COMPARE 39K TRANSVERSE RELAXATION IN VITRO SOLUTIONS & IN CYTOPLASM OF E COLI

大肠杆菌细胞质中最丰富的阳离子和渗透分子， K，已被用于研究DNA的分子相互作用， 蛋白质、核糖体和离子的39K核磁共振谱。在我们之前的实验中， 在稠密区观测到39K的大的横向弛豫速率 大肠杆菌细胞的浆液。由于K核的相互作用 随着周围电场梯度的DNA占主导地位， 在加少量盐的K-DNA溶液中的39K横向弛豫， 这被认为是对测量到的39K松弛的解释 在活体内。然而，在DNA溶液中39K的松弛速率，甚至 浓度非常高(即生理条件)，是 比在活体中慢得多。也得到了类似的结果。 浓缩的K-BSA和KCl溶液。唯一的体外溶液 产生了同样大的横向弛豫量 在体内的速率都是核糖体溶液，带着高度负电荷 细胞中含有最多核酸的核糖体颗粒。 因此，核糖体颗粒被认为是 在体内增强39K的横向弛豫。类似的 还观察到了横向松弛的特征 23Na-核糖体溶液。这些结果还需要进一步的实验。 确认和探索核糖体分子性质的研究 颗粒与K、Na核糖体的相互作用。我们将使用DMX 400分光计，配备10 mm BB探头，可用于39K和23Na(更多 敏感核)核磁共振研究。

The most abundant cation and osmolyte in the cytoplasm of E. coli, K+, has been used in studies of molecular interactions of DNA, proteins, ribosome and ions via 39K NMR. In our previous experiments, a large transverse relaxation rate of 39K has been observed in dense slurries of E. coli cells. Since the interaction of the K nucleus with the surrounding electric field gradient of the DNA dominants the 39K transverse relaxation in a K-DNA solution with little salt added, it was considered as the explanation for the 39K relaxation measured in vivo. However, the relaxation rate of 39K in DNA solutions, even with a very high concentration (i.e., physiological conditions), is much slower than that in vivo. Similar results were obtained for concentrated K-BSA and KCl solutions. The only in vitro solution that gives rise to the same large magnitude of the transverse relaxation rate as in vivo are ribosome solutions, the highly negative charged ribosome particles that have the most nucleic acids in the cell. Therefore, ribosome particles are considered as the key element that enhances the transverse relaxation of 39K in vivo. The similar characteristic of transverse relaxation was also observed in 23Na-ribosome solutions. These results require further experimental studies to confirm and to explore the molecular nature of the ribosome particle and K+, Na+-ribosome interactions. We will be using the DMX 400 spectrometer with the 10mm BB probe for both 39K and 23Na (a more sensitive nucleus) NMR studies.