Landauer formula for phonon heat conduction: relation between energy transmittance and transmission coefficient

A Fibonacci chain is composed of oscillators with two different masses and its total (even) number of oscillators N is associated with Fibonacci numbers. The momentum autocorrelation function of a specific oscillator in the chain is shown to be combination of 1?+?(N/2) cosines, their frequencies and amplitudes are calculated numerically for N????40. The momentum autocorrelation functions are illustrated for Fibonacci chains with N up to 176.     

Enantioselective Zinc‐Catalyzed Hydrosilylation of Ketones using Pybox or Pybim Ligands

The combination of ZnEt₂ and chiral pyridinebisoxazoline (pybox) or pyridinebisimidazoline (pybim) ligands catalyzed the asymmetric hydrosilylation of aryl, alkyl, cyclic, heterocyclic, and aliphatic ketones. Under mild conditions, high yields and good enantioselectivities were achieved. ESI measurements allowed for the characterization of the active catalyst.     

Synthesis, Spectroscopic and Thermal Studies of Zinc(II) Complexes with the Symmetrical Bidentate Schiff-Base Ligand (2,3-MeO-ba)2en: Crystal Structure of Zn((2,3-MeO-ba)2en)I2

Abstract  

Two zinc(II) complexes [ZnI₂((2,3-MeO-ba)₂en)] (1) and [ZnCl₂((2,3-MeO-ba)₂en)] (2), with the symmetrical bidentate Schiff-base ligand (2,3-MeO-ba)₂en [N,N′-bis(2,3-dimethoxybenzylidene)-1,2-diaminoethane] have been synthesized and characterized by elemental analyses (CHN), FT-IR and ¹H-NMR spectroscopy. The thermal behaviors of these complexes were studied using thermogravimetry in order to evaluate their thermal stability and thermal decomposition pathways. The crystal structure of [ZnI₂((2,3-MeO-ba)₂en)] (1) was determined from single-crystal X-ray diffraction. The coordination polyhedron about the zinc(II) center in the complex 1 is best described as a distorted tetrahedron.     

A small molecule two-photon probe for hydrogen sulfide in live tissues

We report a two-photon probe (FS1) which shows a 21-fold two-photon excited fluorescence enhancement in response to H(2)S and can selectively detect H(2)S in a rat hippocampal slice at a depth of 90-190 μm by using two-photon microscopy.     

Enantioselective synthesis of substituted pyrans via amine-catalyzed Michael addition and subsequent enolization/cyclisation

An organocatalytic construction of optically enriched substituted pyran derivatives via amine-catalyzed Michael addition and subsequent enolization/cyclisation has been described starting from electronically poor alkenes. Functionalized pyrans were obtained in high enantioselectivities (up to 96%) and good yields (up to 90%) having three contiguous chiral centers.     

Striking Improvement in Peroxidase Activity of Cytochrome c by Modulating Hydrophobicity of Surface‐Functionalized Gold Nanoparticles within Cationic Reverse Micelles

This work demonstrates a remarkable enhancement in the peroxidase activity of mitochondrial membrane protein cytochrome c (cyt c) by perturbing its tertiary structure in the presence of surface‐functionalised gold nanoparticles (GNPs) within cetyltrimethylammonium bromide (CTAB) reverse micelles. The loss in the tertiary structure of cyt c exposes its heme moiety (which is buried inside in the native globular form), which provides greater substrate (pyrogallol and H₂O₂) accessibility to the reactive heme residue. The surfactant shell of the CTAB reverse micelle in the presence of co‐surfactant (n‐hexanol) exerted higher crowding effects on the interfacially bound cyt c than similar anionic systems. The congested interface led to protein unfolding, which resulted in a 56‐fold higher peroxidase activity of cyt c than that in water. Further perturbation in the protein’s structure was achieved by doping amphiphile‐capped GNPs with varying hydrophobicities in the water pool of the reverse micelles. The hydrophobic moiety on the surface of the GNPs was directed towards the interfacial region, which induced major steric strain at the interface. Consequently, interaction of the protein with the hydrophobic domain of the amphiphile further disrupted its tertiary structure, which led to better opening up of the heme residue and, thereby, superior activity of the cyt c. The cyt c activity in the reverse micelles proportionately enhanced with an increase in the hydrophobicity of the GNP‐capping amphiphiles. A rigid cholesterol moiety as the hydrophobic end group of the GNP strikingly improved the cyt c activity by up to 200‐fold relative to that found in aqueous buffer. Fluorescence studies with both a tryptophan residue (Trp59) of the native protein and the sodium salt of fluorescein delineated the crucial role of the hydrophobicity of the GNP‐capping amphiphiles in improving the peroxidase activity of cyt c by unfolding its tertiary structure within the reverse micelles.     

