Calender

Seminar by Dr. Karan Malik, Indian Institute of Technology, Delhi on October 8, 2021 at 2.30 pm via zoom platform

Title :

Electrochemical Reduction of Carbon Dioxide to Syngas

Abstract :

Over the past few years, electrochemical reduction of CO2 (ERC) has attracted a lot of interest among researchers to convert CO2 into value-added products using renewable energy. Through ERC, CO2 and water using renewable energy can be co-electrolyzed to produce many chemicals such as CH4, C2H4, C2H6, HCOOH, CH3OH, and syngas (CO + H2), which are important industrial chemicals. However, CO2 is a very stable molecule, and thus it is very difficult to reduce it. Therefore, the primary focus of research has been developing an electrocatalyst selective to CO2 reduction. ERC is carried out in the presence of water. Thermodynamically, the reduction potentials of ERC and hydrogen evolution reaction (HER) potential are close to each other. Moreover, HER has fast kinetics as compared to ERC. Thus, the electrical charge spent during ERC is used by the facile HER instead of ERC. Thus suppression of HER poses a huge challenge.

Depending upon the electrode potential, electrolyte, electrocatalyst, and reaction conditions. Sixteen different products can be formed using Cu as an electrocatalyst. However, it requires high overpotential (~1.0 V), have poor selectivity, and fast deactivation are the biggest challenges. The research work in this thesis is focused on the selective formation of syngas using Zn and Cu based electrocatalysts. The effect of the nature of the electrocatalyst layer on the ERC selectivity has been studied. It was found that the degree of gas entrapped in different types of layers was different, leading to different selectivity. The role of the addition of Cu into the ZnO has also been studied for the synthesis of syngas. On varying the concentration of Cu into the ZnO, it was found that at a certain fraction of Cu into the ZnO, charge transfer resistance towards ERC is reduced, which ultimately reduces the overpotential requirements. The role of pressure in gas phase ERC was also investigated. It was found that a mild increase in pressure leads to a shift in Zn/Cu selectivity towards syngas formation by changing the orientation of the adsorbed CO2 molecule.

Seminar by Dr. Abhigyan Sengupta, Technical University of Munich, Germany on October 5, 2021 at 4.00 pm via zoom platform

Title :

Molecules of Life

Abstract :

On day 2, I will discuss (a) chiro-selective folding dynamics of a ribozymal RNA and (b) tweaking proteins into bio-machines. The preponderance of specific D- or L-chirality in fats, sugars, amino acids, and nucleic acids is ubiquitous in nature, yet the biological origin of such chiral dominance remains an open question. One plausible proposal for the predominance of L-chirality in amino acids through evolutionary templating of chiral RNA folding via chaperon activity will be the topic of presentation.

Proteins are unique molecules, which could be tweaked towards developing exciting engineering applications in the emerging field of Bio-nanotechnology by understanding their general design principles and mechanisms of operation. In this section, I will show a transformation of an isolated Ca+2 binding domain to an ion concentration and time pulsing sensor. I shall also discuss how either a repeat protein or a circularly permuted GFP can be used to develop a mechano-fluorescence sensor.

Seminar by Dr. Abhigyan Sengupta, Technical University of Munich, Germany on October 4, 2021 at 4.00 pm via zoom platform

Title :

Molecules of Life

Abtract :

On the first day of the seminar, I will discuss (a) tale of a molecular timekeeper and continue with (b) evolution biology in a single-molecular regime. Proteins switching their structures can act as molecular timekeepers and regulate biochemically relevant reactions. Prolyl isomerization is one of such regulatory mechanisms, which play a crucial role in ion channel gating, cell signaling, and phage virus infection. I will present fascinating evidence showing how a single proline in an isolated protein domain (filamin) controls its folding kinetics and function.

In the second section, I shall talk about the reverse-chaperon effect of cationic amino acid on a ribozymal RNA. In the light of current models for an early nucleic acid-based universe, the potential influence of simple amino acids on RNA tertiary folding into biochemically competent structures is speculated to be of significant evolutionary importance. In this work, the (un)folding kinetics of a ubiquitous RNA motif is investigated in single molecule regime in presence of natural amino acids with protonated side chain residues.

Seminar by Prof. Katarzyna Pernal, Institute of Physics, Lodz University of Technology, Poland, on September 27, 2021 at 4.00 pm (via Zoom)

Title :

Dynamic Electron Correlation with Adiabatic Connection Approaches: describing excited states and molecular interactions

Abstract :

Correlation energy, despite being a small fraction of the total electronic energy, governs binding of atoms into molecules. Similarly, noncovalent molecular interactions are flawed if the correlation of electrons belonging to interacting subsystems is not accounted for. The two main approaches to electron-correlation involve either perturbation theory or are based on density functionals. They are deficient either in accuracy or computational efficiency and a generally applicable, computationally efficient approach remains a challenge.

