Pavel Banerjee

Investigation of Fibril Forming Mechanisms of l-Phenylalanine and l-Tyrosine: Microscopic Insight toward Phenylketonuria and Tyrosinemia Type II

Phenylketonuria and tyrosinemia type II, the two metabolic disorders, are originated due to the complications in metabolism of phenylalanine (Phe) and tyrosine (Tyr), respectively. Several neurological injuries, involving microcephaly, mental retardation, epilepsy, motor disease, and skin problems etc., are the symptoms of these two diseases. It has been reported that toxic amyloid fibrils are formed at high concentrations of Phe and Tyr. Our study indicates that the fibril forming mechanisms of Phe and Tyr are completely different. In the case of Phe, -NH3+ and -COO- groups of neighboring molecules interact via hydrogen bonding and polar interactions. On the other hand, there is no role of - NH3+ group in the fibril forming mechanism of Tyr. In Tyr fibril, the two hydrogen bonding partners are -OH and -COO- groups. In addition, we have also investigated the effect of three lanthanide cations on the fibrillar assemblies of Phe. It has been observed that the efficiencies of three lanthanides to inhibit the fibrillar assemblies of Phe follow the order Tb3+< Sm3+< Eu3+.

Inhibition of Fibrillar Assemblies of l-Phenylalanine by Crown Ethers: A Potential Approach toward Phenylketonuria

In this article, our aim is to investigate the interaction of l-phenylalanine (l-Phe) fibrils with crown ethers (CEs). For this purpose, two different CEs (15-Crown-5 (15C5) and 18-Crown-6 (18C6)) were used. Interestingly, we have observed that both CEs have the ability to arrest fibril formation. However, 18C6 was found to be a better candidate compared to 15C5. Field emission scanning electron microscopy and fluorescence lifetime imaging microscopy were used to monitor the fibril-arresting kinetics of CEs. The arresting process was further confirmed by fluorescence correlation spectroscopy and nuclear magnetic resonance studies.

Sodium Chloride Triggered the Fusion of Vesicle Composed of Fatty Acid Modified Protic Ionic Liquid: A New Insight into the Membrane Fusion Monitored through Fluorescence Lifetime Imaging Microscopy

The development of stable vesicular assemblies and the understanding of their interaction and dynamics in aqueous solution are long-standing topics in the research of chemistry and biology. Fatty acids are known to form vesicle structure in aqueous solution depending on the pH of the medium. Protic ionic liquid of fatty acid with ethyl amine (oleate ethyl amine, OEA) as a component spontaneously forms a vesicle in aqueous solution. The general comparison of dynamics and interaction of these two vesicles have been drawn using fluorescence correlation spectroscopy (FCS) and fluorescence lifetime imaging microscopy (FLIM) measurements. Further, FLIM images of a single vesicle are taken at multiple wavelengths, and the solvation of the probe molecules has been observed from the multiwavelength FLIM images. The lifetime of the probe molecule in OEA vesicle is higher than that in simple fatty acid vesicles. Therefore, it suggests that the membrane of the OEA vesicle is more dehydrated compared to that of fatty acid vesicles, and it facilitates OEA vesicles to fuse themselves in the presence of electrolyte, sodium chloride (NaCl). However, under the same conditions, only fatty acid vesicles do not fuse. The fusion of OEA vesicles is successfully demonstrated by the time scan FLIM measurements. The different events in the fusion process are analyzed in the light of the reported model of vesicle fusion. Finally, the local viscosity of the water pool of the vesicle is determined using kiton red, as a molecular rotor. With addition of NaCl, the fluidity in the interior of the vesicle is increased which leads to disassembly of vesicle. The rich dynamic properties of this vesicular assembly and the FLIM based approach of vesicle fusion will provide better insight into the growth of a protocell membrane.

5-Methyl Salicylic Acid-Induced Thermo Responsive Reversible Transition in Surface Active Ionic Liquid Assemblies: A Spectroscopic Approach

This article describes the formation of stable unilamellar vesicles involving surface active ionic liquid (SAIL), 1-hexadecyl-3-methylimidazolium chloride (C16mimCl), and 5-methyl salicylic acid (5mS). Turbidity, dynamic light scattering (DLS), transmission electron microscopy (TEM), and viscosity measurements suggest that C16mimCl containing micellar aggregates are transformed to elongated micelle and finally into vesicular aggregates with the addition of 5mS. Besides, we have also investigated the photophysical aspects of a hydrophobic (coumarin 153, C153) and a hydrophilic molecule (rhodamine 6G (R6G) perchlorate) during 5mS-induced micelle to vesicle transition. The rotational motion of C153 becomes slower, whereas faster motion is observed for R6G during micelle to vesicle transition. Moreover, the fluorescence correlation spectroscopy (FCS) measurements suggest that the translational diffusion of hydrophobic probe becomes slower in C16mimCl-5mS aggregates in comparison to C16mimCl micelle. However, a reverse trend in translational diffusion motion of hydrophilic molecule has been observed in C16mimCl-5mS aggregates. Moreover, we have also found that the C16mimCl-5mS containing vesicles are transformed into micelles upon enhanced temperature, and it is further confirmed by turbidity, DLS measurements that this transition is a reversible one. Finally, temperature-induced rotational motion of C153 and R6G has been monitored in C16mimCl-5mS aggregates to get a complete scenario regarding the temperature-induced vesicle to micelle transition.

