Synthesis of magnetic nanoparticles Fe3O4@CQD@Si(OEt)(CH2)3@melamine@TC@Ni(NO3) with application in the synthesis of 2-amino-3-cyanopyridine and pyrano[2,3-c]pyrazole derivatives

Research on Chemical Intermediates - In the present study, magnetic nanocatalysts coated by carbon quantum dots (CQDs) and organic functional groups (Fe3O4@CQD@Si(OEt)(CH2)3@melamine@TC@Ni(NO3))...     

Surface Arginine Saturation Effect on Unfolding Reaction of Firefly Luciferase: A Thermodynamic and Kinetic Perspective

Replacement of some hydrophobic solvent‐exposed residues in Lampyris turkestanicus luciferase with arginine increases thermostability of this enzyme. Herein, thermodynamic and kinetic of unfolding reactions of wild type (WT), E354R/356R, E354R/356R‐I232R and E354R/356R‐Q35R/L182R/I232R variants, has been investigated. Fluorescence and Far‐UV circular dichroism measurements using urea as a chemical denaturant indicated that the value of for all variants is greater than that of WT enzyme. Analysis of m‐values, as a measure of difference in the solvent accessible surface area between the native and denatured states of protein, revealed that higher stability of mutants is related to their higher degree of compactness in the folded state. Results of unfolding kinetic experiments showed that all variants have three‐exponential behavior in which they unfolded with three rate constants and corresponding amplitudes. Increasing the rate constants of fast unfolding phase in mutants relative to WT protein may be attributed to more compactness and more kinetic sensitivity of their folded state to urea. However, more population of WT protein was unfolded from fast unfolding phase. Results of this investigation highlight kinetic stability of luciferase via a slow rate of unfolding.     

Nonlinear Optical Crystals for Second Harmonic Generation

Crystallography Reports - Some important nonlinear optical crystal families in three spectral regions (DUV-FIR) have been discussed with reference to their anionic groups. In the M–F–IR...     

Synthesis of spiroindolo[2,1‐b]quinazolines from Huisgen zwitterions and tryptanthrin‐malononitrile adducts

Functionalized spiroindolo[2,1‐b]quinazolines are obtained from the reaction between tryptanthrin‐malononitrile adducts and Huisgen zwitterionic intermediates, generated by addition reaction of aromatic N‐heterocycles with acetylenic esters. The reaction is diastereoselective leading to the formation of a single diastereoisomer. The structure of a typical product established by X‐ray crystallography.     

Formation of N-sulfonylamidines by copper-catalyzed coupling of sulfonyl azides, terminal alkynes, and trialkylamines

A copper-catalyzed synthesis of N-sulfonylamidines via three-component coupling of sulfonyl azides, terminal alkynes, and trialkylamines is reported.     

Triethylamine‐Catalyzed Efficient Synthesis of Oxathiolanes Containing a Highly Polarized Carbon‐Carbon Double Bond from Reaction of Malononitrile,Carbon Disulfide (CS2), and Oxiranes

An efficient synthesis of functionalized 2‐(1,3‐oxathiolan‐2‐ylidene)malononitriles containing a push‐pull C?C bond via a simple reaction between malononitrile, CS₂, and oxiranes in the presence of Et₃N is described (Scheme 1).