Department of Chemical Sciences
School of Natural Sciences


December 13, 2016 at 2.30 pm in AG-69

Title :

Mononuclear copper(II) complexes with the residues in the metal ion binding peptide loop of the CuA center of cytochrome oxidase


December 5, 2016 at 4.00 pm in AG-69

Title :

What XAFS can answer for nano-structure? 

Abstract :

X-ray Absorption Fine Structure (XAFS) is unique local structural tool - particularly useful for disordered systems where long-range-order is absent and diffraction/ HRTEM fail to extract details beyond a certain limit. The talk will present characterization and quantification of structural configurations/ defects / oxidation states for wide-ranged nano-systems (bimetallic and semiconductor-metal composite catalysts, semiconductor biosensors, drugs, spintronics, multiferroics, molecular magnetic switches, metallic glass) and their correlation with respective properties of scientific interest. Technical, analytical and sample considerations for the suitability of XAFS for a certain scientific problem and the scope of XAFS at INDUS-2 synchrotron facility (RRCAT) will be addressed. 

November 28, 2016 at 2.30 pm in B-333 (DBS Seminar R00m)

Title :

Probing the Fate of Excitons in Organic Semiconductors

November 21, 2016 at 4.00 pm in AG-69

Title :

Probing Photoinduced Charge Generation in Organic-inorganic Hybrid Perovskites Using Ultrafast Spectroscopy

November 16, 2016 at 2.30 pm in B-333 (DBS Seminar R00m)

Title :

Supramolecular Chemistry: A Tale of a Container  Novel Proposed Materials for Biomedical and Material Applications

Abstract :

Supramolecular chemistry has evolved from the molecular chemistry over the years as the science of “chemistry beyond the molecule”. Molecules are held-together by intermolecular non-covalent interactions in a supramolecular assembly. In this seminar, I will talk about a new water-soluble synthetic supramolecular host named as "octa acid" (OA) as a reaction cavity for manipulating photochemical and photophysical properties of organic molecules. Most of the guest molecules are enclosed within a capsule made of two OA molecules. The interior of OA capsule is benzene-like nonpolar despite the complex being present in water. Additionally, the confined guests are not isolated but can communicate with molecules present in solution. This part will be discussed with photoinduced electron transfer from the donor incarcerated within OA-capsule to the acceptor free in solution as well as to TiO2 semiconductor. 

In the second part, I will propose a novel “support-free iterative” strategy to build a new class of functionally-controlled architecturally diverse macromolecules. With this strategy, I will discuss how we, as chemists, can create functional materials in a rapid, scalable and economic way for diverse biomedical and material applications. In addition, design of a unique supramolecule-based functional devise will be proposed for advanced applications.  


November 15, 2016 at 2.30 pm in B-333 (DBS Seminar Room)

Title :

A Novel Class of Sequence-Defined Polymers: Design, Synthesis and Applications

Abstract :

Sequence control is a crucial parameter for tuning the structure, property, and function of synthetic macromolecules. However, achieving precise control of monomer sequence with fast reaction kinetics has been the key hurdle. Herein, I will demonstrate an effort to circumvent this difficulty via a de novo approach for the synthesis of a novel class of sequence-defined polymers, named as oligothioetheramides (oligoTEAs). The oligoTEAs look like the biopolymers in our body, but are instead created with synthetic molecules designed in the lab. This unique approach is based on the strategic design of ‘allyl acrylamide monomer’ with orthogonal reactive sites and a liquid-phase fluorous support. Key strengths of our approach include fast solution kinetics, step-wise characterization via common spectroscopic techniques, and a large structural diversity due to the ease of monomer synthesis. 

By creating these synthetic polymers from the bottom up in an iterative and controlled manner, we can precisely tune their size, composition and properties. We further advanced our synthetic strategy by designing monomers that can afford oligoTEA macrocycles via a one-pot acid catalyzed cascade reaction. With an eye towards biological applications, various bioactive side chains were introduced into the primary sequence. The effects of these side chain and backbone groups on the chemical properties and biological function will be discussed. 


November 7, 2016 at 4.00 pm in AG-69

Title :

Form, Function, and Phase Behavior of Intrinsically Disordered Proteins

November 4, 2016 at 2.30 pm in AG-66

Title :

Proteins as Polymers

October 21, 2016 at 2.30 pm. in AG-66

Title :

Design and Synthesis of Polymeric Materials: Structure-Property Relationship via Self-assembly and Biomedical Applications

Abstract :

Design and validation of pericyclic reactions for sensing conformational stretching in polymer materials.

