Singapore Bioimaging Consortium, A(∗)STAR, Singapore.
Biophys J. 2013 Nov 5;105(9):1956-66. doi: 10.1016/j.bpj.2013.09.034.
The rate of exchange of urea across the membranes of human erythrocytes (red blood cells) was quantified on the 1-s to 2-min timescale. (13)C-urea was hyperpolarized and subjected to rapid dissolution and the previously reported (partial) resolution of (13)C NMR resonances from the molecules inside and outside red blood cells in suspensions was observed. This enabled a stopped-flow type of experiment to measure the (initially) zero-trans transport of urea with sequential single-pulse (13)C NMR spectra, every second for up to ~2 min. Data were analyzed using Bayesian reasoning and a Markov chain Monte Carlo method with a set of simultaneous nonlinear differential equations that described nuclear magnetic relaxation combined with transmembrane exchange. Our results contribute to quantitative understanding of urea-exchange kinetics in the whole body; and the methodological approach is likely to be applicable to other cellular systems and tissues in vivo.
在 1 秒至 2 分钟的时间尺度上，量化了人红细胞（红血球）膜上尿素的交换速率。对（13）C-尿素进行超极化处理，并进行快速溶解，观察到先前报道的（部分）悬浮液中红细胞内外分子的（13）C NMR 共振的（部分）分辨率。这使得可以进行类似于停流的实验，使用连续的单脉冲（13）C NMR 光谱每隔一秒测量尿素的（最初）零转运，持续约 2 分钟。使用贝叶斯推理和马尔可夫链蒙特卡罗方法分析数据，该方法使用一组同时的非线性微分方程来描述与跨膜交换相结合的核磁共振弛豫。我们的结果有助于对全身尿素交换动力学的定量理解；并且该方法可能适用于体内其他细胞系统和组织。
