Browsing by Author "Santosh Kumar Dubey"

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Arsenite biotransformation and bioaccumulation by Klebsiella pneumoniae strain SSSW7 possessing arsenite oxidase (aioA) gene
(Springer Netherlands, 2019) Sajiya Yusuf Mujawar; Kashif Shamim; Diviya Chandrakant Vaigankar; Santosh Kumar Dubey
Arsenite oxidizing Klebsiella pneumoniae strain SSSW7 isolated from shipyard waste Goa, India showed a minimum inhibitory concentration of 21 mM in mineral salts medium. The strain possessed a small supercoiled plasmid and PCR amplification of arsenite oxidase gene (aioA) was observed on plasmid as well as chromosomal DNA. It was confirmed that arsenite oxidase enzyme was a periplasmic protein with a 47% increase in arsenite oxidase activity at 1 mM sodium arsenite. Scanning electron microscopy coupled with electron dispersive X-ray spectroscopic (SEM–EDS) analysis of 15 mM arsenite exposed cells revealed long chains of cells with no surface adsorption of arsenic. Transmission electron microscopy combined with electron dispersive X-ray spectroscopic (TEM-EDS) analysis demonstrated plasma membrane disruption, cytoplasmic condensation and periplasmic accumulation of arsenic. The bacterial strain oxidized 10 mM of highly toxic arsenite to less toxic arsenate after 24 h of incubation. Fourier transformed infrared (FTIR) spectroscopy confirmed the interaction of arsenite with functional groups present on the bacterial cell surface. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of 5 mM arsenite exposed cells demonstrated over-expression of 87 kDa and 14 kDa proteins of two subunits aioA and aioB of heterodimer arsenite oxidase enzyme as compared to control cells. Therefore, this bacterial strain might be employed as a potential candidate for bioremediation of arsenite contaminated environmental sites. © 2018, Springer Nature B.V.
Biogenesis of selenium nanospheres using Halomonas venusta strain GUSDM4 exhibiting potent environmental applications
(Springer Science and Business Media Deutschland GmbH, 2022) Diviya Chandrakant Vaigankar; Sajiya Yusuf Mujawar; Ajeet Kumar Mohanty; Santosh Kumar Dubey
Selenite reducing bacterial strain (GUSDM4) isolated from Mandovi estuary of Goa, India was identified as Halomonasvenusta based on 16S rRNA gene sequence analysis. Its maximum tolerance level for sodium selenite (Na2SeO3) was 100 mM. The 2, 3-diaminonaphthalene-based spectroscopic analysis demonstrated 96 and 93% reduction of 2 and 4 mM Na2SeO3 respectively to elemental selenium (Se0) during the late stationary growth phase. Biosynthesis of Se nanoparticles (SeNPs) commenced within 4 h during the log phase, which was evident from the brick red color in the growth medium and a characteristic peak at 265 nm revealed by UV–Vis spectrophotometry. The intracellular periplasmic synthesis of SeNPs in GUSDM4 was confirmed by transmission electron microscopy (TEM). Characterization of SeNPs by X-ray crystallography, TEM and energy-dispersive X-ray analysis (EDAX) clearly demonstrated spherical SeNPs of 20–80 nm diameter with hexagonal crystal lattice. SeNPs (0.8 and 1 mg/L) primed seeds under arsenate [As(V)] stress showed increase in shoot length, root length and biomass by 1.4-, 1.5- and 1.1-fold respectively, as compared to As(V) primed seeds alone. The proline and phenolic content in seeds primed with SeNPs under arsenate stress showed alleviated levels proving its ameliorative potential. SeNPs also demonstrated anti-biofilm activity at 20 µg/mL against human pathogens which was evident by scanning electron microscopic (SEM) analysis. SeNPs interestingly revealed mosquito larvicidal activity also. Therefore, these studies have clearly demonstrated amazing potential of the marine bacterium, Halomonasvenusta in biosynthesis of SeNPs and their applications as ameliorative, anti-biofilm and mosquito larvicidal agents which is the first report of its kind. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Biogenic synthesis and characterization of selenium nanoparticles and their applications with special reference to antibacterial, antioxidant, anticancer and photocatalytic activity
