Red‐Emitting Rhodamines with Hydroxylated,Sulfonated, and Phosphorylated Dye Residues and Their Use in Fluorescence Nanoscopy

Fluorescent dyes emitting red light are frequently used in conventional and super‐resolution microscopy of biological samples, although the variety of the useful dyes is limited. We describe the synthesis of rhodamine‐based fluorescent dyes with absorption and emission maxima in the range of 621–637 and 644–660 nm, respectively and demonstrate their high performance in confocal and stimulated emission depletion (STED) microscopy. New dyes were prepared by means of reliable chemical transformations applied to a rhodamine scaffold with three variable positions. They feature polarity, water solubility, variable net charges, improved stabilities of N‐hydroxysuccinimidyl (NHS) esters, as well as large fluorescence quantum yields in dye solutions and antibody conjugates. The photophysical and imaging properties of dyes containing three different polar groups, namely primary phosphate, sulfonic acid (in two different positions), and hydroxyl were compared. A dye with two primary phosphate groups was explored as a valuable alternative to dyes with “classical” sulfonic acid groups. Due to the increased net charge of the phosphorylated dye (q=?4 at pH 8), it demonstrated a far better electrophoretic mobility compared with analogues with two sulfonic acid groups (q=?2). As an example, one fluorescent dye was designed to be especially convenient for practical use. It is characterized by sufficiently high chemical stability of the NHS ester, its simple isolation, handling, and solubility in aqueous buffers, as well as in organic solvents. All these features, accompanied by a zero net charge in conjugates, were accomplished by the introduction of hydrophilic groups of two types: two hydroxyl groups and one sulfonic acid residue.     

Probing non-Abelian statistics with quasiparticle interferometry

We examine interferometric experiments in systems that exhibit non-Abelian braiding statistics, expressing outcomes in terms of the modular S-matrix. In particular, this result applies to fractional quantum Hall interferometry, and we give a detailed treatment of the Read-Rezayi states, providing explicit predictions for the recently observed nu = 12/5 plateau.     

Detecting non-Abelian statistics in the nu = 5/2 fractional quantum hall state

In this Letter we propose an interferometric experiment to detect non-Abelian quasiparticle statistics--one of the hallmark characteristics of the Moore-Read state expected to describe the observed fractional quantum Hall effect plateau at nu = 5/2. The implications for using this state for constructing a topologically protected qubit as has been recently proposed by Das Sarma et al. are also addressed.     

Are deterministic expert systems for computer-assisted structure elucidation obsolete?

Expert systems for spectroscopic molecular structure elucidation have been developed since the mid-1960s. Algorithms associated with the structure generation process within these systems are deterministic; that is, they are based on graph theory and combinatorial analysis. A series of expert systems utilizing 2D NMR spectra have been described in the literature and are capable of determining the molecular structures of large organic molecules including complex natural products. Recently, an opinion was expressed in the literature that these systems would fail when elucidating structures containing more than 30 heavy atoms. A suggestion was put forward that stochastic algorithms for structure generation would be necessary to overcome this shortcoming. In this article, we describe a comprehensive investigation of the capabilities of the deterministic expert system Structure Elucidator. The results of performing the structure elucidation of 250 complex natural products with this program were studied and generalized. The conclusion is that 2D NMR deterministic expert systems are certainly capable of elucidating large structures (up to about 100 heavy atoms) and can deal with the complexities associated with both poor and contradictory spectral data.     

New practical synthesis of indazoles via condensation of o-fluorobenzaldehydes and their O-methyloximes with hydrazine

The reaction of o-fluorobenzaldehydes and their O-methyloximes with hydrazine has been developed as a new practical synthesis of indazoles. Utilization of the methyloxime derivatives of benzaldehydes (in the form of the major E-isomers) in this condensation effectively eliminated a competitive Wolf-Kishner reduction to fluorotoluenes, which was observed in the direct preparations of indazoles from aldehydes. Reaction of Z-isomers of methyloximes with hydrazine resulted in the formation of 3-aminoindazoles via a benzonitrile intermediate.     

