, HIST1H1D, NCL, FBL, SFPQ, RPL12, ACTB, HIST1H4A, SSBP1, NONO, H2AFJ, and DDX21, or a complex, subunit or fragment thereof.

Methods and compositions are provided for oligonucleotides that bind targets of interest. The targets include cells and microvesicles, such as those derived from various diseases. The oligonucleotides can be used for diagnostic and therapeutic purposes. The target of the oligonucleotides can be a target such as PARP1, HIST1H1B, HIST1H1D, NCL, FBL, SFPQ, RPL12, ACTB, HIST1H4A, SSBP1, NONO, H2AFJ, and DDX21, or a complex, subunit or fragment thereof.

The present disclosure, among other things, provides technologies for synthesis, including reagents and methods for stereoselective synthesis. In some embodiments, the present disclosure provides compounds useful as chiral auxiliaries. In some embodiments, the present disclosure provides reagents and methods for oligonucleotide synthesis. In some embodiments, the present disclosure provides reagents and methods for chirally controlled preparation of oligonucleotides. In some embodiments, technologies of the present disclosure are particularly useful for constructing challenging internucleotidic linkages, providing high yields and stereoselectivity.

Disclosed herein are nucleotide analogs, methods of synthesizing nucleotide analogs and methods of treating diseases and/or conditions such as a HCV infection with one or more nucleotide analogs.

Disclosed herein are nucleotide analogs, methods of synthesizing nucleotide analogs and methods of treating diseases and/or conditions such as a HCV infection with one or more nucleotide analogs.

The invention relates to a method of treating a mitochondrial DNA depletion syndrome, comprising administering to a patient a therapeutically-effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof.

The invention relates to a method of treating a mitochondrial DNA depletion syndrome, comprising administering to a patient a therapeutically-effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof.

Provided herein are compounds, compositions and methods of using thereof for treatment and/or prevention infections of viruses such as HIV and HBV by administering a certain esters and other derivatives of 4′-ethynyl-2-fluoro-2′-deoxyadenosine (EFdA) or a pharmaceutically acceptable salt thereof.

The present invention relates to a nucleoside analog having the structure of the following formula, a method for preparing the nucleoside analog, and an application of the nucleoside analog in nucleic acid sequencing, etc.

##STR00001## wherein L.sub.1, L.sub.2, and L.sub.3 are each independently a covalent bond or a covalently linked group; B is a base or a base derivative; R.sub.1 is —OH or a phosphate group; R.sub.2 is H or a cleavable group; R.sub.3 is a detectable group or a targeting group; R.sub.5 is a polymerase reaction inhibitory group; R.sub.4 is H or —OR.sub.6, wherein R.sub.6 is H or a cleavable group; and C is a cleavable group or a cleavable bond.