(Springer Science and Business Media Deutschland GmbH, 2021) Shraddha Pandey; Nikee Awasthee; Anusmita Shekher; Lal Chand Rai; Subash Chandra Gupta; Santosh Kumar Dubey
Oxyanions of selenium, selenite (SeO3)2− and selenate (SeO4)2− are toxic to terrestrial and aquatic biota but few microorganisms including cyanobacteria are resistant to high levels of selenite. Cyanobacteria evade selenite toxicity through bioreduction and synthesis of selenium nanoparticles (SeNPs). In this study, extracellular biosynthesis of SeNPs (Se0) using cyanobacterium, Anabaena sp. PCC 7120 on exposure to sodium selenite and characterization was done by using UV–visible spectroscopy, SEM–EDX, TEM and FTIR analyses which confirmed spherical shape with size range of 5–50 nm diameter. These biogenic SeNPs demonstrated significant antibacterial and anti-biofilm activity against bacterial pathogens. Furthermore, these SeNPs showed high antioxidant activity at minimum concentration of 50 µg/mL and significant anti-proliferative activity against HeLa cell line with IC50 value of 5.5 µg/mL. The SeNPs also induced accumulation of cancer cells in the sub-G1 phase which was clearly observed in cellular and nuclear morphology. These biofabricated SeNPs also reduced and decolorized toxic methylene blue dye significantly through photocatalytic degradation. Therefore Anabaena sp. PCC 7120 may be employed as a green bioresource to synthesize SeNPs with potential applications in medicine and environmental bioremediation. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Biological characterization of Bacillus flexus strain SSAI1 transforming highly toxic arsenite to less toxic arsenate mediated by periplasmic arsenite oxidase enzyme encoded by aioAB genes
(Springer Science and Business Media B.V., 2021) Sajiya Yusuf Mujawar; Diviya Chandrakant Vaigankar; Santosh Kumar Dubey
Bacillus flexus strain SSAI1 isolated from agro-industry waste, Tuem, Goa, India displayed high arsenite resistance as minimal inhibitory concentration was 25 mM in mineral salts medium. This bacterial strain exposed to 10 mM arsenite demonstrated rapid arsenite oxidation and internalization of 7 mM arsenate within 24 h. The Fourier transformed infrared (FTIR) spectroscopy of cells exposed to arsenite revealed important functional groups on the cell surface interacting with arsenite. Furthermore, scanning electron microscopy combined with electron dispersive X-ray spectroscopy (SEM-EDAX) of cells exposed to arsenite revealed clumping of cells with no surface adsorption of arsenite. Transmission electron microscopy coupled with electron dispersive X-ray spectroscopic (TEM-EDAX) analysis of arsenite exposed cells clearly demonstrated ultra-structural changes and intracellular accumulation of arsenic. Whole-genome sequence analysis of this bacterial strain interestingly revealed the presence of large number of metal(loid) resistance genes, including aioAB genes encoding arsenite oxidase responsible for the oxidation of highly toxic arsenite to less toxic arsenate. Enzyme assay further confirmed that arsenite oxidase is a periplasmic enzyme. The genome of strain SSAI1 also carried glpF, aioS and aioE genes conferring resistance to arsenite. Therefore, multi-metal(loid) resistant arsenite oxidizing Bacillus flexus strain SSAI1 has potential to bioremediate arsenite contaminated environmental sites and is the first report of its kind. © 2021, The Author(s), under exclusive licence to Springer Nature B.V.
