Ultrafast Dynamics of the Medicinal Pigment Curcumin inside the Imidazolium Surface Active Ionic Liquid Containing Giant Vesicles and White Light Generation via Triple-FRET Technique

The naturally occurring yellow polyphenolic medicinal pigment curcumin shows ultrafast dynamics in the excited states. These ultrafast dynamics are strongly influenced by the rigidity of the environments of the systems. The present investigation unveils the ultrafast excited-state intramolecular hydrogen atom transfer (ESIHT) (which is involved in the antioxidant mechanism) and the solvation dynamics of curcumin inside the imidazolium surface active ionic liquid (SAIL), 1-hexadecyl-3-methylimidazolium chloride ([C16mim]Cl) micelle, and giant vesicles after introducing sorbitan monoesters (Span 20 and Span 80) in the aqueous medium. Interestingly, the short hydrocarbon chain containing Span 20 forms smaller, less rigid vesicles, and the long hydrocarbon chain containing Span 80 forms larger, more rigid giant vesicles after being assembled with [C16mim]Cl. The ESIHT and the solvation dynamics are slower in Span 80, containing rigid vesicles, than that in Span 20, comprising less rigid vesicles. Finally, we have established a three-component fluorescence resonance energy transfer (Triple-FRET) system to generate white light (WL) in the micelle and giant vesicles. Here the hydrophobic dye 1,6-diphenyl-1,3,5-hexatriene (DPH) acts as the donor, and the hydrophilic anticancer drug doxorubicin hydrochloride (DOX) serves as the acceptor along with the intermediate donor, curcumin. At a specific combination of the concentrations of these dyes in a particular self-assembled system, WL is generated due to the triple-FRET phenomena.

Insights into the Strong Emission Enhancement of Molecular Rotor Thioflavin T in Aqueous Cellulose Nanocrystal Dispersion: White Light Generation in Protein and Micellar Media

Thioflavin t (THT) is a well-known molecular rotor extensively used to detect amyloid-like structures. But THT shows very weak emission in water. In this article, we have found that THT shows very strong emission in the presence of cellulose nanocrystals (CNCs). Steady-state and time-resolved emission techniques have been used to study the strong emission of THT in aqueous CNC dispersion. The time-resolved study showed that in the presence of CNCs, the lifetime increased by ∼1500 fold compared to pure water (<1 ps). To know the nature of interaction and also the reason for this increase in emission zeta potential, stimuli-dependent and temperature-dependent studies have been carried out. These studies proposed that electrostatic interaction is the main factor for this binding of THT with CNCs. Further, the addition of another anionic lipophilic dye, merocyanine 540 (MC540), with CNCs-THT in both BSA protein (CIE: 0.33, 0.32) and TX-100 micellar (4.5 mM) (CIE: 0.32, 0.30) solutions produced excellent white light emission. Lifetime decay and absorption studies proposed a possible fluorescence resonance energy transfer mechanism in this generation of white light emission.

Deciphering Dual Modes of Parkinsonian Biomolecules Derived Fluorescent Nanoparticles: Protein Specificity and White Light Generation

Dopamine (DA) and 3,4-dihydroxy-l-phenylalanine (L-Dopa or DPA), a marker and medicine for the neurological disorder Parkinson's disease (PD), lead to the formation of polymeric fluorescent nanoparticles (F-Poly NPs or F-NPs or simply, NPs). The interaction study between proteins and NPs shows prominent interaction with strong specificity toward albumin type proteins for DPA derived and mixed NPs. Furthermore, encapsulation of the anticancer drug doxorubicin hydrochloride (Dox) inside the NP-protein conjugates results in excellent white light emission with pronounced specificity toward albumin proteins for F-PDPA and F-Mix NPs. Finally, the use of BSA protein fibril resulting in strong binding with NPs along with Dox assisted white light emission has also been studied.

