Akella Sivaramakrishna

Abstract: Aflatoxin is a mycotoxin produced by Aspergillus flavus and a common contaminant of food and feed, posing health hazards to humans and animals alike. The aim of this study is to explore the ability of Pseudomonas putida to degrade aflatoxin B 1 (AFB 1 ). The toxigenic strain of A. flavus was isolated from sugarcane and used to produce AFB 1 in yeast extract sucrose medium. Two P. putida strains, MTCC 1274 and 2445, were cultured in mineral salt glucose medium (MSG) containing AFB 1 . The AFB 1 was analyzed qualitatively and quantitatively by TLC and HPLC. It was found that Pseudomonas sp. can tolerate AFB 1 in the medium (0.2 μg ml −1 ), and degrades it very efficiently. Within 24 h of incubation, AFB 1 was reduced to an undetectable level in MSG medium. Analysis with TLC, HPLC, UV spectrophotometer, gas chromatography mass spectrometry (GC–MS), and Fourier transform infra-red spectroscopy (FT-IR) showed that AFB 1 was bio-transformed to structurally different compounds (AFD 1 , AFD 2 , and AFD 3 ), with the modified furan and lactone ring on the AFB 1 molecule. A toxicity study on the HeLa cells showed that the new compounds formed are less toxic when compared with AFB 1 .

Abstract: Metal nanoparticles (NPs) are a subject of global interest in research community due to their diverse applications in various fields of science. The stabilization of these metal NPs is of great concern in order to avoid their agglomerization during their applications. There is a huge pool of cations and anions available for the selection of ionic liquids (ILs) as stabilizers for the synthesis of metal NPs. ILs are known for their tunable nature allowing the fine tuning of NPs size and solubility by varying the substitutions on the heteroatom as well as the counter anions. However, there has been a debate over the stability of metal NPs stabilized by ILs over a long period of time and also upon their recycling and reuse in organocatalytic reactions. ILs covalently attached to solid supports (SILLPs) have given a new dimension for the stabilization of metal NPs as well as their separation, recovery, and reuse in organocatalytic reactions. Poly(ILs) (PILs) or polyelectrolytes have created a significant revolution in the polymer science owing to their characteristic properties of polymers as well as ILs. This dual behavior of PILs has facilitated the stabilization of PIL-stabilized metal NPs over a long period of time with negligible or no change in particle size, stability, and size distribution upon recycling in catalysis. This review provides an insight into the different types of imidazolium-based ILs, supported ILs, and PILs used so far for the stabilization of metal NPs and their applications as a function of their cations and counter anions.

Abstract: Poly(ionic liquids)(PILs) of the types poly(1-vinyl-3-alkyl imidazolium)X (where alkyl = ethyl, butyl & pentyl; X = Br − or OH − ) are synthesized and used for the preparation of stable silver, gold and nickel nanoparticles in solution Studies pertaining to the dispersion of metal NP stabilized by PILs are discussed The role of PILs is prominent as carriers towards reversible “solubility switch” of synthesized metal nanoparticles between aqueous and organic media by simple anionic metathesis These PIL stabilized nanoparticles show great stability for longer period without agglomeration At another role of employed PIL is the ability to tune the size of the metal NP, depending on the length of alkyl chains of PIL UV–Visible, SEM and TEM techniques are used for the characterization and morphological study PIL stabilized Ag NP shows very good antimicrobial activity at lower concentrations against Escherichia coli and Staphylococcus aureus Ag NP are used in the catalytic reduction of aromatic nitro compounds with NaBH 4 and that of Ni NP for hydrogen transfer reduction of acetophenone in quantitative yields

Abstract: p-Nitrophenol (PNP) occurs as contaminants of industrial effluents and it is the most important environmental pollutant and causes significant health and environmental risks, because it is toxic to many living organisms. Nevertheless, the information regarding PNP degradation pathways and their enzymes remain limited. To evaluate the efficacy of the Pseudomonas Putida 1274 for removal of PNP. P. putida MTCC 1274 was obtained from MTCC Chandigarh, India and cultured in the minimal medium in the presence of PNP. PNP degradation efficiency was compared under different pH and temperature ranges. The degraded product was isolated and analyzed with different chromatographic and spectroscopic techniques. P. putida 1274 shows good growth and PNP degradation at 37°C in neutral pH. Acidic and alkali pH retarded the growth of P. putida as well as the PNP degradation. On the basis of specialized techniques, hydroquinone was identified as major degraded product. The pathway was identified for the biodegradation of PNP. It involved initial removal of the nitrate group and formation of hydroquinone as one of the intermediates. Our results suggested that P. putida 1274 strain would be a suitable aspirant for bioremediation of nitro-aromatic compounds contaminated sites in the environment.