Characterization of a metagenomic serine metalloprotease and molecular docking studies
(Elsevier Ltd, 2018) Kashif Shamim; Jaya Sharma; Milind Mutnale; Santosh Kumar Dubey; Sajiya Mujawar
Functional screening of marine metagenomic library resulted in a single protease positive clone (GUSK-1) containing a 4.0 kbps insert. The DNA insert was sub-cloned using pET-22b expression vector system. Phenylmethylsulfonyl fluoride (PMSF) caused 28% inhibition of protease activity, while 60% inhibition was observed with Disodium ethylenediaminetetraacetic acid (EDTA-Na2) suggesting it to be a serine metalloprotease. The pH and temperature optima for protease activity were found to be 10 and 70 °C. Bivalent metal cations such as Mg2+, Fe2+, Mn2+, and Ca2+ enhanced the protease activity indicating their possible role either at the catalytic site or in the stabilization of the enzyme. Additionally, common organic solvents viz. isopropanol, ethanol, methanol, butanol, chloroform, and benzene also improved the protease activity. Sequence analysis of the DNA insert demonstrated an open reading frame (ORF) of 861 bps encoding 286 amino acids corresponding to a protease belonging to transpeptidase superfamily. In silico docking revealed interesting interactions of this serine metalloprotease with a gp41 protein of HIV-1 and cell adhesion protein of Listeria monocytogenes. Therefore, the novel characteristics of this protease make it a potential candidate for various biotechnological and pharmaceutical industries. © 2018 Elsevier Ltd
Comparative analysis of DNA binding and abiotic stress tolerance of Dps All4145 and its homologs in Anabaena PCC 7120
(Springer Science and Business Media B.V., 2025) Shilpi Singh; Krishna Kumar Rai; Alka Shankar; Santosh Kumar Dubey; Alka Raj; Ruchi Rai
Background: DNA-binding proteins under starvation (Dps) are mini-ferritins that sequester iron at the ferroxidase center (FOC) of a hollow protein cage. This study characterizes the novel Dps-All4145. Discrepancies between computational predictions and experimental stress responses were addressed using an integrated computational and experimental approach. Additionally, site-directed mutagenesis was performed to explore the mechanistic link between DNA binding and ferroxidation. Methods and results: This study involves the molecular characterization of the novel Dps-All4145 and a comparative biochemical and structural analysis of four Dps homologs (Alr3808, All0458, All1173, and All4145) from Anabaena sp. PCC 7120. In-silico and wet lab approaches were employed to assess their biochemical functions, including iron oxidation and DNA protection. The study confirmed that iron oxidation and DNA protection are common attributes of all four Dps homologs. Additionally, all homologs contributed to abiotic stress management. Among them, Alr3808 exhibited the highest efficiency in iron oxidation and DNA protection. Site-directed mutagenesis of Alr3808K49R led to the loss of DNA-binding ability and a 60% reduction in iron oxidation, indicating the crucial role of the N-terminal lysine (K49) residue in these activities. Conclusion: This study provides first-hand insights into the molecular functions of Dps proteins in Anabaena sp. PCC 7120 and highlights the unique significance of K49 in Alr3808 for iron oxidation and DNA binding. © The Author(s), under exclusive licence to Springer Nature B.V. 2025.
Cyanobacteria: miniature factories for green synthesis of metallic nanomaterials: a review
(Springer Science and Business Media B.V., 2022) Shraddha Pandey; Lal Chand Rai; Santosh Kumar Dubey
Nanotechnology is one of the most promising and advanced disciplines of science that deals with synthesis, characterization and applications of different types of Nanomaterials (NMs) viz. nanospheres, nanoparticles, nanotubes, nanorods, nanowires, nanocomposites, nanoalloys, carbon dots and quantum dots. These nanosized materials exhibit different physicochemical characteristics and act as a whole unit during its transport. The unique characteristics and vast applications of NMs in diverse fields viz. electronics, agriculture, biology and medicine have created huge demand of different type of NMs. Conventionally physical and chemical methods were adopted to manufacture NMs which are expensive and end up with hazardous by-products. Therefore, green synthesis exploiting biological resources viz. algae, bacteria, fungi and plants emerged as a better and promising alternative due to its cost effective and ecofriendly approach and referred as nanobiotechnology. Among various living organisms, cyanobacteria have proved one of the most favourable bioresources for NMs biosynthesis due to their survival in diverse econiches including metal and metalloid contaminated sites and capability to withstand high levels of metals. Biosynthesis of metallic NMs is accomplished through bioreduction of respective metal salts by various capping agents viz. alkaloids, pigments, polysaccharides, steroids, enzymes and peptides present in the biological systems. Advancement in the field of Nanobiotechnology has produced large number of diverse NMs from cyanobacteria which have been used as antimicrobial agents against Gram positive and negative human pathogens, anticancer agents, luminescent nanoprobes for imaging of cells, antifungal agents against plant pathogens, nanocatalyst and semiconductor quantum dots in industries and in bioremediation in toxic pollutant dyes. In the present communication, we have reviewed cyanobacteria mediated biosynthesis of NMs and their applications in various fields. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.
