Papers by Sudipta Chatterjee
Dalton Transactions
Large and small aggregates of Aβ peptides, resembling the morphology and dimensions of fibrillar ... more Large and small aggregates of Aβ peptides, resembling the morphology and dimensions of fibrillar and oligomeric forms of Aβ respectively, relevant to Alzheimer's disease, are stabilized on electrodes using selfassembly. Both of these forms were found to bind redox active Cu and heme, resulting in active sites having distinctive biophysical properties. The reduced metal bound Aβ active sites of both the oligomeric and fibrillar forms of Aβ produce detrimental partially reduced oxygen species (PROS). While the larger aggregates of heme-Aβ produce more PROS in situ, the smaller aggregates of Cu-Aβ produce more PROS. 8-Hydroxy quinoline and methylene blue are inhibitors of Cu and heme bound Aβ respectively, and are shown to efficiently reduce PROS formation in the oligomeric forms. However, these inhibitors are ineffective in reducing the toxicities of the Cu and heme bound Aβ peptides in the fibrils, making them significantly more lethal than the smaller Aβ aggregates.
Polyhedron, 2012
a b s t r a c t Five Fe(III) compounds, [Fe(salophen)(N 3 )(MeOH)] (1) [Fe(salophen)(NCS)(MeOH)] ... more a b s t r a c t Five Fe(III) compounds, [Fe(salophen)(N 3 )(MeOH)] (1) [Fe(salophen)(NCS)(MeOH)] (2), [Fe(vanophen)(HIm) 2 ]ClO 4 (3), [(l-O){Fe(vanophen)} 2 ]Á2H 2 O (4) and [(l-O){Fe(naphophen)} 2 ]Á2CH 2 Cl 2 ( where, H 2 salophen = N,N 0 -bis(salicylidene)phenylediamine, H 2 vanophen = N,N 0 -(1,2-phenylene)-bis(3-methoxysalicylideneimine) and H 2 naphophen = N,N 0 -bis(2-hydroxy-1-naphthaldehyde)-1,2-phenylenediimine, have been prepared and characterized by elemental analysis, IR and UV-Vis spectroscopy and singlecrystal X-ray diffraction studies. In compounds 1, 2 and 3, Fe(III) has six-coordinated pseudo-octahedral geometry in which the O(1), O(2), N(1) and N(2) atoms of the deprotonated di-Schiff base constitute the equatorial plane. Both in compounds 1 and 2, methanol molecules are present in the fifth coordination sites in apical positions. The sixth coordination sites are occupied by one N atom of an azide in compound 1 and an N atom of thiocyanate in compound 2. In compound 3, both axial positions are occupied by nitrogen atoms from two different imidazole molecules. In both compounds 4 and 5, Fe(III) has a fivecoordinated square pyramidal geometry with bridging oxygen atoms in the axial positions.
Polyhedron, 2013
Three heterometallic nickel(II)-sodium(I) complexes, [Ni(vanen)Na(NO 3 )] (1), [Ni(vanen)Na(vanen... more Three heterometallic nickel(II)-sodium(I) complexes, [Ni(vanen)Na(NO 3 )] (1), [Ni(vanen)Na(vanen)Ni] BF 4 (2) and [Ni(vanen)Na(ClO 4 )] n (3), have been synthesized by reacting nickel(II) and H 2 vanen with sodium(I), varying the reaction conditions and stoichiometry of the reactants [H 2 vanen = N,N 0ethylene-bis(3-methoxysalicylideneimine)]. All the three complexes have been characterized by X-ray single-crystal diffraction studies. In all the three complexes, nickel(II) is placed in the N 2 O 2 environment and sodium(I) is placed in the O 4 compartment of the compartmental Schiff base. In each complex, nickel(II) is square planar. Sodium(I) is trigonal dodecahedral in complex 2, and pentagonal pyramidal both in complexes 1 and 3. The nitrate ion is coordinated to sodium(I) in a chelating bidentate fashion. The sodium(I) in complex 1 shows strong p interaction with the phenyl ring of a second molecule. In complex 3, a carbon atom from an aryl group of a symmetry-related molecule is connected with sodium(I) in g 1 fashion to constitute 1D chain. The structure of complex 3 reveals an unprecedented heptadentate coordination mode of the deprotonated Schiff base.
