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Developing Principles for Designing and Synthesizing Supramolecular Gelators and Their Various Applications
Full text linkSelf-assembled supramolecular gels obtained from low molecular weight gelators (LMWGs)have received significant attention over past few decades because of their wide range of applications that includes cosmetics, sensors,bio-mineralization, wound healing, liquid crystalline materials etc. the main objective of the thesis was to develop various drugs and/or bioactive agent based supramolecular gels fro their plausible biomedical applications such as wound healing, drug delivery etc. various new LMWGs were designed and synthesized from well known non-steroidal anti-inflammatory drugs .Research was carried out under the supervision of Prof. P Dastidar of the Organic Chemistry division under SCS [School of Chemical Sciences]Research was conducted under DST & DBT grant and CSIR fellowshi
Role of Nonmuscle Myosin II in Virus-Cell Fusion
Full text linkMembrane fusion is the process whereby two separate lipid bilayers merge to become
one. Despite substantial progress, an integrated concept for protein–mediated membrane fusion
(cellular and viral) is not yet available, and many open questions yet to be answered. Membrane
fusion, the merging/intermixing of two lipid bilayers, is quite a well known process involved in a
number of physiological functions e.g. fertilization, cell division, myoblast differentiation,
transport of impermeant molecules into the cell (endocytosis) and out of the cell (exocytosis).
Among all the cases of membrane fusion, viral entry through membrane fusion gains the special
attention as viruses’ e.g. parainfluenza virus (PIV), human immunodeficiency virus (HIV),
simian immunodeficiency virus (SIV), murine leukemia virus (MLV), herpes simplex virus
(HSV), measles virus (MV) etc fuse directly with plasma membrane to enter inside the host cells.
These viruses are the etiological agents of many biologically important diseases of man and other
animals. The involvement of membrane fusion in all these events makes ‘fusion’ a sizzling issue
always and force the scientists to go into its finer details. Virus-cell surface receptor interactions
can elicit two types of signals; conformational changes of viral particles, and concomitant
intracellular signals triggering specific cellular reactions.1 In this direction, Wang et. al. have
shown evidence that cellular signal transduction pathways and associated protein kinases could
be responsible in modulating retrovirus-induced cell-cell fusion.2 However, little is known about
the virus-induced host cell intracellular signaling in terms of maintaining the actomyosin
complex that influences the membrane fusion. Viruses in the paramyxoviridae family and others
like HIV (Human immunodeficiency virus), bind to the surface proteins of the host cell and fuse
with the plasma membrane to release the nucleoprotein in the cytosol directly to reach the site of
their replication. If we talk about membrane fusion in terms of thermodynamics, it is
energetically a non-spontaneous process and there is a very high kinetic barrier, so the process
needs the catalytic help of proteins (fusion glycoproteins of all viruses and fusogens of all other
kind) for using the free energy, liberated during the conformational change of the membrane
proteins to draw each other together3(Fig. 1). Moreover, as membrane fusion is the critical step
in the course of enveloped animal virus infection, it is logical to think of its regulation by host
cell signaling. Keeping this proposition in mind we have studied a precise effect of membrane fusion on actomyosin signaling in the course of viral infection, taking Sendai virus (Z strain) as the model.Research was conducted under the supervision of Prof. S S Jana of Biological Chemistry division under the SBS [School of Biological Sciences]The research was carried out under CSIR, DBT & DST gran
Molecular characterization of glyceraldehyde-3-phosphate dehydrogenase from normal and malignant cells
Full text linkGlyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key enzyme of
glycolysis and increased glycolysis is a hallmark of malignancy. Previously we showed
that methylglyoxal (MG), a normal metabolite, inhibits glycolysis. Moreover GAPDH,
purified exclusively from different malignant cells, is a heterodimer (~90 kDa) containing
two subunits of 33±2 and 55±3 kDa and is strongly inactivated by MG suggesting a
distinct alteration of GAPDH in malignant cells, whereas GAPDH from normal sources
is a homotetramer (~144 kDa), each subunit of 36 kDa. Here, by MALDI-TOF analysis,
we report that the 55 kDa subunit is either glucose-6-phosphate isomerase (GPI) or
pyruvate kinase M2 (PKM2) isoform which is another important biomarker of
malignancy and GAPDH is associated with these two proteins separately to form a
protein complex which is confirmed by immunoprecipitation analysis. MG can alter the
secondary structure of purified GAPDH protein complex may be due to the glycation at
PKM2 and GAPDH as detected in CD spectroscopy and mass analysis. We also use biocompatible surface functionalized Quantum Dots (QDs) to modulate the enzyme