Micelle-vesicle-micelle transition in aqueous solution of anionic surfactant and cationic imidazolium surfactants: Alteration of the location of different fluorophores

The presence of different surfactants can alter the physicochemical behaviors of aqueous organized assemblies. In this article, we have investigated the location of hydrophobic molecule (Coumarin 153, C153) and hydrophilic molecule (Rhodamine 6G perchlorate, R6G) during micelle-vesicle-micelle transition in aqueous medium in presence of anionic surfactant, sodium dodecylbenzenesulfonate (SDBS) and cationic imidazolium-based surfactant, 1-alkyl-3-methylimidazolium chloride (CnmimCl; n=12, 16). Initially, the physicochemical properties of anionic micellar solution of SDBS has been investigated in presence of imidazolium-based surfactant, CnmimCl (n=12, 16) in aqueous medium by visual observation, turbidity measurement, zeta potential (ζ), dynamics light scattering (DLS), and transmission electron microscopy (TEM). Zeta potential (ζ) measurement clearly indicates that the incorporation efficiency of C16mimCl in SDBS micelle is better than the other one due to the involvement of strong hydrophobic as well as electrostatic interaction between the two associated molecules. Turbidity and DLS measurements clearly suggest the formation of vesicles over a wide range of concentration. Finally, the rotational motion of C153 and R6G has also been monitored at different mole fractions of CnmimCl in SDBS-CnmimCl (n=12, 16) solution mixtures. The hydrophobic C153 molecules preferentially located in the bilayer region of vesicle, whereas hydrophilic R6G can be solubilized at surface of the bilayer, inner water pool or outer surface of vesicles. It is observed that rotational motion of R6G is altered significantly in SDBS-CnmimCl solution mixtures in presence of different mole fractions of CnmimCl. Additionally, the translational diffusion motion of R6G is monitored using fluorescence correlation spectroscopy (FCS) techniques to get a complete scenario about the location and translational diffusion of R6G.

Unveiling the Aggregation Behavior of Doxorubicin Hydrochloride in Aqueous Solution of 1-Octyl-3-methylimidazolium Chloride and the Effect of Bile Salt on These Aggregates: A Microscopic Study

In this article, we have unveiled the aggregation behavior of a potent chemotherapeutic drug, doxorubicin hydrochloride (Dox) in a well-known imidazolium based surface active ionic liquid (SAIL), 1-octyl-3-methylimidazolium chloride (C8mimCl). The aggregates formed by Dox in C8mimCl have been characterized using dynamic light scattering (DLS), fluorescence lifetime imaging microscopy (FLIM), high-resolution transmission electron microscopy (HR-TEM), analytical transmission electron microscopy (analytical TEM), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and Fourier-transform infrared spectroscopy (FTIR) measurements. It is found that Dox forms large spherical aggregates in the presence of C8mimCl SAIL. We have also explored the driving force behind this aggregation behavior of Dox in C8mimCl. Furthermore, it is observed that in the presence of a common bile salt, sodium cholate (NaCh), Dox/C8mimCl spherical aggregates disrupt to form rodlike fibrillar aggregates. Therefore, formation of spherical aggregates and also its disruption into rodlike fibrillar aggregates have been performed, and this is expected to open a new scope for the design of a new generation smart drug delivery system where the drug itself aggregates to form the delivery system.

Concentration-Driven Fascinating Vesicle-Fibril Transition Employing Merocyanine 540 and 1-Octyl-3-methylimidazolium Chloride

In this article, anionic lipophilic dye merocyanine 540(MC540) and cationic surface-active ionic liquid (SAIL) 1-octyl-3-methylimidazolium chloride (C8mimCl) are employed to construct highly ordered fibrillar and vesicular aggregates exploiting an ionic self-assembly (ISA) strategy. It is noteworthy that the concentration of the counterions has exquisite control over the morphology, in which lowering the concentration of both the building blocks in a stoichiometric ratio of 1:1 provides a vesicle to fibril transition. Here, we have reported the concentration-controlled fibril-vesicle transition utilizing the emerging fluorescence lifetime imaging microscopy (FLIM) technique. Furthermore, we have detected this morphological transformation by means of other microscopic techniques such as field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and cryogenic-transmission electron microscopy (cryo-TEM) to gain additional support. Besides, multiwavelength FLIM (MW-FLIM) and atomic force microscopy (AFM) techniques assist us in knowing the microheterogeneity and the height profile of the vesicles, respectively. We have replaced the SAIL, C8mimCl, by an analogous traditional surfactant, n-octyltrimethylammonium bromide (OTAB), and it provides a discernible change in morphology similar to that of C8mimCl, whereas 1-octanol is unable to exhibit any structural aggregation and thus reveals the importance of electrostatic interaction in supramolecular aggregate formation. However, the SAILs having the same imidazolium headgroup with different chain lengths other than C8mimCl are unable to display any structural transition and determine the importance of the correct chain length for efficient packing of the counterions to form a specific self-assembly. Therefore, this study reveals the synergistic interplay of electrostatic, hydrophobic, and π-π stacking interactions to construct the self-assembly and their concentration-dependent morphological transition.

Modification of fatty acid vesicle using an imidazolium-based surface active ionic liquid: a detailed study on its modified properties using spectroscopy and microscopy techniques\(^{\S }\)

Fatty acid vesicles have attracted views as model protocell membranes in understanding the emergence of life, but their properties can be further modified in the presence of some external molecules. In this work, we have investigated the spontaneous formation of large unilamellar vesicles (LUVs) of oleic acid in aqueous medium in presence of a popular imidazolium-based cationic surface active ionic liquid (SAIL) [C16mim]Cl\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}

Probing the Interaction between a DNA Nucleotide (Adenosine-5′-Monophosphate Disodium) and Surface Active Ionic Liquids by Rotational Relaxation Measurement and Fluorescence Correlation Spectroscopy

[\hbox {C}_{16}\hbox {mim}]\hbox {Cl}