Inorganic Chemistry, 2013
Inorganic Chemistry Communications, 2011
A unique heteronuclear Schiff base compound, [(NiL)Na(NiL)]ClO 4 (1), derived from the compartmen... more A unique heteronuclear Schiff base compound, [(NiL)Na(NiL)]ClO 4 (1), derived from the compartmental Schiff base ligand N,N′-(1,2-Phenylene)-bis(3-methoxysalicylideneimine) (H 2 L) has been prepared and its molecular structure has been elucidated on the basis of X-ray crystallography. The compound contains an octa-coordinated Na + in trigonal dodecahedral geometry and two terminal square planar Ni(II).
Dalton Transactions, 2012
= 2-methylthioanilide). The reaction proceeded through temperature induced valence tautomerisatio... more = 2-methylthioanilide). The reaction proceeded through temperature induced valence tautomerisation between the Ru(III) center and its 2-methylthioanilide counterpart in 1a with concomitant reduction of ruthenium from +III to +II oxidation state and oxidation of ligand L 1a , resulting in aromatic ring hydroxylation, N-formylation and C-C bond formation reactions. All the complexes have been characterised by their single-crystal X-ray structure determination and various spectroscopic and electrochemical techniques. The identity of complex 1a has been confirmed by X-ray crystal structure determination of complex 2, a phenyl analogue of complex 1a. The complexes (1a-d) showed intense charge transfer (MLCT/LMCT) transition in the long wavelength region. The paramagnetic compounds, 1a and 1c, along with the diamagnetic compound 1b showed two one-electron responses in the ranges, −0.4 to −1.0 V and 0.3 to 1.1 V. The diamagnetic complex 1d displayed two successive one-electron reversible reductions (−1.31 and −1.55 V) and two one-electron reversible oxidation processes (−0.036 and 0.51 V). The redox processes are characterized by EPR spectroscopy and spectroelectrochemistry. The compound 1c has been found to exhibit solvatochromism and concentration dependent aggregation in solution. † Electronic supplementary information (ESI) available: X-ray crystallographic files in CIF format for 1b-1d and 2; figures of ESI-MS and FT IR of 1a-1d; 1 H NMR of 1b and 1d in chloroform-d solvent; EPR spectra of 1a and electrogenerated species of compound 1b [1b] + and [1b] − ) and 1d ([1d] + and [1d] − ) in CH 3 CN/0.1 M Et 4 NClO 4 at 77 K; solvent and concentration dependent spectral changes of compound 1c are provided. CCDC 860740-860743. For ESI and crystallographic data in CIF or other electronic format see a In acetonitrile solution, supporting electrolyte TEAP, reference electrode Ag/AgCl. b E1 2 = 0.5(E pa + E pc ) where E pa and E pc are anodic and cathodic peak potentials respectively, ΔE p = E pa − E pc , scan rate 50 mV s −1 . c Quasireversible/irreversible. Scheme 3 Resonating form of complex 1c. 7060 | Dalton Trans., 2012, 41, 7057-7066 This journal is
Dalton Transactions
Large and small aggregates of Aβ peptides, resembling the morphology and dimensions of fibrillar ... more Large and small aggregates of Aβ peptides, resembling the morphology and dimensions of fibrillar and oligomeric forms of Aβ respectively, relevant to Alzheimer's disease, are stabilized on electrodes using selfassembly. Both of these forms were found to bind redox active Cu and heme, resulting in active sites having distinctive biophysical properties. The reduced metal bound Aβ active sites of both the oligomeric and fibrillar forms of Aβ produce detrimental partially reduced oxygen species (PROS). While the larger aggregates of heme-Aβ produce more PROS in situ, the smaller aggregates of Cu-Aβ produce more PROS. 8-Hydroxy quinoline and methylene blue are inhibitors of Cu and heme bound Aβ respectively, and are shown to efficiently reduce PROS formation in the oligomeric forms. However, these inhibitors are ineffective in reducing the toxicities of the Cu and heme bound Aβ peptides in the fibrils, making them significantly more lethal than the smaller Aβ aggregates.
