Publications by authors named "Supriya Das"

11 Publications

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Abrasion tolerant, non-stretchable and super-water-repellent conductive & ultrasensitive pattern for identifying slow, fast, weak and strong human motions under diverse conditions.

Mater Horiz 2021 Sep 9. Epub 2021 Sep 9.

Department of Chemistry, Indian Institute of Technology-Guwahati, Kamrup, Assam 781039, India.

The conversion of mechanical deformation into electrical signals is a widely used principle for various relevant applications. Facile & scalable fabrication, ultrahigh-sensitivity, low-response time and uninterrupted performance under severe conditions are hallmarks of an efficient strain-sensor that would be suitable for realistic application. In the past, various approaches were introduced to achieve high gauge factor-mainly associated with a large tensile deformation. But, in reality, a flexible strain sensor that displays a high gauge factor at low applied strain and remains efficient under practically relevant diverse and challenging conditions would be more appropriate for unambiguous and effective monitoring of human motions and other relevant applications. But, a low-strain sensor with ultrahigh sensitivity and durability is yet to be introduced in the literature. Here, a metal-free, chemically reactive and conductive ink is unprecedentedly introduced following a 1,4-conjugate addition reaction. Furthermore, a strategic integration of a chemically reactive porous paper with the prepared conductive ink allowed the development of a chemically reactive and conductive interface that allowed desired post covalent modification with selected alkylamines under ambient conditions. Taking advantage of the spatially selective deposition of the prepared ink on chemically recative paper and the ability of post covalent modification of the prepared ink, an abrasion tolerant superhydrophobic & conductive patterned interface was developed for achieving a low-strain (below 0.2%) based flexible strain sensor with an ultrahigh sensitivity (gauge factor ∼18 300) and low response time (8 ms). The external low-strain induced cracks on the flexible & durable superhydrophobic and conductive patterned interface provided a facile basis for real-time & wireless monitoring of slow, fast, weak and strong human motions & expressions-under diverse conditions, including continuous aqueous exposures, physical abrasions
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http://dx.doi.org/10.1039/d1mh01071aDOI Listing
September 2021

Covalently Modulated and Transiently Visible Writing: Rational Association of Two Extremes of Water Wettabilities.

ACS Appl Mater Interfaces 2020 Jan 2;12(2):2935-2943. Epub 2020 Jan 2.

Department of Chemistry and Centre for Nanotechnology , Indian Institute of Technology-Guwahati , Kamrup , Assam 781039 , India.

Anticounterfeiting measures are of ever-increasing importance in society, e.g., for securing the authenticity of and the proof of origin for medical drugs. Here, an arms race of counterfeiters and valid manufacturers is taking place, resulting in the need of hard-to-forget, yet easy-to-read out marks. Anticounterfeiting measures based on micropatterns-while being attractive for their need in not widely available printing methods while still being easily read out with fairly common basic optical equipment-are often limited by being too easy to be destroyed by wear or handling. Here, nature-inspired wettability is rationally exploited for developing an unprecedented anticounterfeiting method, where hidden information can be only identified under direct exposures to an aqueous phase or mist and disappears again on air-drying the interface. A chemically reactive and hierarchically featured dip coating, capable of spatially selective covalent modification with primary amine containing small molecules, is developed for abrasion-tolerant patterning interfaces with two extremes of water wettabilities, i.e., superhydrophilicity and superhydrophobicity. Arbitrary handwriting with glucamine followed by chemical modification with octadecylamine, provided "invisible" text on the synthesized interface. The glucamine-treated region selectively becomes optically transparent and superhydrophilic due to rapid infiltration of the aqueous phase on exposure to liquid water or mist. The remaining interface remains opaque and superhydrophobic due to metastable entrapment of air. The hidden text became transiently and reversibly visible by the naked eye under exposure to liquid water/mist. Furthermore, microchannel-cantilever spotting (μCS) is adopted for demonstrating well-defined chemical patterning on the microscale. These patterns are at the same time highly resistant against wear and scratching because of the bulk functionalization, retaining the wetting properties (and thus pattern readout) even on serious abrasion. Such a simple synthesis of spatially controlled, direct, and covalently modulated wettability could be useful for various applied and fundamental contexts.
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http://dx.doi.org/10.1021/acsami.9b17470DOI Listing
January 2020

Order, Disorder, and Reorder State of Lysozyme: Aggregation Mechanism by Raman Spectroscopy.

