Elucidating the Role of Catalytic Amino Acid Residues in the Peptide-Mediated Silica Oligomerization Reaction Mechanism

Understanding the detailed mechanism by which the proteins of marine diatoms such as silaffins are able to control the morphology of silica oligomers has eluded synthetic chemists and materials scientists...

Synthesis of Self-colored Thermal Stabilized Acrylonitrile/Itaconic Copolymers

Acrylonitrile (AN) was copolymerized with itaconic acid metal complexes [Co(II),Ni(II),Cu(II)] aiming to synthetize self-colored acrylonitrile fiber. The copolymerization occurred in water at 60°C using sodium bisulfite and potassium persulfate as redox initiators. The resulting copolymers are colored and exhibited high thermal stability as shown from their TGA curves. The investigated copolymers exhibited comparable thermal stability as that of PAN. The AN/ itaconic acid Co(NO3)2copolymer was considerably the most thermal stable copolymer while that of Ni(II) copolymer was the less stable one. Cu(II) copolymer showed an intermediate stability. The data also revealed that the maximum degradation occurred after 300°C (the cyclization temperature). Thus, neither the copolymerization nor the complexation affected the nitrile oligomerization reaction. The effect of adding ammonium hydroxide solution to acrylonitrile – itaconic acid copper(II) complex copolymer on the thermal stability of copolymer was also studied.

Emergence of visible light optical properties of L-phenylalanine aggregates

The ability of phenylalanine to form fibrillar nanostructures was demonstrated on multiple occasions, and such an oligomerization reaction could be the cause of cytotoxicity in patients with phenylketonuria. These findings were supported by claims that L-phenylalanine (Phe) fibrils have amyloid properties and can be detected using thioflavin T fluorescence assay. However, a part of Phe aggregation studies reported the opposite data, suggesting no amyloid structures to be formed. Due to the contradicting reports, the amyloid nature of Phe aggregates remains uncertain. In this work we tested Phe aggregation under conditions where amyloid formation was previously reported. We show the emergence of Phe aggregates with visible light optical properties that overlap with the spectra of dyes used in amyloid fibril assays, which could lead to false-positive identifications.

Different roles of water in secondary organic aerosol formation from toluene and isoprene

Roles of water in the formation of secondary organic aerosol (SOA) from the irradiations of toluene-NO2 and isoprene-NO2 were investigated in a smog chamber. Experimental results show that the yield of SOA from toluene almost doubled as relative humidity increased from 5 % to 85 %, whereas the yield of SOA from isoprene under humid conditions decreased by 2.6 times as compared to that under dry conditions. The distinct difference of RH effects on SOA formation from toluene and isoprene is well explained with our experiments and model simulations. The increased SOA from humid toluene-NO2 irradiations is mainly contributed by O–H-containing products such as polyalcohols formed from aqueous reactions. The major chemical components of SOA in isoprene-NO2 irradiations are oligomers formed from the gas phase. SOA formation from isoprene-NO2 irradiations is controlled by stable Criegee intermediate (SCI) that is greatly influenced by water. As a result, high RH can obstruct the oligomerization reaction of SCI to form SOA.