Recently we have proposed a novel approach to describing electron correlation in multireference systems by adopting the adiabatic connection (AC) formalism [1]. The latter naturally links electron correlation with fluctuation of density at different points in space. Consequently, the final expression for the correlation energy employs density linear response. In our formalism, we use extended random phase approximation (ERPA) to describe the latter. The proposed AC-ERPA method yields excellent results for ground and excited states of molecules described with the CASSCF wavefunction [2-4]. In my talk I will present applications of the AC methods, and their extensions to multiconfigurational DFT [5], to challenging multireference systems and noncovalently bounded excited state systems.

 

References

1. K. Pernal, Phys. Rev. Lett. 120 (2018), 013001.

2. E. Pastorczak, K. Pernal, J. Chem. Theory Comput. 14 (2018), 3493.

3. E. Pastorczak, K. Pernal, J. Phys. Chem. Lett. 9 (2018), 5534.

4. E. Pastorczak, M. Hapka, L. Veis, and K. Pernal, J. Phys. Chem. Lett. 10 (2019), 4668.

5. M. Hapka, E. Pastorczak, A. Krzeminska, and K. Pernal, J. Chem. Phys. 152 (2020), 094102

Seminar by Mr. Dinesh Kumar Yadav, Dept. of Chemical Sciences, TIFR, Mumbai on September 16, 2021 at 4.00 pm (via Zoom)

Title:

Protein Electrochemistry: Metal Complexes as a Promoters of the Electron Transfer from a Gold Electrode to Cytochrome c

Abstract:

Direct protein electrochemistry is an important method to determine the redox potential and electron transfer kinetics of metalloproteins. The bare metal electrode generally causes irreversible adsorption and denaturation of the protein on the electrode surface. There have been extensive studies on modification of the gold electrode using thiol functionalized promoters. We have investigated the effect of metal ion binding to a thiol-based Schiff base complex immobilized on the gold electrode for the electron transfer to cytochrome c. Selfassembled Monolayer (SAM) contains Schiff-Base ligand formed by cysteine and salicylaldehyde on the gold electrode was shown to promote quasi-reversible electrochemistry of cytochrome c. Various transition metal complexes of the Schiff-base ligand immobilized on the gold electrode were also found to promote electrochemistry of cytochrome c. The redox potential of the protein was determined to be 0.05±0.02 V (vs Ag/AgCl), which agrees with the reported value. In heterogeneous electron transfer rates for were determined by analyses of the cyclic voltammetric data using Laviron’s equation. The heterogenous electron rate constant (ks) calculated by Laviron’s equation suggest that there is small increase in the electron transfer rates when metal ion (Cr, Fe, Mn) is coordinated to the Schiff base on the electrode surface, suggesting that metal ion coordination possibly stabilizes the SAM of the Schiff base and favours electron transfer to cytochrome c.

Seminar by Dr. Ahin Roy, Trinity College Dublin, Ireland on September 8, 2021 at 2.30 pm (via Zoom)

Title :

Structure-property Correlation in Oxide Materials through Aberration-corrected Electron Microscopy

Abstract :


The unprecedented control of the electron beam in the modern electron microscopes allows diffraction from nanometer regions, and conjunctionally being equipped with spectrometers, they can explore chemical information of the material – establishing much coveted structure-property correlations on-the-go. This can be of great interest to a materials chemist, and I will illustrate a couple of examples in that direction from recent works on oxides.

Firstly, the talk will focus on WO3, which exists in a plethora of crystallographic phases. With judicious choice of chemistry, hexagonal and orthorhombic phases can be selectively accessed. Detailed conventional TEM coupled with simulations lead to insights on the operative growth mechanism in that process. Moreover, an epitaxial phase transformation, viz. hexagonal to monoclinic has been observed recently, hitherto unknown in literature. This leads to a possibility of phase-selective ion-intercalation in this material, which will be discussed. Such structural changes have pronounced effect on the electrochromic property of the material. In the next part, I will briefly focus on hexagonal perovskite BaMnO3, wherein reduced Mn-states have been observed on the surface and was established as the reason for its catalytic activity.

