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Various biophysical techniques have been extensively employed to study protein aggregation due to its significance. Traditionally, these methods detect aggregation at micrometer length scales and micromolar concentrations. However, unlike in vitro, protein aggregation typically occurs at nanomolar concentrations in vivo. Here, using fluorescence correlation spectroscopy (FCS), we captured bromelain aggregation at concentrations as low as ~20 nM, surpassing the detection limit of traditional methods like thioflavin T fluorescence, scattering, and fluorescence microscopy by more than one order of magnitude. Moreover, using thioflavin T fluorescence‐based FCS, we have detected larger aggregates at higher bromelain concentrations, which is undetectable in FCS otherwise. Importantly, our study reveals inherent heterogeneity in bromelain aggregation, inaccessible to ensemble‐averaged techniques. The presented report may provide a platform for the characterization of premature aggregates at very low protein concentrations, which are thought to be functionally significant species in protein aggregation‐induced diseases. [ABSTRACT FROM AUTHOR]

Conformational heterogeneity is a defining characteristic of a protein and is vital in understanding its function and folding landscape. In the present work, we interrogated the presence of conformational heterogeneity in multi‐domain human serum albumin in a domain‐specific manner using red edge excitation shift (REES) in its native state and also monitored its variation along the unfolding transition. We also looked into the origin of such conformational heterogeneity by varying the solution viscosity. We observed (1) even in the native state, the heterogeneity and dynamics of the side chain exhibit varied behaviors depending on which domain of the multi‐domain human serum albumin (HSA) is being examined. (2) When the protein is in the unfolded state, the extent of REES is rendered unimportant since there is a greater quantity of free water present, in addition to the disruption of the protein's structure. (3) While the rigid protein matrix provides the rigidity of domain‐I and domain‐III, the rigidity of domain‐II is provided by water molecules, which indicates that the role of water molecules in providing the rigidity is significant. Overall, our results provide direct evidence of the rigidity and alternate side chain packing arrangement of protein core that varies domain‐wise in multi‐domain HSA. [ABSTRACT FROM AUTHOR]

Photodetectors that can sense not only light intensity but also light's polarization state add valuable information that is beneficial in a wide array of applications. Polymer semiconductors are an attractive material system to achieve intrinsic polarization sensitivity due to their anisotropic optoelectronic properties. In this report, the thermomechanical properties of the polymer semiconductors PBnDT‐FTAZ and P(NDI2OD‐T2) are leveraged to realize bulk heterojunction (BHJ) films with record in‐plane alignment. Two polymer blends with distinct weight average molar masses (Mw) are considered and either a strain‐ or rub‐alignment process is applied to align the polymer blend films. Optimized processing yields films with dichroic ratios (DR) of over 11 for the high Mw system and nearly 17 for the low Mw system. Incorporating the aligned films into photodetectors results in a polarized photocurrent ratio of 15.25 with corresponding anisotropy ratio of 0.88 at a wavelength of 530 nm, representing the highest reported photocurrent ratio for photodiodes that can operate in a self‐powered regime. The demonstrated performance showcases the ability of polymer semiconductors to achieve BHJ films with exceptional in‐plane polymer alignment, enabling high performance polarization sensitive photodetectors for incorporation into novel device architectures. [ABSTRACT FROM AUTHOR]

In the submicellar solution of anionic surfactants sodium dodecyl sulfate (SDS) and dioctyl sodium sulfosuccinate (AOT), the alkaline fading of methyl violet (MV+) carbocation has been studied spectrophotometrically in the temperature range 293–308 K. The interaction behavior of the dye carbocation with the anionic surfactant and the observed submicellar rate retardation is consistent with the ion pair and subsequent ion‐pair micelle formation. The change in the spectral pattern along with a change in the peak intensity and shoulder intensity with increasing surfactant concentrations indicates the shifting of the equilibrium between the helical and distorted helical isomers of MV+ owing to the existence of dye–surfactant ion pair, ion‐pair micelles, and dye‐embedded micelles. This dynamic dye–surfactant ion‐ion interaction has been corroborated by the tensiometric studies. The decrease in the fading rate and the change in the spectral pattern in the presence of anion, especially I–, support the existence of the dye–anion interaction. The premicellar rate inhibition and the corresponding interaction have been accounted for by the use of two kinetic models namely, Olson–Simonson and Piszkiewicz cooperativity models. The cooperativity index value suggested a 1:1 dye–surfactant association in both the surfactants. The ratio of the concentration of the premicellar complex and the free dye cation indicates appreciable binding. The kinetic and thermodynamic parameters associated with the dye–surfactant complex have been explained in terms of dye–surfactant, dye–water, and surfactant–water interactions. [ABSTRACT FROM AUTHOR]

