Ali U. Shaikh

Antibacterial, antifungal and cytotoxic properties of novel N-substituted sulfonamides from 4-hydroxycoumarin.

A new series of 4-({[2, 4-dioxo-2H-chromen-3 (4H)-ylidene] methyl} amino) sulfonamides have been obtained by the condensation reaction of 4-hydroxycoumarin with various sulfonamides (sulfanilamide, sulfaguanidine, p-aminomethylsufanilamide, p-aminoethylsufanilamide, sulfathiazole, sulfamethoxazole, sulfamethazine and 4-[(2-amino-4-pyrimidinyl) amino] benzenesulfonamide) in the presence of an excess of ethylorthoformate. These compounds were screened for their in-vitro antibacterial activity against four Gram-negative (E. coli, S. flexneri, P. aeruginosa and S. typhi) and two Gram-positive (B. subtilis and S. aureus) bacterial strains and for in-vitro antifungal activity against T. longifusus, C. albicans, A. flavus, M. canis, F. solani and C. glaberata. Results revealed that a significant antibacterial activity was observed by compounds (4) and (5), (6) and (8) against two Gram-negative, (P. aeruginosa and S. typhi) and two Gram-positive (B. subtilis and S. aureus) species, respectively. Of these (4) was found to be the most active. Similarly, for antifungal activity compounds (3) and (8) showed significant activity against M. canis and, (6) and (8) against F. solani. The brine shrimp bioassay was also carried out to study their in-vitro cytotoxic properties and only two compounds, (4) and (8) possessing LD50 = 2.9072 × 10− 4 and 3.2844 × 10− 4 M, respectively, displayed potent cytotoxic activity against Artemia salina

Oxygen Reduction Reaction Electrocatalytic Activity of Glancing Angle Deposited Platinum Nanorod Arrays

The electrocatalytic oxygen reduction reaction (ORR) activity of vertically-aligned Pt nanorods has been evaluated utilizing cyclic voltammetry (CV) and rotating-disk electrode (RDE) techniques in a 0.1 M HClO4 solution at temperatures ranging from 20 to 60 � C. A glancing angle deposition (GLAD) technique was used to fabricate Pt nanorod arrays on glassy carbon (GC) electrodes. GLAD catalyst nanorods, without any carbon support, have been produced at different lengths varying between 50 and 400 nm, corresponding to 0.04–0.32 mg/cm 2 Pt loadings, with diameter and spacing values ranging from about 5 up to 100 nm. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) results reveal that Pt nanorods are well-isolated, vertically aligned, and single-crystal. Crystal orientation analysis demonstrates that large surface area Pt nanorod sidewalls are mainly dominated by Pt(110) planes, which is known to be the most active crystal plane of Pt for the ORR. Compared to a commercial high-surface-area-supported Pt (Pt/C) catalyst, the CV results show that the Pt-nanorod electrocatalyst exhibits a more positive oxide reduction peak potential, indicating that GLAD Pt nanorods are less oxophilic. Moreover, the nanorods exhibit enhanced stability against loss of electrochemically-active surface area as a result of potential cycling in acidic electrolyte as compared to the Pt/C catalyst. Specific ORR activities determined by the RDE technique for GLAD Pt nanorods of different lengths are analyzed and compared to literature values for polycrystalline Pt, nano-structured thin film Pt (3M NSTF Pt), and to those measured for Pt/C. RDE results reveal that Pt-nanorod electrocatalysts exhibit higher area-specific activity, higher electron-transfer rate constant, and comparable activation energy for ORR than those of Pt/C due to their larger crystallite size, single-crystal property, and dominance of the preferred crystal orientations for ORR. However, Pt nanorods show lower mass specific activity than that of Pt/C electrocatalyst due to the large diameter of nanorods. V C 2011 The Electrochemical Society. [DOI: 10.1149/1.3599901] All rights reserved.