activity of GAPDH from cancer cells. Cumulative kinetic studies reveal that both reversible and irreversible inhibition mechanisms owing to the site specific interactions enabling control over the inhibition kinetics of GAPDH activity. This study indicates a different molecular association of GAPDH in cancer cells and tissues, and experimental approach to inhibit its enzymatic activity in cancer cells.Research was conducted under supervision of Prof. S S Jana of the Biological Chemistry division under SBS [School of Biological Sciences] and under Prof. Manju Ray of BI [Bose Institute]Research was carried out under DBT & DST gran
Spectroscopic Properties of Semiconducting Polymer Nanomaterials
Full text linkSemiconducting polymer nanomaterials draw the attention of modern science as
alternative luminescent nanomaterials over normal inorganic quantum dots and fluorescent dye molecules due to their several advantages, e.g- easy synthetic procedure, less cytotoxicity as well
as more bio-compatibility, tunable optoelectronic properties and so on. The fundamental spectroscopic properties of semiconducting polymer nanomaterials strongly depends on the extent of intra/ inter molecular interactions of semiconducting polymer molecules. Eventally, it also strongly influenced by the surface Plasmon band of metal nanoparticles as well as electronic
band alignment of interfacial inorganic quantum dots. Energy/ Charge transfer based photophysics of semiconducting polymer nanomaterials in presence of inorganic nanoparticles should be very much effective for the generation of efficient optoelectronic and solar cell
devices. Furthermore, fluorescent dye doped semiconducting polymer nanoparticles can act as a bright, photostable luminescent source for long term imaging devices. But the fundamental
photophysics of encapsulated dye molecules need to be clarified by different spectroscopic methods for the fabrication of more efficient nanoprobe. Considering these, current thesis is
devoted to the advancement of efficient nanomaterials based on semiconducting polymer for different applications in photonics, optoelectronics, imaging and sensory devices.Research was conducted under the supervision of Prof. Amitava Patra of the Materials Science division under the SPS [School of Physical Sciences]Research was carried out under CSIR fellowshi
Dynamical Aspects Of Quantum Many-Body System
Full text linkIn the last two decades, the access of experimental, tunable systems, described by simple models offers a groundbreaking opportunity to investigate the non-equilibrium dynamics in closed interacting
quantum systems. Quantum systems of many particles far from equilibrium pose notable challenges for theory as they are not susceptible to the general principles and methods that help to realize standard
equilibrium quantum systems. In this thesis, it has been attempted to discuss some interesting dynamical
aspects of quantum many-body system.
We use a perturbative momentum shell renormalization group (RG) approach to study the properties
of a driven quantum system at zero temperature. To illustrate the technique, we consider a bosonic f4
theory with an arbitrary time dependent interaction parameter driven at a frequency w0 and we derive
the RG equations for the system using a Keldysh diagrammatic technique. We show that the scaling of w0 is analogous to that of temperature for a system in thermal equilibrium and its presence provides a cutoff scale for the RG flow. We analyze the resultant RG equations, derive an analytical condition for such a drive to take the system out of the gaussian regime, and show that the onset of the nongaussian regime occurs concomitantly with the appearance of non-perturbative mode coupling terms in the effective action of the system. We supplement the above-mentioned results by obtaining them from equations of motion of the bosons and discuss their significance for systems near critical points described by time-dependent Landau-Ginzburg theories. It has been investigated a system of interacting bosons with two “spin“ states in a lattice. The system shows superfluid-insulator phase transitions in the presence of spin-orbit coupling. Depending on the parameter regime, bosons in the superfluid phase can condense to either a zero-momentum state or to one or
multiple states with finite momentum, leading to an unconventional superfluid phase. We study the response of such a system to modulation of the optical lattice potential. We show that the change in momentum distribution after lattice modulation shows distinct patterns in the Mott and the superfluid phase and these patterns can be used to detect these phases and the quantum phase transition between them. Further, the momentum-resolved optical modulation spectroscopy can identify both the gapless
(Goldstone) and gapped amplitude (Higgs) mode of the superfluid phase and clearly distinguish between the superfluid phases with a zero-momentum condensate and a twisted superfluid phase by looking at
the location of these modes in the Brillouin zone. We discuss experiments which can test our theory.
