Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA.
Magn Reson Chem. 2013 Nov;51(11):722-8. doi: 10.1002/mrc.4007. Epub 2013 Sep 13.
An approach towards precision NMR measurements of four-bond deuterium isotope effects on the chemical shifts of backbone amide nitrogen nuclei in proteins is described. Three types of four-bond (15) N deuterium isotope effects are distinguished depending on the site of proton-to-deuterium substitution: (4)ΔN(N(i-1)D), (4)ΔN(N(i+1)D) and (4)ΔN(Cβ,(i-1)D). All the three types of isotope shifts are quantified in the (partially) deuterated protein ubiquitin. The (4)ΔN(N(i+1)D) and (4)ΔN(C(β,i-1)D) effects are by far the largest in magnitude and vary between 16 and 75 ppb and -18 and 46 ppb, respectively. A semi-quantitative correlation between experimental (4)ΔN(N(i+1)D) and (4)ΔN(C(β,i-1)D) values and the distances between nitrogen nuclei and the sites of (1)H-to-D substitution is noted. The largest isotope shifts in both cases correspond to the shortest inter-nuclear distances.
描述了一种用于精确测量蛋白质中骨架酰胺氮核的四键氘同位素效应对化学位移影响的方法。根据质子到氘取代的位置，区分了三种四键（15）N 氘同位素效应：（4）ΔN（N（i-1）D）、（4）ΔN（N（i+1）D）和（4）ΔN（Cβ，（i-1）D）。在部分氘化的蛋白质泛素中定量了所有三种类型的同位素位移。（4）ΔN（N（i+1）D）和（4）ΔN（Cβ，（i-1）D）效应的幅度迄今为止最大，分别在 16 至 75 ppb 和-18 至 46 ppb 之间变化。注意到实验（4）ΔN（N（i+1）D）和（4）ΔN（Cβ，（i-1）D）值与氮核与（1）H 到 D 取代位置之间的距离之间存在半定量相关性。在这两种情况下，最大的同位素位移对应于最短的核间距离。