Emission switching of ferrocenyl Schiff bases and a representative ruthenium complex in alkaline DMSO: Absorption, electrochemical and microstructural studies
(2007) Lallan Mishra; Santosh Kumar Dubey
N,N′-Bis(4-ferrocenyl)-p-phenylene/octamethylene-diimines (L1/L2) and a representative Ru(II) complex [Ru(DMSO)2Cl2L1]·2H2O were prepared and characterized which showed many fold enhancement in their luminescence in alkaline dimethylsulfoxide (DMSO) solution. Spectral and electrochemical properties of these compounds have been studied. Microstructure (SEM) of L1 and its complex showed single-phase porous material of crystal size ∼1 μm. © 2006 Elsevier B.V. All rights reserved.
Enhanced exopolysaccharide production and biofilm forming ability in methicillin resistant Staphylococcus sciuri isolated from dairy in response to acyl homoserine lactone (AHL)
(Springer India, 2018) Milind Mohan Naik; Shivangi P. Naik; Santosh Kumar Dubey; Chinmay Bhat; Lakshangy S. Charya
Staphylococcus sciuri is an emerging human pathogen widely found in dairy industries. In this study, we have isolated methicillin resistant Staphylococcus sp. from biofilm formed on utensil used in the dairy society situated at Raia, Goa and was designated as NN14. The isolate NN14 was identified through 16S rRNA sequencing as S. sciuri (GenBank accession number MF621976). This report reveals that the S. sciuri strain NN14 responds positively to the, acyl-homoserine lactone (AHL) having 6-carbon long acyl chain i.e. N-hexanoyl-homoserine lactone molecule (C6-HSL) with gradual rise in their biofilm establishing potential as the concentration of AHL was increased from 250 nM, 500 nM to 1 µM when compared to control (without C6-HSL) by performing crystal violet assay using 48 well microtiter plate. Also, exopolysaccharide (EPS) production was found to increase with gradual increase in C6-HSL concentration from 250 nM, 500 nM to 1 µM proving potential role of EPS in biofilm formation. These results were further proved by scanning electron microscopy where increased in biofilm and EPS production with increase in C6-HSL concentration was observed. The biofilm forming capability of S. sciuri strain NN14 was found to decreased significantly when it was subjected to 10 µg/ml of (R)-2-(2-hydroxynaphthalen-1-yl)-thiazolidine-4-carboxylic acid, however with the addition of 250 and 500 nM, C6-HSL in presence of the antimicrobial compound (R)-2-(2-hydroxynaphthalen-1-yl)-thiazolidine-4-carboxylic acid, the biofilm development in bacterial strain NN14 was increased when compared with control. Our results demonstrated that the C6-HSL molecule neutralize the effect of antibacterial compound and enhances EPS production and biofilm development in S. sciuri. © 2018, Association of Food Scientists & Technologists (India).