We also study transport properties of a phosphorene monolayer in the presence of single and Multitiple potential barriers of height U0 and width d, using both continuum and microscopic lattice models,
and show that the nature of electron transport along its armchair edge (x direction) is qualitatively different
from its counterpart in both conventional two-dimensional electron gas with Schrödinger-like quasiparticles and graphene or surfaces of topological insulators hosting massless Dirac quasiparticles. We show that the transport, mediated by massive Dirac electrons, allows one to achieve collimated quasiparticle motion along x and thus makes monolayer phosphorene an ideal experimental platform for
studying Klein paradox. We study the dependence of the tunneling conductance G Gxx as a function of d and U0, and demonstrate that for a given applied voltage V its behavior changes from oscillatory to decaying function of d for a range of U0 with finite non-zero upper and lower bounds, and provide analytical expression for these bounds within which G decays with d. We contrast such behavior of G with that of massless Dirac electrons in graphene and also with that along the zigzag edge (y direction) in phosphorene where the quasiparticles obey an effective Schrödinger equation at low energy. We also study transport through multiple barriers along x and demonstrate that these properties hold for transport
through multiple barrier as well. Finally, we suggest concrete experiments which may verify our theoretical predictions.Research was conducted under the supervision of Prof. Krishnendu Sengupta of the Theoretical Physics division under SPS [School of Physical Sciences]Research had been carried out under DST research gran
Theoretical and computational study of properties and detoxification mechanisms of chemical warfare agents, toxic chemicals and enzyme inhibitors
No full textThe thesis deals with the reaction mechanism, kinetics,
molecular docking, simulation and thermochemistry of molecules having biological and toxicological interest. The high-level theoretical methods are used for accurate results and predictions.An introduction to the thesis is given in the first chapter for understanding the biological
and toxicological chemistry. The second chapter describes briefly theoretical methods and
techniques of computational chemistry. The rest of the chapters of the thesis are based on
the published papers or on the manuscripts currently under consideration for publication. This thesis is a systematic presentation of the author’s original research works.Research was conducted under the supervision of Prof. Abhijit kr. Das of Spectroscopy division under SPS [School of Physical Sciences]Research was carried out under CSIR fellowship and gran
Synthesis, Photo-physical Studies and Applications of Different Doped and Un-doped Semiconductor Nanocrystals
Full text linkHigh quality semiconductor nanocrystals (quantum dots, QDs) are small crystal consisting
of hundreds to a few thousand atoms each with typical dimension ranging from 1-100 nm
which are great interest for fundamental studies and different technological applications
such as light emitting devices, lasers, solar cells and biomedical labeing. The quantum
mechanical coupling of over hundreds to thousands atoms develops the band structure in
semiconductors. In this regime, the spatial confinement of the electronic charge carriers in
the nanocrystal leads to a phenomenon known as Quantum Confinement Effect (QCE).
Due to this effect, the size and shape of these “artificial atoms” can be used to widely tune
the energy of discrete electronic energy states and optical transitions. For this the emission
from these particles can be tuned throughout the ultraviolet, visible, near-infrared, and
mid-infrared spectral ranges, making them useful for both biological imaging and many
types of optoelectronic devices. State-of-the-art semiconductor nanocrystals have been
designed to have a quantum efficiency of radiative recombination approaching unity at
room temperature, far above what has been achieved from bulk materials. The reason of
this high efficiency is also govern by the QCE as the strong overlap between the electron
and hole wave functions in the confined structure increases the probability of radiative
recombination whereas the exciton in bulk semiconductors is not confined in space and can
rapidly dissociate, increasing the probability of non-radiative relaxation process associated with crystalline defects and charge carrier traps on crystal surfaces. Among semiconductor NCs CdSe as the work horse, have been widely studied for their fundamental properties and applications. Despite their so many advantages, the intrinsic toxicity of Cadmium has cast a doubtful commercial future for this promising field. Wide band gap semiconductor nanocrystals, such as zinc chalcogenide doped with transition metal ions, has overcome this concern and yet maintained the advantages of the
nanocrystal emitters. Mn and Cu doped zinc chalcogenide semiconductor NCs can give