4‐(quinolin‐2‐ylmethylene)aminophenol (QMAP) is synthesised in a one‐step synthetic process and was checked for its sensing ability towards metal ions. The molecule is found to be effective for the instantaneous selective and sensitive Cu(II) ion detection in PPB level in methanolic solution with a distinct development of orangish yellow colour from a colourless solution, which can be detected visually. The sensing ability of the QMAP towards Cu(II) is found independent on the type of counter anions and also in the presence of other metal ions. QMAP does not show any colour change in the presence of other metal salts. A 2 : 1 binding stoichiometry between QMAP and Cu(II) with a large binding constant of 3.2 x 1010 M−2 has been measured. Quantum chemical calculations have been used to understand the nature of the complex and the mechanism of the sensing. [ABSTRACT FROM AUTHOR]

An ultra‐slow crystal growth over a period of 24 h of a newly synthesized CH3NH3Pb1/2Bi1/3I3 perovskite (MPBI) nanocrystal in non‐polar toluene medium is reported here. From several spectroscopic techniques as well as from TEM analysis we found that the size of nanocrystals changes continuously with time, in spite of being capped by the ligands. Using a single molecular spectroscopic technique, we also found that this size change is not due to the stacking of nanocrystals but due to crystal growth. The notable temperature dependence and reversible nature of the nanocrystals growth is explained by the dynamic nature of the capping. The observed temperature‐dependent ultra‐slow growth is believed to be a pragmatic step towards controlling the size of perovskite NC in a systematic manner. [ABSTRACT FROM AUTHOR]

When protonic motion is explained as a purely quantum mechanical phenomenon, two extreme situations can be visualized as either the adiabatic or the nonadiabatic limit of proton transfer (PT). Strong orbital coupling between the donor and the acceptor pair in the proton transfer step drives PT mechanism in the adiabatic limit whereas in nonadiabatic limit PT predominantly occurs through tunneling. Here we proposed a unique way to experimentally observe the adiabaticity of PT by introducing chirality in the reaction coordinate of excited state proton transfer (ESPT). We successfully established the existence of prominent role of diastereomerism in the ESPT by both steady state and femtosecond time‐resolved transient absorption spectroscopic measurements in the adiabatic limit. The presented novel approach can overcome the limitations of only available experimental technique, i. e. kinetic isotope effect, to elucidate proton transfer mechanism. [ABSTRACT FROM AUTHOR]

This work describes the design and synthesis of fluorescent triphenylamine‐thiazolothiazole based donor‐acceptor‐donor chemosensor 4,4′‐(thiazolo[5,4‐d]thiazole‐2,5‐diyl)bis(N,N‐bis(4‐methoxyphenyl)aniline) (TTz‐1). TTz‐1 exhibited positive solvatochromism effect in the excited state due to its strong intramolecular charge transfer (ICT) properties. Potential application of TTz‐1 toward metal ion detection were explored systematically. It was established that the addition of Cu(ClO4)2. 6H2O into TTz‐1 resulted in near‐infrared (NIR) colorimetric and fluorescent quenching allowing for Cu2+ detection. EPR studies indicate that formation of radical cation occurs when Cu2+ and TTz‐1 interact. TTz‐1 was also able to detect Fe3+ employing a color change from orange to colourless (fluorescent). It was observed that the TTz‐1 emission peak at 567 nm was quenched after addition of Cu2+ and Fe3+ metal ions. Electrochemical analysis showed that LUMO values of the TTz‐1 decreased after addition of Fe3+ and Cu2+. The limits of detection (LOD) for Cu2+ and Fe3+ detection by TTz‐1 were found to be 0.30 μM and 0.29 μM, respectively. These results suggest that the TTz‐1 is a highly selective and sensitive sensor for the detection of Cu2+ or Fe3+ ions. [ABSTRACT FROM AUTHOR]