In-vitro antibacterial, antifungal and cytotoxic properties of metal-based furanyl derived sulfonamides

A new series of antibacterial and antifungal furanyl-derived sulfonamides and their cobalt (II), copper (II), nickel (II) and zinc (II) metal complexes have been synthesized, characterized and screened for their in-vitro antibacterial activity against four Gram-negative (Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and, for in-vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata. The results of these studies revealed that all compounds showed significant to moderate antibacterial activity. However, the zinc (II) complexes were found to be comparatively much more active as compared to the others. For antifungal activity generally, compounds (22) and (24) showed significant activity against Escherichia coli (a), (6) against Shigella flexeneri (b), (16) and (22) against Pseudomonas aeruginosa (c), (14) and (16) against Salmonella typhi (d), (9) against Staphylococcus aureus (e) and, (14) and (16) against Bacillus subtilis (f) fungal strains. The brine shrimp (Artemia salina) bioassay was also carried out to study their in-vitro cytotoxic properties. Only three compounds, (6), (10) and (23) displayed potent cytotoxic activity with LD50 = 1.8535 × 10− 4, 1.8173 × 10− 4 and 1.9291 × 10− 4 respectively.

In-vitro Antibacterial, Antifungal and cytotoxic activity of cobalt (II), copper (II), nickel (II) and zinc (II) complexes with furanylmethyl- and thienylmethyl-dithiolenes: [1, 3-dithiole- 2-one and 1,3-dithiole-2-thione]

Some antibacterial and antifungal furanylmethyl-and thienylmethyl dithiolenes and, their Co(II), Cu(II), Ni (II) and Zn (II) complexes have been synthesized, characterized and screened for their in vitro antibacterial activity against four Gram-negative; Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Shigella flexeneri, and two Gram-positive; Bacillus subtilis and Staphylococcus aureus bacterial strains, and for in-vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata. All compounds showed significant antibacterial and antifungal activity. The metal complexes, however, were shown to possess better activity as compared to the simple ligands. The brine shrimp bioassay was also carried out to study their in-vitro cytotoxic properties.

Microwave assisted synthesis and characterization of silicon and phosphorous co-doped carbon as an electrocatalyst for oxygen reduction reaction

Doped carbon materials have gained a lot of attention recently due to their wide array of applications. These doped carbon materials have a tremendous potential to replace expensive metal based electrocatalysts in fuel cells. A recently established microwave assisted technique, which does not make use of any inert or reducing gases, has been used to synthesize novel silicon (Si), phosphorous (P) co-doped carbon (SiPDC), as yet not reported in the literature. The method is simple, rapid and economical. Tannin, a renewable resource material is chosen as the carbon source, polyphosphoric acid is utilized as the dehydrating agent/P source and silicone oil is chosen as the Si source. Brunauer–Emmett–Teller analysis reveals the surface area of SiPDC to be 641.51 m2 g−1 and X-ray photoelectron spectroscopy confirms the doping of Si and P at 8.80% and 4.20% respectively. The doped carbon material is utilized for oxygen reduction reaction (ORR) in 0.1 M KOH. The mechanism of ORR is found to be a four electron reduction process based on rotating disk electrode studies. Electrochemical stability studies are performed to evaluate the effectiveness of the catalyst for practical applications.

Relationships among direct-acting mutagenicity, nitro group orientation and polarographic reduction potential of 6-nitrobenzo[a]pyrene, 7-nitrobenz[a]anthracene and their derivatives

The direct-acting mutagenicity in Salmonella typhimurium strains TA98 and TA100 and the half-wave reduction potentials of 6-nitrobenzo[a]pyrene (6-nitro-BaP), 7-nitrobenz[a]anthracene (7-nitro-BA), and a series of their derivatives were compared. The common structural feature of these compounds is that their nitro substituents, in order to minimize steric hindrance, preferentially adopt an orientation perpendicular or nearly perpendicular to the aromatic rings. All of the compounds, except 7-hydroxy-6-nitro-BaP and 7-acetoxy-6-nitro-BaP, were found to exhibit very weak or no direct-acting mutagenicity. 7-Acetoxy-6-nitro-BaP and 7-hydroxy-6-nitro-BaP were also found to have the lowest reduction potentials among the tested compounds. The results suggest that a combination of the orientation of the nitro substituent and the first half-wave reduction potential of the compound may correlate with the direct-acting bacterial mutagenicity of nitro-polycyclic aromatic hydrocarbons.