J Phys Chem B 2020 01 27;124(1):50-60. Epub 2019 Dec 27.

Structural Biology and Bioinformatics Division , Indian Institute of Chemical Biology, Council of Scientific and Industrial Research , 4, Raja S.C. Mullick Road , Kolkata 700032 , India.

Lysozyme, like many other well-folded globular proteins, under stressful conditions produces nanoscale oligomer assembly and amyloid-like fibrillar aggregates. With engaging Raman microscopy, we made a critical structural analysis of oligomer and other assembly structures of lysozyme obtained from hen egg white and provided a quantitative estimation of a protein secondary structure in different states of its fibrillation. A strong amide I Raman band at 1660 cm and a N-Cα-C stretching band at ∼930 cm clearly indicated the presence of a substantial amount of α-helical folds of the protein in its oligomeric assembly state. In addition, analysis of the amide III region and Raman difference spectra suggested an ample presence of a PPII-like secondary structure in these oligomers without causing major loss of α-helical folds, which is found in the case of monomeric samples. Circular dichroism study also revealed the presence of typical α-helical folds in the oligomeric state. Nonetheless, most of the Raman bands associated with aromatic residues and disulfide (-S-S-) linkages broadened in the oligomeric state and indicated a collapse in the tertiary structure. In the fibrillar state of assembly, the amide I band became much sharper and enriched with the β-sheet secondary structure. Also, the disulfide bond vibration in matured fibrils became much weaker compared to monomer and oligomers and thus confirmed certain loss/cleavage of this bond during fibrillation. The Raman band of tryptophan and tyrosine residues indicated that some of these residues experienced a greater hydrophobic microenvironment in the fibrillar state than the protein in the oligomeric state of the assembly structure.
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http://dx.doi.org/10.1021/acs.jpcb.9b09139DOI Listing
January 2020

Catalyst-Free and Rapid Chemical Approach for in Situ Growth of "Chemically Reactive" and Porous Polymeric Coating.

ACS Appl Mater Interfaces 2019 Sep 5;11(37):34316-34329. Epub 2019 Sep 5.

Design of "chemically reactive" coating with a tailored topography is a simple basis for optimizing various physical and chemical parameters, which is essential for achieving different biomimicked liquid wettability. In general, the essential topography and appropriate chemistry in the superhydrophobic coating is optimized following various top-down and bottom-up approaches, where various hydrophilic building blocks are associated using electrostatic interaction, hydrogen bonding, and other weak bonding (e.g., metal-thiol etc.), for both developing the desired hierarchical features and optimizing the appropriate chemistry on top of this featured interface. Such designs are inappropriate to sustain practically relentlessly harsh settings. So, further development for the synthesis of a durable and substrate-independent superhydrophobic coating is essential for various prospective applications in "real-world" scenarios. However, the design of highly abrasion-tolerant and "absolutely" substrate-independent artificial superhydrophobicity following a simple and scalable synthesis procedure is rare in literature. In this current work, a catalyst-free and facile chemical approach is adopted for an in situ and rapid deposition of a "chemically reactive" nanocomplex for decorating a wide range of substrates, including water-soluble, water-sensitive, highly flexible, rigid, and fibrous substrates with a highly tolerant biomimicked superhydrophobicity property. Branched poly(ethylenimine) (BPEI) and dipentaerythritol pentaacrylate (5Acl) mutually react through 1,4-conjugate addition reaction, and a hierarchically featured "chemically reactive" dip-coating is synthesized by the appropriate selection of the alcoholic solvent that is 1-heptanol. Furthermore, the choice of small alkylamines for post-covalent modifications of the "chemically reactive" dip-coating provided superhydrophobicity with a tailored water adhesion. A gradual increase in both roll-off angles, and the contact angle hysteresis (from 5° to 30°) was noted with a decrease in the hydrocarbon tail of selected alkylamines. The synthesized biomimicked interfaces are capable of performing under various practically relevant, severe physical and chemical challenges including bending, creasing, twisting, different physical abrasions (i.e., adhesive tape peeling test, abrasive sand paper test, etc.), high compressive strain, highly acidic and alkaline aqueous phases, artificial sea water, river water, etc. Moreover, this current approach was extended in developing various relevant functional materials, including superhydrophilic/superhydrophobic physical patterns on flexible papers and highly compressible super-oil-absorbent, etc.
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http://dx.doi.org/10.1021/acsami.9b11113DOI Listing
September 2019

Envisaging Structural Insight of a Terminally Protected Proline Dipeptide by Raman Spectroscopy and Density Functional Theory Analyses.