Largest freshwater lake 'Loktak' in Manipur needs urgent conservation
(Indian Academy of Sciences, 2018) Komal Salkar; Vishwanath Gadgil; Santosh Kumar Dubey; Milind Mohan Naik; Radha Raman Pandey
[No abstract available]
Metal Cu(II) and Zn(II) bipyridyls as inhibitors of lactate dehydrogenase
(2008) Raj Kumar Koiri; Surendra Kumar Trigun; Santosh Kumar Dubey; Santosh Singh; Lallan Mishra
Metal complex-protein interaction is an evolving concept for determining cellular targets of metallodrugs. Lacatate dehydrogenase (LDH) is critically implicated in tumor growth and therefore, considered to be an important target protein for anti-tumor metal complexes. Due to efficient biocompatibility of copper (Cu2+) and zinc (Zn2+), we synthesized CubpyAc 2 · H2O (Cu-bpy) and ZnbpyAc2 · H2O (Zn-bpy; where bpy = 2,2′ bipyridine, Ac = CH 3COO-) complexes and evaluated their interaction with and modulation of LDH in mouse tissues. The increasing concentration of both the complexes showed a significant shift in UV-Vis spectra of LDH. The binding constant data (Kc = 1 × 103 M-1 for Cu-bpy and 7 × 106 M-1 for Zn-bpy) suggested that Zn-bpy-LDH interaction is stronger than that of Cu-bpy-LDH. LDH modulating potential of the complexes were monitored by perfusing the mice tissues with non-toxic doses of Cu-bpy and Zn-bpy followed by activity measurement and analysis of LDH isozymes on non-denaturing polyacrylamide gel electrophoresis (PAGE). As compared to the control sets, Cu-bpy caused a significant decline (P < 0.05-0.001) in the activity of LDH in all the tissues studied. However, Zn-bpy showed inhibition of LDH only in liver (P < 0.01), kidney (P < 0.001) and heart (P < 0.01), but with no effect in spleen, brain and skeletal muscle tissues. PAGE analysis suggested that all the five LDH isozymes are equally sensitive to both the complexes in the respective tissues. The results suggest that Cu- and Zn-bpy are able to interact with and inhibit LDH, a tumor growth supportive target protein at tissue level. © 2007 Springer Science+Business Media BV.
Microcystis aeruginosa mediated biofabrication of silver nanoparticles exhibiting antibacterial, antioxidant, anticancer, and azo dye degrading catalytic activities
(Springer Science and Business Media Deutschland GmbH, 2024) Shraddha Pandey; Nikee Awasthee; Anusmita Shekher; Pooja Yadav; Lal Chand Rai; Subash Chandra Gupta; Santosh Kumar Dubey
In this study, a green, facile, and cost-effective method to synthesize silver nanoparticles (AgNPs) from silver nitrate using cell extract of unicellular cyanobacterium, Microcystis aeruginosa, has been reported. These biosynthesized AgNPs were characterized by UV-visible spectroscopy showing absorption peak at 470 nm. TEM and EDX analyses confirmed spherical shape of AgNPs with diameter range of 5–45 nm. The results of Fourier transform infrared (FTIR) spectroscopy analyses revealed proteins as reducing/capping agent. These AgNPs clearly demonstrated considerable antibacterial action against Gram positive and Gram negative bacterial pathogens. AgNPs also revealed notable antioxidative potential (71.08±0.78%) at minimum concentration of 100 μg/mL and significant cytotoxic activity against SiHa cancer cell line with IC50 value of 0.89 μg/mL after 72-h treatment. The AgNP treatment also promoted arrest of cancer cells in the sub-G1 phase of cell cycle. Western blot analysis of SiHa cells treated with increasing doses of AgNPs clearly demonstrated decreasing expression of apoptotic proteins, pro-caspase-3 and intact PARP suggesting activation of apoptosis. These AgNPs significantly degrade toxic azo dye and Congo red through catalytic reduction. The degradation observed was 77.21% in 60 min under visible light irradiation. Graphical Abstract: (Figure presented.) © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023.
