Fluorescence chemosensing and bioimaging of metal ions using schiff base probes working through photo-induced electron transfer (PET).

Though metal ions like copper, iron, zinc, etc. are essential, but their dyshomeostasis is associated with several disorders. Therefore, fast, sensitive, and cost-effective monitoring of these cations will have a significant impact.

Applications of Functionalized Carbon-Based Quantum Dots in Fluorescence Sensing of Iron(III).

Iron, an essential trace element exhibits detrimental effects on human health when present at higher or lower concentration than the required. Therefore, there is a pressing demand for sensitive and selective detection of Fe in water, food etc. Unfortunately, in several instances, the traditional approaches suffer from a number of shortcomings like complicated procedures, limited sensitivity, poor selectivity and more expensive and time consuming.

Method for highly selective, ultrasensitive fluorimetric detection of Cu and Al by Schiff bases containing o-phenylenediamine and o-aminophenol.

Schiff base probes (1 and 2) made from o-phenylenediamine and o-aminophenol were appeared as highly selective fluorimetric chemosensor of Cu and Al ions respectively. Strong fluorescence emission of probe 1 at 415 nm (excitation at 350 nm) was instantly turned off on addition of Cu. Very weak fluorescence of probe 2 at 506 nm (excitation at 400 nm) was immediately turned on specifically by Al.

Enhancement in chaperone activity of human αA-crystallin by nanochaperone gold nanoparticles: Multispectroscopic studies on their molecular interactions.

The chaperone activity of human αA-crystallin (HAA) against aggregation of human γD-crystallin (HGD) was enhanced by gold nanoparticles (AuNPs). Chaperone activity of HAA was almost doubled in the presence of 5.5 nM gold nanoparticles (AuNPs).

Multispectroscopic studies on the molecular interactions between bovine γ-globulin and borohydride-capped silver nanoparticles.

Interactions between bovine γ-globulin (BGG) and borohydride-capped silver nanoparticles (BAgNPs) were studied using dynamic light scattering (DLS) and spectroscopic techniques such as UV-vis spectroscopy, fluorescence, and circular dichroism. The results were compared with earlier reported interactions between γ-globulin and citrate-coated AgNPs (CAgNPs). BAgNPs were synthesized and characterized.

Recent advances (2017-20) inthe detection of copper ion by using fluorescence sensors working through transfer of photo-induced electron (PET), excited-state intramolecular proton (ESIPT) and Förster resonance energy (FRET).

An essential trace element copper plays several physiological roles in living systems. But at excess concentration, it exerts toxicity and becomes associated with numerous disorders. In this article, we have reviewed the recent developments (from 2017 to 2020) in the field of fluorescence-based chemosensors for the detection of Cu ion.

2-Aryl benzazole derived new class of anti-tubercular compounds: Endowed to eradicate mycobacterium tuberculosis in replicating and non-replicating forms.

The high mortality rate and the increasing prevalence of Mtb resistance are the major concerns for the Tuberculosis (TB) treatment in this century. To counteract the prevalence of Mtb resistance, we have synthesized 2-aryl benzazole based dual targeted molecules. Compound 9m and 9n were found to be equally active against replicating and non-replicating form of Mtb (MIC 1.

Inhibition of fibrillation of human γd-crystallin by a flavonoid morin.

To inhibit the formation of amyloid fibrils by human γd-crystallin (HGD), a series of four flavonoids (quercertin, rutin, morin and hesperetin) was tested. Only morin had demonstrated significant inhibition of HGD fibrillation. Results from fluorimetric assay techniques (using thioflavin T and ANS), FTIR, circular dichroism and microscopic imaging (fluorescence microscopy and transmission electron microscopy) confirmed HGD fibrillation inhibition by morin.

Inhibition of amyloid fibrillation of human γD-crystallin by gold nanoparticles: Studies at molecular level.

