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Journal of Zhejiang University SCIENCE B
ISSN 1673-1581(Print), 1862-1783(Online), Monthly
2025 Vol.26 No.1 P.58-75
ATP-binding cassette (ABC) transporters: structures and roles in bacterial pathogenesis
Abstract: Adenosine triphosphate (ATP)-binding cassette (ABC) transporter systems are divided into importers and exporters that facilitate the movement of diverse substrate molecules across the lipid bilayer, against the concentration gradient. These transporters comprise two highly conserved nucleotide-binding domains (NBDs) and two transmembrane domains (TMDs). Unlike ABC exporters, prokaryotic ABC importers require an additional substrate-binding protein (SBP) as a recognition site for specific substrate translocation. The discovery of a large number of ABC systems in bacterial pathogens revealed that these transporters are crucial for the establishment of bacterial infections. The existing literature has highlighted the roles of ABC transporters in bacterial growth, pathogenesis, and virulence. These roles include importing essential nutrients required for a variety of cellular processes and exporting outer membrane-associated virulence factors and antimicrobial substances. This review outlines the general structures and classification of ABC systems to provide a comprehensive view of the activities and roles of ABC transporters associated with bacterial virulence and pathogenesis during infection.
Key words: ATP-binding cassette (ABC) transporter; Bacterial pathogenesis; Virulence
机构:浙江大学,航空航天学院,中国杭州,310027
目的:大多数湍流模型都难以对尾喷管中的亚/超声速流动做出准确预测。本文旨在探索一种新的湍流模型-代数应力模型k-kL-ARSM+J,以提高湍流数值模拟的精度,并采用该高精度模型对三维截短偏置超声速尾喷管进行非设计工况下的数值计算,以获得其变化规律。
创新点:1.基于已有的计算流体动力学(CFD)程序,发展集成了新型代数应力模型k-kL-ARSM+J;2.获得了所设计的三维截短偏置超声速尾喷管非设计工况下的影响规律。
方法:1.采用NASA标准算例,对所实现的代数应力模型k-kL-ARSM+J进行模型验证,确保其正确性和有效性(图2~6);2.将设计工况下尾喷管的计算值与设计值进行对比,验证湍流模型在该尾喷管数值计算的正确性和有效性(图11);3.通过改变入口马赫数、入口压力和飞行高度等工况,获得该尾喷管非设计工况下的性能变化规律(图12~23)。
结论:1.根据NASA标准测试算例表明,k-kL-ARSM+J代数应力模型能够精确模拟超声速喷管,且与实验值吻合,验证了该湍流模型的正确性和有效性。2.随着入口马赫数的增加,推力和俯仰力矩增加,增长速率逐渐减小,且升力在设计马赫数附近达到峰值,然后迅速减小;随着入口压力的增加,喷管推力、升力和俯仰力矩均呈线性增长。3.随着飞行高度的增加,由于相同的超声速喷管入口条件,喷管的内部流场基本保持不变;然而,喷管外部的压力变化导致喷管出口从过膨胀过渡到欠膨胀;因此,喷管后的剪切层首先朝向喷管中心汇聚,然后发散。
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DOI:
10.1631/jzus.B2300641
CLC number:
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On-line Access:
2025-01-14
Received:
2023-09-12
Revision Accepted:
2023-12-17
Crosschecked:
2024-10-11