Nano-Enhanced Biopolymers for Antimicrobial Applications
(Springer Science and Business Media B.V., 2024) Pooja Yadav; Shraddha Pandey; Santosh Kumar Dubey
Nanotechnology plays a very important role in biological research due to its small size as well as lower toxicity with their greater efficiency. The natural biopolymers include such as chitosan, cellulose, starch, collagen, gelatin, fibrin, hyaluronic acids, and alginates which are widely distributed in nature. The biopolymeric nanoparticles are developed due to their properties such as biocompatibility, antioxidant, antibacterial, photoprotection, biodegradability, minimal toxicity, and eco-friendliness. Due to these properties and various applications, the nano-based biopolymer attracted in food industry, agricultural domain, biomedicine via drug delivery, antibacterial activity, and slow release of fertilizers. This chapter mainly covers application of nano-based biopolymer as antimicrobial agent. In addition, this chapter also covers the types of biopolymeric nanoparticles, their synthesis, and characterization. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
New ruthenium(II) thiolato complexes: Synthesis, reactivity, spectral, structural and DFT studies
(Elsevier S.A., 2010) Sudhakar Dhar Dwivedi; Santosh Kumar Dubey; Ashish Kumar Singh; Krishna Kumar Pandey; Daya Shankar Pandey
Ruthenium complexes [Ru(mpy)2(DMSO)2] (1) and [Ru(mbtz)2(DMSO)2] (2) containing 2-mercaptopyridine (mpy) and 2-mercaptobenzothiazole (mbtz) have been synthesized. Reactivity of 1 have been examined with 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen), EPh3 (E = P, As) and 1,2-bis(diphenylphosphino)-methane (dppm). It reacted with bipy or phen in DMF to afford [Ru(mpy)2(bipy)] (3) and [Ru(mpy)2(phen)] (4) while, its reaction with EPh3 or dppm in common organic solvents failed to afford products containing EPh3 or dppm. Complexes under investigation have been characterized by elemental analyses, spectral, electrochemical studies and structures of 1-4 have been determined crystallographically. Density functional theory calculations have been performed on 1-4 and the model complex [Ru(mpy)(PMe3) 2] (5) using exchange correlation functionals BP86. Optimized bond length and angles are in good agreement with the structural data. The Ru-N and Ru-S bond distances in [Ru(mpy)2]-moiety of 1 are relatively shorter than 5, indicating higher stability of 1 in comparison to 5. The WBI values of Ru-N1, Ru-N2, Ru-S1 and Ru-S2 bonds indicate Ru-mpy bonding trend as 3 > 4 > 1 > 5. There is an overall charge flow in the direction L → [Ru(mpy)2] (L = DMSO, bipy, phen and PMe3). Due to greater ionic character and Pauli repulsive interactions for Ru-PMe3 bond in comparison to Ru-DMSO, the DMSO ligands in 1 may not be substituted by phosphine ligands experimentally. © 2010 Elsevier B.V. All rights reserved.
Rapid arsenite oxidation by Paenarthrobacter nicotinovorans strain SSBW5: unravelling the role of GlpF, aioAB and aioE genes
(Springer Science and Business Media Deutschland GmbH, 2023) Sajiya Yusuf Mujawar; Kashif Shamim; Diviya Chandrakant Vaigankar; Milind Mohan Naik; Santosh Kumar Dubey
A novel arsenite resistant bacterial strain SSBW5 was isolated from the battery waste site of Corlim, Goa, India. This strain interestingly exhibited rapid arsenite oxidation with an accumulation of 5 mM arsenate within 24 h and a minimum inhibitory concentration (MIC) of 18 mM. The strain SSBW5 was identified as Paenarthrobacter nicotinovorans using 16S rDNA sequence analysis. Fourier-transformed infrared (FTIR) spectroscopy of arsenite-exposed cells revealed the interaction of arsenite with several important functional groups present on the cell surface, possibly involved in the resistance mechanism. Interestingly, the whole genome sequence analysis also clearly elucidated the presence of genes, such as GlpF, aioAB and aioE encoding transporter, arsenite oxidase and oxidoreductase enzyme, respectively, conferring their role in arsenite resistance. Furthermore, this strain also revealed the presence of several other genes conferring resistance to various metals, drugs, antibiotics and disinfectants. Further suggesting the probable direct or indirect involvement of these genes in the detoxification of arsenite thereby increasing its tolerance limit. In addition, clumping of bacterial cells was observed through microscopic analysis which could also be a strategy to reduce arsenite toxicity thus indicating the existence of multiple resistance mechanisms in strain SSBW5. In the present communication, we are reporting for the first time the potential of P. nicotinovorans strain SSBW5 to be used in the bioremediation of arsenite via arsenite oxidation along with other toxic metals and metalloids. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Reactivity of metal (ZnII, RuII)-2,2′-bipyridyl with some bifunctional ligands
