Stereoselective synthesis of beta-substituted phenylalanine-beta-phenylisoserine-derived tripeptides using N-cinnamoyl-L-proline as template: synthesis of structural analogues of HIV protease inhibitors

N-Cinnamoyl-L-proline can be used as a template on which beta-substituted phenylalanine and beta-phenylisoserine residues can be synthesized leading to tripeptide derivatives as structural analogues of HIV protease inhibitors.     

Antisense oligonuclotides with oxetane-constrained cytidine enhance heteroduplex stability,and elicit satisfactory RNase H response as well as showing improved resistance to both exo and endonucleases

Antisense oligonucleotides (AONs) with single and double oxetane C modifications [1',2'-oxetane constrained cytidine, 1-(1',3'-O-anhydro-beta-D-psicofuranosyl)cytosine] have been evaluated, in comparison with the corresponding T-modified AONs, for their antisense potentials by targeting to a 15mer complementary RNA. Although the C modified mixmer AONs show approximately 3 degrees C drop per modification in melting temperature (Tm) of their hybrid AON-RNA duplexes, they are found to be good substrates for RNase H, in comparison with the native AON-RNA duplex. An AON with double C modifications along with 3'-DPPZ (dipyridophenazine) conjugation shows the Tm of the hybrid duplexes as high as that of the native, and the RNase H activity as good as its unconjugated counterpart. A detailed Michaelis-Menten kinetic analysis of RNase H cleavage showed that the single and double C modified AON-RNA duplexes as well as double C modifications along with 3'-DPPZ have catalytic activities (kcat) close to the native. However, the R Nase H binding affinity (1/Km) showed a slight decrease with increase in the number of modifications, which results in less effective enzyme activity (kcat/Km) for C modified AON-RNA duplexes. All oxetane modified AON-RNA hybrids showed a correlation of Tm with the 1/Km, Vmax, or Vmax/Km. The C modified AONs (with 3'-DPPZ), as in the T counterpart, showed an enhanced tolerance towards the endonuclease and exonuclease degradation compared to the native (the oxetane-sugar and the DPPZ based AONs are non-toxic to K562 cell growth, ref. 18). Thus a balance has been found between exo and endonuclease stability vis-a-vis thermostability of the heteroduplex and the R Nase H recruitment capability and cleavage with the oxetane-constrained cytidine incorporated AONs as potential antisense candidates with a fully phosphate backbone for further biological assessment.     

Nonvanishing of symmetric square -functions of cusp forms inside the critical strip

We shall give a certain nonvanishing result for the symmetric square -function of an elliptic cuspidal Hecke eigenform w.r.t. the full modular group inside the critical strip.

     

Acetalization of glycerol using mesoporous MoO3/SiO2 solid acid catalyst

Acetalization of glycerol with various aldehydes has been carried out using mesoporous MoO₃/SiO₂ as a solid acid catalyst. A series of MoO₃/SiO₂ catalysts with varying MoO₃ loadings (1–20 mol%) were prepared by sol–gel technique using ethyl silicate-40 and ammonium heptamolybdate as silica and molybdenum source respectively. The sol–gel derived samples were calcined at 500 °C and characterized using various physicochemical characterization techniques. The XRD of the calcined samples showed the formation of amorphous phase up to 10 mol% MoO₃ loading and at higher loading of crystalline α-MoO₃ on amorphous silica support. TEM analyses of the materials showed the uniform distribution of MoO₃ nanoparticles on amorphous silica support. Raman spectroscopy showed the formation of silicomolybdic acid at low Mo loading and a mixture of α-MoO₃ and polymolybdate species at high Mo loadings. Moreover the Raman spectra of intermediate loading samples also suggest the presence of β-MoO₃. Acetalization of glycerol with benzaldehyde was carried out using series of MoO₃/SiO₂ catalysts with varying MoO₃ loadings (1–20 mol%). Among the series, MoO₃/SiO₂ with 20 mol% MoO₃ loadings was found to be the most active catalyst in acetalization under mild conditions. Maximum conversion of benzaldehyde (72%) was obtained in 8 h at 100 °C with 60% selectivity for the six-membered acetal using 20% MoO₃/SiO₂. Interestingly with substituted benzaldehydes under same reaction conditions the conversion of aldehydes decreased with increase in selectivity for six-membered acetals. These results indicate the potential of this catalyst for the acetalization of glycerol for an environmentally benign process.     

