Experimental evidence for the role of paramagnetic oxygen concentration on the decay of long-lived nuclear spin order.
Experimental evidence for the role of paramagnetic oxygen concentration on the decay of long-lived nuclear spin order.
复制标题
作者：
核单重态寿命通常取决于溶液中存在的顺磁性氧物质的量，尽管淬灭或去除分子氧对延长单重态寿命的影响程度通常是未知因素。在这里，我们调查的单重态弛豫时间常数作为溶液中的氧浓度的函数的行为。实验演示了一个化学上不等价的质子对的三肽丙氨酸-甘氨酸-甘氨酸在溶液中。我们介绍了一种简单的方法，以确保溶液是饱和的预定浓度的氧气之前的单重态寿命的测量。利用自旋锁诱导交叉脉冲序列测量了单重态寿命。我们提出了溶解在溶液中的氧的量和单线态弛豫速率常数之间的线性关系。单重态弛豫被认为是2.7倍，不敏感的顺磁氧诱导的弛豫相比，纵向弛豫。弛豫行为描述通过使用相关的波动场的模型。我们还研究了延长单重态寿命的掺杂溶液与螯合剂抗坏血酸钠，清除溶液中的氧自由基。实验研究了纵向磁化强度和单重态阶数对溶解顺磁氧弛豫的敏感性。
Nuclear singlet lifetimes are often dependent on the quantity of paramagnetic oxygen species present in solution, although the extent to which quenching or removing molecular oxygen has on extending singlet lifetimes is typically an unknown factor. Here we investigate the behaviour of the singlet relaxation time constant as a function of the oxygen concentration in solution. An experimental demonstration is presented for a chemically inequivalent proton pair of the tripeptide alanine–glycine–glycine in solution. We introduce a simple methodology to ensure the solution is saturated with predetermined concentrations of oxygen gas prior to measurements of the singlet lifetime. Singlet lifetimes were measured by using the spin-lock induced crossing pulse sequence. We present a linear relationship between the amount of oxygen dissolved in solution and the singlet relaxation rate constant. Singlet relaxation was found to be ∼2.7 times less sensitive to relaxation induced by paramagnetic oxygen compared with longitudinal relaxation. The relaxation behaviour is described by using a model of correlated fluctuating fields. We additionally examine the extension of singlet lifetimes by doping solutions with the chelating agent sodium ascorbate, which scavenges oxygen radicals in solution. The sensitivity of longitudinal magnetization and singlet order to relaxation from dissolved paramagnetic oxygen sources in solution is investigated experimentally.
登录
查看更多内容
影响因子：
1.7
作者：
Elliott, Stuart J.;Kaderavek, Pavel;Levitt, Malcolm H.
通讯作者：
Levitt, Malcolm H.
DOI：
10.1039/c8cp00253c
发表时间：
2018-04-18
期刊：
Physical chemistry chemical physics : PCCP
影响因子：
--
作者：
Elliott SJ ;Meier B ;Vuichoud B ;Stevanato G ;Brown LJ ;Alonso-Valdesueiro J ;Emsley L ;Jannin S ;Levitt MH
通讯作者：
Levitt MH
影响因子：
15
作者：
Claytor, Kevin;Theis, Thomas;Warren, Warren S.
通讯作者：
Warren, Warren S.
影响因子：
8.6
作者：
Carravetta, M;Johannessen, OG;Levitt, MH
通讯作者：
Levitt, MH
影响因子：
4.4
作者：
FREEMAN, R;WITTEKOEK, S;ERNST, RR
通讯作者：
ERNST, RR