New Chemodosimetric Reagents as Ratiometric Probes for Cysteine and Homocysteine and Possible Detection in Living Cells and in Blood Plasma

In this work, we have rationally designed and synthesized two new reagents ( L₁ and L₂ ), each bearing a pendant aldehyde functionality. This aldehyde group can take part in cyclization reactions with β‐ or γ‐amino thiols to yield the corresponding thiazolidine and thiazinane derivatives, respectively. The intramolecular charge‐transfer (ICT) bands of these thiazolidine and thiazinane derivatives are distinctly different from those of the molecular probes ( L₁ and L₂ ). Such changes could serve as a potential platform for using L₁ and L₂ as new colorimetric/fluorogenic as well as ratiometric sensors for cysteine (Cys) and homocysteine (Hcy) under physiological conditions. Both reagents proved to be specific towards Cys and Hcy even in the presence of various amino acids, glucose, and DNA. Importantly, these two chemodosimetric reagents could be used for the quantitative detection of Cys present in blood plasma by using a pre‐column HPLC technique. Such examples are not common in contemporary literature. MTT assay studies have revealed that these probes have low cytotoxicity. Confocal laser scanning micrographs of cells demonstrated that these probes could penetrate cell membranes and could be used to detect intracellular Cys/Hcy present within living cells. Thus, the results presented in this article not only demonstrate the efficiency and specificity of two ratiometric chemodosimeter molecules for the quantitative detection of Cys and Hcy, but also provide a strategy for developing reagents for analysis of these vital amino acids in biological samples.     

Bismuth nitrate-catalyzed multicomponent reaction for efficient and one-pot synthesis of densely functionalized piperidine scaffolds at room temperature

A simple, straightforward, and highly efficient diastereoselective multicomponent one-pot synthesis of a series of pharmaceutically interesting functionalized piperidine derivatives has been developed based on a low-cost and environmentally benign Bi(NO₃)₃·5H₂O catalyst via tandem reactions of 1,3-dicarbonyl compounds, aromatic aldehydes, and various amines in ethanol at room temperature. High atom-economy, good yields, eco-friendliness, and mild reaction conditions are some of the important features of this protocol.     

Solid supported palladium(0) nano/microparticle: a ligand-free efficient recyclable heterogeneous catalyst for mono- and β,β-double-Heck reaction

Solid supported palladium nano/microparticles were found to be active catalysts to perform mono- and β,β-double-Heck reactions. Different β-unsubstituted and substituted alkenes including acrylate, methacrylate, crotonate, styrene, acrylonitrile, and acrylamide were investigated successfully for mono- and β,β-double-Heck reactions with aryl iodide under milder reaction condition. One-pot β,β-double-Heck reaction of aryl iodides with α,β-unsaturated ester, amide, nitrile, and styrene derivatives were also performed under standard reaction conditions. Wide functional group tolerance, easy catalyst recovery, and recyclability up to twelve times without significant loss of catalytic activity added extra importance to the present process.     

Solvation and rotational relaxation of coumarin 153 in a new hydrophobic ionic liquid: An excitation wavelength dependence study

The solvent relaxation and rotational dynamics of coumarin 153 have been investigated in a new room temperature ionic liquid, 1-(2-methoxyethyl)-1-methylpyrrolidiniumtris(pentafluorethyl)trifluorophosphate [[MOEMPL][FAP]], at three different excitation wavelengths with a variation in temperature. Wavelength -dependent fluorescence decay behavior of the probe molecule in the present medium has been investigated by studying the time dependent fluorescence Stokes shift in the ps–ns time scale. The dynamic fluorescence Stokes shift measurements suggest that the time-resolvable part of the solvation dynamics is biphasic in nature and the average solvation time depends on the excitation wavelengths. Rotational coupling constants, obtained from the time- resolved anisotropy data, indicate no specific interaction between the probe molecule and the ionic liquids. The excitation wavelength dependent solvation dynamics is attributed to the heterogeneous nature of the present ionic liquid.