Publications by authors named "Priyanka Dogra"

The conformational plasticity of intrinsically disordered proteins (IDPs) allows them to adopt a range of conformational states that can be important for their biological functions. The driving force for the conformational preference of an IDP emanates from an intricate interplay between chain-chain and chain-solvent interactions. Using ultrafast femtosecond and picosecond time-resolved fluorescence measurements, we characterized the conformational and solvation dynamics around the N- and C-terminal segments of a disordered repeat domain of a melanosomal protein Pmel17 that forms functional amyloid responsible for melanin biosynthesis.

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Unlabelled: NUP98 fusion oncoproteins (FO) are drivers in pediatric leukemias and many transform hematopoietic cells. Most NUP98 FOs harbor an intrinsically disordered region from NUP98 that is prone to liquid-liquid phase separation (LLPS) in vitro. A predominant class of NUP98 FOs, including NUP98-HOXA9 (NHA9), retains a DNA-binding homeodomain, whereas others harbor other types of DNA- or chromatin-binding domains.

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Hofmeister ions are thought to play fundamentally important roles in protein solubility, folding, stability, and function. Salt ions profoundly influence the course of protein misfolding, aggregation, and amyloid formation associated with devastating human diseases. However, the molecular origin of the salt-effect in protein aggregation remains elusive.

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Liquid-liquid phase separation of intrinsically disordered proteins into mesoscopic, dynamic, liquid-like supramolecular condensates is thought to govern critical cellular functions. These condensates can mature from a functional liquid-like state to a pathological gel-like or solid-like state. Here, we present a unique case to demonstrate that an unusual cascade of intermolecular charge-transfer coupled with a multitude of transient noncovalent interactions and conformational fluctuations can promote liquid phase condensation of a pH-responsive, intrinsically disordered, oligopeptide repeat domain of a melanosomal protein.

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Liquid-liquid phase separation occurs via a multitude of transient, noncovalent, and intermolecular interactions resulting in phase transition of intrinsically disordered proteins/regions (IDPs/IDRs) and other biopolymers into mesoscopic, dynamic, nonstoichiometric, and supramolecular condensates. Here we present a unique case to demonstrate that unusual conformational expansion events coupled with solvation and fluctuations drive phase separation of tau, an IDP associated with Alzheimer's disease. Using intramolecular excimer emission as a powerful proximity readout, we show the unraveling of polypeptide chains within the protein-rich interior environment that can promote critical interchain contacts.

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Protein hydration water plays a fundamentally important role in protein folding, binding, assembly, and function. Little is known about the hydration water in intrinsically disordered proteins that challenge the conventional sequence-structure-function paradigm. Here, by combining experiments and simulations, we show the existence of dynamical heterogeneity of hydration water in an intrinsically disordered presynaptic protein, namely α-synuclein, implicated in Parkinson's disease.

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In contrast to pathological amyloids, functional amyloids are involved in crucial physiological functions. For instance, the melanosomal protein comprising a highly amyloidogenic polypeptide repeat domain assembles into amyloid fibrils that act as templates for melanin biosynthesis within acidic melanosomes. However, the mechanism-morphology-function relationship of functional amyloids is poorly understood.

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Amyloid assembly is inherently a stochastic and a hierarchical process comprising the genesis of heterogeneous, transiently populated prefibrillar aggregates that are characterized to be non-native oligomeric conformers. These oligomers could be either off-pathway or on-pathway species en route to amyloid fibrils that are associated with a variety of neurodegenerative disorders, namely, Alzheimer's disease, Parkinson's disease, and prion disease, as well as in localized and systemic amyloidoses (type II diabetes and dialysis related, respectively). Morphological characterizations of these prefibrillar aggregates indicated that apparently the doughnut or annular structure is commonly shared among various prefibrillar species irrespective of the diverse native structures and aggregation mechanisms.

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A novel thermotolerant lipase from Bacillus aerius was immobilized on inexpensive silica gel matrix. The immobilized lipase was used for the synthesis of biodiesel using castor oil as a substrate in a solvent free system at 55°C under shaking in a chemical reactor. Several crucial parameters affecting biodiesel yield such as incubation time, temperature, substrate molar ratio, and amount of lipase were optimized.

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Gallic acid (3, 4, 5- trihydroxybenzoic acid) is an important antioxidant, anti-inflammatory, and radical scavenging agent. In the present study, a purified thermo-tolerant extra-cellular lipase of Bacillus licheniformis SCD11501 was successfully immobilized by adsorption on Celite 545 gel matrix followed by treatment with a cross-linking agent, glutaraldehyde. The celite-bound lipase treated with glutaraldehyde showed 94.

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In the present study, a purified lipase from Bacillus aerius immobilized on celite matrix was used for synthesis of ethyl ferulate. The celite-bound lipase exposed to glutaraldehyde showed 90.02% binding efficiency.

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Ever growing resistance of pathogenic bacteria against the existing antibiotics has forced researchers to look for new methods and techniques to design effective antimicrobial agents. In the present study a new tetracycline-based antimicrobial polymer (AMP) was synthesized from tetracycline and methacrylic acid (MAAc) using lipase as catalyst. The AMP, thus obtained, was transformed into nanoparticles via an emulsion method.

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Modification of biopolymers by oxidation is an easy process to develop effective adsorbents for the removal of toxic metal ions from their aqueous solutions. In the present study, guar gum (GG) was crosslinked with epichlorohydrin and then oxidized to the polydialdehyde form (GG-clPDA). The latter was converted to a Schiff-base, GG-clCHN(CH2)6NCHGG, by reaction with hexamethylenediamine.

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Protein aggregation leading to various nanoscale assemblies is under scrutiny due to its implications in a broad range of human diseases. In the present study, we have used ovalbumin, a model non-inhibitory serpin, to elucidate the molecular events involved in amyloid assembly using a diverse array of spectroscopic and imaging tools such as fluorescence, laser Raman, circular dichroism spectroscopy, and atomic force microscopy (AFM). The AFM images revealed a progressive morphological transition from spherical oligomers to nanoscopic annular pores that further served as templates for higher-order supramolecular assembly into larger amyloid pores.

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