The kinetics of the oxidative degradation of d‐fructose by nanoparticles of MnO2 has been studied in dilute sulfuric acid medium and also in the presence of surfactants of cetyl trimethyl ammonium bromide (CTAB), Triton X‐100 (TX‐100), and Tween 20. Amorphous nanoparticles of MnO2 in the form of spherical particulates of size 50–200 nm, as detected by a transmission electron microscope, have been found to exist, supported on two‐dimensional gum acacia sheets. The reaction is first order in MnO2 but complex order with respect to fructose and H+. The reaction is inhibited due to adsorption of reaction products on the surface of MnO2 nanoparticles. The reaction takes place through an intermediate complex formation between β‐d‐fructopyranose and protonated MnO2. A one‐step two‐electron transfer reaction ultimately leads to the formation of an aldonic acid and formic acid. The entropy of activation plays the key role for the reaction in the absence of surfactants. In the surfactant‐mediated reaction, partitioning of both the reactants takes place between the aqueous and micellar pseudophases and reaction occurs following Berezin's model. Binding of fructose with the surfactants in the Stern/palisade layer takes place through the ion–dipole interaction and H‐bonding while protonated MnO2 remains at the outer side of the Stern/palisade layer within the micelle. Both the enthalpy and entropy changes associated with the fructose–water interaction, fructose–micelle interaction, and micelle–water interaction finally control the fructose–micelle binding. [ABSTRACT FROM AUTHOR]

ABSTRACT Oxidative degradation of l-isoleucine (Ileu) by Au3+ complexes has been studied spectrophotometrically in weakly acid medium (acetic acid-sodium acetate buffer, pH range 3.72-4.80) in the temperature range 288-308 K. The reaction is first order with respect to AuIII but complex order (<1) with respect to isoleucine. Ionic strength has no significant effect on the reaction kinetics. Both H+ and Cl− ions have been found to show inhibiting effect on the reaction rate. Decreasing solvent polarity exerts an adverse effect on the reaction. Au3+ complexes react with the zwitterion form of isoleucine in a one-step two-electron transfer redox process. The reaction passes through intermediate formation of iminic cation, which hydrolyzes to produce 2-methyl butanal, identified by 1H NMR. The activation parameters Δ H≠ and Δ S≠ related to the rate-limiting step of the reaction are evaluated. The derived rate law is in excellent agreement with the experimental results. The kinetic and activation parameters of this investigation have been compared and analyzed with those of the oxidation of l-leucine by gold(III). [ABSTRACT FROM AUTHOR]

Organostannoxanes have been used as scaffolds for the preparation of multi-chromophore assemblies. A single-step synthesis procedure allows the preparation of compounds in which the number of chromophore units can be varied from two to six. Thus, the reactions of pyrene sulfonic acid (PySO3H) or C16H9CHNC6H3(COOH)2 (LH2) with various organotin precursors gave pyrene-containing organostannoxanes, that is, [Ph3SnPySO3]6 ( 1), [{(Me2Sn)2(μ3-O)(μ-OH)PySO3}2{(Me2Sn)2(μ3-O)(μ-OH)H2O}2 ⋅2 PySO3] ( 2), [{ tBu2Sn(OH)PySO3}2] ( 3), [{( nBuSn)12(O)14(OH)6{PySO3}2] ( 4), and [{( nBu2Sn)L}3]2 ⋅C6H5CH3 ( 5). Compounds 1- 5 were characterized by using X-ray crystallography. Compounds 1 and 5 are 24-membered macrocycles. Macrocycle 1 possesses intramolecular π-π stacking interactions. An unusual co-crystal of two tetrameric ladders in 2 was observed in which one of the components of the co-crystal is neutral whereas the other is dicationic and two pyrenesulfonate counterions are present to balance the overall charge. In the solid state these compounds reveal rich supramolecular structures. Photophysical studies on 1- 5 reveal that interactions in the solid state lead to considerable broadening of the emission bands. [ABSTRACT FROM AUTHOR]

Aminonaphthalimide-BODIPY energy transfer cassettes were found to show very fast ( kEET≈1010-1011 s−1) and efficient BODIPY fluorescence sensitization. This was observed upon one- and two-photon excitation, which extends the application range of the investigated bichromophoric dyads in terms of accessible excitation wavelengths. In comparison with the direct excitation of the BODIPY chromophore, the two-photon absorption cross-section δ of the dyads is significantly incremented by the presence of the aminonaphthalimide donor [ δ≈10 GM for the BODIPY versus 19-26 GM in the dyad at λexc=840 nm; 1 GM (Goeppert-Mayer unit)=10−50 cm4 s molecule−1 photon−1]. The electronic decoupling of the donor and acceptor, which is a precondition for the energy transfer cassette concept, was demonstrated by time-dependent density functional theory calculations. The applicability of the new probes in the one- and two-photon excitation mode was demonstrated in a proof-of-principle approach in the fluorescence imaging of HeLa cells. To the best of our knowledge, this is the first demonstration of the merging of multiphoton excitation with the energy transfer cassette concept for a BODIPY-containing dyad. [ABSTRACT FROM AUTHOR]

