Behaviors and kinetics of toluene adsorption-desorption on activated carbons with varying pore structure

This work was undertaken to investigate the behaviors and kinetics of toluene adsorption and desorption on activated carbons with varying pore structure. Five kinds of activated carbon from different raw materials were selected. Adsorption isotherms and breakthrough curves for toluene were measured. Langmuir and Freundlich equations were fitted to the equilibrium data, and the Freundlich equation was more suitable for simulating toluene adsorption. The process consisted of monolayer, multilayer and partial active site adsorption types. The effect of the pore structure of the activated carbons on toluene adsorption capacity was investigated. The quasi-first-order model was more suitable for describing the process than the quasi-second-order model. The adsorption data was also modeled by the internal particle diffusion model and it was found that the adsorption process could be divided into three stages. In the external surface adsorption process, the rate depended on the specific surface area. During the particle diffusion stage, pore structure and volume were the main factors affecting adsorption rate. In the final equilibrium stage, the rate was determined by the ratio of meso-and macro-pores to total pore volume. The rate over the whole adsorption process was dominated by the toluene concentration. The desorption behavior of toluene on activated carbons was investigated,and the process was divided into heat and mass transfer parts corresponding to emission and diffusion mechanisms, respectively. Physical adsorption played the main role during the adsorption process.

Lysine residues K66, K109, and K110 in the bovine foamy virus transactivator protein are required for transactivation and viral replication

Bovine foamy virus(BFV) is a complex retrovirus that infects cattle. Like all retroviruses, BFV encodes a transactivator Tas protein(BTas) that increases gene transcription from viral promoters.BFV encodes two promoters that can interact with BTas, a conserved promoter in the 5' long terminal repeat(LTR) and a unique internal promoter(IP). Our previous study showed that BTas is acetylated by p300 at residues K66, K109, and K110, which markedly enhanced the ability of BTas to bind to DNA. However, whether these residues are important for BFV replication was not determined. Therefore, in this study we provide direct evidence that BTas is required for BFV replication and demonstrate that residues K66, K109, and K110 are critical for BTas function and BFV replication. Full-length infectious clones were generated, which were BTas deficient or contained lysine to arginine(K→R) mutations at position 66, 109, and/or 110. In vivo data indicated that K→R mutations at positions 66, 109, and 110 in BTas impaired transactivation of both the LTR and IP promoters. In addition, the K→R mutations in full-length infectious clones reduced expression of viral proteins, and the triple mutant and BTas deletion completely abrogated viral replication. Taken together, these results indicate that lysine residues at positions 66, 109, and 110 in the BTas protein are crucial for BFV replication and suggest a potential role for BTas acetylation in regulating the viral life cycle.