Abstract: Hexacoordinate silicon bischelates with bulky monodentate alkyl ligands tend to ionize, while those with electron-withdrawing CF 3 substituents on the chelate rings resist ionization. A hexacoordinate silicon complex withboth of these structural features was prepared and was found, by its temperature-dependent 2 9 Si NMR spectroscopy, to undergo a reversible neutral dissociation of the N-Si dative bond, which satisfies both tendencies. The results are supported by crystallographic structure analyses and by nonempirical MO calculations of isodesmic reaction energies.

Abstract: Ionic liquids are remarkable chemical compounds, which find applications in many areas of modern science. Because of their highly tunable nature and exceptional properties, ionic liquids have become essential players in the fields of synthesis and catalysis, extraction, electrochemistry, analytics, biotechnology, etc. Apart from physical and chemical features of ionic liquids, their high biological activity has been attracting significant attention from biochemists, ecologists, and medical scientists. This Review is dedicated to biological activities of ionic liquids, with a special emphasis on their potential employment in pharmaceutics and medicine. The accumulated data on the biological activity of ionic liquids, including their antimicrobial and cytotoxic properties, are discussed in view of possible applications in drug synthesis and drug delivery systems. Dedicated attention is given to a novel active pharmaceutical ingredient-ionic liquid (API-IL) concept, which suggests using traditional drugs in ...

Abstract: We review recent works on the synthesis and application of poly(ionic liquid)s (PILs). Novel chemical structures, different synthetic strategies and controllable morphologies are introduced as a supplement to PIL systems already reported. The primary properties determining applications, such as ionic conductivity, aqueous solubility, thermodynamic stability and electrochemical/chemical durability, are discussed. Furthermore, the near-term applications of PILs in multiple fields, such as their use in electrochemical energy materials, stimuli-responsive materials, carbon materials, and antimicrobial materials, in catalysis, in sensors, in absorption and in separation materials, as well as several special-interest applications, are described in detail. We also discuss the limitations of PIL applications, efforts to improve PIL physics, and likely future developments.

Abstract: Recent advances in the area of Olefin Oligomerization via metallacycles that include dimerization, trimerization, tetramerization, and beyond, are reviewed. Studies have found that metallacyclopentane decomposition to 1-butene many not be particularly facile due to the absence of metallacycle expansion. Follow-up studies concentrated on the N-H functionality and the Cr oxidation state and role of MAO show that activities and selectivities to 1-hexene are similar to the original Cr(III) complexes. Nenu and Weckhuysen prepared silica-supported triazacyclohexane complexes, by treating the reduced Phillips polymerization catalyst with triazacyclohexane ligands in dichloromethane. The influence of N-aryl functionality investigated by Killian et al. shows that the selectivity was mainly dependent upon the steric bulk attached to nitrogen, and less so on the group's basicity.

Abstract: Ring-closing metathesis (RCM) of dienes is one of the most important methodologies now in use for the assembly of cyclic organic compounds. First employed by Villemin and by Tsuji nearly three decades ago,1,2 the reaction has risen to astonishing prominence in organic synthesis over the past decade, owing largely to the development of easily handled catalysts that enable controlled reaction.3 RCM represents a key step in many synthetic sequences: recent reviews describe its use in, inter alia, construction of synthetically valuable building blocks such as heterocyclic rings containing phosphorus,4 sulfur,4 oxygen,5 or nitrogen,5,6 including aromatic heterocycles;7 spirocyclic,8,9 cyclophane,8 and polycyclic compounds;8,9 and compounds of biological and medicinal relevance such as peptidomimetics,10,11 carbohydrate derivatives,11-14 alkaloids,11,15-19 bioactive cyclic molecules,20,21 and polycyclic ethers,22 including macrocyclic aza-crown ethers23 and topologically interesting molecules and “molecular machines”.24,25 While the common rings of 5-7 members have historically been dominant, owing in part to their greater ease of access, important advances have been made in the synthesis of medium20,26-30 and macrocyclic16,17,23,27,31-35 targets. One aspect of this review will examine the increased tendency of many medium and large rings to participate in equilibrium metathesis, and the resulting implications for selectivity and yields.