2-(Trimethylsilyl)ethyl chloroformate: A convenient reagent for protection of hydroxyl function

2-(Trimethylsilyl)ethyl chloroformate reacts with alcohols to give carbonates in high yield. n-Bu₄NF in THF(0.2M) solution for 10 min or ZnBr₂ or ZnCl₂ in CH₃NO₂ for 10 min regenerate the alcohol at 20°C.     

Effects of Dielectric Barrier Discharge Plasma on Physicochemical Characteristics,Mechanical Properties and Biocompatibility of Silk/PVA Nanofibers

Plasma Chemistry and Plasma Processing - This work reports an investigation of the discharge characteristics of atmospheric dielectric barrier discharge (DBD) plasma in terms of I-V curves and...     

Fabrication of dissolved O2 metric uric acid biosensor using uricase epoxy resin biocomposite membrane

Uricase purified from 20-day-old leaves of cowpea was immobilized on to epoxy resin membrane with 80% retention of initial activity of free enzyme and a conjugation yield of 0.056 mg/cm². The uricase epoxy resin bioconjugate membrane was mounted over the sensing part of the combined electrode of ‘Aqualytic’ dissolved O₂ (DO) meter to construct a uric acid biosensor. The biosensor measures the depletion of dissolved O₂ during the oxidation of uric acid by immobilized uricase, which is directly proportional to uric acid concentration. The biosensor showed optimum response within 10-12 s at a pH 8.5 and 35 °C. A linear relationship was found between uric acid concentration from 0.025 to 0.1 mM and O₂ (mg/l) consumed. The biosensor was employed for measurement of uric acid in serum. The mean value of uric acid in serum was 4.92 mg/dl in apparently healthy males and 3.11 mg/dl in apparently healthy females. The mean analytic recoveries of added uric acid in reaction mixture (8.9 and 9.8 mg/dl) were 93.6 ± 2.34 and 87.18 ± 3.17% respectively. The within and between batch CVs were <6.5 and <5.0%, respectively. The serum uric acid values obtained by present method and standard enzymic colorimetric method, showed a good correlation (r = 0.996) and regression equation being y = 0.984x + 0.0674. Among the various metabolites tested only, glucose (11%), urea (38%), NaCl (25%) and cholesterol (13%) and ascorbic acid (56%) caused decrease, while, MgSO₄ and CaCl₂ had no effect on immobilized enzyme. The enzyme electrode showed only 32% decrease during its use for 100 times over a period of 60 days at 4 °C.     

Numerical simulation of low loss silicon photonic wire waveguide with multiple cladding layers

A different silicon photonic wire waveguide is proposed, which uses multiple thin cladding layers in order to reduce the index contrast between core and cladding interface. The reduced index contrast in the proposed waveguide has led to reduction in the scattering losses by 37% as compared to silicon wire waveguide for 400 nm × 220 nm waveguide dimension. The proposed waveguide has shown significant reduction in bending losses. It offers the bending loss of 0.0118 dB at the radius of 1 μm and 0.0063 dB for a radius of 2 μm at 1.55 μm wavelength as compared to 0.086 and 0.013 dB at the radius of 1 and 2 μm, respectively, offered by silicon photonic wire waveguide at 1.5 μm wavelength. The use of polymer material as top cladding layer resulted in decreasing the sensitivity of effective index against temperature for the designed waveguide by a factor of 2 as compared to silicon wire waveguide.     

Hydrothermal processing of waste pine wood into industrially useful products

An ongoing major outbreak of mountain pine beetle in Western Canada has provided a clear opportunity to utilize waste pinewood as a source of renewable energy. Therefore hydrothermal processing of waste pinewood as a feedstock for bio-oil and biochar production using subcritical and supercritical water technology was carried out in semi-batch mode to investigate the effect of pressure (200–400 bar) and temperature (300–400 °C) on the yield and composition of bio-oil. The pinewood samples have very high cellulose and hemicellulose content but low ash content and are thus a formidable feedstock for bioenergy production. The optimum conditions for the hydrothermal processing of the pinewood in a tubular reactor were found to be 400 °C and 250 bars with respect to biochar and bio-oil yield based on the highest calorific value analysis. Detailed characterization of bio-oil and biochar was performed using GCMS, NMR, SEM, calorific value, and elemental analysis, respectively. The critical components of bio-oil were found to be phenols, methoxyphenols, hydroxymethyl furfural (HMF), and vanillin, whereas as compared to the raw pine wood, the biochar was considerably lower H:C and O:C ratios than those of the unprocessed pinewood. The analyses of bio-oil by means of GCMS and ¹H NMR showed that it was mainly composed of heterocyclic compounds, phenols, aldehydes and acids.