November 11, 2014 at 2.30 pm in AG-69
Computational Understanding on Structural and Bonding Aspects of Molecules and Enzymes
Atomic and electronic structure is the origin of all the chemical and physical properties of chemical matter. Knowing the structure of molecules is extremely helpful to interpretthe experimental outcomes of various structural characterizations, reactivity and as well improves and predicts the properties of novel materials. Depicting the bonding aspects of the chemical matter is the holy grail of structural chemistry.
In this perspective, I will illustrate the insights that have emerged from theoretical studies on borodiphospholes and phosphodiesterase enzyme.In borodiphospholes, we found a structural diversity in various isolobalcyclopentadienyl ligands and through molecular orbital studies we depict the bonding aspects and origin for different stability of structures. Interestingly, in phosphodiesteraseenzymes we unravel the origin for secondary structural changes in the protein and how the structure is influential withcrystalline pH conditions and further implications in designing inhibitors. I finally discuss the strategic plan to model spectroscopic properties of the metalloenzymes and a few challenging enzymatic oxidation reactions that shall open up new vistas in understanding these enzymes.
November 10, 2014 at 4.00 pm in AG-69
QMMM Approach for Elucidating the Reaction Mechanisms of Heme and Nonheme Enzymes
Warshel and Levitt’sidea of quantum mechanical/molecular mechanical (QM/MM)approach has opened the door to model complex chemical systems such as enzymes and probe their reaction mechanisms. This approach combines a QM level of theory to describe the site where chemical reactions or electronic excitations occur and classical force field MM level to capture effects of the environment. In the recent times, state-of-the-art in QM/MM method gained immense importance as it provided high-accurate barriers, atomistic-level insights on mechanistic proposals, spectroscopic properties, and effects of mutations on reactivity of enzymes.
In the present talk I will focus on the highlights of the approach and the insights obtained recently in understanding the insilico mutation of F429H of heme (CYP 2B4) enzyme and reveal a novelDNA repair mechanism by AlkB a nonheme enzyme. Besides, I will discuss briefly my future interest in using this approach to understand the fundamental process in biological catalysts of oxidative enzymes that have broad academic and industrial applications.
October 27, 2014 at 4.00 pm in AG-69
Anti-Fouling Slippery Surface: An Approach to Design Advanced Materials
Fabrication of robust synthetic materials with antifouling properties would have broad technological implications for areas ranging from biomedical devices to fuel transport to architecture but has proven to be extremely challenging. Natural inspired non-wetting structures, particularly, Slippery Lubricant-Infused Porous Surfaces (SLIPS) that outperform state-of-the-art synthetic surfaces in their ability to resist ice and microbial adhesion and repel various simple and complex liquids. By coordinating surface nanostructuring, chemical functionalization and lubricant properties, one can design stable, shear-tolerant liquid-repellent coatings and manufacture them on arbitrary materials and complex shapes. The slippery surfaces can find important applications in fluid handling and transportation, small molecule sensing, and as antifouling surfaces against highly contaminating media operating in extreme environments. I will talk about how to design a polymer based universal SLIPS coating on various substrate that are with arbitrary shape and size. I will also give brief overview of some fundamental aspects which controls the adhesive behavior of this property that can be useful in microfluidics application. Aspects of controlled & guided transfer of small aqueous droplet based on SLIPS by applying rotational motion will be discussed and I will also talk about selective transfer and transport of liquid using hydrophilic-SLIPS patterned surface. It’s always hard to visualize directly with bare eyes a phenomena that is happening in nano scale, - but slippery surface (with proper designing) that is loaded with anisotropic lubricant allows events that occur at the nanoscale level to be observed at the spatial scale of the naked eye without the need for additional instrumentation. Finally, I will present its strong resistance towards fungal and bacterial attachment, thus eventually help to prevent biomass/biofilm formation.
October 28, 2014 at 11.30 am in AG-80
Smart Polymer Coating: Deigning of Anti-wetting Surfaces & Developing Stable Liquid Crystal Based Chemical Sensor
Nature remains inspiration behind various interesting findings in literature and one of them is anti-wetting property that noticed in several living objects such as lotus leaves, rice leaves, butterfly wings, water strider legs etc. provides a platform to design materials for wide range of practical applications. Extremely water repelling surfaces in air called as superhydrophobic surfaces are one of the most recognized and well-studied anti-wetting material in literature. Intense efforts have been directed toward the design of synthetic mimics of these materials for the design of self-cleaning surfaces, coatings that prevent corrosion or fogging, and advanced materials for water harvesting, oil-water separation, and a host of other emerging applications. A common approach to the design of synthetic superhydrophobic surfaces is one inspired by the natural structure of the lotus leaf, and generally involves the fabrication of surfaces with (i) appropriate combinations of microscale and nanoscale topography topped by (ii) a thin, low surface energy coating. While this approach is both useful and widely practiced, the practical utility of materials having this design is reduced in scenarios that expose them to physical insults (e.g., scratches) that can compromise low-energy coatings or physically degrade, remove, or destroy micro- and nanoscale surfaces features required to repel water and maintain non-wetting behavior. The pursuit of superhydrophobic surfaces that are physically robust and mechanically durable is a vibrant area of research and is important in both fundamental and applied contexts. Here, in my talk I will talk about how to design a robust and self-healing superhydrophobic coating based on three dimensional porous polymer coating and their several prospective applications such as drug delivery, guided water transfer etc. In second part of my presentation, I will talk about thermotropic liquid crystal droplets in context of sensing amphiphilic molecules. Liquid crystal droplet has immense prospect in sensing application-but at the same time, they are extremely sensitive, and they lose their property even after interacting with bare glass surface. Very Briefly, I will talk about how to decorating the thermotropic liquid crystal droplets with polymer assembly so that I can easily attach them on surface of various objects without disrupting their property.
October 20, 2014 at 4.00 pm in AG-69
Theoretical Studies on Size Selected Solvated Clusters: Understanding Towards Certain Macroscopic Properties
Small size molecular systems encapsulated in solvent clusters of different size are considered as model system for studying the influence of solvation on various fundamental molecular properties and processes. We will talk on structure, stability, vibrational and photoelectron spectroscopic properties of molecules in different size solvent clusters. We will discuss on a new general relation derived for size dependent detachment energy of negatively charged finite size clusters based on a microscopic theory and its performance to predict bulk detachment energy. We will also compare conformational averaged IR spectra of size selected hydrated clusters with measured spectra.
In macroscopic description, a strong acid means an acid that ionizes fully in aqueous solution whereas a weak acid does not ionize completely in such an environment. Thus, the ability to transfer a proton to a water molecule is the key to the characteristic feature of an acid. In the context of microscopic description of strength of an acid, one may ask a fundamental question: how many water molecules are required to ionize an acid molecule? In this talk, we plan to quest for answers of such queries based on a few case studies.