Seminar by Dr. Ahin Roy, Trinity College Dublin, Ireland on September 6, 2021 at 4.00 pm (via Zoom)

Title :

Atomic and Electronic Structure of Ultrathin Single-crystalline Nanowires from Electron Microscopy and Simulations

Abstract :

Being the eye of nanomaterials space with atomic-scale resolution, aberration-corrected (scanning) transmission electron microscopy (AC-(S)TEM) can provide a wealth of structural information in low-dimensional materials. With a judicious choice of system of interest, atomistic simulations can facilitate such microscopy. In this talk, I will discuss a couple of such simulation-aided microscopy experiments for different inorganic nanowires.


The talk will focus on structural aspect of symmetry-broken single-crystalline ultrathin Au nanowires, wherein simulations predict that the {111} atomic planes of Au undergo wrinkling, leading to formation of saddle surfaces. Detailed AC-TEM on such wires confirms this prediction. Crystallographic arguments pinpoint the nature of surface stress to be the driving factor behind such structural transformation. Recent AC-STEM experiments with similar scale Pt nanowires show that with a priori crystallographic information, it is possible to reconstruct a 3-D structure from a single projection image of the material, paving a way for suitable alternative to conventional electron tomography. Lastly, in terms of electronic properties, I will briefly talk about Te nanowires, wherein simple adsorption of NO2 shows a semiconductor to metal transition- predicted in simulations and verified by experiments.

Seminar by Dr. Sumit Kumar, Institute of Basic Science CSLM, South Korea on August 31, 2021 at 4.00 pm (via Zoom)

Title :

Nano-brick: Designing Nanomaterials for Living system

Abstract :

Nanomaterials have been widely explored in the biomedical field, and it is crucial to choose the right material and engineer it appropriately to achieve the desired properties. A variety of natural and synthetic polymers have been investigated in the field, and they can be engineered for different formulations. Here, I will mainly present how biomolecules can be used to engineer the different forms for surface texturing, self-assembling nanoparticles, and creating a confined nanoenvironment. To be effective in medicine, I will introduce new methods for creating diversity in nanostructures to enable seamless integration with living tissue, where the understanding of nanoscale is necessary. These advanced nanomaterials could enable an effective, minimally invasive, personalized healthcare system. Thorough understanding of underlying mechanisms, and advancing to a robust biomedical solution for healthcare, cellular energy generation, and nanobio-manufacturing, could be further translated into commercial products and therapies. These sophisticated nanobio-hybrid platforms with advanced synthetic routes have potential applications in early disease detection and targeted therapy. 

Seminar by Dr. Sumit Kumar, Institute of Basic Science CSLM, South Korea on August 30, 2021 at 3.00 pm (via Zoom)

Title:

Exosome: A Journey from Garbage Bags to Life-Saving Case

Abstract:

Biological membranes provide a fascinating example of a separation system that is multifunctional, tunable, and efficient for biocatalytic transformations such as enzyme cascades that involve complex networks proceeding in spatially confined nonreactors. Synthetic mimics of cellular compartments based on real membrane, lack the feasibility to encapsulate desired number of reactants together and precisely control the mixing of reactants during chemical transformation due to its mechanical and chemical fragility. Inspired by multicompartment structures of cellular architectures, we present a novel strategy to encapsulate of multiple enzymes and other reactants, in naturally secreted nanosized extracellular vesicles (EV) that act as nanoreactors for effective biocatalytic cascades in vitro and inside cells, and displays long time stability to work as an artificial organelles (AO). EV membrane proteins are chemically engineered by functionalizing the catechol moiety on the outer surface to drive the fusion of vesicles. This strategy is based on supramolecular metal complex formation that bridges the membrane proteins to allow controlled fusion for encapsulating multiple reactants and mixing them inside the EV. The integration of the multienzyme system inside AO leads to dramatically enhancements in their activity of the catalytic cascades, respectively, compared with the bulk mixture of the catalysts in solution. Importantly, our AO are functional after assembling a minimal electron transport chain capable of adenosine triphosphate synthesis (ATP), combining Escherichia coli F1F0 ATP-synthase and the primary proton pump bo3-oxidase, which demonstrates the feasibility of our method for using this as cellular implants in living organisms. As a programmable tool to work as membrane fusion machinery, catechol-tethers can be further applied to regulate other biological processes where capturing and bridging of two membranes are the prerequisites.

