Ishani Mitra - Academia.edu (original) (raw)

Papers by Ishani Mitra

Research paper thumbnail of Effects of carbon quantum dots (CQD) on the energy storage capacity of a novel synthesized short-chain dyad

Chemical Physics Letters, 2019

On photoexcitation 80% trans-structure of nanocomposite dyad remain unaffected. • The dyad-CQD na... more On photoexcitation 80% trans-structure of nanocomposite dyad remain unaffected. • The dyad-CQD nanocomposites look better energy-storage systems than pristine dyad. • Primarily surface trap effect stabilizes trans-structure.

Research paper thumbnail of Comparative Analysis to Explore the Suitability of a Short Chain Dyad in Its Pristine and Nanocomposite Forms for Designing Artificial Light Energy Conversion Device

Journal of Nanoscience and Nanotechnology, 2018

Research paper thumbnail of To reveal the nature of interactions of human hemoglobin with gold nanoparticles having two different morphologies (sphere and star-shaped) by using various spectroscopic techniques

Journal of photochemistry and photobiology. B, Biology, Jan 22, 2017

The nature of interactions between heme protein human hemoglobin (HHb) and gold nanoparticles of ... more The nature of interactions between heme protein human hemoglobin (HHb) and gold nanoparticles of two different morphologies that is GNP (spherical) and GNS (star-shaped) have been investigated by using UV-vis absorption, steady state fluorescence, synchronous fluorescence, resonance light scattering (RLS), time resolved fluorescence, FT-IR, and circular dichroism (CD) techniques under physiological condition of pH ~7 at ambient and different temperatures. Analysis of the steady state fluorescence quenching of HHb in aqueous solution in the presence of GNP and GNS suggests that the nature of the quenching is of static type. The static nature of the quenching is also confirmed from time resolved data. The static type of quenching also indicates the possibility of formation of ground state complex for both HHb-GNP and HHb-GNS systems. From the measurements of Stern-Volmer (SV) constants KSV and binding constants, KA and number of binding sites it appears that HHb forms stronger binding...

Research paper thumbnail of Contrasting spectroscopic response of human hemoglobin in presence of graphene oxides and its reduced form: Comparative approach with carbon quantum dots

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2021

Recently, a considerable amount of research is being directed towards study of graphene oxide (GO... more Recently, a considerable amount of research is being directed towards study of graphene oxide (GO) and its reduced form (RGO) since their exposed functional groups make them better candidates in nanobiotechnolgy. In order to assess their biocompatibility, the nature of interactions between Human Hemoglobin (HHb) and GO/RGO are monitored since a comparative spectroscopic approach towards understanding their nature of interactions has not been investigated previously. UV-vis spectroscopy reveals hyperchromicity for HHb-GO system and hypochromicity for HHb-RGO system in the region of absorption of tryptophan/tyrosine residues. Notably, although steady-state fluorescence static quenching of HHb for GO and enhancement of fluorescence for RGO is noticed, but average fluorescence-lifetime is remaining unchanged in presence of GO/RGO. Calorimetric data illustrates three-site and five-site binding model to be the best-fit model for GO and RGO respectively. Also, synchronous fluorescence quenching corresponding to alterations in microenvironment of tryptophan/ tyrosine residues is observed only in presence of GO. Likewise FTIR spectroscopy elucidates involvement of both amide I and amide II bond of HHb backbone through H-bonding interaction only for GO. Furthermore RLS spectra demonstrate an increase and a decrease in signal for GO and RGO respectively. Surprisingly, secondary structure of HHb is maintained upon interaction with both GO/RGO, as revealed by CD spectroscopy, thus supporting their potential application in biological microenvironment. Thus it appears that the spectroscopic properties of HHb upon interaction with GO is altered upon its reduction to RGO. Furthermore the role of HHb as good candidate for bimolecular interaction has been highlighted.