The capability of citrate-stabilized gold nanoparticles (AuNps) has been explored for the inhibition of amyloid fibrillation of human γD-crystallin (HGD), a major protein of eye lens. Citrate-capped AuNps were synthesized, characterized and used further for amyloid inhibition. The results from intrinsic and extrinsic (in the presence of Thioflavin T and ANS) fluorescence based assays and CD spectroscopy clearly suggest that AuNps at nanomolar concentrations can act as an effective inhibitor against fibrillation of HGD.

Elucidation of molecular interactions between human γD-crystallin and quercetin, an inhibitor against tryptophan oxidation.

Different post-translational changes in eye lens crystallin proteins contribute towards the development of cataract. We have studied oxidative modification of tryptophan (Trp) residues of human γD-crystallin (HGD) towards formation of N-formylkynurenine (NFK) associated with cataractogenesis. This oxidation was found to be inhibited by quercetin at relatively low concentration.

Studies on Molecular Interactions between Bovine β-Lactoglobulin and Silver Nanoparticles.

Background: Silver Nanoparticles (AgNPs) were found to modulate the fibrillation of Bovine Β-Lactoglobulin (BLG).

Objective: To gain an insight regarding the mechanism of BLG aggregation modulation by AgNPs at molecular level, studies on the interactions between BLG and AgNPs were carried out.

Methods: Protein-ligand interactions were studied based on Trp fluorescence quenching (at four different temperatures), synchronous and three-dimensional fluorescence and circular dichroism spectroscopy (far-UV and near-UV).

Crystallins and Their Complexes.

The crystallins (α, β and γ), major constituent proteins of eye lens fiber cells play their critical role in maintaining the transparency and refractive index of the lens. Under different stress factors and with aging, β- and γ-crystallins start to unfold partially leading to their aggregation. Protein aggregation in lens basically enhances light scattering and causes the vision problem, commonly known as cataract.

Protective role of hesperetin against posttranslational oxidation of tryptophan residue of human γD-crystallin: A molecular level study.

Crystallin proteins undergo various posttranslational modifications with aging of eye lens. Oxidation of tryptophan (Trp) residues of a major γ-crystallin namely human γD-crystallin (HGD) was found to be inhibited by a naturally occurring flavonoid hesperetin at relatively low concentration mostly due to its antioxidant activity. Further the molecular interactions between HGD and hesperetin were elucidated on the basis of the quenching of Trp fluorescence of the protein by the flavonoid.

Inhibition of copper-induced aggregation of human γD-crystallin by a diimine molecule and investigations on their molecular interactions.

Communicated by Ramaswamy H. Sarma.

Inhibition of Amyloid Fibrillation by Small Molecules and Nanomaterials: Strategic Development of Pharmaceuticals Against Amyloidosis.

Amyloid fibrils are a special class of self-assembled protein molecules, which exhibit various toxic effects in cells. Different physiological disorders such as Alzheimer's, Parkinson's, Huntington's diseases, etc. happen due to amyloid formation and lack of proper cellular mechanism for the removal of fibrils.

Inhibition of amyloid fibrillation and destabilization of fibrils of human γD-crystallin by direct red 80 and orange G.

Inhibition of amyloid fibril formation by a lens protein namely human γD-crystallin (HGD) under stressful conditions was targeted by using some small molecules like direct red 80 (DR), orange G (OG) and rhodamine B (RH). The protein itself was found to form matured fibrils after 48h of incubation at pH 3.0 at 37°C.

Inhibition of copper-mediated aggregation of human γD-crystallin by Schiff bases.

Protein aggregation, due to the imbalance in the concentration of Cu and Zn ions is found to be allied with various physiological disorders. Copper is known to promote the oxidative damage of β/γ-crystallins in aged eye lens and causes their aggregation leading to cataract. Therefore, synthesis of a small-molecule 'chelator' for Cu with complementary antioxidant effect will find potential applications against aggregation of β/γ-crystallins.

Interaction of different prototropic species of an anticancer drug ellipticine with HSA and IgG proteins: multispectroscopic and molecular modeling studies.

