Deprotection of allylgroups from internucleotide phosphotriester functions can be achieved not only with Pdo-mediated cleavage in the presence of an appropriate nucleophile but also under standard conditions for DNA fragments using conc. ammonia at elevated temperature. This observation widens the scope for chemical phosphorylation procedures based on phosphoramidite chemistry and creates possibilities
Solid-Phase Oligodeoxynucleotide Synthesis: A Two-Step Cycle Using Peroxy Anion Deprotection
作者:Agnieszka B. Sierzchala、Douglas J. Dellinger、Jason R. Betley、Tadeusz K. Wyrzykiewicz、Christina M. Yamada、Marvin H. Caruthers
DOI:10.1021/ja030376n
日期:2003.11.1
phosphoramidite based oligodeoxynucleotide two-step synthesismethod has been developed. Keys to this method are replacement of the 5'-dimethoxytrityl blocking group with an aryloxycarbonyl and the use of N-dimethoxytrityl protection for the exocyclic amines of adenine and cytosine. With these modifications, coupling of each 2'-deoxynucleoside 3'-phosphoramidite to the growing oligodeoxynucleotide
Compounds for protecting hydroxyls and methods for their use
申请人:——
公开号:US20020015961A1
公开(公告)日:2002-02-07
A hydrocarbyldithiomethyl-modified compound of the Formula:
R
1
—O—CH
2
—S—S—R
2
or a salt thereof wherein R
1
is an organic molecule and R
2
is a hydrocarbyl is useful for protecting and/or blocking hydroxyl groups in organic molecules such as nucleotides. The hydrocarbyldithiomethyl-modified compounds can also be used for chemically synthesizing oligonucleotides and for sequencing nucleic acid compounds.
Synthetic Approach to Stop-Codon Scanning Mutagenesis
作者:Lihua Nie、Jason J. Lavinder、Mohosin Sarkar、Kimberly Stephany、Thomas J. Magliery
DOI:10.1021/ja106894g
日期:2011.4.27
A general combinatorial mutagenesis strategy using common dimethoxytrityl-protected mononucleotide phosphoramidites and a single orthogonally protected trinucleotide phosphoramidite (Fmoc-TAG; Fmoc = 9-fluorenylmethoxycarbonyl) was developed to scan a gene with the TAG amber stop codon with complete synthetic control. In combination with stop-codon suppressors that insert natural (e.g., alanine) or unnatural (e.g., p-benzoylphenylalanine, Bpa) amino acids, a single DNA library can be used to incorporate different amino acids for diverse purposes. Here, we scanned TAG codons through part of the gene for a model four-helix bundle protein, Rop, which regulates the copy number of ColE1 plasmids. Alanine was incorporated into Rop for mapping its binding site using an in vivo activity screen, and subtle but important differences from in vitro gel-shift studies of Rop function are evident. As a test, Bpa was incorporated using a Phe14 amber mutant isolated from the scanning library. Surprisingly, Phel4Bpa-Rop is weakly active, despite the critical role of Phe14 in Rop activity. Bpa is a photoaffinity label unnatural amino acid that can form covalent bonds with adjacent molecules upon UV irradiation. Irradiation of Phe14Bpa-Rop, which is a dimer in solution like wildtype Rop, results in covalent dimers, trimers, and tetramers. This suggests that Phel4Bpa-Rop weakly associates as a tetramer in solution and highlights the use of Bpa cross-linking as a means of trapping weak and transient interactions.
In connection with the synthesis of guanosine-capped of oligodeoxynucleotides on polymer supports, we found an unprecedented Si-O bond cleavage reaction, which occurred when polymer-linked oligodeoxynucleoticles having unprotected internucleotidic phosphate groups were allowed to react with the guanosine 5'-phosphorimidazolide derivative 18 in the presence of 4-nitro-6-(trifluoromethyl)-1H-benzotriazol-1-ol (Ntbt-OH) as an effective activator in pyridine. This side reaction was confirmed by the fact that the liquid-phase reaction of DMTrTpT-O-Si(iPr(2))OEt 42 with a simpler model compound. methyl phosphorimidazolide 34. in the presence of Ntbt-OH gave DMTrTpT 43. It turned out that the side reaction hardly occurs without unprotected internucleotidic phosphate groups on oligodeoxyriucleotides. The detailed study of this side reaction disclosed that Ntbt-OH directly attacks the Si-atom to release oligonucleotides from the resin. It is likely that Ntbt-OH serves as a very strong nucleophile in pyridine, especially to the Si-atom of the linker.