J Phys Chem A 2016 Dec 6;120(49):9829-9840. Epub 2016 Dec 6.

Structural Biology & Bio-informatics Division and ‡Organic & Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology ; 4, Raja S.C. Mullick Road, Kolkata 700032, West Bengal, India.

The proline residue in a protein sequence generates constraints to its secondary structure as the associated torsion angles become a part of the heterocyclic ring. It becomes more significant when two consecutive proline residues link via amide linkage and produce additional configurational constraint to a protein's folding and stability. In the current manuscript we have illustrated conformation preference of a novel dipeptide, (R)-tert-butyl 2-((S)-2-(methoxycarbonyl)pyrrolidine-1-carbonyl)pyrrolidine-1-carboxylate. The dipeptide crystallized in the orthorhombic crystalline state and produced rod-shaped macroscopic material. The analysis of the crystal coordinates showed dihedral angles (φ, ψ) of the interlinked amide groups as (+72°, -147°) and the dihedral angles (φ, ψ) produced with the next carbonyl were (-68°, +151°), indicating polyglycine II (PGII) and polyproline II (PPII)-like helix states at the N- and C-terminals, respectively. These two states, PGII and PPII, are mirror image configurations and are expected to produce similar vibration bands from the associated carbonyl groups. However, the unique atomic arrangement in the molecule produces three carbonyl groups and one of them was very specific, being part of the main peptide linkage that connects both the pyrrolidine rings. The carbonyl group in the peptide bond exhibited a Raman vibration frequency at ∼1642 cm and is considered a signatory Raman marker band for the peptide bond linking two heterochiral proline residues. The carbonyl group (t-Boc) at the N-terminal of the peptide showed a characteristic vibration at ∼1685 cm and the C-terminal carbonyl group as a part of the ester showed a vibration signature at a significantly high frequency (1746 cm). Conformation analyses performed with density functional theory (DFT) calculations depicted that the dipeptide was stabilized in vacuum with dihedral angles (+72°, -154°) and (-72°, +151°) at the N- and C-terminals, respectively. Molecular dynamics (MD) simulation also showed that the peptide conformation having dihedral angles around (+75°, -150°) and (-75°, +150°) at the N- and C-terminals, respectively, was reasonably stable in water. Due to unique absence of the amide N-H, the peptide was ineffective in forming any intramolecular hydrogen bonding. MD investigation, however, revealed an intermolecular hydrogen bonding interaction with the water molecules, leading to its stability in aqueous solution. Metadynamics simulation analysis of the dipeptide in water also supported the PGII-PPII-like conformation at the N- and C-terminals, respectively, as the energetically stable conformation among the other possible combinations of conformations. The possible electronic transitions along with the HOMO-LUMO analysis further depicted the stability of the dipeptide in water and their possible absorption pattern. Time-dependent density functional theory (TDDFT) analysis showed strong negative rotatory strength of the dipeptide around 210 nm in water and acetonitrile, and it could be the source of experimentally observed high-amplitude negative absorption in the circular dichroism (CD) spectra around 200-203 nm. The very weak positive band (signature) in the region at ∼228 nm in CD spectra could also be correlated to the positive rotatory strength at 228 nm observed in ECD. To test the effect of such a dipeptide on a living cell, an MTT assay was performed and the result indicated no cytotoxic effect toward human hepatocellular carcinoma Hep G2 cancer cell lines.
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http://dx.doi.org/10.1021/acs.jpca.6b10017DOI Listing
December 2016

Orientation of tyrosine side chain in neurotoxic Aβ differs in two different secondary structures of the peptide.

R Soc Open Sci 2016 Oct 5;3(10):160112. Epub 2016 Oct 5.

Structural Biology and Bioinformatics Division , Indian Institute of Chemical Biology, Council of Scientific and Industrial Research , 4, Raja S.c. Mullick Road, Kolkata 700032 , India.

