Engineering equipment served in harsh environments for a long time will inevitably corrode,resulting in a loss of mechanical performance and a reduction in a lifetime,and even threatening production safety.Although co...Engineering equipment served in harsh environments for a long time will inevitably corrode,resulting in a loss of mechanical performance and a reduction in a lifetime,and even threatening production safety.Although conventional post-treatment anti-corrosion technologies can slow down the corrosion rate,it is important to consider the corrosion effect on the structural performance in design.This paper proposes a topology optimization method with prior consideration of structural corrosion resistance during the design phase,so the structures designed by the approach can have excellent corrosion resistance,considerably reducing the cost of post-treatment anti-corrosion technologies.First,an erosion-based method is utilized to identify the structural surface layer.In the procedure,the initial structure is eroded to generate a reduced-scale eroded structure,and then,the eroded regions are specified as the surface layer.Second,dual-material interpolation is used to create the corrosion model by modifying the material properties of elements on the structural surface layer,which is set to 0 to simulate uniform corrosion.Finally,the topology optimization method with structural surface corrosion considered is enforced through a two-step filtering/projection process.After the entire lifetime corrosion analysis,various numerical examples indicate that the structural performance of the proposed method is superior to that of the standard method(SIMP interpolation)without considering the influence of corrosion,demonstrating the effectiveness of the proposed method.展开更多
Surface (S)-layer proteins are model systems for studying protein glycosylation in bacteria and simultaneously hold promises for the design of novel, glyco-functionalized modules for nanobiotechnology due to their 2D ...Surface (S)-layer proteins are model systems for studying protein glycosylation in bacteria and simultaneously hold promises for the design of novel, glyco-functionalized modules for nanobiotechnology due to their 2D self-assembly capability. Understanding the mechanism governing S-layer glycan biosynthesis in the Gram-positive bacterium Paenibacillus alvei CCM 2051T is necessary for the tailored glyco-functionalization of its S-layer. Here, the putative oligosaccharyl:S-layer protein transferase WsfB from the P. alvei S-layer glycosylation gene locus is characterized. The enzyme is proposed to catalyze the final step of the glycosylation pathway, transferring the elongated S-layer glycan onto distinct tyrosine O-glycosylation sites. Genetic knock-out of WsfB is shown to abolish glycosylation of the S-layer protein SpaA but not that of other glycoproteins present in P. alvei CCM 2051T, confining its role to the S-layer glycosylation pathway. A transmembrane topology model of the 781-amino acid WsfB protein is inferred from activity measurements of green fluorescent protein and phosphatase A fused to defined truncations of WsfB. This model shows an overall number of 13 membrane spanning helices with the Wzy_C domain characteristic of O-oligosaccharyl:protein transferases (O-OTases) located in a central extra-cytoplasmic loop, which both compares well to the topology of OTases from Gram-negative bacteria. Mutations in the Wzy C motif resulted in loss of WsfB function evidenced in reconstitution experiments in P. alvei ΔWsfB cells. Attempts to use WsfB for transferring heterologous oligosaccharides to its native S-layer target protein in Escherichia coli CWG702 and Salmonella enterica SL3749, which should provide lipid-linked oligosaccharide substrates mimicking to some extent those of the natural host, were not successful, possibly due to the stringent function of WsfB. Concluding, WsfB has all features of a bacterial O-OTase, making it the most probable candidate for the oligosaccharyl:S-layer protein transferase展开更多
基金the financial support to this work by the National Natural Science Foundation of China(Grant Nos.U1808215 and 11821202)the 111 Project(B14013)the Fundamental Research Funds for the Central Universities of China(DUT21GF101).
文摘Engineering equipment served in harsh environments for a long time will inevitably corrode,resulting in a loss of mechanical performance and a reduction in a lifetime,and even threatening production safety.Although conventional post-treatment anti-corrosion technologies can slow down the corrosion rate,it is important to consider the corrosion effect on the structural performance in design.This paper proposes a topology optimization method with prior consideration of structural corrosion resistance during the design phase,so the structures designed by the approach can have excellent corrosion resistance,considerably reducing the cost of post-treatment anti-corrosion technologies.First,an erosion-based method is utilized to identify the structural surface layer.In the procedure,the initial structure is eroded to generate a reduced-scale eroded structure,and then,the eroded regions are specified as the surface layer.Second,dual-material interpolation is used to create the corrosion model by modifying the material properties of elements on the structural surface layer,which is set to 0 to simulate uniform corrosion.Finally,the topology optimization method with structural surface corrosion considered is enforced through a two-step filtering/projection process.After the entire lifetime corrosion analysis,various numerical examples indicate that the structural performance of the proposed method is superior to that of the standard method(SIMP interpolation)without considering the influence of corrosion,demonstrating the effectiveness of the proposed method.
文摘Surface (S)-layer proteins are model systems for studying protein glycosylation in bacteria and simultaneously hold promises for the design of novel, glyco-functionalized modules for nanobiotechnology due to their 2D self-assembly capability. Understanding the mechanism governing S-layer glycan biosynthesis in the Gram-positive bacterium Paenibacillus alvei CCM 2051T is necessary for the tailored glyco-functionalization of its S-layer. Here, the putative oligosaccharyl:S-layer protein transferase WsfB from the P. alvei S-layer glycosylation gene locus is characterized. The enzyme is proposed to catalyze the final step of the glycosylation pathway, transferring the elongated S-layer glycan onto distinct tyrosine O-glycosylation sites. Genetic knock-out of WsfB is shown to abolish glycosylation of the S-layer protein SpaA but not that of other glycoproteins present in P. alvei CCM 2051T, confining its role to the S-layer glycosylation pathway. A transmembrane topology model of the 781-amino acid WsfB protein is inferred from activity measurements of green fluorescent protein and phosphatase A fused to defined truncations of WsfB. This model shows an overall number of 13 membrane spanning helices with the Wzy_C domain characteristic of O-oligosaccharyl:protein transferases (O-OTases) located in a central extra-cytoplasmic loop, which both compares well to the topology of OTases from Gram-negative bacteria. Mutations in the Wzy C motif resulted in loss of WsfB function evidenced in reconstitution experiments in P. alvei ΔWsfB cells. Attempts to use WsfB for transferring heterologous oligosaccharides to its native S-layer target protein in Escherichia coli CWG702 and Salmonella enterica SL3749, which should provide lipid-linked oligosaccharide substrates mimicking to some extent those of the natural host, were not successful, possibly due to the stringent function of WsfB. Concluding, WsfB has all features of a bacterial O-OTase, making it the most probable candidate for the oligosaccharyl:S-layer protein transferase
