DFT Study on the Antioxidant Activity of a Modeled p-Terphenyl Derivative

Relationships between the structure characteristics of natural p-terphenyl com- pounds isolated from three edible mushrooms （Thelephora ganbajun, Thelephora aeronautical, and Boletopsis grisea） indigenous to China and their mechanism of antioxidant activity were studied. Geometry structures of terphenyl molecule and four corresponding radicals, bond dissociation energy （BDE）, frontier orbitals （HOMO and LUMO） and single electron density were calculated using DFT methods （B3LYP/6-311G＊＊）. The computational results which are consistent with the experimental data well show that terphenyl molecule scavenges DPPH radical by hydrogen abstract mechanism and the high antioxidant activity depends on the substitution position of hydroxyls. Two active 7-, 8-hydroxyls facilitate the hydrogen abstraction due to the intramolecular hydrogen bond and the resonance effect makes 4-hydroxyl radical more stable.

Effect of TiO2 on the Photodegradation Mechanism of Poly(butylene succinate)

The photodegradation behaviors of poly（butylene succinate）（PBS） and TiO2/PBS nanocomposite were monitored over a period of six months. Material properties and aging mechanisms were studied and explored by various characterizations including 1HNMR, FTIR, XRD, mass spectrum, and TGA. The TiO2/PBS nanocomposite was found to be more thermally stable and mechanically robust than the PBS. During aging, crystal formation and the final crystal structure changed notably. Based on the characterization results, it is proposed that the polymer chains have cleaved at the ester linkage by the dissociation of O–H groups and the conversion of C=O to C–O bonds. It was also believed that polymer chain transfer took place, which resulted in the formation of C=C bonds and O–H groups, and the polyester changed to enol or polyether.

Solid phase synthesis of peptide–siRNA conjugates containing disulfde bond unit

A disulfide-modified nucleoside was designed and synthesized. After loading the modified nucleoside on controlled pore glass （CPG）, solid phase synthesis strategy was used to prepare peptide-oligonucleotide conjugates （N-3＇） containing disulfide bond unit. The 3＇-sense strand peptide-siRNA conjugate （VII） maintained good gene silencing activity, while that of the 3＇-antisense strand conjugate decreased somewhat. And the sense strand off-target effect of VII decreased remarkably.

Cascade reaction involving intramolecular oxygen-migration:Efficient synthesis of 3-allylidene-indolin-2-one compounds under metal-free conditions

An efficient synthesis of 3-(diarylallylidene)oxindoles from 3-(1 H-indol-3-yl)-1,1-diarylpropan-1-ol under metal-free conditions is described.NBS serves as a critical medium leading to a facile oxygenmigration in the transformation.The protocol has advantages of high efficiency,simple opreation,mild reaction conditions,good atom-economy,wide substrate scope and good yields of products.A detailed mechanism is proposed after careful investigation.