【目的】验证根癌农杆菌(Agrobacterium fabrum,以前也叫Agrobacterium tumefaciens)两种储铁蛋白——饥饿细胞的DNA结合蛋白(DNA-binding protein from starved cells, Dps)和细菌铁蛋白(bacterioferritin, Bfr)的编码基因atu2477和atu...【目的】验证根癌农杆菌(Agrobacterium fabrum,以前也叫Agrobacterium tumefaciens)两种储铁蛋白——饥饿细胞的DNA结合蛋白(DNA-binding protein from starved cells, Dps)和细菌铁蛋白(bacterioferritin, Bfr)的编码基因atu2477和atu2771的功能。确定Bfr编码基因的开放阅读框。研究末端融合、血红素和个别关键氨基酸突变对Bfr功能和体外自组装的影响。探讨两种储铁蛋白的可能应用潜力。【方法】通过质粒将编码储铁蛋白的基因重新引入根癌农杆菌储铁蛋白缺失突变体中,回补储铁蛋白,验证回补的储铁蛋白编码基因是否能表达出具有储铁能力的储铁蛋白。用非变性凝胶电泳分离细胞粗提液中的蛋白质,铁特异性染色的方法鉴定电泳分离的蛋白质中是否有储铁蛋白。将不同的肽或蛋白质融合到储铁蛋白的末端,通过异源过量表达和纯化储铁蛋白的重组蛋白,用非变性凝胶电泳分析这些重组蛋白在体外的自组装。用血红素重构处理和氨基酸定点突变的方法研究血红素和个别关键氨基酸对Bfr功能和体外自组装的影响。【结果】非变性凝胶电泳和铁特异性染色结果显示,在根癌农杆菌的野生菌株、其相关突变体以及对应的回补菌株中,均仅检测到Bfr的表达,未检测到Dps的存在。当分别回补能编码161个和169个氨基酸Bfr的基因后,发现野生型菌株中的Bfr与回补编码161个氨基酸Bfr的回补菌株一样大。多肽和蛋白质的末端融合对Bfr的功能和自组装有一定影响,但不会使Bfr完全失去功能和自组装能力。结果还表明,血红素和预测可络合血红素铁的Met60的替换也只影响Bfr的功能和自组装,并未使Bfr功能完全丧失。【结论】根癌农杆菌主要通过Bfr存储铁元素。bfr基因的开放阅读框(open reading frame, ORF)以少见的UUG为起始密码子,编码产生包含161个氨基酸的蛋白质,而非169个氨基酸。根癌农杆菌的dps基因在本文的测定条件下均处于不表达状态。根癌农杆菌的Bfr和Dps蛋白均比较稳定,能够承受末端的多肽或蛋白质融合,不会使蛋白质的结构完全破坏,因此,经适当改造后具有开发应用的潜力。展开更多
溴阻燃剂(Brominated fire retardants,BFRs)的生产和使用对人类自身健康及其居住环境的影响问题,特别是“二恶英”(Dioxins)的问题,已引起全球范围广泛的重视。欧盟“限制电子电器产品中有害物质”的指令(RoHS)明确规定限制某些溴阻燃...溴阻燃剂(Brominated fire retardants,BFRs)的生产和使用对人类自身健康及其居住环境的影响问题,特别是“二恶英”(Dioxins)的问题,已引起全球范围广泛的重视。欧盟“限制电子电器产品中有害物质”的指令(RoHS)明确规定限制某些溴阻燃剂的使用。笔者就溴阻燃剂近十年来在空气、下水道淤泥和沉积物等非生命环境体系以及动物和人等生命体系的分布情况进行了综合分析,结果发现溴阻燃剂在非生命和生命环境体系中均有增加的趋势。对溴阻燃剂在生物体内的富集和放大作用研究发现,部分溴阻燃剂会在生物体内富集并表现出一定的放大作用。笔者对我国阻燃剂的发展方向提出了见解和建议。展开更多
bjectives:Whether low-load resistance training(RT)without muscle failure,with or without bloodflow restriction(BFR),is suffcient to increase strength and muscle growth of calf musclesin trained individualsisstill uncle...bjectives:Whether low-load resistance training(RT)without muscle failure,with or without bloodflow restriction(BFR),is suffcient to increase strength and muscle growth of calf musclesin trained individualsisstill unclear.This study aimed to compare the effects of low-intensity BFR RT vs.traditional low-intensity RT(noBFR)with moderate training volume on strength and circumference.Methods:We designed a parallel,randomized controlled trial including 36 RT-trained participants(BFR:7 females,32.9±8.8 years,11 males,28.4±3.6 years;noBFR;8 females,29.6±3.4 years;10 males,28.6±4.9 years)who underwent eight weeks of twice-weekly low-load RT with a total of 16 RT sets(30%of one-repetition maximum[1RM]).RT consisted of bilateral calf raises and seated unilateral calf raises,each conducted with 4 sets(30,15,15,15 repetitions not to failure)of either BFR or noBFR.Outcome measures included calf circumference(CC),leg stiffness(LS),and various strength tests(seated and standing calf raise 