Syntheses and characterization of a new class of zirconia precursors of oxime-modified zirconium(IV) isopropoxide

Some oxime modified complexes of the type [Zr{OPrⁱ}_4?n{L}_n] {where, n = 1–4 and LH=(CH₃)₂C=NOH (1–4) and C₉H₁₆C=NOH (5–8)} have been synthesized by the reaction of [Zr(OPrⁱ)₄·PrⁱOH] with oximes, in anhydrous refluxing benzene. These synthesized complexes were characterized by elemental analyses, molecular weight measurements, ESI-mass, FT-IR and NMR (¹H and ¹³C{¹H}) spectral studies. The ESI-mass spectral studies indicate dimeric nature for [Zr{OPrⁱ}₂{ONC(CH₃)₂}₂] (2), [Zr{OPrⁱ}₃{ONC₁₀H₁₆}] (5) and [Zr{OPrⁱ}{ONC₁₀H₁₆}₃] (7) and monomeric nature for [Zr{ONC₁₀H₁₆}₄] (8). Oximato ligands appear to bind the zirconium in side on manner in all the complexes. Thermogravimetric curves of (2) and (8) exhibit multi-step decomposition with the formation of ZrO₂, under nitrogen atmosphere. Sol–gel transformations of precursors (5), (6), (7) and (8) in organic medium, yielded nano-sized tetragonal phase of zirconia samples (a), (b), (c) and (d), respectively, on sintering at ~600 °C. All these samples were characterized by Powder XRD patterns and EDX analyses. Surface morphologies of these samples were investigated by SEM images.     

Target-Directed Azide-Alkyne Cycloaddition for Assembling HIV-1 TAR RNA Binding Ligands

The highly conserved HIV-1 transactivation response element (TAR) binds to the trans-activator protein Tat and facilitates viral replication in its latent state. The inhibition of Tat–TAR interactions by selectively targeting TAR RNA has been used as a strategy to develop potent antiviral agents. Therefore, HIV-1 TAR RNA represents a paradigmatic system for therapeutic intervention. Herein, we have employed biotin-tagged TAR RNA to assemble its own ligands from a pool of reactive azide and alkyne building blocks. To identify the binding sites and selectivity of the ligands, the in situ cycloaddition has been further performed using control nucleotide (TAR DNA and TAR RNA without bulge) templates. The hit triazole-linked thiazole peptidomimetic products have been isolated from the biotin-tagged target templates using streptavidin beads. The major triazole lead generated by the TAR RNA presumably binds in the bulge region, shows specificity for TAR RNA over TAR DNA, and inhibits Tat–TAR interactions.     

Tunable Surface Wrinkling by a Bio-Inspired Polyamine Anion Coacervation Process that Mediates the Assembly of Polyoxometalate Nanoclusters

A bio-inspired method is used to render controlled wrinkling surface patterns on supramolecular architectures assembled from polyoxometalate (POM) clusters. It involves a polyamine-multivalent anion interaction generating positively charged coacervates, which while dictating the assembly of POM into spherical structures further facilitate an interesting surface morphogenesis with wrinkling patterns. This spontaneous surface wrinkling depends on the type of multivalent anion and the pH. As the polyamine-anion interaction becomes stronger, the wrinkles turn denser with lesser depth, which eventually undergoes post-buckling to engender a complex surface pattern. Interestingly, the order of influence exerted by different anions on the morphology follows the Hofmeister series. Moreover, the mild synthesis conditions keep the functional POM units dispersed in the sphere with a structural transformability to their lacunary form.     

Synthesis,characterization, in silico and in vitro biological activity studies of Ru(II) (η6-p-cymene) complexes with novel N-dibenzosuberene substituted aroyl selenourea exhibiting Se type coordination

A series of N-dibenzosuberene substituted aroyl selenourea ligands L1–L3 and their Ru(II) (η⁶-p-cymene) complexes 1–3, [Ru(II) (η⁶-p-cymene) L] (L?=?monodentate aroyl selenourea ligand) were synthesized and characterized. The molecular structures of the ligand L3 and complex 3 were confirmed by single-crystal XRD method. The single-crystal XRD study results revealed that aroyl selenourea ligand coordinates with ruthenium via Se neutral monodentate atom. In vitro DNA interaction studies were investigated by UV–Visible and fluorescence spectroscopic methods which showed that the intercalative mode of binding is in the order of 3?>?2?>?1 with the Ru(II) (η⁶-p-cymene) complexes. The binding affinity of the bovine serum albumin with complexes was calculated using spectroscopic methods. Quantum chemical computations were made using DFT (density functional theory), BL3YP; LANL2DZ basis set in order to determine the frontier molecular orbital parameters and MESP for the newly synthesized complexes. The complexes 1–3 have shown intensive cytotoxicity against the cancer lines HepG-2 and A549 under in vitro conditions. Complex 3 (IC₅₀?=?62 μM) has shown significant cytotoxic activity against HepG-2 compared to cisplatin standard drug. The complexes also examined for their antimicrobial activity. The complex 2 exhibited good activity against B. subtilis (MIC: 13.60 μg/mL), E. coli (MIC: 8.01 μg/mL) and A. flavus (MIC?=?15.60 μg/mL), respectively, compared to reference drugs Streptomycin and Ketoconazole.

     

A feedback fluid queue with two congestion control thresholds

Feedback fluid queues play an important role in modeling congestion control mechanisms for packet networks. In this paper we present and analyze a fluid queue with a feedback-based traffic rate adaptation scheme which uses two thresholds. The higher threshold B ₁ is used to signal the beginning of congestion while the lower threshold B ₂ signals the end of congestion. These two parameters together allow to make the trade-off between maximizing throughput performance and minimizing delay. The difference between the two thresholds helps to control the amount of feedback signals sent to the traffic source. In our model the input source can behave like either of two Markov fluid processes. The first applies as long as the upper threshold B ₁ has not been hit from below. As soon as that happens, the traffic source adapts and switches to the second process, until B ₂ (smaller than B ₁) is hit from above. We analyze the model by setting up the Kolmogorov forward equations, then solving the corresponding balance equations using a spectral expansion, and finally identifying sufficient constraints to solve for the unknowns in the solution. In particular, our analysis yields expressions for the stationary distribution of the buffer occupancy, the buffer delay distribution, and the throughput.     

Asymmetric,Three‐Component,One‐Pot Synthesis of Spiropyrazolones and 2,5‐Chromenediones from Aldol Condensation/NHC‐Catalyzed Annulation Reactions

A novel one‐pot, three‐component diastereo‐ and enantioselective synthesis of spiropyrazolones has been developed involving the aldol condensation of an enal to generate α,β‐unsaturated pyrazolones, which react with a second equivalent of enal through an N‐heterocyclic carbene (NHC)‐catalyzed [3+2] annulation. The desired spirocyclopentane pyrazolones are obtained in moderate to good yields and good to excellent stereoselectivities. Alternatively, starting from cyclic 1,3‐diketones, 2,5‐chromenediones are available through [2+4] annulation.     

Introduction to session 3

Applied Biochemistry and Biotechnology -