Amyloid β (Aβ) peptide is present as a major component in amyloid plaque that is one of the hallmarks of Alzheimer's disease. The peptide contains a single tyrosine residue and Aβ has a major implication in the pathology of the disease progression. Current investigation revealed that the tyrosine side chain attained two different critical stereo orientations in two dissimilar conformational states of the peptide. The extended α-helical structure of the peptide observed in an apolar solvent or methanol/water mixture became disordered in aqueous medium and the radius of gyration decreased. In aqueous medium, the torsional angle around C-C of tyrosine group became -60°. However, in its α-helical conformation in an apolar system, the measured angle was 180° and this rotameric state may be reasoned behind stronger tyrosine fluorescence compared with the disordered state of the peptide. Molecular dynamics simulation analyses and spectroscopic studies have helped us to understand the major structural changes in the secondary structure of the peptide in the two conformational states. A conformational clustering indicated that the compact state is more stable with tyrosine residue attaining the torsion angle value of -60°, whereas the native state (in HFIP/water mixture) is prevalent at a torsion angle value of -180°. High solvent accessibility has possibly stabilized the particular rotameric state (-60°) of the tyrosine residue and could be the reason behind decrease in fluorescence of the sole tyrosine residue in an aqueous buffer solution (pH 7.4) compared with its fluorescence in the α-helical structure in the micellar environment.
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http://dx.doi.org/10.1098/rsos.160112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5098961PMC
October 2016

Synthesis and biological evaluation of a novel betulinic acid derivative as an inducer of apoptosis in human colon carcinoma cells (HT-29).

Eur J Med Chem 2015 Sep 21;102:93-105. Epub 2015 Jul 21.

Organic and Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata 700032, India. Electronic address:

A novel family of betulinic acid analogues, carrying a triazole unit at C-3 attached through a linker, was synthesized by the application of azide-alkyne "Click reaction". These were screened for their anticancer activity against different cancer cells and normal human PBMC by MTT assay. Compound 2c [(3S)-3-{2-(4-(hydroxymethyl-1H-1,2,3-triazol-1-yl)acetyloxy}-lup-20(29)-en-28-oic acid] was found as the most potent inhibitor of cell line HT-29 with IC50 value 14.9 μM. Its role as an inducer of apoptosis was investigated in this cell line by Annexin-V/PI binding assay and by following its capability for ROS generation, depolarization of mitochondrial transmembrane potential, activation of caspases, PARP cleavage, nuclear degradation and expression of pro- and anti-apoptotic proteins. It exhibited much higher cytotoxicity than the standard drug 5-fluorouracil but showed negligible cytotoxicity towards normal PBMC. Elevated level of ROS generation, activation of caspase 3 and caspase 9, DNA fragmentation, higher expression of Bax and Bad, lower expression of Bcl2 and Bcl-xl, and increased level of Bax/Bcl-xl ratio identified 2c as a promising inducer of apoptosis that follows a mitochondria dependent pathway. Bio-physical studies indicate that compound 2c acts as a minor groove binder to the DNA.
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http://dx.doi.org/10.1016/j.ejmech.2015.07.035DOI Listing
September 2015

ZnI2-Catalyzed Diastereoselective [4 + 2] Cycloadditions of β,γ-Unsaturated α-Ketothioesters with Olefins.

J Org Chem 2015 Mar 9;80(6):2972-88. Epub 2015 Mar 9.

†Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032, India.

The potential of β,γ-unsaturated α-ketothioesters participating in hetero-Diels-Alder reaction has remained unexplored. We report herein the first study of a ZnI2-catalyzed highly diastereoselective inverse electron demand hetero-Diels-Alder reaction of β,γ-unsaturated α-ketothioesters with olefins to access highly substituted 3,4-dihydro-2H-pyrans. All the reactions proceed with cis-selectivity in moderate to excellent yields. Under similar reaction conditions, terminal alkynes undergo direct conjugate 1,4-addition to yield δ,ε-acetylenic α-ketothioesters. Furthermore, the utility of these cycloadducts has been demonstrated by an NBS-MeOH mediated stereospecific efficient access to fully substituted pyran rings. The product bromoethers undergo E2 elimination with DBU, resulting in substituted 3,6-dihydro-2H-pyrans. In addition, the thioester moiety of the products has been used for further transformations, such as amidations and Fukuyama coupling reactions.
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http://dx.doi.org/10.1021/jo5024766DOI Listing
March 2015

Stability and binding interaction of bilirubin on a gold nano-surface: steady state fluorescence and FT-IR investigation.

Phys Chem Chem Phys 2014 Oct;16(37):20013-22

Division of Structural Biology and Bioinformatics, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Kolkata, 700032, India.