1RM,isokinetic strength of plantar-and dorsiflexion).Results:There were no significant interactions or group effects for most measures.Both groups showed significant improvementsin seated calf raise strength(p=0.046,η^(2)p=0.17).Pairwise comparisons indicated moderate to large effect sizes for strength improvements(standardized mean differences:0.35–1.11),but no changes in calf circumference were observed in either group.Conclusions:Low-load RT with and without BFR are useful to increase strength without necessarily affecting hypertrophy.Low-intensity BFR training did not confer additional benefits over traditional low-intensity RT for calf muscle strength or circumference,questioning its general advantage under such conditions.展开更多
文摘溴阻燃剂(Brominated fire retardants,BFRs)的生产和使用对人类自身健康及其居住环境的影响问题,特别是“二恶英”(Dioxins)的问题,已引起全球范围广泛的重视。欧盟“限制电子电器产品中有害物质”的指令(RoHS)明确规定限制某些溴阻燃剂的使用。笔者就溴阻燃剂近十年来在空气、下水道淤泥和沉积物等非生命环境体系以及动物和人等生命体系的分布情况进行了综合分析,结果发现溴阻燃剂在非生命和生命环境体系中均有增加的趋势。对溴阻燃剂在生物体内的富集和放大作用研究发现,部分溴阻燃剂会在生物体内富集并表现出一定的放大作用。笔者对我国阻燃剂的发展方向提出了见解和建议。
文摘bjectives:Whether low-load resistance training(RT)without muscle failure,with or without bloodflow restriction(BFR),is suffcient to increase strength and muscle growth of calf musclesin trained individualsisstill unclear.This study aimed to compare the effects of low-intensity BFR RT vs.traditional low-intensity RT(noBFR)with moderate training volume on strength and circumference.Methods:We designed a parallel,randomized controlled trial including 36 RT-trained participants(BFR:7 females,32.9±8.8 years,11 males,28.4±3.6 years;noBFR;8 females,29.6±3.4 years;10 males,28.6±4.9 years)who underwent eight weeks of twice-weekly low-load RT with a total of 16 RT sets(30%of one-repetition maximum[1RM]).RT consisted of bilateral calf raises and seated unilateral calf raises,each conducted with 4 sets(30,15,15,15 repetitions not to failure)of either BFR or noBFR.Outcome measures included calf circumference(CC),leg stiffness(LS),and various strength tests(seated and standing calf raise 1RM,isokinetic strength of plantar-and dorsiflexion).Results:There were no significant interactions or group effects for most measures.Both groups showed significant improvementsin seated calf raise strength(p=0.046,η^(2)p=0.17).Pairwise comparisons indicated moderate to large effect sizes for strength improvements(standardized mean differences:0.35–1.11),but no changes in calf circumference were observed in either group.Conclusions:Low-load RT with and without BFR are useful to increase strength without necessarily affecting hypertrophy.Low-intensity BFR training did not confer additional benefits over traditional low-intensity RT for calf muscle strength or circumference,questioning its general advantage under such conditions.
