Department of Chemical Sciences
School of Natural Sciences


July 28, 2014 at 4.00 pm in AG-69

Title :

Regio- and Stereo-selective Approaches for Glycoconjugate Synthesis


Cell surface carbohydrates in the form of glycoconjugates play vital roles in various important life processes. They are structurally complex and diverse. Since they are present in microheterogeneous forms in nature, they cannot be isolated in acceptable amount and purity. Chemical synthesis, however challenging, provides an opportunity for obtaining structurally well defined and chemically pure glycoconjugates for biological studies. Regio- and stereoselective approaches make the synthesis less arduous and more efficient. Recent examples from our studies on the synthesis of complex carbohydrates will be presented.

July 21, 2014 at 4.00 pm in AG-69

Title :

Towards Understanding the Mechanism of Amyloid Beta Mediated Toxicity in Alzheimer's Disease

June 16, 2014 at 4.00 pm in AG-69

Title :

Understanding Bio-molecular Interactions for Novel Drug Discovery: Biophysical Approach

Abstract :

More than the synthesis of a large number of new molecules, the challenge faced by the pharmaceutical industries is to exploit the wealth of these compounds and relate their activity to the mode of interaction with the relevant targets of biological importance. This requires an in-depth understanding of intermolecular interactions responsible for therapeutic intervention. Recent advances in methodologies to unravel the intricate intermolecular interactions have added tremendous amount of understanding in such phenomenon. The talk will address biophysical approach to understand the binding of some antibiotic and anti cancer drugs with serum albumin in view of the importance of drug-protein interactions in drug delivery. This requires a detailed structural, conformational and energetic investigation. The talk will also address the screening of GlaxoSmithKline compound library in search of tuberculosis active compounds which target Mycobacterium tuberculosis topoisomerase-I through stabilized cleaved topoisomerase I - DNA complex mechanism and serve as Mycobacterium tuberculosis topoisomerase I poison to cure XDR and MDR tuberculosis.

May 30, 2014 at 2.30 pm in AG-80

Title :

A Journey from Ordered Mesostructures to Chalcogels: Porous Semiconducting Metal Chalcogenide Aerogels

Abstract :

Mesoporous materials are important in shape selective separations, catalysis, nano-electronics and in the case of metal sulfides, photonics and nanotechnology. Aerogels are another class of low density porous materials. A wide range of binary and mixed metal oxide analogues have been developed in the past. However, non-oxidic counterparts of those are less studied and could be of great interest as well. The goal of the project is to build high surface area metal chalcogenide frameworks and aerogels to create a general methodology. Surfactant directed assembly of metal chalcogenide building units is shown as a method to construct semiconducting mesostructured materials. In addition, a simple metathesis reaction is applied for the first time to generate a broad class of metal-chalcogenide gels and aerogels. The chalcogenide surfaces of these novel semiconductors possess interesting adsorption properties and show promise towards removing heavy metals from water and separating CO2 over H2. Additionally, these aerogels act as efficient hydrodesulfurization and solar fuel catalysts. In this talk an overview of the semiconducting nanoporous project will be presented.

May 29, 2014 at 4.00 pm in AG-80

Title :

Earth-Abundant Thin-Film Solar Cells

Abstract :

Given the remarkable potential of photovoltaic (PV) technology to displace non-renewable electricity generation based on fossil fuels if associated manufacturing costs can be made competitive, there is a tremendous need for low-cost, environmentally benign materials and fabrication processes for preparing high-performance solar cells. In this regard, thin-film heterojunction PVdevices are particularly interesting because of their reduced material utilization and simple cell design. In thin-film devices, a wide range of semiconducting materials can be used as the solar absorber, among which the kesterite Cu2ZnSn(SxSe1-x)4 (CZTSSe) family has been getting significant recent attention due to its earth-abundant and less toxic constituents. Here I will present development of >10% efficiency CZTSSe solar cells based on a novel thin-film deposition approach.

May 27, 2014 at 2.30 pm in AG-69

Title : to be announced

May 26, 2014 at 4.00 pm in AG-69

Title : To be announced

May 22, 2014 at 2.30 pm in AG-80

Title :

Excitation Dynamics in Low Band-gap Conjugated Polymers: Implications on Photoinduced Charge Generation

May 21, 2014 at 2.30 pm in AG-69

Title : 

Understanding Cement: An Experimental and Theoretical Approach

Abstract :

Ordinary Portland Cement (OPC) is widely used as a construction material in modern world. Cement is an inorganic material and is highly complex due to its multi-component, multi-phase nature.Cement powder readily reacts with water, undergoing hydration process which results into the formation of a number of reaction products, all embedded into a system called cement paste. The major reaction products are calcium silicate hydrate and calcium hydroxide. Calcium silicate hydrate is the dominant hydration product (constitutes about 70% of the cement paste) and is primarily responsible for the binding properties of cement. In order to tailor the final performance of cement it is necessary to understand the structure and properties of the principal hydration product. However, calcium silicate hydrate is also a very complex phase as it evolves both structurally and chemically as a function of time throughout the hydration process and its exact constitution is not yet known.Efforts were made in this work to develop an insight and understand the nature, composition, structure of the calcium silicate hydrate phase of a commercially manufactured OPC cement by combining different analytical techniques viz: XRF, SEM, FTIR, Solid State NMR, XRD  and theoretical modeling by Quantum Chemical techniques. Based on the comparison of experimental and theoretical results, a basic structural model has been proposed which could be further developed in order to elucidate the exact structure of calcium silicate hydrate formed in the OPC cement used in this work