This study is devoted to understand the unfolding mechanism of a multidomain protein, human serum albumin (HSA), in absence and presence of the sucrose by steady-state and time-resolved fluorescence spectroscopy with domain specific marker molecules and is further being substantiated by molecular dynamics (MD) simulation. In water, the domain III of HSA found to unfold first followed by domains I and II as the concentration of GnHCl is increased in the medium. The sequential unfolding behavior of different domains of HSA remains same in presence of sucrose; however, a higher GnHCl concentration is required for unfolding, suggesting stabilizing effect of sucrose on HSA. Domain I is found to be most stabilized by sucrose. The stabilization of domain II is somewhat similar to domain I, but the effect of sucrose on domain III is found to be very small. MD simulation also predicted a similar behavior of sucrose on HSA. The stabilizing effect of sucrose is explained in terms of the entrapment of water molecules in between HSA surface and sucrose layer as well as direct interaction between HSA and sucrose. [ABSTRACT FROM AUTHOR]

The effect of nonionic micelles of Triton X-100 on the oxidative decarboxylation of l-glutamic acid by chloroaurate(III) complexes has been investigated in acetate buffer medium. The reaction is first order with respect to Au(III), but a complex order with respect to glutamate. H+ ion has both accelerating and retarding effects in the pH range 3.72-4.80, whereas a Cl− ion has an inhibiting effect in the range 0.02-0.56 mol dm−3. Under the experimental conditions, AuCl−4 and AuCl3(OH)− are the predominant and effective oxidizing species, whereas the zwitterion (H2A) and mononegative anion (HA−) are the predominant reducing species of the amino acid. The reaction involves a one-step two-electron transfer process and passes through the intermediate formation of iminic cation. In the presence of surfactant, the reaction passes through a maximum and it appears to follow Berezin's model, where both the oxidant and the substrate are partitioned between the aqueous and the micellar phase and then react. The binding constants between the reactants and the surfactant have been evaluated at different temperatures. Compensation between substrate-water interaction and substrate-micelle interaction plays an important role in such redox reactions in the presence of a surfactant. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 482-493, 2012 [ABSTRACT FROM AUTHOR]

The kinetics of the oxidation of alanine by chloroaurate(III) complexes in acetate buffer medium has been investigated. The major oxidation product of alanine has been identified as acetaldehyde by 1H NMR spectroscopy. Under the experimental conditions, AuCl-4 and AuCl3(OH)- are the effective oxidizing species of gold(III). The reaction is first order with respect to Au(III) as well as alanine. The effects of H+ and Cl- on the second-order rate constant k2′ have been analyzed, and accordingly the rate law has been deduced: k2′ = (k1[H+][Cl-] + k3K4K5)/(K4K5 + [H+][Cl-]). Increasing dielectric constant of the medium has an accelerating effect on the reaction rate. Activation parameters associated with the overall reaction have been calculated. A mechanism involving the two effective oxidizing species of gold(III) and zwitterionic species of alanine, consistent with the rate law, has been proposed. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 473–482, 2009 [ABSTRACT FROM AUTHOR]

In this report, a high‐performance all‐polymer organic photodetector that is sensitive to linearly polarized light throughout the visible spectrum is demonstrated. The active layer is a bulk heterojunction composed of an electron donor polymer PBnDT‐FTAZ and acceptor polymer P(NDI2OD‐T2) that have complementary spectral absorption resulting in efficient detection from 350 to 800 nm. The blend film exhibits good ductility with the ability to accommodate large strains of over 60% without fracture. This allows the film to undergo large uniaxial strain resulting in in‐plane alignment of both polymers making the film optically anisotropic and intrinsically polarization sensitive. The films are characterized by UV–vis spectroscopy and grazing incidence wide‐angle X‐ray scattering showing that both polymers have similar in‐plane backbone alignment and maintain packing order after being strained. The films are integrated into devices and characterized under linear polarized light. The strain‐oriented detectors have maximum photocurrent anisotropies of 1.4 under transverse polarized light while maintaining peak responsivities of 0.21 A W−1 and a 3 dB cutoff frequency of ≈1 kHz. The demonstrated performance is comparable to the current state of the art all‐polymer photodetectors with the added capability of polarization sensitivity enabling new application opportunities. An all‐polymer organic photodetector with intrinsic polarization sensitivity is demonstrated. The polymers are chosen due to their ductility and complimentary absorption characteristics. This allows the films to be strain oriented resulting in anisotropic optical properties and when applied in a photodetector displays efficient photosensitivity across the visible spectrum. [ABSTRACT FROM AUTHOR]