A gold nanoparticle exhibits strong absorption and emission due to its unique physical geometry and surface plasmon resonance phenomena. A further modification with organic molecules makes it more appropriate for biological applications. The current manuscript illustrated the optical behavior and stability of bilirubin (BR) coated gold (AuBR) nanoparticles, using BR itself as a reducing agent. In addition, FT-IR and steady state fluorescence measurements were performed to illustrate the binding interaction of BR with the Au(III) ion and the nanoparticles. BR showed a strong affinity towards Au(III) and the measured binding constant was ∼4.3 × 10(5) M(-1). It caused reduction of the Au(III) ion and rendered the formation of cubic face centered AuBR nanoparticles, which were ∼20 nm in diameter. The particles were stabilized as BR was bound to the gold nanoparticle surface, which was confirmed by FT-IR measurement. An intense carboxyl C=O stretching vibration at 1695 cm(-1) was observed for the BR powder but was absent for the AuBR nanoparticles. However, two weak bands at ∼1563 and 1391 cm(-1), presumably due to the asymmetric and symmetric stretching vibrations of the carboxylate form (COO(-)), were found for the AuBR nanoparticles. A stretching vibration of lactam C[double bond, length as m-dash]O appeared at 1645 cm(-1) for BR and the band was shifted to 1647 cm(-1) for the AuBR nanoparticles. The stretching modes of pyrrole N-H and lactam N-H were detected at 3406 cm(-1) and 3267 cm(-1), respectively, for BR. However, the pyrrole N-H band shifted to 3446 cm(-1) and became broader for the AuBR nanoparticles. The observed blue shift in the lactam C[double bond, length as m-dash]O and N-H vibrations of the AuBR nanoparticles indicated a weakening/absence of internal hydrogen bonds between the carboxyl groups and the four N-H bonds in the BR moiety. The binding of BR to the surface provides great stability to the nanoparticles, which remained monodispersed in the large pH range (pH 4 to 12) for more than a month. However, under acidic pH conditions the particles associated to form bigger particles and the plasmon resonance band shifted as they grew; the plasmon resonance band shifted from 525 nm (at pH 7.0) to 555 nm (at pH 3.0). The particles also remained stable in the presence of a higher concentration of salt (KCl and NaCl) in the dispersing media.
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http://dx.doi.org/10.1039/c4cp02649gDOI Listing
October 2014

Synthesis and biological evaluation of andrographolide analogues as anti-cancer agents.

Eur J Med Chem 2014 Oct 24;85:95-106. Epub 2014 Jul 24.

Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata 700032, India. Electronic address:

A new family of andrographolide analogues were synthesized and screened in vitro against kidney (HEK-293) and breast (MCF-7) cancer cells. The anti-cancer effects of the active analogues (2b, 2c and 4c) were determined by multiple cell based assays such as MTT, immunostaining, FACS, western blotting and transcriptional inhibition of NF-κB activity. Importantly, these compounds were found to possess higher anti-cancer potency than andrographolide and low toxicity to normal (VERO and MCF-10A) cells. Increased level of Bax/Bcl-xL ratio, caspase 3, and sub G1 population, higher expression level of tumor suppressor protein p53 and lower expression level of NF-κB suggested potent apoptotic property of the active analogues. Data revealed that the andrographolide derivative-mediated cell death in cancer cells was p53 dependent.
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http://dx.doi.org/10.1016/j.ejmech.2014.07.088DOI Listing
October 2014

Sequence complexity of amyloidogenic regions in intrinsically disordered human proteins.

PLoS One 2014 3;9(3):e89781. Epub 2014 Mar 3.

Structural Biology and Bioinformatics Division, Council of Scientific and Industrial Research (CSIR)-Indian Institute of Chemical Biology (IICB), Kolkata, India.

An amyloidogenic region (AR) in a protein sequence plays a significant role in protein aggregation and amyloid formation. We have investigated the sequence complexity of AR that is present in intrinsically disordered human proteins. More than 80% human proteins in the disordered protein databases (DisProt+IDEAL) contained one or more ARs. With decrease of protein disorder, AR content in the protein sequence was decreased. A probability density distribution analysis and discrete analysis of AR sequences showed that ∼8% residue in a protein sequence was in AR and the region was in average 8 residues long. The residues in the AR were high in sequence complexity and it seldom overlapped with low complexity regions (LCR), which was largely abundant in disorder proteins. The sequences in the AR showed mixed conformational adaptability towards α-helix, β-sheet/strand and coil conformations.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0089781PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3940659PMC
January 2015
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