Theoretical modeling of the nonenzymatic solvolysis of CMP-NeuAc in an acidic environment

A density-functional-theory investigation of the nonenzymatic solvolysis of the cytydine 5′-monophosphate N-acetylneuraminic acid and its derivatives in the acidic environment is presented. The theoretical calculations of the second stage of the reaction mechanism are in agreement with the hypothesis of a dissociative oxocarbenium-like transition state with proton transfer as a key part of the reaction. The geometries of the transition states of the reactions yielding -methyl and β-methyl glycosides are essentially different. This study provides new theoretical data that can be helpful in elucidating the mechanism of the carbohydrates hydrolysis as well as other reactions catalyzed by the glycosyltransferases.     

Study of the structural and electronic properties of 1-(4, 5 and 6-selenenyl derivatives-3-formyl-phenyl) pyrrolidinofullerenes

A series of 1-(4, 5 and 6-selenenyl derivatives-3-formyl-phenyl) pyrrolidinofullerenes molecules C₆₀-C₂H₄N-[3-(CHO)C₆H₃SeX] were investigated theoretically by performing Density Functional Theory calculations at the B3LYP/3-21G^∗ level of the theory. The substituents include: X = CN, CH₂CH(NH₂)CO₂H and CH₂CH₂CH(NH₂)CO₂H. We have selected these substituents to be in ortho, meta and para positions with relation to formyl group in order to show the effect of such structural change on the electronic properties of the molecules. The theoretical IR spectra, physical, chemical and thermodynamics properties of the molecules studied are obtained and discussed.     

"Nanoions": fundamental properties and analytical applications of charged nanoparticles.

Mixtures of oppositely charged nanoparticles (NPs) precipitate sharply only at the point of NP electroneutrality. This behavior-reminiscent of the threshold precipitation of inorganic ions-is specific to the nanoscale and can be attributed to the formation of like-charged NP clusters stabilized in solution by mutual electrostatic repulsions. NP titrations based on this phenomenon provide a uniquely accurate tool for measuring charges tethered onto nanoscopic objects and for studying the thermodynamics of surface reactions at the nanoscale.     

Theoretical investigation of the electronic structure of 1-(3,4; 3,5 and 3,6-bis-selenocyanato-phenyl) pyrrolidinofullerenes

The electronic structures and geometries of 1-(3,4; 3,5 and 3,6-bis-Selenocyanato-phenyl) pyrrolidinofullerenes were investigated theoretically using Density Functional theory at the B3LYP/3-21G∗ and B3LYP/6-31G∗ levels of theory. On all levels of theory the ortho isomer is predicted to be the most stable. The obtained optimized geometries, electronic properties and energetics of structural variables are discussed.     

Engineering Gram Selectivity of Mixed‐Charge Gold Nanoparticles by Tuning the Balance of Surface Charges

Nanoparticles covered with ligand shells comprising both positively and negatively charged ligands exhibit Gram‐selective antibacterial action controlled by a single experimental parameter, namely the proportion of [+] and [?] ligands tethered onto these particles. Gram selectivity is attributed to the interplay between polyvalent electrostatic and non‐covalent interactions that work in unison to disrupt the bacterial cell wall. The [+/?] nanoparticles are effective in low doses, are non‐toxic to mammalian cells, and are tolerated well in mice. These results constitute the first example of rational engineering of Gram selectivity at the (macro)molecular level.     

Application of 1′,2,3,3′,4,4′-Hexa-O-benzylsucrose in the Preparation of Sucrose Macrocycles via a Click Chemistry Route: Regioselectivity Study

Abstract

1′,2,3,3′,4,4′-Hexa-O-benzyl-sucrose was applied in the preparation of sucrose-based macrocycles via a click chemistry route. This was realized by protection of the 6′?OH with silyl block followed by elongation of the glucose end with the ?CH₂CH₂N₃ unit. Removal of the silyl block and subsequent propargylation of the released C6′?OH afforded the corresponding synthon, cyclization of which under the click condition provided the desired macrocycle with the expected 1,4-pattern of substituents at the triazole ring.     

4‐Naphthylmethyl Proline Forms a Channel Structure

Proline and proline derivatives are useful tools to control the structural properties of peptides and proteins, and thereby modulate numerous processes. Here, we show that proline derivatives can have unique structural properties in the solid state by presenting the crystal structure of zwitterionic (2S,4S)/(2S,4R)‐4‐[(naphthalen‐2‐yl)methyl]proline (H‐Nap‐OH). This amphiphilic proline derivative forms a columnar structure around large hydrophilic and small hydrophobic channels with diameters of 9 Å and 4 Å, respectively. We show that this architecture, which is unprecedented for amino acids, results from the combination of a hydrogen bond network between the ammonium and carboxylate moieties and π–π as well as CH–π interactions between the aromatic moieties.     

Customized fastSLAM algorithm: analysis and assessment on real mobile platform

Nonlinear Dynamics - The task of simultaneous localization and mapping (SLAM) allows a mobile robot to localize itself in the unknown environment, while building the map of the surrounding...