Numerous theories of how and why aging occurs have been postulated but a definitive comprehensive explanation remains elusive. Attempts to unravel genetic details of aging resulted in the identification of a yeast gen...Numerous theories of how and why aging occurs have been postulated but a definitive comprehensive explanation remains elusive. Attempts to unravel genetic details of aging resulted in the identification of a yeast gene known as Sir2 as a modulator of life span. Identification and characterization of mammalian Sir2 homologs followed and has catapulted aging research to exciting new levels. This review begins with basic definitions of aging and then describes some of the most common theories of the aging process. The review presents information related to the initial discovery of the Sirtuins and summarizes some of the recent advances in defining roles for Sirtuin family members. SIRT6 is discussed in greater detail because it is one of the best characterized of the mammalian Sirtuins and seems to be one of the most important in the aging process and metabolic regulation.展开更多
Sir2(silent information regulator 2)结构域蛋白作为沉默信息调节因子Sirtuins家族的一员,存在于从细菌到人类的各种生物体中。在真核生物中,Sir2结构域蛋白是烟酰胺腺嘌呤二核苷酸(NAD+)依赖性脱乙酰酶,作为蛋白质去乙酰化酶或ADP核...Sir2(silent information regulator 2)结构域蛋白作为沉默信息调节因子Sirtuins家族的一员,存在于从细菌到人类的各种生物体中。在真核生物中,Sir2结构域蛋白是烟酰胺腺嘌呤二核苷酸(NAD+)依赖性脱乙酰酶,作为蛋白质去乙酰化酶或ADP核糖基转移酶发挥作用,参与调节转录抑制、基因重组、DNA修复和细胞周期过程。最近研究发现,在原核生物中,含有Sir2结构域的蛋白广泛分布于多种微生物免疫系统中,并作为NAD水解酶即NADase,在细菌被噬菌体感染时,能够快速水解细菌体内的NAD+,从而引起被感染的细菌的死亡。研究表明,Thoeris、SPARSA、Sir2-HerA、DSR2和Kongming等防御系统均通过Sir2结构域依赖的NAD水解酶发挥作用。该综述主要介绍了这五种抗噬菌体防御系统,并讨论了Sir2结构域在噬菌体防御中发挥的重要作用,为深入了解原核生物Sir2 NADase介导的抗噬菌体机制提供了理论支撑。展开更多
BIM(building information modeling,BIM)外包已成为一种有效的BIM应用策略。当前BIM外包应用效果未达预期,BIM外包模式与项目特征不匹配是导致该现象的重要因素,不同形态的BIM外包模式在跨组织边界的信息传递路径及风险传导机制上存在...BIM(building information modeling,BIM)外包已成为一种有效的BIM应用策略。当前BIM外包应用效果未达预期,BIM外包模式与项目特征不匹配是导致该现象的重要因素,不同形态的BIM外包模式在跨组织边界的信息传递路径及风险传导机制上存在显著差异。为明确不同BIM外包模式下信息沟通效率的差异,本文聚焦于2种主要模式:咨询企业主导(以下简称咨询主导)和业主主导的BIM外包模式。以实际案例为基础,构建不同BIM外包模式下的信息沟通网络,分别从静态和动态的视角对不同BIM外包模式中信息沟通的效率进行对比:在静态视角中,应用社会网络分析方法对网络结构进行对比分析,以此明确不同BIM外包模式的信息传递路径;在动态视角中,应用SIR(susceptible-infected-recovered,SIR)模型对错误的传播和扩散进行对比分析,探究不同BIM外包模式的风险传导机制。仿真结果表明,在咨询主导下的BIM外包模式中,BIM决策效率较高,但协同效率较低,信息传递效率也较低;相反,在业主主导下的BIM外包模式中,BIM协同效率较高,信息传递效率也较高。本研究为建筑工程企业在实际工程项目中BIM外包模式的选择提供决策参考和理论支持。展开更多
文摘Numerous theories of how and why aging occurs have been postulated but a definitive comprehensive explanation remains elusive. Attempts to unravel genetic details of aging resulted in the identification of a yeast gene known as Sir2 as a modulator of life span. Identification and characterization of mammalian Sir2 homologs followed and has catapulted aging research to exciting new levels. This review begins with basic definitions of aging and then describes some of the most common theories of the aging process. The review presents information related to the initial discovery of the Sirtuins and summarizes some of the recent advances in defining roles for Sirtuin family members. SIRT6 is discussed in greater detail because it is one of the best characterized of the mammalian Sirtuins and seems to be one of the most important in the aging process and metabolic regulation.
文摘Sir2(silent information regulator 2)结构域蛋白作为沉默信息调节因子Sirtuins家族的一员,存在于从细菌到人类的各种生物体中。在真核生物中,Sir2结构域蛋白是烟酰胺腺嘌呤二核苷酸(NAD+)依赖性脱乙酰酶,作为蛋白质去乙酰化酶或ADP核糖基转移酶发挥作用,参与调节转录抑制、基因重组、DNA修复和细胞周期过程。最近研究发现,在原核生物中,含有Sir2结构域的蛋白广泛分布于多种微生物免疫系统中,并作为NAD水解酶即NADase,在细菌被噬菌体感染时,能够快速水解细菌体内的NAD+,从而引起被感染的细菌的死亡。研究表明,Thoeris、SPARSA、Sir2-HerA、DSR2和Kongming等防御系统均通过Sir2结构域依赖的NAD水解酶发挥作用。该综述主要介绍了这五种抗噬菌体防御系统,并讨论了Sir2结构域在噬菌体防御中发挥的重要作用,为深入了解原核生物Sir2 NADase介导的抗噬菌体机制提供了理论支撑。
文摘BIM(building information modeling,BIM)外包已成为一种有效的BIM应用策略。当前BIM外包应用效果未达预期,BIM外包模式与项目特征不匹配是导致该现象的重要因素,不同形态的BIM外包模式在跨组织边界的信息传递路径及风险传导机制上存在显著差异。为明确不同BIM外包模式下信息沟通效率的差异,本文聚焦于2种主要模式:咨询企业主导(以下简称咨询主导)和业主主导的BIM外包模式。以实际案例为基础,构建不同BIM外包模式下的信息沟通网络,分别从静态和动态的视角对不同BIM外包模式中信息沟通的效率进行对比:在静态视角中,应用社会网络分析方法对网络结构进行对比分析,以此明确不同BIM外包模式的信息传递路径;在动态视角中,应用SIR(susceptible-infected-recovered,SIR)模型对错误的传播和扩散进行对比分析,探究不同BIM外包模式的风险传导机制。仿真结果表明,在咨询主导下的BIM外包模式中,BIM决策效率较高,但协同效率较低,信息传递效率也较低;相反,在业主主导下的BIM外包模式中,BIM协同效率较高,信息传递效率也较高。本研究为建筑工程企业在实际工程项目中BIM外包模式的选择提供决策参考和理论支持。
