Stepping towards highly flexible aptamers: enzymatic recognition studies of unlocked nucleic acid nucleotides

Enzymatic recognition of unlocked nucleic acid (UNA) nucleotides was successfully accomplished. Therminator DNA polymerase was found to be an efficient enzyme in primer extension reactions. Polymerase chain reaction (PCR) amplification of a 81 mer UNA-modified DNA library was efficiently achieved by KOD DNA polymerase.     

An introduction to variational quantum algorithms for combinatorial optimization problems

4OR - Noisy intermediate-scale quantum computers (NISQ computers) are now readily available, motivating many researchers to experiment with Variational Quantum Algorithms (VQAs). Among them, the...     

Polymer-supported electron-rich diene for hetero Diels-Alder reactions

A Brassard diene analogue was grafted on a modified Merrifield resin and used in a hetero Diels-Alder reaction with various aldehydes or ketones. The reaction gave access to 6-substituted 5,6-dihydropyrones (5a-u). This new immobilized electron-rich diene is more stable than the corresponding native diene, and is a versatile supported reagent.     

Catalytic C-H amination: the stereoselectivity issue

Catalytic C-H amination has recently emerged as a unique tool for the synthesis of amines. This tutorial review highlights the existing protocols catalyzed by metal complexes (rhodium, copper, ruthenium, manganese and palladium) allowing diastereo- and enantioselective C-H amination. Substrate-, catalyst- and reagent-controlled methodologies are detailed. They involve either catalytic nitrene C-H insertion or C-H activation.     

Diastereoselective functionalizations of enecarbamates derived from pipecolic acid towards 5-guanidinopipecolates as arginine mimetics

Various substituents could be diastereoselectively introduced into the 5-position of pipecolic acid via electrophilic or free-radical-initiated addition to the carbon-carbon double bond of endocyclic enecarbamates derived from pipecolic acid. This study allowed the diastereoselective synthesis of both cis- and trans-5-guanidino pipecolates, which were designed as constrained arginine mimetics and whose potential inhibition of nitric oxide synthase (NOS) was evaluated with three NOS isoforms.     

Facile Synthesis of 1,2-bis-(Cyanomethyl)Benzenes

3-Alkoxy-1,2-bis-(cyanomethyl)benzenes can be prepared in two steps, in high yield, from m-alkoxy-N.N-dimethylbenzylamines by directed metallation followed by ethyl chloroformate-promoted cyanide displacement.     

An ab initio study of O2 and CO2 transport by perfluorocarbons

Fluorocarbons have been successfully applied as oxygen carriers replacing blood. In order to understand the nature of the interaction between fluorocarbons and hydrocarbons on the one hand and O₂, N₂ and CO₂ on the other, STO-3G calculations have been performed on their complexes. The very slight energies of interaction that were obtained seem to substantiate the contention that O₂, N₂ and CO₂ are physically dissolved in fluorocarbons. This energy of interaction is, however, distinctly larger for fluorocarbons than for hydrocarbons. Electrostatic potentials have been computed around several fluorocarbons. They make it possible to predict the geometries of the complexes that are formed.     

Synthesis of fluorinated pseudopeptides: metal mediated reversal of stereochemistry in diastereoselective addition of organometallic reagents to N-(tert-butanesulfinyl)-α-fluoroenimines

The addition reaction of organometallic reagents to N-(tert-butanesulfinyl)-α-fluoroenimines was studied. Depending of the nature of the organometallic species (Grignard reagents or zincate complexes), we were able to control the configuration of the newly created stereogenic centers in high yields with good to high diastereomeric ratios. The chiral β-fluoro allylamines are key synthons toward the synthesis of fluorinated pseudopeptides bearing a fluoroolefin moiety as a peptide bond mimic.     

Rheological properties of starch suspensions using a rotational rheometer fitted with a starch stirrer cell

The rheological properties of a starch suspension are usually studied through two viscosity measurements-pasting behavior and flow behavior of the resulting starch pastes-performed separately with two different tools and demanding rather high starch concentrations (6–10 wt %). This study focused on the feasibility of using a rheometer fitted with a starch stirrer cell to characterize, in a single experiment, the starch suspension’s behavior during and after pasting, all the while involving only low concentrations (2–4 wt %), more representative of a real-food context. A calibration of the starch stirrer cell in comparison to the coaxial cylinders one was done using model fluids (Newtonian and shear-thinning). A link between torque, rotational speed, and rheological properties was determined through two recalculated conversion factors (shear rate and shear stress). An operating diagram was then set indicating the laminar flow and good sensitivity domain for this cell. The accuracy of those constants to starch suspensions in the concentration range 2–4 wt % was demonstrated. The pasting behaviors of 2 wt % starch suspensions were followed successfully at two selected shear rates (13.5 and 135 s^?1). The impact of the level of turbulence on the profiles obtained was stressed, a result that is not limited to low-concentration starch suspensions. Finally, the method developed was used to compare the pasting behaviors of 2 wt % native and modified waxy maize starch suspensions.