The naphthalene and anthraquinone based fluorescent reporter molecules were synthesized in multistep for monitoring pericyclic reactions in polymers. These reporter molecules were incorporated into polymer backbones by click reactions. The reaction was monitored optically and optimized using organic chemistry characterization techniques. The mechanical force felicitate to bonds to come into proper orientation for claisen reaction to occur. The overall goal of the research is to design, implement, and validate functional groups designed to react specifically within stressed polymer materials to signal the onset of mechanical failure.


Design and synthesis of Novel Alternating sulfone copolymers for biomedical applications

Interest in stimulus-responsive polymers and materials has been increasing in recent years. In particular, efforts to apply these polymers for biomedical applications have focused on changing the structure of assemblies and particles in response to both endogenous molecules and externally-applied energy sources to release drugs, activate contrast agents, or initiate fluorescent signal. Sulfur dioxide has been shown to copolymerize with certain vinyl monomers in a specifically alternating manner, provided that the vinyl group is immediately adjacent to an electron-donating group; examples include vinyl acetate, vinyl carbonate, and olefins. The resulting copolymer possesses a low ceiling temperature. The depolymerisation of poly(vinyl acetate-alt- sulfur dioxide) as initiated by chemical stimuli such as reactive oxygen species (ROS) and mechanical stimuli was studied as a proof of concept. Then, a novel class of hydrolytically depolymerizable macromolecules, poly(O-vinyl carbamate-alt-sulfones), were synthesized via free radical polymerization with excellent functional group tolerance. The polymers were then found to form nanoparticles capable of encapsulating both Rhodamine B and Alexa Fluor 488, and the resulting particles were labile at pH > 6. Finally, these particles were found to retain their contents in mucus at pH 5 but release it at pH 8, resulting in an increase in diffusivity of encapsulated fluorophores from very small to matching that of free dye. Current efforts are focused on adapting the polymers and their particles for mucosal drug delivery.


During doctoral studies, my research focussed on the self assembling behavior of various pyrene labeled polymers having different architecture like homopolymers, block, and random copolymers, where the pyrene labeling was varied from 1-100%. The photophysical properties were studied using various fluorescence techniques like steady-state and life time decay analysis as well as time resolved emission spectra (TRES). The applicative aspect of the pyrene labeled polymers was also shown by rhodamine dye encapsulation and release studies as a function of temperature and its temperature triggered release was also used as a handle to understand the microstructural changes inside the polymer microcapsule.


Thus, the thesis analyses the following important aspects:


1.    Exploration of fundamental aspects of the self assembly of different pyrene labelled polymers like block, random or homopolymers by the detailed photophysical analyses


2.    Applicative aspects of the pyrene labeled polymers: probed by rhodamine B encapsulation and release.


3.    Self assembly behavior in H-bonded versus non-H-bonded polymers at very dilute concentrations: differences and similarities.


 4.       Architectural differences among the polymers: probed by TRES and temperature dependent fluorescence.

October 17, 2016 at 4.00 pm in AG-69

Title :

Design and development of optical probes for imaging signal mediating phospholipids

October 3, 2016 at 4.00 pm in AG-69

Title :

 An energy landscape perspective of biomolecular structure and dynamics

 Abstract :

 During the last decade, the concept of energy landscapes has emerged as a unifying theme in seemingly disparate disciplines, such as biomolecular folding and aggregation, self-assembly, and glassy dynamics, and have provided fundamental insight into the thermodynamics and kinetics of complex systems. For many practical applications, it is often sufficient to consider a coarse-grained description of the landscape, in terms of stationary points (energy minima and transition states). This coarse-graining eliminates the need for dynamical sampling, and stationary points on the underlying landscape can be located in a time-independent fashion, exploiting tools of geometry optimisation. This approach offers several key advantages over conventional rare event sampling techniques, particularly for complex landscapes featuring broken ergodicity, and characterised by multiple relaxation time scales. My talk will discuss the methodological aspects of the computational energy landscape framework, and highlight some recent applications to the study of biophysical problems of contemporary interest, such as RNA folding, conformational switching between alternative folds in DNA and peptides, and structural heterogeneity in intrinsically disordered proteins.