Research paper thumbnail of Fluorescence enhancement via aggregation effect due to microenvironmental alterations in human hemoglobin protein in presence of carbon quantum dots (CQD): Comparative spectroscopic approach

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

CQDs have emerged with outstanding properties as a star member of carbon nanomaterial family and ... more CQDs have emerged with outstanding properties as a star member of carbon nanomaterial family and in order to reveal its wide-range of application in biological microenvironment the interactions between human hemoglobin (HHb) and CQD and also with ethylenediamine-functionalized CQD (NCQD) are assessed using several techniques. Firstly, UV-vis absorption spectra of HHb reveal hyperchromic effect in the region of absorbance of tryptophan and tyrosine residues and also hypochromicity of Soret band in presence of CQD and NCQD. Interestingly, steady-state fluorescence spectroscopy reveal distinct fluorescence enhancement of HHb with significant red shift thereby indicating exposures of tryptophan and tyrosine residues to a more hydrophilic environment. However synchronous fluorescence spectra reveal that the microenvironment of tryptophan and tyrosine residues is altered in opposite manner, i.e. exposure of tryptophan residues to a more hydrophilic environment and the tyrosine residues to a more hydrophobic environment. Moreover the fluorescence enhancement is observed to be accompanied by increase in average fluorescence-lifetime and decrease in steady-state anisotropy thus signifying a decrease in restriction of rotational motion. Furthermore tryptophan residues within HHb appear to interact more with CQD compared to NCQD. Thermodynamic parameters as revealed by Isothermal Titration Calorimetry (ITC) demonstrate that electrostatic, hydrogen bonding and hydrophobic interactions are the predominant modes of interactions in presence of CQD. Whereas hydrophobic and hydrogen bonding interactions are the major interacting forces in presence of NCQD with five-site sequential binding as best-fit model in both the cases. Such interactions also appear to be associated with an increase in aggregation of HHb as evident from the measurements by atomic force microscopy (AFM) and dynamic light scattering (DLS) study. Although FT-IR spectra display alteration of amide I band, but the overall secondary structure of HHb seems to be nearly retained even in presence of CQDs, as evident in the CD spectra. These observations thus highlight the potential biomedical application of CQDs in biological microenvironment of human especially as drug-delivery system. Also bimolecular interaction of HHb as a model protein with other nanoparticles at the nano bio-interface has been outlined.

Research paper thumbnail of Effects of carbon quantum dots (CQD) on the energy storage capacity of a novel synthesized short-chain dyad

Chemical Physics Letters, 2019

On photoexcitation 80% trans-structure of nanocomposite dyad remain unaffected. • The dyad-CQD na... more On photoexcitation 80% trans-structure of nanocomposite dyad remain unaffected. • The dyad-CQD nanocomposites look better energy-storage systems than pristine dyad. • Primarily surface trap effect stabilizes trans-structure.

Research paper thumbnail of Comparative Analysis to Explore the Suitability of a Short Chain Dyad in Its Pristine and Nanocomposite Forms for Designing Artificial Light Energy Conversion Device

Journal of Nanoscience and Nanotechnology, 2018

Research paper thumbnail of To reveal the nature of interactions of human hemoglobin with gold nanoparticles having two different morphologies (sphere and star-shaped) by using various spectroscopic techniques

Journal of photochemistry and photobiology. B, Biology, Jan 22, 2017

The nature of interactions between heme protein human hemoglobin (HHb) and gold nanoparticles of ... more The nature of interactions between heme protein human hemoglobin (HHb) and gold nanoparticles of two different morphologies that is GNP (spherical) and GNS (star-shaped) have been investigated by using UV-vis absorption, steady state fluorescence, synchronous fluorescence, resonance light scattering (RLS), time resolved fluorescence, FT-IR, and circular dichroism (CD) techniques under physiological condition of pH ~7 at ambient and different temperatures. Analysis of the steady state fluorescence quenching of HHb in aqueous solution in the presence of GNP and GNS suggests that the nature of the quenching is of static type. The static nature of the quenching is also confirmed from time resolved data. The static type of quenching also indicates the possibility of formation of ground state complex for both HHb-GNP and HHb-GNS systems. From the measurements of Stern-Volmer (SV) constants KSV and binding constants, KA and number of binding sites it appears that HHb forms stronger binding...

