Surface-Initiated Polymerization with an Initiator Gradient: A Monte Carlo Simulation.

Due to the difficulty of accurately characterizing properties such as the molecular weight (Mn) and grafting density (σ) of gradient brushes (GBs), these properties are traditionally assumed to be uniform in space to simplify analysis. Applying a stochastic reaction model (SRM) developed for heterogeneous polymerizations, we explored surface-initiated polymerizations (SIPs) with initiator gradients in lattice Monte Carlo simulations to examine this assumption. An initial exploration of SIPs with 'homogeneously' distributed initiators revealed that increasing σ slows down the polymerization process, resulting in polymers with lower molecular weight and larger dispersity (D) for a given reaction time. In SIPs with an initiator gradient, we observed that the properties of the polymers are position-dependent, with lower Mn and larger D in regions of higher σ, indicating the non-uniform properties of polymers in GBs. The results reveal a significant deviation in the scaling behavior of brush height with σ compared to experimental data and theoretical predictions, and this deviation is attributed to the non-uniform Mn and D.

In vitro transcriptomes analysis identifies some special genes involved in pathogenicity difference of the Beauveria bassiana against different insect hosts.

Typical entomopathogenic filamentous fungi such as Beauveria bassiana infect susceptible hosts via penetration of insect cuticle. The pathogenicity of B. bassiana strain to diverse insect hosts is different. While the molecular mechanisms of B. bassiana adapt to different insects are not well clear. B. bassiana GXsk1011 is a hyper-virulent strain from silkworm, which was investigated on the metabolic responses to three cuticle extracts of Bombyx mori, Helicoverpa armigera and Clanis bilineata at 24 h by RNA-seq method. A total of 638 up- and 400 down-regulated differentially expressed genes (DEGs) were identified in B. bassiana grown on H. armigera compared with B. mori, and 910 up- and 401 down-regulated genes for C. bilineata compared with B. mori. Functional categorization showed that DEGs are mainly involved in metabolic processes, localization, catalytic activity and transporter activity. Analysis of 20 highest fold change genes in DEGs showed that when B. bassiana transferred to non-original hosts as H. armigera and C. bilineata, the adhesion (Mad1), protease (Pr2) and cell surface protein (BBA_09174), etc. were down-regulated. While the class III chitinase ChiA2 (BBA_05353, Bbchi-17), major allergen Asp f 2-like protein (BBA_05395, Bb-f2) and nonribosomal peptide synthase, etc. were up-regulated. The secretory lipase that responded to H. armigera and the phosphate permease responded to C. bilineata were also up-regulated in the Top 20 DEGs. These special expressed genes indicate when the B. bassiana transferred to non-original hosts (or called as non-natural hosts), the strain appeared the changes of metabolic response and infection strategies to adapt to new hosts, and implied the key actions of infected adaptation were to break the barrier of different cuticle chitin component and against the immune stress of hosts. This study provided an insight into the B. bassiana that with wide host ranges how to adapt to infect different insect hosts, which will help us to further understand the pathogenesis of B. bassiana infection.

Characterization of the endothiapepsin-like protein in the entomopathogenic fungus Beauveria bassiana and its virulence effect on the silkworm, Bombyx mori.

Endothiapepsin is an aspartic proteinase that was first isolated from the plant pathogenic fungus Endothia parasitica. In previous studies, we reported on three endothiapepsin-like proteins in the entomopathogenic fungus Beauveria bassiana; the genes were up-regulated in B. bassiana hyper-virulent strain GXsk1011 at early stage infection in the silkworm. However, whether these proteins play a role in pathogenicity or not remains unknown. In this study, we cloned one protein, BbepnL-1 gene (BBA-07766), that has 98% homology with B. bassiana strain Bb2860, and expressed it in the yeast Pichia pastoris to investigate its function. The endothiapepsin-like protein is a secreted proteinase of molecular weight approximately 40 kDa. It has an N-glycosylation site and a mutation in the C-terminal conserved domain- a Thr was mutated to Gly in B. bassiana GXsk1011 and is different than the endothiapepsin of Endothia parasitica. The recombinant endothiapepsin-like protein showed enzyme activity and degraded the protein components of the silkworm cuticle. To further investigate the activity of the endothiapepsin-like protein, we knocked out the gene BbepnL-1 and showed that the loss of BbepnL-1 reduced the virulence in the silkworm. These results demonstrated that the endothiapepsin-like protein of B. bassiana is a virulence factor.

Thermal stability and oral absorbability of astaxanthin esters from Haematococcus pluvialis in Balb/c mice.

BACKGROUND: Astaxanthin is used as a functional nutraceutical and pigment in many food products. It is mostly exists in the form of a fatty acid ester in nature. However, no detailed descriptions are available concerning the stability and oral absorbability of astaxanthin esters. In the present study, the thermal stability and absorbability of astaxanthin esters from Haematococcus pluvialis were evaluated in comparison with free-form astaxanthin. RESULTS: The thermal stability of astaxanthin esters was found to be higher than that of free-form astaxantin. After gavage with astaxanthin esters, only free-form astaxanthin was detected in the digestive tract wall, blood plasma and liver, indicating that astaxanthin esters must be hydrolyzed to free-form astaxanthin in the gut before absorption. Furthermore, there was a considerable selective accumulation of different astaxanthin isomers in Balb/c mice, which selectivity decreased in the order: 13-cis > all-trans > 9-cis. Accumulated astaxanthin was mainly distributed in the heart, liver, spleen, muscle and adipose tissue, although significant differences between tissues were observed. CONCLUSION: From the present study, it can be concluded that astaxanthin esters had a higher thermal stability and higher bioavailability than free-form astaxanthin. These results provide important evidence with respect to using astaxanthin esters as bioactive components to replace free-form astaxanthin in functional food products. © 2019 Society of Chemical Industry.