Debugging Eukaryotic Genetic Code Expansion for Site‐Specific Click‐PAINT Super‐Resolution Microscopy

Super‐resolution microscopy (SRM) greatly benefits from the ability to install small photostable fluorescent labels into proteins. Genetic code expansion (GCE) technology addresses this demand, allowing the introduction of small labeling sites, in the form of uniquely reactive noncanonical amino acids (ncAAs), at any residue in a target protein. However, low incorporation efficiency of ncAAs and high background fluorescence limit its current SRM applications. Redirecting the subcellular localization of the pyrrolysine‐based GCE system for click chemistry, combined with DNA‐PAINT microscopy, enables the visualization of even low‐abundance proteins inside mammalian cells. This approach links a versatile, biocompatible, and potentially unbleachable labeling method with residue‐specific precision. Moreover, our reengineered GCE system eliminates untargeted background fluorescence and substantially boosts the expression yield, which is of general interest for enhanced protein engineering in eukaryotes using GCE.     

Furfural Dipropyl Acetal as a New Fuel Additive: Synthesis and Properties

Russian Journal of Applied Chemistry - Liquid-phase acetalization of 1-propanol with furfural was studied. A procedure was recommended for preparing furfural dipropyl acetal on a sulfonic...     

CF3-Carbenoid functionalization of N-(pyrimidin-2-yl)indole catalyzed by cobalt complexes: Ligand control of selectivity

The carbonyl cobalt complex Cp*Co(CO)I₂ catalyzes carbenoid Co alkylation of N-(pyrimidin-2-yl)indole with methyl 3,3,3-trifluoro-2-diazopropionate regioselectively giving 2-substituted indole, while the N,N’-ligated cations [CpCo(L)I]⁺ (L = bipy, phen) provide 3-substitution exclusively. The structure of [CpCo(phen)I]PF₆ was investigated by X-ray diffraction.

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Thermal decomposition of dichloroketene and its reaction with H atoms

The thermal unimolecular decomposition of dichloroketene CCl₂CO → CCl₂ + CO (reaction 1) was studied experimentally and computationally. Dichloroketene was produced by the pulsed laser photolysis of hexachloroacetone, and the kinetics of its decay due to reaction 1 was monitored using photoionization mass spectrometry. Rate constants of reaction 1 were determined in direct time-resolved experiments as a function of temperature (740–870 K) and bath gas density ([He] = (3–25) × 10¹⁶ atom cm⁻³, [N₂] = 12 × 10¹⁶ molecule cm⁻³). Reaction 1 is in the falloff region under these conditions. The potential energy surface (PES) of reaction 1 was studied using quantum chemical methods. The experimental k₁ (T, P) dependence was reproduced with an RRKM/master equation model based on quantum chemical calculations. Parameterized expressions for the rate constants of reaction 1 and the reverse reaction, that of CCl₂ with CO, were obtained over wide ranges of temperatures and pressures. The enthalpy of formation of CCl₂CO was determined in quantum chemical calculations. The kinetics of the reaction of dichloroketene with hydrogen atoms (reaction 2), an important channel of destruction of CCl₂CO in flames, was studied computationally. The PES of reaction 2 was studied using quantum chemical methods. Temperature and pressure dependences of the rate constants of the four dominant reaction channels were obtained in transition state theory and master equation calculations; the technique of isodesmic reactions for transition states was applied to the channel of Cl atom abstraction. Analysis of the experimental data and the computational models of reactions 1 and 2 demonstrates that thermal decomposition is a major pathway of destruction for dichloroketene in combustion systems.     

A priori information in a regularized sinogram‐based method for removing ring artefacts in tomography

Ring artefacts in X‐ray computerized tomography reconstructions are considered. The authors propose a ring artefact removal method based on a priori information regarding the sinogram including smoothness along the horizontal coordinate, symmetry of the first and the final rows and consideration of small perturbations during acquisition. The method does not require prior reconstruction of the original or corrected sinograms. Its numerical implementation is based on quadratic programming. Its efficacy is examined with regard to experimental data sets collected on graphite and bone.     

Harrison pseudo-hamiltonian and nonstandard matching conditions

Justification is given for nonstandard matching conditions for solutions of the Schrödinger equation for quasiparticles with different effective masses. A method of differential transformations of functions is used for the Schrödinger equation. The method makes it possible to obtain the mass-resonance condition and to analyze the characteristic features of the conditions of the total internal reflection and the electron emission.Translated from Matematicheskie Melody i Fiziko-mekhanicheskie Polya, No. 26, pp. 101–105, 1987.