July 19, 2021 at 4.00 pm (Via Zoom)

Title :

Investigations into Mechanism of Sequence and Conformation Specific Photo-induced DNA Self-repair

Abstract :

The study of UV-induced photo-damage and repair of nucleic acids is fascinating due to its connections to the molecular origins of life. The role of sunlight is particularly interesting as it not only served as a source of energy for forming new molecules but also quite likely broke down what formed, creating a cycle in which only the toughest could survive. Many molecules of life, including the canonical nucleobases, are thought to have emerged from this competition between photo-creation and photo-destruction. Naturally, their photo-stability would make them ideal building blocks for more complex structures. Despite this the nucleobases are not completely immune to chemical and radiation induced damage. In fact, DNA absorbs in the UV region of solar spectrum and undergoes several photophysical and photochemical processes which lead to formation of harmful photoproducts like cyclobutane pyrimidine dimers (CPDs), 6-4 photo lesion etc. Enzymatic machineries have evolved which can selectively repair different types of photodamage.1 However, in the absence of such sophisticated machinery when life initially evolved, it is tempting to speculate that the nucleotide sequences could be capable of self-repair.2 Investigations into such a self-repair mechanism has received a lot of attention due to the interesting photophysics involved and connections to chemical evolution.3-5 Recently, a tetranucleotide sequence (GATT) was reported to have inherent capability to repair a CPD lesion via a sequence specific sequential electron transfer.6 The details of the mechanisms and the sequence specificity has yet to be rationalized. I will present our findings revealing the possibility of photoinduced self-repair in a commonly occurring tetranucleotide sequence, TTAG. By employing a judicious combination of linear response and real time time-dependent density function theory, we obtain a detailed description of the mechanism of repair, the states involved at the various stages, factors influencing the forward and backward electron transfer as well as the driving force for the CPD repair. We find that, in contrast to the GATT sequence, the forward electron transfer process is promoted by a crucial ultrafast excitation energy transfer (EET) across the nucleobases resulting in charge-injection into the CPD dimer. The conditions favouring this EET are absent in the spectra of other conformations of the same sequence, indicating conformation specificity to the mechanism in addition the sequence specificity. Using examples from our research I will also emphasise on the challenges faced by current theoretical approaches to answer questions posed in the field.

References:

1. https://www.nobelprize.org/uploads/2018/06/popular-chemistryprize2015.pdf

2. Beckstead, A. A.; Zhang, Y.; de Vries, M. S.; Kohler, B., Phys. Chem. Chem. Phys., 2016,18, 24228-24238

3. M. R. Holman , T. Ito and S. E. Rokita , J. Am. Chem. Soc., 2007, 129 , 6-7.

4. D. J. F. Chinnapen and D. Sen , Proc. Natl. Acad. Sci. U. S. A., 2004, 101 , 65-69.

5. N. Khiem Van and C. J. Burrows , Acc. Chem. Res., 2012, 45 , 2151-2159.

6. Bucher, D. B.; Kufner, C. L.; Schlueter, A.; Carell, T.; Zinth, W., J. Am. Chem. Soc. 2015, 138, 186–190. ; Szabla, R.; Kruse, H.; Stadlbauer, P.; Sponer, J.; Sobolewski, A. L. Chem. Sci. 2018, 9, 3131–3140. 

July 12, 2021 at 10.00 am (Via Zoom)

Title :

Theoretical Physics of Disordered Proteins reveal Biological Insights

Abstract :

Protein sequence -- encoding the unique folded structure and consequently function -- plays a profound role in biological information processing. This central notion, however, appears to be at odds with Intrinsically Disordered Proteins (IDP)s that lack unique folded structure. In spite of being disordered and interconverting beween different conformations, IDPs have specific conformational features and critical function. The clues to conformation, function -- and their relation, if any -- must be in the sequence. But how do we decipher this code from the sequence ? Recent advances in heteropolymer theory -- based on a coarse grain Hamiltonian -- unmasked the existence of several elegant mathematical formulae hidden in the sequence that describe IDPs conformational features. We will focus on the set of these formulae/metric that arise specifically from the placement of charges -- and not just their total number -- in the protein sequence. These simple mathematical relations reveal many surprises in IDP conformation and yield biological insights. For example, they show how IDPs can induce collapse and swelling at different length scales. Extending this, we can detect role of phosphorylation at specific hot spots to induce drastic conformation changes, even far from the modification sites, reminiscing `action at a distance'. These information rich molecular blueprints can even help us identify functionally similar IDPs, not possible by traditional sequence alignment tools used for folded proteins. 
 