(2008) Rishikesh Prajapati; Vinod Kumar Yadav; Santosh Kumar Dubey; Bill Durham; Lallan Mishra
Complexation of cis-bis(2,2′-bipyridyl)dichlororuthenium(II) dihydrate with carboxaldehyde and carboxylate bearing ligand (4-carboxybenzaldehyde; L1H) and with bis-acetyl and pyridine containing ligand (2,6-diacetylpyridine; L2) yields [Ru(bpy) 3](PF6)2 (bpy = 2,2′-bipyridyl), as the major product in both reactions along with [Ru(bpy)2(L 1)]PF6 (1) and [Ru(bpy)2(L2)] (PF6)2(2) as minor products. However, reaction of cu-bis(2,2′-bipyridyl)dichlororuthenium(II) dihydrate with ligand containing bis-triazolo and diimino donor sites [1,4-bis(1,2,4-triazolo-3-imino) benzene; L3H2] provides [Ru(bpy)2Cl 2]PF6 (3) crystals characterized by its single crystal X-ray data along with some unidentified product. Similar to ruthenium bipyridyl, reaction of (2,2′-bipyridyl)dichlorozinc(II) monohydrate with L 2 has also been carried out which yields [Zn(bpy)3] (PF6)2 as a crystalline product along with a polymeric product with the composition [{Zn(bpy)(L2)Cl2} ·DMSO]n-.
Ruthenium(II), rhodium(III) and iridium(III) based effective catalysts for hydrogenation under aerobic conditions
(Elsevier Ltd, 2008) Sanjay Kumar Singh; Santosh Kumar Dubey; Rampal Pandey; Lallan Mishra; Ru-Qiang Zou; Qiang Xu; Daya Shankar Pandey
The new cationic mononuclear complexes [(η6-arene)Ru(Ph-BIAN)Cl]BF4 [η6-arene = benzene (1), p-cymene (2)], [(η5-C5H5)Ru(Ph-BIAN)PPh3]BF4 (3) and [(η5-C5Me5)M(Ph-BIAN)Cl]BF4 [M = Rh (4), Ir (5)] incorporating 1,2-bis(phenylimino)acenaphthene (Ph-BIAN) are reported. The complexes have been fully characterized by analytical and spectral (IR, NMR, FAB-MS, electronic and emission) studies. The molecular structure of the representative iridium complex [(η5-C5Me5)Ir(Ph-BIAN)Cl]BF4 has been determined crystallographically. Complexes 1-5 effectively catalyze the reduction of terephthaldehyde in the presence of HCOOH/CH3COONa in water under aerobic conditions and, among these complexes the rhodium complex [(η5-C5Me5)Rh(Ph-BIAN)Cl]BF4 (4) displays the most effective catalytic activity. © 2008 Elsevier Ltd. All rights reserved.
Selenite bioreduction with concomitant green synthesis of selenium nanoparticles by a selenite resistant EPS and siderophore producing terrestrial bacterium
(Springer Science and Business Media B.V., 2023) Pooja Yadav; Shraddha Pandey; Santosh Kumar Dubey
Environmental bacterial isolates play a very important role in bioremediation of metals and toxic metalloids. A bacterial strain with high selenite (SeO32−) tolerance and reducing capability was isolated from electronic waste dump site in Banaras Hindu University, Varanasi, India. Based on 16 S rRNA sequencing and BLAST search, this bacterial isolate was identified as Bacillus paramycoides and designated as strain MF-14. It tolerated Sodium selenite up to 110 mM when grown aerobically in LB broth and reduced selenite into elemental selenium (Se0) significantly within 24 h with concomitant biosynthesis of selenium nanoparticles as clearly revealed by brick red precipitate and specific surface plasmon resonance peak at 210 nm using UV–Visible spectrophotometer. Scanning electron microscopy (SEM) analysis of this bacterial strain exposed to 1mM and 5 mM selenite also demonstrated morphological alterations as cell enlargement due to accumulation and bioprecipitation of elemental selenium (Se0). The FTIR analysis clearly demonstrated that functional groups present on the surface of biogenic selenium nanoparticles (SeNPs) play a significant role in the stabilization and capping of SeNPs. Furthermore, these SeNPs were characterized using spectroscopic analysis involving Dynamic light scattering, zeta potential, XPS, FTIR, XRD and Raman spectroscopy which clearly revealed particle size 10–700 nm, amorphous nature, stability as well as it’s oxidation state. The biochemical studies have demonstrated that membrane bound reductase enzyme may be responsible for significant reduction of selenite into elemental selenium. Therefore, we may employ Bacillus paramycoides strain MF-14 successfully for bioremediation of selenite contaminated environmental sites with concomitant green synthesis of SeNPs. © 2023, The Author(s), under exclusive licence to Springer Nature B.V.
