NMR spectroscopy has been utilized to demonstrate that oligonucleotide d(TG4T) in contrast to the commonly excepted notion does not form a single tetrameric G-quadruplex in solution. One of the two coexisting structures exhibits a T-quartet in addition to the four G-quartets. Substitution of T for U at the 5’-end of the parent sequence leads to dimerization of G-quadruplex units. We have established that NH4+ ion movement along the central ion cavity of tetramolecular G-quadruplexes is ca. 10 times faster in comparison to bi- and monomolecular analogues.
COBISS.SI-ID: 4487962
Using NMR spectroscopy we described the structure of a 42-nt dimeric siRNA construct, which consisted of alternating 2'-F and 2'-OMe modifications on the sugar moiety. 3D structure showed that the construct adopts an antiparallel double helical structure with 3' UU overhangs. The stability of individual base pairs along the construct is not uniform. The imino protons of some base pairs exchange with solvent, which suggests a difference in the stability of duplex ends and is of importance for the correct incorporation of the antisense siRNA strand into RISC.
COBISS.SI-ID: 4541466
We have determined solution-state NMR structure of a 34-nt RNA construct, which mimics the interaction of let-7 miRNA to the first complementary binding site, LCS1. Structure shows two non-canonical parts characteristic for the seed region: an asymmetric internal loop (residues U9-G10 and G23-U24-U25) and a bulge (residue A30). The internal loop demonstrates that residues G23 and U25 are bulged-out and residue U24 looped-in. Residue A30 is not stacked-in but points into the minor groove.
COBISS.SI-ID: 4554778
We have prepared a new series of P-stereogenic 1,2-bis[(o-RO-phenyl)(phenyl)phosphino]ethane and named it ''R-SMS-Phos'' series. The methyl groups of the o-anisyl of the DiPAMP ligand were switched to various branched hydrocarbon chains. The new ligands display large increase in reaction rates and exhibit high enantioselectivity in the asymmetric hydrogenation of a wide range of olefins. The overall results obtained with ''t-Bu-SMS-Phos'' ligand are amongst the best ever reported in the rhodium-phosphine catalyzed hydrogenation.
COBISS.SI-ID: 4355098
A series of R-SMS-Phos ligands was prepared and evaluated in the Rh(I)-catalyzed asymmetric hydrogenation of a set of olefins showing a marked influence of the cyclic nature and structure of the R groups. Overall, cPen- and Cy-SMS-Phos performed efficiently while Ph- and Bn-SMS-Phos exhibited slower kinetics and lower ee’s even when compared with C6F5CH2-SMS-Phos. The Rh(I)-(Cy-SMS-Phos) catalyst was screened under mild conditions displaying excellent enantioselectivities and high TOFs. Cases of catalysis under catalyst- or substrate-control were identified.
COBISS.SI-ID: 4447514