bright yellow orange and tunable blue green emission respectively which has been found very stable and having high quantum yield making them useful for different practical application without having highly toxic Cd metal. Besides their low toxicity by replacing cadmium in CdSe quantum dots with zinc, these doped materials do not also reabsorb the photon which avoids self-quenching, a common phenomenon in quantum dots because of small stokes shift. In contrast, the emission color from a dopant, involving d–states of transition metal ions, to a large extent is fixed and independent of the size of the host. The only way to get substantially different dopant colours is to use different dopant ions. Unfortunately, doping such impurity ions into nanoparticle hosts has proven to be unexpectedly difficult, and different synthesis methods have to be followed to get different d–dots.Research was carried out under the supervision of Prof. Narayan Pradhan of Materials Science division under the SMS [School of Materials Science]Research was conducted under IACS fellowship and DST research gran
Studies on the optical and electrical properties of some semiconductor nanomaterials
Full text linkThe present dissertation entitled “STUDIES ON THE OPTICAL AND
ELECTRICAL PROPERTIES OF SOME SEMICONDUCTOR NANOMATERIALS” is
submitted to fulfill the requirements for the degree of Doctor of Philosophy
(Science) of Jadavpur University. The thesis provides the results of the optical
and electrical properties of some semiconductor nanomaterials containing
phthalocyanine grown on various substrates i.e. glass, quartz glass, ITO
(Indium Tin Oxide coated glass), Silicon wafers etc. under various
experimental conditions and their heterojunctions with suitable nanostructured materials. The thesis comprises of nine chapters and concluding remarks
(Appendix-I) along with a list of publications (Appendix-II) and abbreviation
(Appendix-III) at the end. The first chapter contains a general introduction
describing the discovery, structure and properties of phthalocyanines. Second
chapter describe briefly the review of theoretical concepts. Details about the
experimental techniques, set-up, procedure, sample and chemicals used in this
work are described in chapter three. The rest of the chapters of the thesis are
based on the published papers or on the communicated manuscript. To make
the chapters self content repetition of some scientific statements, references and
relevant experimental procedures could not be avoided. Several results have
already been published/ in press or communicated for publication in the
internationally reputed scientific journals.The research was carried out under the supervision of Prof. Biswanath Mullick of the Spectroscopy division under SPS [School of Physical Sciences]The research was conducted under IACS research fellowship and gran
The interplay between magnetism, defects and disorder in polycrystalline oxides
Full text linkThis thesis investigates the crucial role of defects and disorder in determining the structural,
electrical and magnetic properties of a few transition metal oxides. In solid state physics,
crystallinity or the periodicity of lattice plays a very significant role. All the basic theories are
formulated considering perfectly ordered crystalline materials because this simplifies the
structural description. However in reality, the arrangement of atoms or molecules in most
crystalline materials is not perfect and often interrupted by crystallographic defects disrupting
the perfect crystalline order in solids. Still, many technologically significant materials are based
on weakly or strongly disordered materials. A group of such materials is dilute magnetic
semiconductors, where random site occupancy of doped transition metal ions introduces
disorder and an associated ferromagnetism critically dependent on defect concentration is often
found. Following a general introduction in chapter 1, sample growth and characterization
techniques are described in chapter 2. In chapters 3 and 4, rigorous macro- and microscopic
studies have been carried out on two dilute magnetic oxides like float-zone grown single
crystalline BaTi0.95Fe0.05O3-d with different oxygen stoichiometry as well as Ca and Fe co-doped
BaTiO3 with different Ca and Fe concentrations. Here, the room temperature ferromagnetism
and crystal structures are shown to be modified strongly with increasing doping and oxygen vacancies. In chapter 5, presence of larger amount of bound oxygen vacancy defects at the cores is shown to induce room temperature ferromagnetism in solvothermally synthesized Co-doped BaTiO3 nanocrystals. In chapter 6, a strong covalency driven structural instability is reported to
modulate the transport, dielectric and magnetic properties of flux grown Ba5Co5ClO13 and Ba6Co6ClO16 single crystalline as well as polycrystalline samples. In chapter 7, Sr3FeMoO7 (n=2 Ruddlesden-Popper compound) polycrystalline powder synthesis and detailed studies revealing the possible effects of disorder (due to the presence of antisite defects and antiphase boundaries) on the magnetic and magnetotransport properties of the system is described. In the end, a brief discussion and summary of all the works in the thesis are presentedThe research was conducted under the supervision of Prof. Sugata Roy of the Materials Science division under SMS [ School of Materials Science]The research was carried out under DST grant & IACS fellowshi
Multifunctional Composite Nanomaterials for Biomedical Applications
No full textResearch was conducted under the supervision of Prof. N R Jana of SMS [School of Materials Sciences]Research was carried out under CSIR fellowshi