Polyhedron, 2012
a b s t r a c t Five Fe(III) compounds, [Fe(salophen)(N 3 )(MeOH)] (1) [Fe(salophen)(NCS)(MeOH)] ... more a b s t r a c t Five Fe(III) compounds, [Fe(salophen)(N 3 )(MeOH)] (1) [Fe(salophen)(NCS)(MeOH)] (2), [Fe(vanophen)(HIm) 2 ]ClO 4 (3), [(l-O){Fe(vanophen)} 2 ]Á2H 2 O (4) and [(l-O){Fe(naphophen)} 2 ]Á2CH 2 Cl 2 ( where, H 2 salophen = N,N 0 -bis(salicylidene)phenylediamine, H 2 vanophen = N,N 0 -(1,2-phenylene)-bis(3-methoxysalicylideneimine) and H 2 naphophen = N,N 0 -bis(2-hydroxy-1-naphthaldehyde)-1,2-phenylenediimine, have been prepared and characterized by elemental analysis, IR and UV-Vis spectroscopy and singlecrystal X-ray diffraction studies. In compounds 1, 2 and 3, Fe(III) has six-coordinated pseudo-octahedral geometry in which the O(1), O(2), N(1) and N(2) atoms of the deprotonated di-Schiff base constitute the equatorial plane. Both in compounds 1 and 2, methanol molecules are present in the fifth coordination sites in apical positions. The sixth coordination sites are occupied by one N atom of an azide in compound 1 and an N atom of thiocyanate in compound 2. In compound 3, both axial positions are occupied by nitrogen atoms from two different imidazole molecules. In both compounds 4 and 5, Fe(III) has a fivecoordinated square pyramidal geometry with bridging oxygen atoms in the axial positions.
Polyhedron, 2013
Three heterometallic nickel(II)-sodium(I) complexes, [Ni(vanen)Na(NO 3 )] (1), [Ni(vanen)Na(vanen... more Three heterometallic nickel(II)-sodium(I) complexes, [Ni(vanen)Na(NO 3 )] (1), [Ni(vanen)Na(vanen)Ni] BF 4 (2) and [Ni(vanen)Na(ClO 4 )] n (3), have been synthesized by reacting nickel(II) and H 2 vanen with sodium(I), varying the reaction conditions and stoichiometry of the reactants [H 2 vanen = N,N 0ethylene-bis(3-methoxysalicylideneimine)]. All the three complexes have been characterized by X-ray single-crystal diffraction studies. In all the three complexes, nickel(II) is placed in the N 2 O 2 environment and sodium(I) is placed in the O 4 compartment of the compartmental Schiff base. In each complex, nickel(II) is square planar. Sodium(I) is trigonal dodecahedral in complex 2, and pentagonal pyramidal both in complexes 1 and 3. The nitrate ion is coordinated to sodium(I) in a chelating bidentate fashion. The sodium(I) in complex 1 shows strong p interaction with the phenyl ring of a second molecule. In complex 3, a carbon atom from an aryl group of a symmetry-related molecule is connected with sodium(I) in g 1 fashion to constitute 1D chain. The structure of complex 3 reveals an unprecedented heptadentate coordination mode of the deprotonated Schiff base.
Inorganic Chemistry, 2013
Inorganic Chemistry Communications, 2011
A unique heteronuclear Schiff base compound, [(NiL)Na(NiL)]ClO 4 (1), derived from the compartmen... more A unique heteronuclear Schiff base compound, [(NiL)Na(NiL)]ClO 4 (1), derived from the compartmental Schiff base ligand N,N′-(1,2-Phenylene)-bis(3-methoxysalicylideneimine) (H 2 L) has been prepared and its molecular structure has been elucidated on the basis of X-ray crystallography. The compound contains an octa-coordinated Na + in trigonal dodecahedral geometry and two terminal square planar Ni(II).
