DNA single strands tethered to fused quartz/water interfaces studied by second harmonic generation

Second harmonic generation (SHG) is used to study oligonucleotides at aqueous/solid interfaces for the first time. Detailed thermodynamic state information for interfacial DNA single strands, namely, the interfacial charge density, the interfacial potential, and the change in the interfacial energy density, is obtained. The phosphate groups on the DNA backbone serve as intrinsic labels that do not require DNA modification other than surface attachment. This approach is broadly applicable for the investigation of DNA during its interaction with biological targets, as well as charged biopolymers in general, and has important implications for predicting and controlling macromolecular interactions, improving biodiagnostics, and understanding life processes.     

An Indirect Method for Effecting the Addition of Methylmalonate to 2-Methylcyclohex-2-enone

The adduct (1a) of methylmalonate and 2-methylcyclohex-2-enone (2a) is best made by adding malonate to 2a to give 1b, protecting the ketone 0 in 1b as a ketal (3b), methylation to 3a and finally removal of the ketal.     

Development of a strategy for the asymmetric synthesis of polycyclic polyprenylated acylphloroglucinols via N-amino cyclic carbamate hydrazones: application to the total synthesis of (+)-clusianone

A broadly applicable asymmetric synthetic strategy utilizing N-amino cyclic carbamate alkylation that provides access to the various stereochemical permutations of a common structural motif found in many polycyclic polyprenylated acylphloroglucinols is described. The utility of this methodology is demonstrated through the first asymmetric total synthesis of the antiviral agent (+)-clusianone.     

Molecular simulations of electroosmotic flows in rough nanochannels

A highly efficient molecular dynamics algorithm for micro and nanoscale electrokinetic flows is developed. The long-range Coulomb interactions are calculated using the Particle–Particle Particle–Mesh (P³M) approach. The Poisson equation for the electrostatic potential is solved in physical space using an iterative multi-grid technique. After validation, the method is used to study electroosmotic flow in nanochannels with regular or random roughness on the walls. The results show that roughness reduces the electroosmotic flow rate dramatically even though the roughness is very small compared to the channel width. The effect is much larger than for pressure driven flows because the driving force is localized near the walls where the charge distribution is high. Non-Newtonian behavior is also observed at much lower flow rates. Systematic investigation of the effect of surface charge density and random roughness will help to better understand the mechanism of electrokinetic transport in rough nanochannels and to design and optimize nanofluidic devices.