Structural characterization and cytotoxicity studies of ruthenium(II)-dmso-chloro complexes of chalcone and flavone derivatives
(Elsevier Ltd, 2010) Rishikesh Prajapati; Santosh Kumar Dubey; Ruchi Gaur; Raj Kumar Koiri; Brajesh Kumar Maurya; Surendra Kumar Trigun; Lallan Mishra
A synthetic precursor cis-[RuIICl2(dmso)4] is complexed separately with 3-(4-benzyloxyphenyl)-1-(2-hydroxylphenyl)-prop-2-en-1-one (L1H) and 2-(4-benzyloxyphenyl)-3hydroxy-chromen-4-one (L2H). The resulting complexes are assigned the composition fac-[RuCl(S-dmso)3(L1)] 1 and fac-[RuCl(S-dmso)3(L2)] 2 using elemental analyses, FAB mass data and spectroscopic (IR, 1H NMR, UV-Vis, emission) spectral properties. The X-ray diffraction analysis shows that complexes self-associate through non-covalent interactions and provide 1D and 2D supramolecular structures. These complexes are assayed for their cytotoxicity studies on Dalton Lymphoma cell lines. © 2009 Elsevier Ltd. All rights reserved.
Synthesis and reactivity of homo-bimetallic Rh and Ir complexes containing a N,O-donor Schiff base
(2009) Ashish Kumar Singh; Sudhakar Dhar Dwivedi; Santosh Kumar Dubey; Sanjay Kumar Singh; Sanjeev Sharma; Daya Shankar Pandey; Ru-Qiang Zou; Qiang Xu
Binuclear complexes [{(η5-C5Me5)RhCl}2(μ-bsh)] (1) and [{(η5-C5Me5)IrCl}2(μ-bsh)] (2) containing N,N′-bis(salicylidine)hydrazine (H2bsh) are reported. The complexes 1 and 2 reacted with EPh3 (E = P, As) to afford cationic complexes [(η5-C5Me5)Rh(PPh3)(κ2-Hbsh)]PF6 (3), [(η5-C5Me5)Rh(AsPh3)(κ2-Hbsh)]PF6 (4), [(η5-C5Me5)Ir(PPh3)(κ2-Hbsh)]PF6 (5), and [(η5-C5Me5)Ir(AsPh3)(κ2-Hbsh)]PF6 (6) which were isolated as their hexafluorophosphate salts. Representative complexes 3 and 5 have been used as a metallo-ligand in the synthesis of binuclear complexes [(η5-C5Me5)RhCl(μ-bsh)Ru(η6-C10H14)Cl]PF6 (7) and [(η5-C5Me5)IrCl(μ-bsh)Ru(η6-C10H14)Cl]PF6 (8). The complexes under study have been fully characterized by analytical and spectral (FAB/ESI-MS, IR, NMR, electronic and emission) studies. Molecular structures of 1, 2, 3 and 5 have been determined crystallographically. Structural studies on 1 and 2 revealed the presence of extensive inter- and intra-molecular C-H···O and C-H···π weak bonding interactions. The complexes 1, 2, 3 and 5 moderately emit upon excitation at their respective MLCT bands. © 2009 Elsevier B.V. All rights reserved.