Dalton Transactions, 2012
= 2-methylthioanilide). The reaction proceeded through temperature induced valence tautomerisatio... more = 2-methylthioanilide). The reaction proceeded through temperature induced valence tautomerisation between the Ru(III) center and its 2-methylthioanilide counterpart in 1a with concomitant reduction of ruthenium from +III to +II oxidation state and oxidation of ligand L 1a , resulting in aromatic ring hydroxylation, N-formylation and C-C bond formation reactions. All the complexes have been characterised by their single-crystal X-ray structure determination and various spectroscopic and electrochemical techniques. The identity of complex 1a has been confirmed by X-ray crystal structure determination of complex 2, a phenyl analogue of complex 1a. The complexes (1a-d) showed intense charge transfer (MLCT/LMCT) transition in the long wavelength region. The paramagnetic compounds, 1a and 1c, along with the diamagnetic compound 1b showed two one-electron responses in the ranges, −0.4 to −1.0 V and 0.3 to 1.1 V. The diamagnetic complex 1d displayed two successive one-electron reversible reductions (−1.31 and −1.55 V) and two one-electron reversible oxidation processes (−0.036 and 0.51 V). The redox processes are characterized by EPR spectroscopy and spectroelectrochemistry. The compound 1c has been found to exhibit solvatochromism and concentration dependent aggregation in solution. † Electronic supplementary information (ESI) available: X-ray crystallographic files in CIF format for 1b-1d and 2; figures of ESI-MS and FT IR of 1a-1d; 1 H NMR of 1b and 1d in chloroform-d solvent; EPR spectra of 1a and electrogenerated species of compound 1b [1b] + and [1b] − ) and 1d ([1d] + and [1d] − ) in CH 3 CN/0.1 M Et 4 NClO 4 at 77 K; solvent and concentration dependent spectral changes of compound 1c are provided. CCDC 860740-860743. For ESI and crystallographic data in CIF or other electronic format see a In acetonitrile solution, supporting electrolyte TEAP, reference electrode Ag/AgCl. b E1 2 = 0.5(E pa + E pc ) where E pa and E pc are anodic and cathodic peak potentials respectively, ΔE p = E pa − E pc , scan rate 50 mV s −1 . c Quasireversible/irreversible. Scheme 3 Resonating form of complex 1c. 7060 | Dalton Trans., 2012, 41, 7057-7066 This journal is
Chemical Engineering Journal - CHEM ENG J, 2010
The performances of aqueous mixtures of the model nonionic surfactant Triton X-100 (TX100) and ch... more The performances of aqueous mixtures of the model nonionic surfactant Triton X-100 (TX100) and chitosan (CS) for the solubilization of the hydrophobic organic compound phenanthrene (PHE) were evaluated by varying mixture compositions. The addition of minute amounts of CS into TX100 solutions above the critical micelle concentration significantly increased PHE solubility. The PHE solubility was maximized at certain optimal concentrations of CS increasing in proportion to the TX100 concentrations, which were 2, 10, and 20 mg/L CS for 5, 10, and 20 g/L TX100, respectively. At each optimal concentration of CS, PHE solubility was increased by 46%, 39%, and 43% for the 5, 10, and 20 g/L TX100 solutions, respectively. The enhanced solubilization of PHE by the addition of CS to TX100 solutions may be attributable to multiple factors, such as an increase of micellar size and hydrophobicity as well as to the formation of variously configured micelle-polymer aggregates.
Separation Science and Technology, 2011
The structural organization of chitosan hydrogel beads (CSBs) formed by various anionic surfactan... more The structural organization of chitosan hydrogel beads (CSBs) formed by various anionic surfactants, sodium dodecyl sulfate (SDS), sodium decyl sulfate (DS), dodecyl benzenesulfonic acid sodium salt (SDBS), and dioctyl sulfosuccinate sodium salt (DSS), and their applications as adsorbents for environmental purifications were investigated using Congo red (CR) as a model dye. The adsorption capacities of CSB as a function of
Pure and Applied Chemistry, 2000
A variant of subtilisin Carlsberg thiolsubtilisin, in which the active site serine residue is rep... more A variant of subtilisin Carlsberg thiolsubtilisin, in which the active site serine residue is replaced by a thiol-containing cysteine has been synthesized in our laboratory. From the results of analysis of the resulting enzyme it can be argued that the mechanism of subtilisin suspended in organic solvents involves Ser221, undoubtedly in the formation of an acyl-enzyme intermediate. Further, the active site of the enzyme is not interacting with bulk solvent, and the environment of Ser221 is not radically altered by changing the solvent in which the enzyme is suspended. The enzyme structure has also been analyzed with FT-IR t o demonstrate that the global secondary structure is the same in organic dispersants as in water. Finally, the morphology of subtilisin particles has been studied during hydration in the gas phase using ESEM.
