Synthesis of deuterium and C-13-labelled ethyl glycolate and their subsequent use in the synthesis of labelled analogues of the DNA adduct O6-carboxymethyl-2′-deoxyguanosine
细菌托酚酮天然产物,如托酚酮、托托二硫代酸或玫瑰杀菌剂,在各种陆地和海洋共生相互作用中起着至关重要的作用,如毒力因子、抗生素、除藻剂或群体感应信号。我们现在表明,它们知之甚少的生物合成依赖于需氧 CoA 依赖性苯乙酸分解代谢的分流产物,该分流产物由专用的酰基辅酶 A 脱氢酶样黄素酶 TdaE 挽救。TdaE 的进一步表征揭示了一种意想不到的复杂催化,包括底物脱氢、非经典 CoA-酯氧解和最终环氧化。因此,该酶作为一种典型的黄素蛋白双加氧酶发挥作用,它结合了来自 O 2的两个氧原子进入底物,最有可能涉及黄素-N5-过氧化物和黄素-N5-氧化物物质,分别用于连续的 CoA-酯裂解和环氧化。随后反应性酶产物的自发脱羧产生托酚酮,它是由病原性土壤植物伯克霍尔德菌引起的水稻穗枯病的关键毒力因子。或者, TdaE产物最有可能转化为更复杂的含硫次生代谢物,例如来自主要海洋红杆菌科(如抑制嗜热菌)的原二硫代硫酸。
Rotational-resonance distance measurements in multi-spin systems
作者:Aswin Verhoeven、Philip T.F. Williamson、Herbert Zimmermann、Matthias Ernst、Beat H. Meier
DOI:10.1016/j.jmr.2004.03.009
日期:2004.6
It is demonstrated that internuclear distances can be evaluated from rotational-resonance (RR) experiments in uniformly C-13-labelled compounds. The errors in the obtained distances are less than 10%, without the need to know any parameters of the spin system except the isotropic chemical shifts of all spins. We describe the multi-spin system with a simple fictitious spin-1/2 model. The influence of the couplings to the passive spins (J and dipolar coupling) is described by an empirical constant offset from the rotational-resonance condition. Using simulated data for a three-spin system, we show that the two-spin model describes the rotational-resonance transfer curves well as long as none of the passive spins is close to a rotational-resonance condition with one of the active spins. The usability of the two-spin model is demonstrated experimentally using a sample of acetylcholine perchlorate with labelling schemes of various levels of complexity. Doubly-, triply-, and fully labelled Compounds lead to strongly varying RR polarization-transfer curves but the evaluated distances using the two-spin model are identical within the expected error limits and coincide with the distance from the X-ray structure. Rotational-resonance distance measurements in fully labelled compounds allow, in particular, the measurement of weak couplings in the presence of strong couplings. (C) 2004 Elsevier Inc. All rights reserved.