Small-scale vorticity filaments and structure functions of the developed turbulence

We develop a theory of turbulence based on the Navier-Stokes equation, without using dimensional or phenomenological considerations. A small scale vortex filament is the main element of the theory. The theory allows to obtain the scaling law and to calculate the scaling exponents of Lagrangian and Eulerian velocity structure functions in the inertial range. The obtained results are shown to be in very good agreement with numerical simulations and experimental data. The introduction of stochasticity into the equations and derivation of scaling exponents are discussed in details. A weak dependence on statistical propositions is demonstrated. The relation of the theory to the multifractal model is discussed.     

A Facile Approach to Bis(isoxazoles), Promising Ligands of the AMPA Receptor

A convenient synthetic approach to novel functionalized bis(isoxazoles), the promising bivalent ligands of the AMPA receptor, was elaborated. It was based on the heterocyclization reactions of readily available electrophilic alkenes with the tetranitromethane-triethylamine complex. The structural diversity of the synthesized compounds was demonstrated. In the electrophysiological experiments using the patch clamp technique on Purkinje neurons, the compound 1,4-phenylenedi(methylene)bis(5-aminoisoxazole-3-carboxylate) was shown to be highly potent positive modulator of the AMPA receptor, potentiating kainate-induced currents up to 70% at 10⁻¹¹ M.     

Heterogeneous 1H and 13C Parahydrogen-Induced Polarization of Acetate and Pyruvate Esters

Magnetic resonance imaging of [1-¹³C]hyperpolarized carboxylates (most notably, [1-¹³C]pyruvate) allows one to visualize abnormal metabolism in tumors and other pathologies. Herein, we investigate the efficiency of ¹H and ¹³C hyperpolarization of acetate and pyruvate esters with ethyl, propyl and allyl alcoholic moieties using heterogeneous hydrogenation of corresponding vinyl, allyl and propargyl precursors in isotopically unlabeled and 1-¹³C-enriched forms with parahydrogen over Rh/TiO₂ catalysts in methanol-d₄ and in D₂O. The maximum obtained ¹H polarization was 0.6±0.2 % (for propyl acetate in CD₃OD), while the highest ¹³C polarization was 0.10±0.03 % (for ethyl acetate in CD₃OD). Hyperpolarization of acetate esters surpassed that of pyruvates, while esters with a triple carbon-carbon bond in unsaturated alcoholic moiety were less efficient as parahydrogen-induced polarization precursors than esters with a double bond. Among the compounds studied, the maximum ¹H and ¹³C NMR signal intensities were observed for propyl acetate. Ethyl acetate yielded slightly less intense NMR signals which were dramatically greater than those of other esters under study.     

Design and Application of In Vivo FRET Biosensors to Identify Protein Prenylation and Nanoclustering Inhibitors

1. Download : Download high-res image (170KB)
2. Download : Download full-size image

Highlights? Cellular FRET biosensors for Ras, Rho, and Rab membrane anchorage were developed ? We provide evidence for Rab protein nanoclustering on cellular membranes ? Two FRET biosensors were demonstrated to be suitable for high-throughput screening ? Macrotetrolides were identified as nanoclustering and MAPK signaling disruptors     

Oligomer orientation in vapor-molecular-layer-deposited alkyl-aromatic polyamide films

The surface-limited molecular-layer deposition of alkyl-aromatic polyamide films using sequential doses of 1,4-butane diamine (BDA) and terephthaloyl dichloride (TDC) is characterized using in situ quartz crystal microbalance and ex situ spectroscopy analysis. For the first time, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is used to offer insight into molecular orientation in films deposited via molecular-layer deposition (MLD). The results show that the oligomer units are lying nearly parallel to the surface, which differs from the linear vertical growth mode often used to illustrate film growth.