Korean Journal of Chemical Engineering, 2011
ABSTRACT The coagulation of soil particles from a soil-washing solution containing the nonionic s... more ABSTRACT The coagulation of soil particles from a soil-washing solution containing the nonionic surfactant Triton X-100 (TX100) was investigated using various coagulants, such as chitosan (CS), polyacrylamide (PAA), and polyaluminum chloride (PAC). Soil contaminated with phenanthrene (PHE) was washed with aqueous TX100 solutions at concentrations ranging from 0.1 to 20 g/L. The effectiveness of CS (5 mg/L) as a coagulant in the system was compared with PAA (50mg/L) and PAC (50 mg/L), and the results indicated that the system with CS exhibited a more effective separation of soil than those with PAA and PAC. The removal efficiency of PHE (R j =81.7%) and the selective separation factor (SSF=14.2) at 10 g/L TX100 were the highest for the system with CS (5 mg/L), indicating that the selection of CS as a coagulant in surfactant-mediated soil washing markedly improved both PHE removal and soil separation. Key wordsChitosan–Coagulation–Phenanthrene–Soil Washing–Surfactant
Enzyme and Microbial Technology, 1993
Environmental Technology, 2011
Chitosan hydrogel beads (CSB) formed by sodium dodecyl sulphate (SDS) gelation were used for the ... more Chitosan hydrogel beads (CSB) formed by sodium dodecyl sulphate (SDS) gelation were used for the removal of a cationic dye, methylene blue (MB), from aqueous solutions. The adsorption capacity of chitosan beads (CB) formed by alkali gelation was low because of charge repulsions between the chitosan (CS) and the MB. The adsorption capacity of CSB (4 g/L SDS gelation) for MB (100 mg/L) was 129.44 mg/g, and it decreased significantly with increasing SDS concentration during gelation. This decrease was a result of increased density of the CSB membrane materials. The CSB membrane materials formed with the 4 g/L SDS gelation showed the highest volumetric adsorption capacity. The MB adsorption on to CB and CSB increased with increasing values for the initial pH of solution. Data from both CB and CSB showed good fit to Sips isotherm models, and the maximum adsorption capacity of CSB (226.24 mg/g) was higher than that of CB (99.01 mg/g).
Desalination and Water Treatment, 2012
ABSTRACT The solubility of solid phenanthrene (PHE) powder in aqueous solutions of surfactant and... more ABSTRACT The solubility of solid phenanthrene (PHE) powder in aqueous solutions of surfactant and chitosan (CS) was evaluated by varying the composition of aqueous mixtures. Cetyltrimethyl ammoniumbromide (CTAB) and sodium dodecyl sulfate (SDS) were used as model cationic and anionic surfactants, respectively. CS at a particular concentration in the mixture especially above the CMC value of the anionic surfactant exhibited somewhat higher PHE solubility values than surfactant itself. CS (20 mg/l)-SDS (20 g/l) solution showed higher PHE solubility (422.05 mg/l) than that of 20 g/l SDS (377.92 mg/g). However, CS-CTAB did not show any additional enhancing effect on PHE solubilization, and CS (5 mg/l)-CTAB (10 g/l) solution showed almost similar PHE solubility (867.23 mg/l) of 10 g/l CTAB (865.25 mg/g). The maximum increase in absorbance value of a 20 ml CS solution (5, 20 and 100 mg/l) at 540 nm with stepwise addition of SDS (10 g/l) was found at a SDS concentration much less than its CMC value (2.33 g/l) in the mixture, indicating strong complex formation between CS and SDS because of oppositely charged molecules in the experimental conditions
Chemosphere, 2009
Effective coagulation and separation of particles in a soil-washed solution is required for a suc... more Effective coagulation and separation of particles in a soil-washed solution is required for a successful soil washing process. The effectiveness of chitosan (CS), a polycationic biodegradable polymer, as a coagulant was compared to polyacrylamide (PAA) and polyaluminium chloride (PAC) for the coagulation of a soil suspension (5 gL(-1)). The effect of surfactants in the coagulation process was investigated using Triton X-100 (TX-100), a nonionic surfactant, and sodium dodecyl sulfate (SDS), an anionic surfactant. CS (5 mgL(-1)) removed 86% and 63% of the suspended soil in the presence of TX-100 (5 gL(-1)) and SDS (5 gL(-1)), respectively, after 30 min at a pH of 6. The results prove that coagulation in the presence of TX-100 is more effective than with SDS. CS was found to be more efficient compared to PAA and PAC under all coagulation conditions. The optimum concentration of CS required for maximum coagulation of soil suspension was 5 mgL(-1). PAA and PAC could not achieve the same degree soil removal as CS even after increasing their concentrations up to 50 mgL(-1). Maximum levels of 50% and 60% soil removal were achieved using PAA (50 mgL(-1)) and PAC (50 mgL(-1)), respectively, after 30 min from a 5 gL(-1) suspension containing TX-100 (5 gL(-1)). The soil coagulation process was found to decrease with an increase in the pH of the suspension, and maximum coagulation was achieved with an acidic pH.
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Papers by Sudipta Chatterjee