Microwave-assisted synthesis and biological evaluation of pyrazole-4-carbonitriles as antimicrobial agents

An efficient microwave-assisted method of synthesis of pyrazole-4-carbonitriles has been developed. Condensation of pyrazole-4-carbaldehydes with hydroxylamine hydrochloride followed by reaction of the resulting oximes with the Vilsmeier-Haack reagent pre-formed from phthaloyl dichloride and dimethylformamide under microwave irradiation afforded the corresponding pyrazole-4-carbonitriles in 73% to 91% yield. The operational simplicity, avoidance of toxic reagents such as POCl₃, shorter reaction time, higher yield compared to the classical version, easy work up, and the use of the by-product in the regeneration of phthaloyl dichloride are the advantages of this methodology. All the target compounds were tested for antimicrobial activity against Gram-positive bacteria Bacillus cereus and Staphylococcus aureus; Gram-negative bacteria Escherichia coli and Yersinia enterocolitica, and the fungal species Candida albicans.     

Degradation of Polyethylene: Effect of Phosphorylated Poly (2,6-DimethyM, 4-phenylene Oxide)

The effect of phosphorylated poly(2,6-dimethyl-l,4-phenylene oxide) (PPOP) on the stability of high-density polyethylene (HDPE) is described. One and 5% (w/w) of PPOP was melt blended with HDPE (Samples A₁ and A₅, respectively). The samples were extruded in ribbon form and irradiated with UV light for several hours. In the presence of PPOP, suppression of double bond formation in HDPE was indicated by IR spectroscopy. HDPE became very brittle after 2 5 h irradiation, while Samples A₁ and A₅ showed much better retention of mechanical properties. The limiting oxygen index of HDPE did not change by incorporation of PPOP. The effect of thermal aging at 100°C on the mechanical properties of HDPE and Samples A₁ and A₅was also studied.     

Reaction of barbituric acid with organic azides and phosphonium ylides

Amination by organic azides has been carried out to provide aminobarbiturates by fusion of a triazole ring to the 5,6-positions of barbituric acid followed by cleavage and thermal elimination of nitrogen, whereas aza-Wittig reaction gave phosphoranylidene barbituric acid salts.      

Inapproximability of Edge-Disjoint Paths and low congestion routing on undirected graphs

In the undirected Edge-Disjoint Paths problem with Congestion (EDPwC), we are given an undirected graph with V nodes, a set of terminal pairs and an integer c. The objective is to route as many terminal pairs as possible, subject to the constraint that at most c demands can be routed through any edge in the graph. When c = 1, the problem is simply referred to as the Edge-Disjoint Paths (EDP) problem. In this paper, we study the hardness of EDPwC in undirected graphs.     

Application of multilayered strategy for variable selection in QSAR modeling of PET and SPECT imaging agents as diagnostic agents for Alzheimer’s disease

Structural Chemistry - Non-invasive imaging of amyloid beta (Aβ) and tau fibrils in the brain may support an early and precise diagnosis of Alzheimer’s disease. Molecular imaging...     

QSAR modeling of antiradical and antioxidant activities of flavonoids using electrotopological state (E-State) atom parameters

In the present paper QSAR modeling using electrotopological state atom (E-state) parameters has been attempted to determine the antiradical and the antioxidant activities of flavonoids in two model systems reported by Burda et al. (2001). The antiradical property of a methanolic solution of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and the antioxidant activity of flavonoids in a β-carotenelinoleic acid were the two model systems studied. Different statistical tools used in this communication are stepwise regression analysis, multiple linear regressions with factor analysis as the preprocessing step for variable selection (FA-MLR) and partial least squares analysis (PLS). In both the activities the best equation is obtained from stepwise regression analysis, considering, both equation statistics and predictive ability (antiradical activity: R ² = 0.927, Q² = 0.871 and antioxidant activity: R ² = 0.901, Q² = 0.841).      

Graphical balanced allocations and the (1 + β)‐choice process

Suppose m balls are sequentially thrown into n bins where each ball goes into a random bin. It is well‐known that the gap between the load of the most loaded bin and the average is , for large m. If each ball goes to the lesser loaded of two random bins, this gap dramatically reduces to independent of m. Consider a constrained setting where not all pairs of bins can be sampled. We are given a graph where each node corresponds to a bin. The process sequentially samples an edge from the graph and places a ball in the lesser loaded of its endpoints. We show the gap is at most where σ is the edge expansion of the graph. Our results extend naturally to the hypergraph version of this question. Our technique involves a tight analysis of what we call the “‐choice” process for some parameter : each ball goes to a random bin with probability and the lesser loaded of two random bins with probability β. For this process we show that the gap is , irrespective of m. Moreover the gap stays at in the weighted case for a large class of weight distributions. No non‐trivial bounds were previously known in the weighted case, even for the 2‐choice case. © 2014 Wiley Periodicals, Inc. Random Struct. Alg., 47, 760–775, 2015     

Biofunctionalized block copolymer nanoparticles based on ring‐opening metathesis polymerization

We present an approach to the synthesis of biofunctionalized block copolymer nanoparticles based on ring‐opening metathesis polymerization; these nanoparticles may serve as novel scaffolds for the multivalent display of ligands. The nanoparticles are formed by the self‐assembly of diblock copolymers composed of a hydrophobic block and a hydrophilic activated block that can be functionalized with thiolated ligands in aqueous media. The activated block enables control over the orientation of the displayed ligands, which may be sugars, peptides, or proteins engineered to contain cysteine residues at suitable locations. The nanoparticle diameter can be varied over a wide range through changes in the composition of the block copolymer, and biofunctionalization of the nanoparticles has been demonstrated by the attachment of a peptide previously shown to inhibit the assembly of anthrax toxin. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 928–939, 2006