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Ultrafast dynamics of the antibiotic Rifampicin in solution†
Photochemical & Photobiological Sciences ( IF 3.1 ) Pub Date : 2018-09-25 00:00:00 , DOI: 10.1039/c8pp00192h
Lorenzo Angiolini 1, 2, 3, 4, 5 , Boiko Cohen 1, 2, 3, 4, 5 , Abderrazzak Douhal 1, 2, 3, 4, 5
Affiliation  

Rifampicin (Rif) is an effective antibiotic against mycobacterial infections and a wide range of Gram-positive and Gram-negative bacteria. The geometry, conformation and the intramolecular H-bond network of Rif can affect its antibacterial efficiency. In this work, we report on the excited-state dynamics of Rif in sodium phosphate buffer and dichloromethane solutions using femtosecond time-resolved spectroscopic methods. The femtosecond UV-Vis-nearIR transient absorption and fluorescence up-conversion experiments reveal an ultrafast (<100 fs) Franck–Condon relaxation with a partial charge transfer character in S1, and a short-lived emission (τ ∼ 6 ps) due to a non-radiative relaxation to the ground state, associated with the stretching of the vibrational mode of the Rif internal H-bond network. The large Stokes-shifted emission (∼6800 cm−1) indicates a significant electronic change in the excited-state. In deuterated potassium phosphate buffer, the decay time becomes longer (∼20 ps). The large kinetic isotope effect (KIE) of ∼4 on the decay rate indicates that the stretching modes of the internal H-bond network are slowed by the H/D isotope substitution. The results provide new information on the dynamics of Rif structures and the related processes in aqueous solutions, showing that the internal H-bonding interactions are the ones that govern the ground and excited state properties of Rif but water molecules exert additional stabilization of its zwitterionic form through intermolecular H-bonds, which is responsible for its high antimicrobial activity.

中文翻译:

溶液中抗生素利福平的超快速动力学

利福平(Rif)是抗分枝杆菌感染和多种革兰氏阳性和革兰氏阴性细菌的有效抗生素。Rif的几何形状,构象和分子内H键网络可影响其抗菌效率。在这项工作中,我们报告了飞秒时间分辨光谱方法在磷酸钠缓冲液和二氯甲烷溶液中Rif的激发态动力学。飞秒的UV-Vis-nearIR瞬态吸收和荧光上转换实验表明,超快(<100 fs)的Franck-Condon弛豫具有S 1中的部分电荷转移特性,并且发射寿命短(τ约6 ps)是由于对基态的非辐射弛豫,与Rif内部H键网络的振动模式的拉伸有关。较大的斯托克斯位移发射(〜6800 cm -1)表示激发态发生了重大的电子变化。在氘化磷酸钾缓冲液中,衰减时间变长(〜20 ps)。约4的大动力学同位素效应(KIE)对衰变速率的影响表明,内部H键网络的拉伸模式因H / D同位素取代而减慢了。结果提供了有关Rif结构动力学及其在水溶液中的相关过程的新信息,表明内部的H键相互作用是控制Rif的基态和激发态性质的相互作用,但水分子对其两性离子形式起到了额外的稳定作用。通过分子间的氢键,这是其高抗菌活性的原因。
更新日期:2018-09-25
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