The folding behavior of five different amine-functionalized m-poly(phenyleneethynylene) (m-PPE) oligomers containing 24 phenyl rings (12 residues, where a residue includes 2 phenyl rings) in water was examined by using a combination of molecular dynamics (MD) and replica exchange molecular dynamics (REMD) simulation techniques. The REMD method employed the highly parallelized GROMACS MD software and a modified OPLS-AA force field to simulate 44 replicas of each solvated system in parallel, with temperatures ranging from 300 to 577 K. Our results showed that the REMD method was more effective in predicting the helical conformation of the m-PPE in water, from an extended structure, than canonical MD methods in the same simulation time. Furthermore, we observed from canonical MD simulations of the explicitly solvated helical m-PPEs at 300 K that the radius of gyration, average helix inner diameter, and average helix pitch of the helical structure all pass through a minima when the side group is R = OC(2)H(5) as R is changed from R = H through OC(4)H(9).

We present here the results of all-atom and united-atom molecular dynamics (MD) simulations that were used to examine the folding behavior of an amine-functionalized m-poly(phenyleneethynylene) (m-PPE) oligomer in aqueous environment. The parallelized GROMACS MD simulation code and OPLS force field were used for multiple MD simulations of m-PPE oligomers containing 24 phenyl rings in extended, coiled and helix conformations separately in water to determine the minimum energy conformation of the oligomer in aqueous solvent and what interactions are most important in determining this structure. Simulation results showed that the helix is the preferred minimum energy conformation of a single oligomer in water and that Lennard-Jones interactions are the dominant forces for the stabilization of the helix. In addition, these solvophobic interactions are strong enough to maintain the helix conformation at temperatures up to 523 K.

We report here the use of 4th and 5th generation dendrimers poly(propylene)imine (CU-D32 and CU-D64) as templating agents for the synthesis of mesoporous titanosilicate and vanadosilicate oxidation catalysts via sol-gel techniques. The physical properties of these mesoporous materials were characterized by TGA, BET, PXD and SEM/EDX analyses and these showed that the transition metals are evenly distributed throughout these silicates, which have interconnected spherical pores (approx. 12 Å in diameter) and high surface areas of about 650 m 2 g À1 . Kinetic studies showed that all transition metal-doped catalysts were highly selective at oxidizing cyclohexene to the corresponding epoxide. Additionally, CU-D64-templated catalysts were more catalytically active for cyclohexene epoxidation than CU-D32-templated catalysts as a result of differences in pore size. All CU-D64-templated catalysts exhibited epoxidation catalytic activity comparable to that of titanium doped MCM-41 materials.