Srikrishna Pramanik

Bio-templated luminescent noble metal nanoclusters (NCs) have attracted great attention for their intriguing physicochemical properties. Continuous efforts are being made to prepare NCs with high fluorescence quantum yield (QY), good biocompatibility, and tunable emission properties for their widespread practical applications as new-generation environment-friendly photoluminescent materials in materials chemistry and biological systems. Herein, we explored the unique photophysical properties of silver nanoclusters (AgNCs) templated by cytosine-rich customized hairpin DNA. Our results indicate that a 36-nucleotide containing hairpin DNA with 20 cytosine (C20) in the loop can encapsulate photostable red-emitting AgNCs with an absolute QY of ∼24%. The luminescent properties in these DNA-templated AgNCs were found to be linked to the coupling between the surface plasmon and the emitter. These AgNCs exhibited excellent thermal sensitivity and were employed to produce high-quality white light emission with an impressive color rendering index of 90 in the presence of dansyl chloride. In addition, the as-prepared luminescent AgNCs possessing excellent biocompatibility can effectively mark the nuclear region of HeLa cells and can be employed as a luminescent probe to monitor the cellular dynamics at a single molecular resolution.

Liquid–liquid phase separation (LLPS) exhibited by an ordered protein β-lactoglobulin (β-LG) under crowded environment prompts alterations in conformational distribution leading to emergence of new promiscuous (esterase-like) activity.

Developing environmentally friendly, sustainable, and biocompatible artificial light-harvesting systems has become an essential area of research to understand natural light-harvesting processes involving multistep resonance energy transfer and building efficient energy conversion systems related to energy and optoelectronic applications. In this direction, bio-scaffolded artificial energy transfer systems for panchromatic light collection and sequential energy transfer have fascinated the scientific community. In this review, we have discussed what the dynamic structure and intrinsic physical properties of biomolecules like deoxyribonucleic acid, proteins, and peptides can provide for the development of new optical devices, sustainable and environmentally friendly white emitting materials, and cascaded energy transfer systems for energy harvesting from light. In doing so, we have highlighted some of the recent advances in bio-scaffolds as a platform for the assembly of different types of donor–acceptor chromophores involved in fluorescence energy transfer.

The understanding of interactions between organic chromophores and biocompatible luminescent noble metal nanoclusters (NCs) leading to an energy transfer process that has applications in light-harvesting materials is still in its nascent stage. This work describes a photoluminescent supramolecular assembly, made in two stages, employing an energy transfer process between silver (Ag) NCs as the donor and a host-guest system as the acceptor that can find potential applications in diverse fields. Initially, we explored the host-guest chemistry between a cationic guest ethidium bromide and cucurbit[8]uril host to modulate the fluorescence property of the acceptor. The host-guest interactions were characterized by using UV-vis absorption, steady-state and time-resolved spectroscopy, molecular docking, proton ¹H nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and isothermal calorimetry studies. Next, we prepared a series of blue-emitting AgNCs using different templates such as proteins and peptides. We have found that these AgNCs can be employed as a donor in the energy transfer process upon mixing with the above acceptor for emission color tuning. Our in-depth studies also revealed that surface ligands could play a key role in modulating the energy transfer efficiency. Overall, by employing a noncovalent strategy, we have tried to develop Förster resonance energy transfer (FRET) pairs using blue-emitting NCs and a host-guest complex that could find potential applications in constructing advanced sustainable light-harvesting, white light-emitting, and anti-counterfeiting materials.

This work delineates an integrative approach combining spectroscopic and computational studies to decipher the association-induced fluorescence properties of a fluorescent molecular rotor, viz., auramine O (AuO), after interacting with 20-mer duplex DNA having diverse well-matched base pairs. While exploring the scarcely explored sequence-dependent interaction mechanism of AuO and DNA, we observed that DNA could act as a conducive scaffold to the formation of AuO dimer through noncovalent interactions at lower molecular density. The photophysical properties of AuO depend on the nucleotide compositions as described from sequence-dependent shifting in the emission and absorption maxima. Furthermore, we explored such DNA base pair-dependent fluorescence spectral characteristics of AuO toward discriminating the thermodynamically most stable single nucleotide mismatch in a 20-mer sequence. Our results are interesting and could be useful in developing analogues with further enhanced emission properties toward mismatched DNA sequences.

Monitoring the DNA dynamics in solution has great potential to develop new nucleic acid-based sensors and devices. With spectroscopic approaches, both at the ensemble average and single-molecule resolution, this study is directed to differentiate a single nucleotide mismatch (SNM) via a metal ion-stabilized mismatched base-pairing (C–Ag⁺–C/C–Cu²⁺–T) (C = cytosine, T = thymine) and site-selective extrinsic fluorophore, specifically, Thioflavin T (ThT). This is the first approach of its kind where dynamic quantities like molecular diffusion coefficients and diffusion times have been utilized to distinguish the least-stable SNM (CC & CT) formed by the most discriminating nucleobase, specifically, cytosine in a 20-mer duplex DNA. Additionally, this work also quantifies metal ions (Ag⁺ and Cu²⁺) at lower concentrations using fluorescence correlation spectroscopy. Our results can provide greater molecular-level insights into the mismatch-dependent metal–DNA interactions and also illuminate ThT as a new fluorophore to monitor the dynamics involved in DNA–metal composites.

A pressure-driven change of the carbon nanostructure encapsulating Au nanoparticles induces a transition of the face-centered cubic to two primitive phases in the Au nanoparticles which impacts the electrical conductivity of the Au/C-nanohybrid.

Herein we report the effect of different nucleobase pair compositions on the association induced fluorescence enhancement property of Thioflavin T (ThT), upon binding with 20 base pair long double stranded deoxyribonucleic acid (dsDNA). Analysis of binding and decay constants along with the association (Kass) and dis-sociation (Kdiss) rate constants obtained from the fluctuation in the fluorescence intensity of ThT after binding with different DNA revealed selective affinity of ThT towards AT rich dsDNA. Molecular Docking also substantiates the experimental results. We also observed that addition of orange emitting Ethidium Bromide (EtBr) to cyan emitting ThT-DNA complexes leads to bright white light emission (WLE) through FRET. Additionally, the emission of white light is far more in the case of intra-DNA strands. Besides endorsing the binding insights of ThT to AT rich dsDNA, the present investigations open a new perspective for realizing promising WLE from two biomarkers without labelling the DNA.