Studies on interactions between an anticancer alkaloid, ellipticine, and various carrier proteins in blood serum show tangible results to gain insight into the solubility and transport of the drug under physiological conditions. In this report, we extensively studied the interactions of different prototropic species of ellipticine with two prominent serum proteins namely human serum albumin (HSA) and immunoglobulin G (IgG) in their native and partially unfolded states using steady state and time resolved fluorescence spectroscopy, molecular docking and circular dichroism (CD). Both the fluorescence techniques and molecular modeling studies elucidate that only neutral species of ellipticine binds to HSA in the sudlow site II.

Involvement of non-polyalanine (polyA) residues in aggregation of polyA proteins: Clue for inhibition of aggregation.

Presence of polyalanine (polyA) stretches in some proteins is found to be associated with their aggregation, which causes disorders in various developmental processes. In this work, inherent propensities towards aggregation of some residues, which are not part of the polyA stretches, have been identified by using the primary sequences of seven polyA proteins with the help of Betascan, PASTA and Tango programs and explored unambiguously. This provides a basis for proposing molecular mechanism of this type of aggregation.

An investigation into the altered binding mode of green tea polyphenols with human serum albumin on complexation with copper.

Green tea is rich in several polyphenols, such as (-)-epicatechin-3-gallate (ECG), (-)-epigallocatechin (EGC), and (-)-epigallocatechin-3-gallate (EGCG). The biological importance of these polyphenols led us to study the major polyphenol EGCG with human serum albumin (HSA) in an earlier study. In this report, we have compared the binding of ECG, EGC, and EGCG and the Cu(II) complexes of EGCG and ECG with HSA.

Inherent aggregation propensity of flanking residues attached to polyglutamines: implication to aggregation inhibition.

Expansion of polyglutamine (polyQ) sequence in some proteins leads to their aggregation, which is responsible for neurodegenerative diseases like Huntington's disease, ataxia etc. A flanking domain is usually fused at the N-terminal to polyQ in these proteins. On linking the flanking residues to polyQ, they accelerate aggregation of the proteins, which initiates from the flanking residues.

An investigation of the molecular interactions of diacetylcurcumin with ribonuclease A.

Curcumin is a natural product with diverse pharmacological activities. Studies of curcumin and its structural derivatives have been a subject of growing interest as a result of their diverse biological activities. We report the interaction of diacetylcurcumin (DAC) with Ribonuclease A (RNase A).

A spectroscopic investigation into the interactions of 3'-O-carboxy esters of thymidine with bovine serum albumin.

Binding studies of 3'-O-carboxy esters of thymidine, reported inhibitors of ribonucleases, with bovine serum albumin (BSA) have been explored in this report. Fluorescence spectroscopy in combination with Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy have been used to determine the nature and mode of binding. The binding and quenching parameters were determined from tryptophan fluorescence quenching by Scatchard plots and modified Stern-Volmer plots.

Molecular interactions of isoxazolcurcumin with human serum albumin: spectroscopic and molecular modeling studies.

Curcumin is a nontoxic natural product with diverse pharmacological potencies. We report the interaction of a potent synthetic derivative of curcumin, isoxazolcurcumin (IOC) with human serum albumin (HSA) using various biophysical methods. The observed fluorescence quenching of HSA by IOC is due to a complex formation by a static quenching process with a quenching constant of the order of 10(5) M(-1).

Using proton nuclear magnetic resonance to study the mode of ribonuclease A inhibition by competitive and noncompetitive inhibitors.

The C(2) proton resonances of the active site histidines (His 12 and His 119) of ribonuclease A have been exploited to study the inhibition pattern of both noncompetitive (four green tea polyphenols and their copper complexes) and competitive (3'-O-carboxy esters of thymidine and 3'-amino derivatives of uridine) inhibitors. Competitive inhibitors devoid of any phosphate group have the ability to change the pK(a) of the histidine residues at the active site. Their mode of inhibition, albeit competitive, is found to be different compared to known phosphate inhibitors 2'-CMP and 3'-CMP as revealed by changes in the pK(a) values.