Conformational heterogeneity is a defining characteristic of a protein and is vital in understanding its function and folding landscape. In the present work, we interrogated the presence of conformational heterogeneity in multi‐domain human serum albumin in a domain‐specific manner using red edge excitation shift (REES) in its native state and also monitored its variation along the unfolding transition. We also looked into the origin of such conformational heterogeneity by varying the solution viscosity. We observed (1) even in the native state, the heterogeneity and dynamics of the side chain exhibit varied behaviors depending on which domain of the multi‐domain human serum albumin (HSA) is being examined. (2) When the protein is in the unfolded state, the extent of REES is rendered unimportant since there is a greater quantity of free water present, in addition to the disruption of the protein's structure. (3) While the rigid protein matrix provides the rigidity of domain‐I and domain‐III, the rigidity of domain‐II is provided by water molecules, which indicates that the role of water molecules in providing the rigidity is significant. Overall, our results provide direct evidence of the rigidity and alternate side chain packing arrangement of protein core that varies domain‐wise in multi‐domain HSA. [ABSTRACT FROM AUTHOR]

The kinetics of the oxidative degradation of d‐fructose by nanoparticles of MnO2 has been studied in dilute sulfuric acid medium and also in the presence of surfactants of cetyl trimethyl ammonium bromide (CTAB), Triton X‐100 (TX‐100), and Tween 20. Amorphous nanoparticles of MnO2 in the form of spherical particulates of size 50–200 nm, as detected by a transmission electron microscope, have been found to exist, supported on two‐dimensional gum acacia sheets. The reaction is first order in MnO2 but complex order with respect to fructose and H+. The reaction is inhibited due to adsorption of reaction products on the surface of MnO2 nanoparticles. The reaction takes place through an intermediate complex formation between β‐d‐fructopyranose and protonated MnO2. A one‐step two‐electron transfer reaction ultimately leads to the formation of an aldonic acid and formic acid. The entropy of activation plays the key role for the reaction in the absence of surfactants. In the surfactant‐mediated reaction, partitioning of both the reactants takes place between the aqueous and micellar pseudophases and reaction occurs following Berezin's model. Binding of fructose with the surfactants in the Stern/palisade layer takes place through the ion–dipole interaction and H‐bonding while protonated MnO2 remains at the outer side of the Stern/palisade layer within the micelle. Both the enthalpy and entropy changes associated with the fructose–water interaction, fructose–micelle interaction, and micelle–water interaction finally control the fructose–micelle binding. [ABSTRACT FROM AUTHOR]

In the mononuclear title complex, [CuBr(C20H12N3O2)(C3H7NO)], synthesized from the quinoline-derived reduced Schiff base 4-(quinolin-2-ylmeth-yl)amino-phenol, the coordination geometry around Cu(2+) is distorted square-pyramidal, comprising a bromide anion at the apex [Cu-Br = 2.4671 (5) Å]. The base of the pyramid is built up from one di-methyl-formamide O-atom donor [Cu-O = 2.078 (2) Å] and three N-atom donors from the monoanionic, tridentate bis-(quinolin-2-ylcarbon-yl)di-imide ligand [Cu-Ndi-imide = 1.941 (3) Å, and Cu-Nquinol-yl = 2.060 (3) and 2.049 (3) Å]. An intra-molecular C-H⋯O occurs. In the crystal, weak methyl and aromatic C-H⋯Br and formyl C-H⋯Ocarbon-yl hydrogen-bonding inter-actions generate an overall layered structure lying parallel to (001).

In the mononuclear title complex, [HgCl2(C16H12N2O)], synthesized from the phenolic Schiff base 4-[(quinolin-2-yl-methyl-idene)amino]-phenol (QMAP), the coordination geometry around Hg(2+) is distorted tetra-hedral, comprising two Cl atoms [Hg-Cl = 2.3565 (12) and 2.5219 (12) Å] and two N-atom donors from the QMAP ligand, viz. one imine and the other quinoline [Hg-N = 2.392 (2) and 2.237 (2) Å, respectively]. In the crystal, O-H⋯Cl hydrogen bonds generate a chain structure extending along the c-axis direction. Weak C-H⋯Cl and π-π stacking inter-actions [minimum ring centroid separation = 3.641 (3) Å] give an overall layered structure lying parallel to (001).