Determination of bile acid profiles in scat samples of wild animals by liquid chromatography-electrospray mass spectrometry

A practical and accurate analytical method using liquid chromatography-mass spectrometry (LC-MS) was developed to determine the bile acid profile in the scat samples of various wild animals such as mountain lion, bobcat, coyote, raccoon, fox, etc. Bile acid extraction from the scat sample of the wild animals and its detection using the LC-MS technique are very easy and can be done in a short period of time with good resolution. The bile acid profiles are different in each species and the analytical method is very effective in identifying the wild animals under investigation. The detection limits of all bile acids were very low (∼1.0 ng mL−1) and the analytical method provides excellent reproducibility.

Photo-electrochemical hydrogen production using novel carbon based material

A transition to hydrogen as a major fuel could transform the US as well as global energy system increasing energy security while reducing environmental impact. This major transformation of our energy system would require a sustainable production of hydrogen using renewable resources. Hydrogen production using photo-electrochemical water splitting has been considered as a “holy grail” of sustainable hydrogen economy. Despite four decades of research since it was first shown that n-type TiO2 can be used for water splitting using sunlight, the search for a material that can efficiently harness solar energy for photo-electrolysis is still on. This paper will address some of the key challenges in the development of a material that is photoactive, stable, corrosion resistant and cost effective. This paper presents for the first time photo-electrochemical characterization of novel phosphorus, nitrogen doped carbon material (PNDC). The photocurrent density obtained was 0.416 mA/cm2, which is quite significant under visible radiation. This discovery opens up a large number of possibilities in development of a new class of carbon based materials for photo-electrochemical hydrogen production.

SAD-GLAD core-shell nanorod arrays for fuel cell, photodetector, and solar cell electrode applications

The glancing angle deposition (GLAD) technique, unlike a conventional physical vapor deposition (PVD) process, incorporates a flux of atoms that are obliquely incident on a tilted and rotating substrate. Instead of a continuous thin film coating, these atoms can form arrays of three-dimensional nanostructures due to a shadowing effect. By simply controlling the deposition angle and substrate rotation speed, nanostructures of a large variety of materials in the shapes of rods, screws, or springs can be obtained easily that are otherwise difficult to produce by conventional lithographical techniques. In this study, a brief overview of the growth mechanisms of GLAD nanostructures is presented. In addition, a new small angle deposition (SAD) technique as a simple means of conformally coating nanorod or nanowire arrays is described. SAD utilizes a small tilt angle during PVD on nanostructured substrates, which allows the effective exposure of nanorod sidewalls to the incoming flux and leads to enhanced thin film conformality. In this work, some recent results on core-shell nanorod arrays obtained by coating GLAD nanorods with a SAD shell will be presented. It will be shown that core-shell nanostructured geometries obtained by the simple SAD-GLAD method can significantly enhance catalyst activity for fuel cell electrodes, and charge carrier collection efficiency in photoconductive/semiconductor nanostructured materials.

CHEMILUMINESCENCE EMISSION DURING REACTIONS BETWEEN SUPEROXIDE AND SELECTED ALIPHATIC AND AROMATIC HALOCARBONS IN APROTIC MEDIA

The reactions between superoxide free radical anion (.O2-) with the halocarbons CCl4. CHCl3, BrCH2CH2Br(EDB), decachlora-biphenyl (DCBP), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in dimethyl sulphoxide (DMSO) results in the emission of chemiluminescence (CL). The chemiluminescence reactions are characterized as having biphasic second order kinetics, CL wavelengths between 350 nm and 650 nm, and exhibiting perturbation by chemicals reactive with singlet oxygen. These data suggest that singlet oxygen species are the excited state responsible for the light emissions. Polarographic studies confirm .O2- consumption and halide release in the reactions, while gas liquid chromatography and NBT reduction demonstrate the decomposition of the halocarbons into products. A chemiluminescent reaction mechanism is proposed involving reductive dehalogenation of the halocarbons and the generation of singlet oxygen. The significance of singlet oxygen generation is discussed with respect to a general mechanism for explaining the rapid initiation of lipid peroxidative membrane damage in halocarbon toxigenicity in animal and plant tissues.