Research paper thumbnail of Contrasting spectroscopic response of human hemoglobin in presence of graphene oxides and its reduced form: Comparative approach with carbon quantum dots

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2021

Recently, a considerable amount of research is being directed towards study of graphene oxide (GO... more Recently, a considerable amount of research is being directed towards study of graphene oxide (GO) and its reduced form (RGO) since their exposed functional groups make them better candidates in nanobiotechnolgy. In order to assess their biocompatibility, the nature of interactions between Human Hemoglobin (HHb) and GO/RGO are monitored since a comparative spectroscopic approach towards understanding their nature of interactions has not been investigated previously. UV-vis spectroscopy reveals hyperchromicity for HHb-GO system and hypochromicity for HHb-RGO system in the region of absorption of tryptophan/tyrosine residues. Notably, although steady-state fluorescence static quenching of HHb for GO and enhancement of fluorescence for RGO is noticed, but average fluorescence-lifetime is remaining unchanged in presence of GO/RGO. Calorimetric data illustrates three-site and five-site binding model to be the best-fit model for GO and RGO respectively. Also, synchronous fluorescence quenching corresponding to alterations in microenvironment of tryptophan/ tyrosine residues is observed only in presence of GO. Likewise FTIR spectroscopy elucidates involvement of both amide I and amide II bond of HHb backbone through H-bonding interaction only for GO. Furthermore RLS spectra demonstrate an increase and a decrease in signal for GO and RGO respectively. Surprisingly, secondary structure of HHb is maintained upon interaction with both GO/RGO, as revealed by CD spectroscopy, thus supporting their potential application in biological microenvironment. Thus it appears that the spectroscopic properties of HHb upon interaction with GO is altered upon its reduction to RGO. Furthermore the role of HHb as good candidate for bimolecular interaction has been highlighted.

Research paper thumbnail of Fluorescence enhancement via aggregation effect due to microenvironmental alterations in human hemoglobin protein in presence of carbon quantum dots (CQD): Comparative spectroscopic approach

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

CQDs have emerged with outstanding properties as a star member of carbon nanomaterial family and ... more CQDs have emerged with outstanding properties as a star member of carbon nanomaterial family and in order to reveal its wide-range of application in biological microenvironment the interactions between human hemoglobin (HHb) and CQD and also with ethylenediamine-functionalized CQD (NCQD) are assessed using several techniques. Firstly, UV-vis absorption spectra of HHb reveal hyperchromic effect in the region of absorbance of tryptophan and tyrosine residues and also hypochromicity of Soret band in presence of CQD and NCQD. Interestingly, steady-state fluorescence spectroscopy reveal distinct fluorescence enhancement of HHb with significant red shift thereby indicating exposures of tryptophan and tyrosine residues to a more hydrophilic environment. However synchronous fluorescence spectra reveal that the microenvironment of tryptophan and tyrosine residues is altered in opposite manner, i.e. exposure of tryptophan residues to a more hydrophilic environment and the tyrosine residues to a more hydrophobic environment. Moreover the fluorescence enhancement is observed to be accompanied by increase in average fluorescence-lifetime and decrease in steady-state anisotropy thus signifying a decrease in restriction of rotational motion. Furthermore tryptophan residues within HHb appear to interact more with CQD compared to NCQD. Thermodynamic parameters as revealed by Isothermal Titration Calorimetry (ITC) demonstrate that electrostatic, hydrogen bonding and hydrophobic interactions are the predominant modes of interactions in presence of CQD. Whereas hydrophobic and hydrogen bonding interactions are the major interacting forces in presence of NCQD with five-site sequential binding as best-fit model in both the cases. Such interactions also appear to be associated with an increase in aggregation of HHb as evident from the measurements by atomic force microscopy (AFM) and dynamic light scattering (DLS) study. Although FT-IR spectra display alteration of amide I band, but the overall secondary structure of HHb seems to be nearly retained even in presence of CQDs, as evident in the CD spectra. These observations thus highlight the potential biomedical application of CQDs in biological microenvironment of human especially as drug-delivery system. Also bimolecular interaction of HHb as a model protein with other nanoparticles at the nano bio-interface has been outlined.