对氨基苯甲酸对牙龈卟啉单胞菌生长的影响

目的：测量不同浓度PABA对P.gingivalis生长的影响,以探讨血链球菌在龈下菌斑微生态平衡中的作用。方法：用1/2浓度的BHI培养基为实验培养基,分别加入不同浓度的PABA,对P.gingivalis行厌氧培养后测定培养物的A值。结果：PABA对P.gingivalis的生长有一定影响。结论：血链球菌产生的PABA影响P.ginivalis的生长,该结果提示血链球菌对龄下菌斑的微生态平衡具有调节作用。     

Structure and action of the N-oxygenase AurF from Streptomyces thioluteus

Nitro groups are found in a number of bioactive compounds. Most of them arise by a stepwise mono-oxygenation of amino groups. One of the involved enzymes is AurF participating in the biosynthesis of aureothin. Its structure was established at 2.1 A resolution showing a homodimer with a binuclear manganese cluster. The enzyme preparation, which yielded the analyzed crystals, showed activity using in vitro and in vivo assays. Chain fold and cluster are homologous with ribonucleotide reductase subunit R2 and related enzymes. The two manganese ions and an iron content of about 15% were established by anomalous X-ray diffraction. A comparison of the cluster with more common di-iron clusters suggested an additional histidine in the coordination sphere to cause the preference for manganese over iron. There is no oxo-bridge. The substrate p-amino-benzoate was modeled into the active center. The model is supported by mutant activity measurements. It shows the geometry of the reaction and explains the established substrate spectrum.     

Insights of synthetic analogues of anti-leprosy agents

Today, the emergence of the phenomenon of drug or multidrug-resistance for community-associated diseases represents a major concern in the world. In these contexts, the chronic infectious disease, leprosy, grounded by a slow-growing bacterium called Mycobacterium leprae or Mycobacterium lepromatosis is a leading cause of severe disfiguring skin sores and nerve damage in the arms, legs, and skin areas around the body. Even, over 200,000 new leprosy cases are being accounted every year along with the relapsed leprosy cases. Nonetheless, this has been considered a curable disease with a higher dose of multidrug therapy (MDT) for a long period of time. The prolonged action of a high dose of combination drugs administration may cause an adverse reaction that can significantly affect patient compliance, particularly the outbreak of multidrug-resistance in the infected person. To overcome these shortfalls or prevent the resistance-associated problems, researchers are diligently involved in the structural modifications of the clinically used anti-leprosy drugs or the allied compounds for the structure-antimycobacterial activity relationship study. This review article described the detailed synthesis and biological assays of different anti-leprosy compounds reported by several research groups.     

共生因子PABA对P.gingivalis生长代谢影响的实验培养基的筛选

目的 为了研究其生因子PABA在龈下菌斑微生态平衡中的作用,拟筛选出一种既能满足P.gingivalis基本生长要求,又含最低浓度PABA的培养基。方法 在Carlsson培养基中加入营养成分进行改良,将BHI培养基系列稀释,共6个培养基系列进行筛选。结果 P.ginsivalis在改良Carlsson培养基中不生长,在BHI系列稀释培养基中只有1／2浓度才达到理想效果。结论 将稀释至原油质1／2的BHI培养基作为本研究的实验培养基。     

Arylamine N-acetyltransferase aggregation and constitutive ubiquitylation

Arylamine N-acetyltransferases (NAT1 and NAT2) acetylate and detoxify arylamine carcinogens. Humans harboring certain genetic variations within the NAT genes exhibit increased likelihood of developing various cancer types, especially urinary bladder cancer. Such DNA polymorphisms result in protein products with reduced cellular activity, which is proposed to be due to their constitutive ubiquitylation and enhanced proteasomal degradation. To identify the properties that lead to the reduced cellular activity of certain NAT variants, we introduced one such polymorphism into the human NAT1 ortholog hamster NAT2. The polymorphism chosen was human NAT1*17, which results in the replacement of R64 with a tryptophan residue, and we demonstrate this substitution to cause hamster NAT2 to be constitutively ubiquitylated. Biophysical characterization of the hamster NAT2 R64W variant revealed that its overall protein structure and thermostability are not compromised. In addition, we used steady-state kinetics experiments to demonstrate that the R64W mutation does not interfere with NAT catalysis in vitro. Hence, the constitutive ubiquitylation of this variant is not caused by its inability to be acetylated. Instead, we demonstrate this mutation to cause the hamster NAT2 protein to aggregate in vitro and in vivo. Importantly, we tested and confirmed that the R64W mutation also causes human NAT1 to aggregate in cultured cells. By using homology modeling, we demonstrate that R64 is located at a peripheral location, which provides an explanation for how the NAT protein structure is not significantly disturbed by its mutation to tryptophan. Altogether, we provide fundamental information on why humans harboring certain NAT variants exhibit reduced acetylation capabilities.     

系统发育分析中检测数据不相合性的方法

在进行生物系统发育研究的过程中,不同性质或来源的数据产生的结果之间往往存在差异,这种数据的不相合性已经成为我们重建系统发育历史的重要影响因素.本文介绍了数据不相合性存在的范围和成因,目前用于检测数据不相合性的主要方法:ILD检测,SH检测,PABA检测和PCI系数检测等,并对这些方法进行了比较,讨论了对不相合性数据的处理方法.