May 19, 2014 at 4.00 pm in AG-80

Title :

Mn Selective Fluorescent Sensors and the Effects of Mn Exposure on a Zebrafish Larval Model

May 13, 2014 at 2.30 pm in AG-69

Title :

Reshapint Amyloid Beta Aggregation Using Endogenous Proteins

May 12, 2014 at 4.00 pm in AG-69

Title :

Electron Transport Through Single Molecular Junctions: Molecular Wires, Switches to Energy Storage Devices

Abstract :

The idea of building electronic devices using single molecule as active component was first proposed by Aviram and Ratner in the early seventies. Indeed, molecules are of great interest for application in electronic devices because of their small size, their recognition properties, their ability of self-organization and their possibility of chemical modification and customisation. Thus, the ability to measure and control charge transport across metal/molecule/metal junction is of considerable fundamental interest and represents a key step towards the development of molecular electronics.

During my PhD, I have employed STM break junctions (STM-BJ) and a complimentary mechanically controllable break junction (MCBJ) technique to scrutinise the electron transport properties of metal/molecule/metal junctions under well controlled experimental conditions (in liquid at room temperature)1,2. Using these two experimental techniques, I will try to demonstrate the devise independence and reproducibility of the charge transport characteristics of metal/molecule/metal junctions. Due to the fact that, large number of measurements possible for STM-BJ and MCBJ techniques provides robust statistical analysis of the conductance data and shows clear evidence for the formation of molecular junctions. Many configurations can be sampled and characterized quantitatively by analyzing statistically significant number of conductance-distance and /or current-voltage traces. In addition to the conductance features, the characteristic length analysis of the conductance-distance traces provides additional information about the stability and evolution of molecular junctions. Using these expertise, we systematically studied correlation between molecular structure and conductance properties of metal/molecule/metal junctions formed with a family of thiol terminated oligo (phenylene ethynylene) (OPE) molecular wires (role of molecular length, conjugation, HOMO-LUMO gap, solvent)2,3and roll of anchoring group on single molecular junction conductance4. Furthermore, we also systematically studied the conductance switching of the pyridyl terminated dimethyldyhydropyrene photo chrome molecules upon visible light irradiation4.

Increase of the molecular length and/or of the HOMO-LUMO gap leads to a decrease of the single junction conductance of the linearly conjugated OPE molecules. The experimental data simulations suggest a non-resonant tunneling mechanism involving hole transport through the molecular HOMO, with a decay constant  Δ = (3.4 ± 0.1) nm-1 and a contact resistance Rc= 40kΩ per Au-S bond. Furthermore, decreasing the HOMO-LUMO gap by keeping the molecular length constant, we found that value of single molecular junction conductance was increasing. We also found effect of solvent on the single molecular junction conductances formed with mono thiol terminated OPE molecules. We also investigated the conductance properties of a photoswitchable dimethyldihydropyrene (DHP) derivative for the first time in single molecule junctions using the mechanically controllable break junction technique. We demonstrate that the reversible structure changes induced by photoisomerization of a single bis-pyridine-substituted DHP molecule are correlated with a large drop of the conductance value. We found a very high ON-OFF ratio (> 104) and an excellent reversibility of conductance switching5.

My present work is mainly focusing on modifying the Au, ITO, Pt electrode surfaces with functional molecules (electroactive or Photo active) and studying their properties at single molecule level under electrochemical conditions for molecular electronics and energy storage applications.


1.  Hong, W.J et al., Beilstein J. Nanotechnol. 2011. 2, 699-713.

2.  Kaliginedi et al., Journal of American chemical society. 2012, 134 (11), 5262–5275.

3.  Kaliginedi et al., Journal of American chemical society. 2014, in preparation.

4.  Moreno-Garcia et al., Journal of American chemical society. 2013, 135, 12228−12240.

5.  Roldan, D., Kaliginedi et al., Journal of American chemical society.  2013, 135, 5974-5977.

April 28, 2014 at 4.00 pm in AG-69

Title :

Elastic Network Model in describing equilibrium properties of proteins

Abstract :

In this talk, I will describe why elastic network model (ENM) is a faster alternative to standard molecular dynamics (MD) simulations in understanding the dynamics of proteins under equilibrium conditions. I will discuss the approaches taken for optimal parametrization of the model and how the parameters are used to study intrinsic flexibility of proteins. I will also talk about some future applications of ENM in studying specific functional motions of proteins.

April 22, 2014 at 2.30 pm in AG-69

Title :

Peptide Models of Lipid-protein Interaction and Protein Aggregation into Amyloids

Abstract :

Short peptides corresponding to the discrete protein modules offer an attractive system to study the structural and functional details of proteins and several biomolecular processes. We have exploited the manipulative versatility and design diversity offered by short peptides to address the phenomena of fatty acid acylation of proteins in context of their membrane association and of self-assembly of proteins into highly ordered amyloids aggregates. Our studies have shown that covalent modification of proteins with long chain fatty acid serves not just as lipid anchor but also as a regulator of the submembrane topology of the peptide chain. Using short peptides derived from the core sequences of amyloidogenic proteins, we have shown peptide concentration-dependent heterogeneity in amyloids aggregates and the existence of off-pathway aggregates. We have also probed the time-resolved tryptophan fluorescence intensity decay and have demonstrated that the immediate microenvironment of the indole moiety greatly influences the heterogeneity of the tryptophan lifetime distribution.

April 21, 2014 at 4.00 pm in AG-69

Title : 

Probing Plant Metabolism and Biomolecular Interaction: Studies by NMR