The Dietary Nutrient Trimethylamine N-Oxide Affects the Phospholipid Vesicle Membrane: Probable Route to Adverse Intake

Trimethylamine N-oxide (TMAO), a choline-containing dietary supplement obtained from red meat, egg, and other animal resources, on excess accumulation is known to cause cardiovascular diseases (CVDs) like atherosclerosis. To understand the molecular mechanism of the pathogenesis of TMAO-induced CVDs, we have set up 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membrane in water that mimicked the endothelial cell membrane-blood interface of the artery wall and investigated the effect of an elevated concentration of TMAO on the membrane. We found that TMAO exerts an "action at a distance" mechanism through electrostatic force of attraction that significantly alters various properties of the membrane, like hydrophobicity, lateral organization, and interfacial water dynamics, which elevates the rigidity of the membrane. Such an effect was found to be further amplified in the presence of known causes of CVDs, i.e., high content of cholesterol (Chol). Therefore, TMAO-induced membrane rigidity may restrict the intrinsic elasticity of an artery membrane, expected to be introducing "hardening of the arteries", which makes the membrane atherosclerotic.

Formation of lipid tubules induced by a sugar-like molecule myo-inositol

The sugar-like molecule myo-inositol (InOH) bears an uncanny structural resemblance to the pyranose form of the sugar D-glucose (DG). InOH and its derivatives play a pivotal role in cell biology; whereby its interaction with the model membrane needs to be studied. Here, we have demonstrated that lipid tubules are formed as a result of the above-said interactions and that these interactions can be prevented by using hydroxyl protected InOH derivatives. We have tried to elucidate the nature of the InOH-membrane interactions by comparing them with DG-membrane interactions and have proposed a mechanism for the same.

Influence of a Polyneurotransmitter on DNA-Mediated Förster-Based Resonance Energy Transfer: A Path Leading to White Light Generation

The physiologically important biomolecule, dopamine (DA), shows strong self-oxidation and aggregation behaviors, which have been controlled and modulated to result in fluorescent polydopamine (F-PDA) nanoparticles. On the other hand, the simultaneous binding of two diverse deoxyribonucleic acid (DNA) binding probes, 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) and ethidium bromide (EtBr), has been elaborately established to follow the Förster-based resonance energy transfer (FRET) pathway. The comparative understanding of this DNA-mediated FRET in three media, phosphate buffer saline (PBS) of pH 7.4, DA, and F-PDA, has concluded that the FRET efficiency in the three media follows the order: PBS > DA > F-PDA. This controlled FRET in the fluorescent F-PDA matrix serves a pivotal role for efficient white light (WL) generation with excellent Commission Internationale de l'Eclairage (CIE) parameters that match well with that of pure WL emission. The obtained WL emission has been shown to be very specific with respect to concentrations of different participating components and the excitation wavelength of the illuminating source. Furthermore, the optical properties of the WL emitting solution have been observed to be retained excellently inside the well-known agarose gel matrix. Finally, the mechanistic pathway behind such a FRET-based WL generation has been established in detail, and to the best of our knowledge, the current study offers the first and only report that discloses the influence of a fluorescent polyneurotransmitter matrix for successful generation of WL emission.

Self-assembly of artificial sweetener aspartame adversely affects phospholipid membranes: plausible reason for its deleterious effects

The prolonged intake of the artificial sweetener aspartame is known to have deleterious effects. Our biophysical experimentations indicate that aspartame forms self-assembled cytotoxic fibrillar etiologies that affect the intrinsic integrity of the phospholipid membrane bilayer through electrostatic interaction and hydrophobic insertion, thereby making the membrane less rigid and more heterogeneous.

Phenylalanine Interacts with Oleic Acid-Based Vesicle Membrane. Understanding the Molecular Role of Fibril-Vesicle Interaction under the Context of Phenylketonuria