July 8, 2021 at 4.00 pm (Via Zoom)

Title :

CO2 capture and conversion to fuels using magnesium nanoparticles under ambient conditions

Abstract :

Extensive use of fossil fuels is a major cause of anthropogenic CO2. Thus, CO2 capture and conversion are the keys in reducing its increased concentration in the earth's atmosphere.1 Many technologies were deployed to tackle the excess of CO2 present in the atmosphere.2,3 But the desired rate of CO2 conversion has not been yet achieved under ambient conditions. The harsh conditions of temperature and pressure make it less approachable. In this work, we have reported the use of magnesium (Mg) nanoparticles as well as bulk powder to capture and convert CO2 into valuable products under ambient conditions.4 It was observed that the Mg nanoparticles can also be deployed for the capture and conversion of CO2 from air. The mechanistic insights for CO2 conversion into methane, methanol and formic acid was studied by different techniques. This study demonstrates the first step towards sustainable CO2 utilization to produce fuel and chemicals.    

 

References:

  1. C. Breyer, M. Mahdi Fasihi, C. Bajamundi and F. Creutzig, Direct air capture of CO2: a key technology for ambitious climate change mitigation, Joule, 2019, 3, 2053–2065.
  2. T. Kong, Y. Jiang and Y. Xiong, Photocatalytic CO2 conversion: What can we learn from conventional COx hydrogenation?, Chem. Soc. Rev., 2020, 49, 6579–6591.
  3. J. Artz, T. E. Müller, K. Thenert, J. Kleinekorte, R. Meys, A. Sternberg, A. Bardow, and W. Leitner, Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle Assessment, Chem. Rev. 2018, 118, 2, 434–504.
  4. S. A. Rawool, R. Belgamwar, R. Jana, A. Maity, A. Bhumla, N. Yigit, A. Datta, G. Rupprechter and V. Polshettiwar, Direct CO2 capture and conversion to fuels on magnesium nanoparticles under ambient conditions simply using water, Chem. Sci., 2021, 12, 5774-5786.

 

 

July 5, 2021 at 4.00 pm (Via Zoom)

Title :

Electron-molecule reactions probed with photons

Abstract :

Electron-molecule reactions are ubiquitous in nature and technology. However, probing the details of such reactions remains both an experimental and computational challenge. Here, I will show recent developments from our group in experimentally probing these reactions by using light rather than electrons. This offers some key advantages that have enabled us to probe aspects that were previously not accessible through experiment. These include time-resolution and probing the effect of solvation. Examples of these will be given and some general features that drive electron capture will be discussed.

June 23, 2021 at 12.30 pm (Via zoom)

Title :

Guide to ICPMS

June 21, 2021 at 4.00 pm (Via Zoom)

Title :

Conformation of biomolecules in phase-separated systems investigated by a line-confocal Raman microscope

June 14, 2021 at 4.00 pm (Via Zoom)

Title :

Transient Raman Spectroscopy for Probing Charge Transfer States

Abstract :

Charge transfer (CT) states form the basis for multitude of chemical reactions, and has become relevant due to its ubiquity in all light energy conversion paradigms.[1] In order to discover new materials with optimized charge transfer rates at molecular interfaces for energy conversion technologies, it is imperative to diagnose the structure-function corrleations “in operando”. Tracking the non-equilibrium nuclear dynamics leading up to the charge transfer states and probing the subsequent separation of charges requires time-resolved spectroscopy with structural sensitivity. In this talk, I will discuss the utility of transient Raman spectroscopy as a tool to structurally probe the formation of CT states in molecular dyes with large Stokes shift,[2] and uncover the hidden lengthscale of the photochemistry inside the active site of metalloproteins.[3] Both frequency domain and time-domain methods will be elaborated with emphasis on challenges of real-time Raman detection during chemical reactions.

References

1. Sajjad Dadashi-Silab, Sean Doran and Yusuf Yagci; Chem. Rev. 2016, 116, 17, 10212–10275; Alexey V. Akimov, Amanda J. Neukirch and Oleg V. Prezhdo; Chem. Rev. 2013, 113, 6, 4496–4565.

2. Shreetama Karmakar, Abhinandan Ambastha, Ajay Jha, Aditya Dharmadhikari, Jayashree Dharmadhikari, Ravindra Venkatramani, and Jyotishman Dasgupta; J. Phys. Chem. Lett. 2020, 11, 12, 4842–4848.

 

3. Soumyajit Mitra, ASR Koti, and Jyotishman Dasgupta; to be submitted.

June 17, 2021 at 4.00 pm (Via Zoom)

Title :

Modulating Mechanical Properties of β-Rich Proteins

June 10, 2021 at 4.00 pm (Via Zoom)

Title :

Overcoming resistance in cancer cells – Exploring new metal compounds for broader spectrum of anticancer activity

June 3, 2021 at 4.00 pm (Via Zoom)

Title :

Towards Understanding the Photodynamics of Tris(pentafluronyl)Borane-doped P3HT