Extended Peptide Nucleic Acid Nucleobases Based on Isoorotic Acid for the Recognition of A–U Base Pairs in Double-Stranded RNA

Peptide nucleic acids (PNA) with extended isoorotamide containing nucleobases ( I _o ) were designed for binding A–U base pairs in double-stranded RNA. Isothermal titration calorimetry and UV thermal melting experiments revealed improved affinity for A–U using the Io scaffold in PNA. PNAs having four sequential Io extended nucleobases maintained high binding affinity.     

Projection-reconstruction of three-dimensional NMR spectra

When three-dimensional NMR spectra are presented as two stereoscopic images, they create a convincing three-dimensional impression for the viewer. In an extension of this principle, we record plane projections of a three-dimensional spectrum at different angles, and use this limited information to reconstruct the entire spectrum. Projections onto different skew planes are derived by Fourier transformation of signals acquired while the two evolution parameters are incremented simultaneously at different rates. By limiting the amount of data gathering, this offers an appreciable economy of instrument time. Normally two to six different projections suffice, depending on the complexity of the spectra. There is an order-of-magnitude speed advantage over the conventional methodology, where both evolution dimensions must be explored independently. Results are presented for reconstructed HNCA and HN(CO)CA spectra of ubiquitin and the HNCO spectrum of a 187-residue protein HasA.     

Monomers for preparation of amide linked RNA: synthesis of C3′-homologated nucleoside amino acids from d-xylose

Amides as neutral and hydrophobic internucleoside linkages in RNA are highly interesting modifications for RNA interference. However, testing amides in siRNAs is hampered by the shortage of efficient methods to synthesize the monomeric building blocks, the nucleoside amino acid equivalents. This paper reports an efficient synthesis of protected ribonucleoside 5′-amino 3′-carboxylic acids from d-xylose in 14 steps 7% overall yield. The key features that ensure efficiency and ease of operations are chemoselective reduction of the ester and minimization of protecting group manipulation.     

Triple helical recognition of pyrimidine inversions in polypurine tracts of RNA by nucleobase-modified PNA

Peptide nucleic acids containing 2-pyrimidinone (P) and 3-oxo-2,3-dihydropyridazine (E) heterocycles recognized C-G and U-A inversions in a polypurine tract of double helical RNA with high affinity and sequence selectivity at pH 6.25. E-modified PNA bound strongly to bacterial A-site RNA, while no binding was observed to the human A-site RNA.     

Natural-abundance 15N--13C correlation spectra of vitamin B-12

Two-dimensional nitrogen-carbon NMR correlation spectra have been derived by a new reconstruction technique based on standard two-dimensional HMQC and HMBC spectra, and operating with natural 15N and 13C isotopic abundances. Compared with conventional three-dimensional spectroscopy in which 15N and 13C spins must be present in the same molecule, the reconstruction method offers two orders of magnitude improvement in sensitivity. Vitamin B-12 serves as an illustrative example.     

Obtaining ZnO/CIS heterostructures

ZnO/CuInSe₂ heterostructures were obtained by sequential evaporation of elements. Firstly, a layer of Zn was deposited on the glass substrate by the magnetron sputtering method in vacuum. Needle-shaped nanostructures of ZnO were grown from the prepared Zn films by thermal annealing in the air. Secondly, Se, In and Cu layers were sequentially deposited onto these structures. The obtained samples were then annealed at 400 °C to form the CuInSe₂ (CIS) compound. The morphology, composition and phase identification were obtained using the scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analysis methods.