September 20, 2016 at 2.30 pm in AG-69

Title :

Nano-bioconjugation of Mutant Cytochrome P450cam for Biocatalysis

September 19, 2016 at 4.00 pm in AG-69

Title :

Catalysis for Sustainable Development

Abstract :

Catalysis plays a key role in chemical industry. More than 90% of all chemical reactions use catalysts. It is projected that the world demand for catalysts may grow by 4.8% per year, to a value of about US$ 20.6 billion in 2018. This growth will be primarily led by polymer and chemical industries. Additionally, it is speculated that the majority of the share of this growth would occur from developing areas such as the Asia/Pacific and Africa/Mideast regions. Raw material availability is one of the issues the chemical industry is facing. While most of our energy and chemical needs are derived from non-renewable fossil feedstocks (petroleum, natural gas and coal), time has come to switch the chemical processing from the conventional to the non-conventional, renewable feedstocks. There is a great challenge to tune the catalysts for such transformations. My talk addresses catalytic conversion of biomass and carbon dioxide into fuels and chemicals. India has a surplus amount of inedible biomass and at the same time bound to follow the COP-21 resolution for reduction in carbon emissions. Utilization of biomass and CO2 would perhaps lead to low carbon footprint. The influence of catalyst hydrophobicity in biomass transformations and acid/base bi-functionality in CO2 conversions would be discussed.   

September 15, 2016 at 2.30 pm in AG-80

Title :

Alkyl Chain Tethered Dansyl, 1-Naphthyl and Acridinyl Fluorophores: Synthesis and Photophysical Studies

Abstract :

Conjugated fluorescent molecular probes are known to be efficient in probing structural and dynamical information of a variety of aggregates and organized systems. As these find a definite location into the organized assembly they cause less perturbation to the system. The main advantage of this type of probes is to design such probes as per the demand of the site to be investigated. 1  The hydrophobic tail contains dansylamide, 1-naphthol and 9-aminoacridine derivatives have been synthesized and evaluates towards their fluorescent probe properties. The long hydrophobic chain containing dansylamide derivative (DAN-PA) shows better sensitivity towards solvent polarity as compared to the short hydrophobic chain analogue (DAN-ACYL). DAN-PA can monitor premicellar aggregation of sodium deoxycholate (NaDC) in water. DAN-PA is also found useful to understand the micellization process of surfactants like NaC, SDS and CTAB. 2 DAN-PA shows more affinity towards β-CD as compared to DAN-ACYL. Its fluorescence intensity is quite sensitive towards thermotropic phase changes of lipid bilayer membrane. 1-Naphthol (NpOH) is an excited state proton transfer (ESPT) molecular probe which is a weak acid in the ground state (pKa = 9.2), but a strong acid (pKa* = 0.4) in the excited state. 3 In the aqueous medium, the proton transfer of short hydrophobic tail containing p-5C-NpOH is faster than long tail containing p-13C-NpOH. Shorter chain derivative (p-5C-NpOH) is a better ESPT probe to understand the micellization of CTAB, SDS and Tween-20 as compare to p-13C-NpOH because its proton transfer process shows the significant amount of anionic and neutral intensities in the aqueous medium. Acridine is a good DNA binding probe. In acidic pH, it exists in the protonated form (AcH + ) and in alkaline pH, it exists in neutral form (Ac). 4 The decrease in fluorescence intensity of 9-aminoacridine (AC) and its derivative (AC-PA) (the substrate is bound to DNA) is because of static quenching. 9-aminoacridine upon substitution (AC-PA) binds more efficiently to DNA by an order of magnitudes as compared to the un-substituted 9-aminoacridine (AC). DNA melting studies suggest that both 9-aminoacridine (AC) and its derivative (AC-PA) bind with DNA through intercalation binding.



1. Rohacova, J., Marin, M. L., and Miranda, M. A., J. Phys. Chem. B, 2010, 114, 4710.

2.Tripathi, A. K., Mohapatra, M., and Mishra, A. K., Phys.Chem.Chem.Phys.,2015, 17, 29985.

3. Mandal, D., Pal, S. K., and Bhattacharyya, K., J. Phys. Chem. A, 1998, 102, 9710–9714.

4. Sayed, M., and Pal, H., Phys. Chem. Chem. Phys., 2015, 17, 9519.

August 9, 2016 at 4.00 pm in AG-80

Title :

Structural and Functional Characterization of an Unusual Ca2+ Binding Protein from E. histolytica