No abstract

The enantioselective degradation of benalaxyl has been investigated to elucidate its behavior in several agricultural soils and plants (cucumber). Racemic benalaxyl was fortified into five types of agricultural soils and sprayed leaves of cucumber plants, respectively. The degradation kinetics and the enantiomer fraction (EF) were determined by normal-phase high-performance liquid chromatography (HPLC) with diode array detection (DAD) on the chiral column filled cellulose-tri-(3,5-dimethylphenylcarbamate)-based chiral stationary phase (CDMPC-CSP). The process of the degradation of benalaxyl enantiomers followed pseudo-first-order kinetics in cucumber plant. However, the dissipation phases of benalaxyl enantiomers in soils were biphasic ("slow-fast-slow" process). It has been shown that the degradation of benalaxyl was stereoselective. The results indicated that the (+)-S-benalaxyl showed a faster degradation in plants, while the (-)-R-benalaxyl showed a faster degradation in Soils 3, 4, and 5. No stereoselective degradation was observed in other soils.

No abstract

Reconstructed ferritin nanocages with expanded 4-fold channels can self-assemble into 2D square arrays through channel-directed electrostatic interactions with poly(α, l-lysine) at pH 7.0. Structurally, protein cages are aligned along their common 4-fold symmetry axis, imposing a fixed disposition of neighboring ferritins.

A scheme was developed to elucidate the dissipation behaviors of the two enantiomers of the herbicide lactofen in soils using a normal-phase high-performance liquid chromatograph (HPLC) with UV detector and a column with a cellulose-tri-(3,5-dimethylphenylcarbamate)-based chiral stationary phase (CDMPC-CSP). Eight soils with a wide range of soil properties were studied. Racemic and the enantiopure (S)-(+)- and (R)-(-)-lactofen were incubated under aerobic and anaerobic conditions. The data from sterilized controls indicated that the dissipation of lactofen was biological. The dissipation was shown to be enantioselective with (S)-(+)-enantiomer being degraded faster than the (R)-(-)-enantiomer, resulting in residues enriched with (R)-(-)-lactofen when the racemic compound was incubated. Lactofen was configurationally stable in soil, showing no interconversion of (S)-(+)- to (R)-(-)- enantiomer and vice versa. Significant correlations of the enantioselectivity, expressed as ES = (k((S)) - k((R)))/(k((S)) + k((R))) of lactofen with soil pH were observed under aerobic and anaerobic conditions. In addition, we found that the enantioselectivity correlated with the soil texture rather than the organic carbon.

Precise manipulation of protein self-assembly by noncovalent interactions into programmed networks to mimic naturally occurring nanoarchitectures in living organisms is a challenge due to its structural heterogeneity, flexibility, and complexity. Herein, by taking advantage of both the hydrophobic forces contributed by the "GLMVG" motif, a kind of amyloidogenic motif (AM), and the high symmetry of protein nanocages, we have built an effective protein self-assembly strategy for the construction of twodimensional (2D) or three-dimensional (3D) protein nanocage arrays. According to this strategy, "GLMVG" AMs from β-amyloid 42 were grafted onto the outer surface of a 24-mer ferritin nanocage close to its C 4 symmetry channels, initially resulting in the production of subgrade 2D nanocage arrays and ultimately generating 3D highly ordered arrays with a simple cubic packing pattern as the reaction time increases. More importantly, the reversibility and the formation rate of these protein arrays can be modulated by pH. This work provides a de novo design strategy for accurate control over 2D or 3D protein selfassemblies.

Tebuconazole[(RS)-1-p-chlorophenyl-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pentan-3-ol] is a potent triazole fungicide and consists of a pair of enantiomers. The enantioselective degradation kinetics of tebuconazole was investigated in rabbits by intravenous (iv) injection. The concentrations of (-)-(R)-tebuconazole and (+)-(S)-tebuconazole in plasma and tissues were determined by HPLC with a cellulose tris(3,5-dimethylphenylcarbamate)-based chiral stationary phase. Enantioselective analysis methods for this fungicide in plasma and tissues were developed and validated. Good linearities were obtained over the concentration range of 0.25-25 mg/l for both enantiomers. The degradation followed pseudo-first-order kinetics and the degradation of the (+)-(S)-tebuconazole was much faster than that of the (-)-(R)-tebuconazole in plasma after administration of racemic tebuconazole. This study also indicated that environmental assessment of enantiomeric degradation may be needed to fully evaluate risks of tebuconazole use.

Protein nanocages represent a class of nanovehicles for a variety of applications. However, precise manipulation of selfassembly behavior of these protein nanocages in response to multiple external stimuli for custom-tailored applications remains challenging. Herein, we established a simple but effective strategy for controlling protein nanocage self-assembly that combines a dual property of His motifs (their significantly pH-dependent protonation state and their capacity to coordinate with transition metals) with its high symmetry. With this strategy, we enabled two different ferritin nanocages to disassemble into protein tetramers under neutral solution by introducing His 6 motifs at the 4-fold channel interfaces. Notably, these tetramers are able to self-assemble into ferritin-like protein nanocages in response to multiple external stimuli such as transition metal ions and pH, and vice versa, indicative of a reversible self-assembly process. Furthermore, such His-mediated reversible protein self-assembly has been explored for encapsulation of bioactive cargo molecules within these reconstituted protein nanocages with higher loading efficiency under milder conditions as compared to the reported acid denaturation encapsulation method for ferritin.