In the present contribution, on the basis of a spectroscopic and microscopic investigation, the characterization and photophysics of various assemblies of oleic acid/oleate solution at three pH values, namely, 8.28, 9.72, and 11.77, were explored. The variation in the dynamic response of aqua molecules in and around the assemblies has been interrogated by a picoseconds solvation dynamics experiment using a time-correlated single-photon counting setup employing coumarin-153 as a probe. On the one hand, the time-resolved fluorescence anisotropy measurement along with the fluorescence correlation spectroscopy experiment was executed to extract information regarding the comparison of the extent of the internal restricted confinement of these assemblies. On the other hand, an effort to investigate the cross-interaction between the self-assembled architectures of l-phenylalanine (l-Phe), responsible for phenylketonuria (PKU) disorder, and the oleic acid at the vesicle-forming pH established that the l-Phe fibrillar morphologies strongly alter the dynamic properties of the vesicle membrane formed by the oleic acid. Specifically, the interaction of the l-Phe assemblies with the oleic acid vesicle membrane is found to introduce the flexibility of the vesicle membrane and alter the hydration properties of the membrane. To track the fibril-induced alterations of the oleic acid vesicle properties, various spectroscopic and microscopic investigations were performed. The mutual reconciliation of the experimental outputs, therefore, portrays the state of the art, which accounts for the fibril-induced alterations of the properties of the oleic acid vesicle membrane, the mimicking setup of the cellular membrane, thereby informing us that alterations of such a property of the membrane should be taken into active consideration during the rational development of therapeutic modulators against disorders like PKU.

XAS studies of pressure-induced structural and electronic transformations in α-FeOOH

Structural and electronic transformation taking place in α-FeOOH goethite have been studied by Fe K-edge x-ray absorption spectroscopy at pressures up to 50 GPa. These studies have shown the symmetrization of FeO₆ octahedra coinciding with the Fe³⁺ high to low spin transition at pressure above ~45 GPa. Our data are in excellent agreement with the results of recent single crystal XRD and Mössbauer spectroscopy studies (Xu et al 2013 Phys. Rev. Lett. 111 175501), supporting the H-bonds symmetrization in iron oxyhydroxide, resulting from the Fe³⁺ high-to-low spin crossover at above 45 GPa. Our study shows an applicability of the x-ray absorption spectroscopy in a further study of the H-bonds symmetrization phenomenon.

The influence of precursors on phase evolution of nano iron oxides/oxyhydroxides: optical and magnetic properties

The present investigation describes the evolution of nanoiron oxide/oxyhydroxide phases synthesized under identical conditions of precipitation using different starting reagents.

Fluoride adsorption studies on mixed-phase nano iron oxides prepared by surfactant mediation-precipitation technique

Mixed nano iron oxides powder containing goethite (α-FeOOH), hematite (α-Fe(2)O(3)) and ferrihydrite (Fe(5)HO(8)·4H(2)O) was synthesized through surfactant mediation-precipitation route using cetyltrimethyl ammonium bromide (CTAB). The X-ray diffraction, FTIR, TEM, Mössbauer spectroscopy were employed to characterize the sample. These studies confirmed the nano powder contained 77% goethite, 9% hematite and 14% ferrihydrite. Fluoride adsorption onto the synthesized sample was investigated using batch adsorption method. The experimental parameters chosen for adsorption studies were: pH (3.0-10.0), temperature (35-55°C), concentrations of adsorbent (0.5-3.0 g/L), adsorbate (10-100 mg/L) and some anions. Adsorption of fluoride onto mixed iron oxide was initially very fast followed by a slow adsorption phase. By varying the initial pH in the range of 3.0-10.0, maximum adsorption was observed at a pH of 5.75. Presence of either SO(4)(2-) or Cl(-) adversely affected the adsorption of fluoride in the order of SO(4)(2-)>Cl(-). The FTIR studies of fluoride loaded adsorbent showed that partly the adsorption on the surface took place at surface hydroxyl sites. Mössbauer studies indicated that the overall absorption had gone down after fluoride adsorption that implies it has reduced the crystalline bond strength. The relative absorption area of ferrihydrite was marginally increased from 14 to 17%.

A green Hunsdiecker reaction: synthesis of beta-bromostyrenes from the reaction of alpha,beta-unsaturated aromatic carboxylic acids with KBr and H2O2 catalysed by Na2MoO4.2H2O in aqueous medium

Reaction of alpha,beta-unsaturated aromatic carboxylic acids with KBr and H2O2 in the presence of Na2MoO4.2H2O in aqueous medium affords beta-bromo alkenes in high yield.