Isolation of (CO)1- and (CO2)1- radical complexes of rare earths via Ln(NR2)3/K reduction and [K2(18-crown-6)2]2+ oligomerization

Deep-blue solutions of Y(2+) formed from Y(NR(2))(3) (R = SiMe(3)) and excess potassium in the presence of 18-crown-6 at -45 °C under vacuum in diethyl ether react with CO at -78 °C to form colorless crystals of the (CO)(1-) radical complex, {[(R(2)N)(3)Y(μ-CO)(2)][K(2)(18-crown-6)(2)]}(n), 1. The polymeric structure contains trigonal bipyramidal [(R(2)N)(3)Y(μ-CO)(2)](2-) units with axial (CO)(1-) ligands linked by [K(2)(18-crown-6)(2)](2+) dications. Byproducts such as the ynediolate, [(R(2)N)(3)Y](2)(μ-OC≡CO){[K(18-crown-6)](2)(18-crown-6)}, 2, in which two (CO)(1-) anions are coupled to form (OC≡CO)(2-), and the insertion/rearrangement product, {(R(2)N)(2)Y[OC(═CH(2))Si(Me(2))NSiMe(3)]}[K(18-crown-6)], 3, are common in these reactions that give variable results depending on the specific reaction conditions. The CO reduction in the presence of THF forms a solvated variant of 2, the ynediolate [(R(2)N)(3)Y](2)(μ-OC≡CO)[K(18-crown-6)(THF)(2)](2), 2a. CO(2) reacts analogously with Y(2+) to form the (CO(2))(1-) radical complex, {[(R(2)N)(3)Y(μ-CO(2))(2)][K(2)(18-crown-6)(2)]}(n), 4, that has a structure similar to that of 1. Analogous (CO)(1-) and (OC≡CO)(2-) complexes of lutetium were isolated using Lu(NR(2))(3)/K/18-crown-6: {[(R(2)N)(3)Lu(μ-CO)(2)][K(2)(18-crown-6)(2)]}(n), 5, [(R(2)N)(3)Lu](2)(μ-OC≡CO){[K(18-crown-6)](2)(18-crown-6)}, 6, and [(R(2)N)(3)Lu](2)(μ-OC≡CO)[K(18-crown-6)(Et(2)O)(2)](2), 6a.     

An approach to therapeutic agents through selective targeting of destabilised nucleic acid duplex sequences

The binding of ΔΔ/ΛΛ-[{Ru(phen)(2)}(2)(μ-bb(n))](4+) {where phen = 1,10-phenanthroline, bb(n) = 1,n-bis[4(4'-methyl-2,2'-bipyridyl)]-alkane (ΔΔ/ΛΛ-Rubb(n))} to the non-self complementary oligonucleotide 5'-d(CGCGATAAGCCGC·5'-GCGGCATTACGCG) (3-DB) has been examined using a 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) displacement assay. The 3-DB oligonucleotide contains two single adenine bulge nucleotides that are separated by three base pairs. (1)H NMR spectroscopy data demonstrated that the adenine bases are intra-helical and that the segment containing the two bulge nucleotides and the three A·T base pairs between the bulges forms a destabilised segment within the stable duplex oligonucleotide. The DAPI displacement assay demonstrated that ΔΔ-Rubb(7)-bound 3-DB with higher affinity than the other members of the ΔΔ/ΛΛ-Rubb(n) series. Molecular models suggested that the seven-carbon chain length in ΔΔ-Rubb(7) was ideal to span the distance between the two bulge sites. The binding of ΔΔ-Rubb(7) to 3-DB was also studied by (1)H NMR spectroscopy and molecular modelling. The selective changes in chemical shifts for the resonances from 3-DB upon addition of ΔΔ-Rubb(7) suggested that the metal complex specifically bound at the destabilised segment between A(5) and A(19). Observation in NOESY spectra of NOE cross peaks between 3-DB and ΔΔ-Rubb(7) confirmed that one of the ruthenium centres bound at the A(5) bulge site, with the other metal centre positioned at the A(19) bulge. In addition, ΔΔ-Rubb(7) was found to bind chromosomal DNA extracted from a suspension of Staphylococcus aureus that had been incubated with the ruthenium(ii) complex. As inert dinuclear ruthenium(ii) complexes are capable of being transported into a bacterial cell and bind chromosomal DNA, it is possible that they could be developed into anti-microbial agents that specifically target destabilised segments of DNA that are recognised by essential DNA-binding proteins.     

Dinucleosides with Non‐Natural Backbones: A New Class of Ribonuclease A and Angiogenin Inhibitors

Ribonuclease A (RNase A) serves as a convenient model enzyme in the identification and development of inhibitors of proteins that are members of the ribonuclease superfamily. This is principally because the biological activity of these proteins, such as angiogenin, is linked to their catalytic ribonucleolytic activity. In an attempt to inhibit the biological activity of angiogenin, which involves new blood vessel formation, we employed different dinucleosides with varied non‐natural backbones. These compounds were synthesized by coupling aminonucleosides with dicarboxylic acids and amino‐ and carboxynucleosides with an amino acid. These molecules show competitive inhibition with inhibition constant (K_i) values of (59±3) and (155±5) μM for RNase A. The compounds were also found to inhibit angiogenin in a competitive fashion with corresponding K_i values in the micromolar range. The presence of an additional polar group attached to the backbone of dinucleosides was found to be responsible for the tight binding with both proteins. The specificity of different ribonucleolytic subsites were found to be altered because of the incorporation of a non‐natural backbone in between the two nucleosidic moieties. In spite of the replacement of the phosphate group by non‐natural linkers, these molecules were found to selectively interact with the ribonucleolytic site residues of angiogenin, whereas the cell binding site and nuclear translocation site residues remain unperturbed. Docked conformations of the synthesized compounds with RNase A and angiogenin suggest a binding preference for the thymine–adenine pair over the thymine–thymine pair.     

High Channel Count, Low Cost, Multiplexed FBG Sensor Systems

With rich products development experience in WDM telecommunication networks, we introduce a few of high channel count, multiplexed FBG fiber optic sensor systems featured in reliable high performance and low cost.     

Temperature Insensitive Open Loop Attenuation Control of a Liquid Crystal Based VOA

A patent pending open-loop liquid crystal based variable optical attenuator is introduced. The temperature dependent performance is compensated through electric monitoring and adjustment utilizing liquid crystal’s opto-electronic properties.     

Simplified Fast Transient Control in Coolerless Pump EDFA for Metro Applications

A novel optical transient suppression technique to dramatically reduce gain variation of EDFA with un-cooled pump is demonstrated experimentally, showing excellent performance of 50μs transient time with no more than 0.5dB excursion and 0.25dB offset.     

Electrical characterization of tin disulphide crystals

Tin disulphide crystals have been grown by the physical vapour transport method and the electrical conduction mechanism in these crystals using MIM structures is reported. The conduction is found to be space charge limited. Trap concentration, trap depth, free carrier mobility and Fermi level etc. have been determined. Dependence of the current on temperature in the ohmic region gives an activation energy of 0.40 ± 0.05 eV.