11B NMR Sensing of d-Block Metal Ions in Vitro and in Cells Based on the Carbon鈥揃oron Bond Cleavage of Phenylboronic Acid-Pendant Cyclen (Cyclen = 1,4,7,10-Tetraazacyclododecane)

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• 作者：Masanori Kitamura ; Toshihiro Suzuki ; Ryo Abe ; Takeru Ueno ; Shin Aoki
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：November 21, 2011
• 年：2011
• 卷：50
• 期：22
• 页码：11568-11580
• 全文大小：1356K
• 年卷期：v.50,no.22(November 21, 2011)
• ISSN：1520-510X

文摘

Noninvasive magnetic resonance imaging (MRI) including the 鈥渃hemical shift imaging (CSI)鈥?technique based on ¹H NMR signals is a powerful method for the in vivo imaging of intracellular molecules and for monitoring various biological events. However, it has the drawback of low resolution because of background signals from intrinsic water protons. On the other hand, it is assumed that the ¹¹B NMR signals which can be applied to a CSI technique have certain advantages, since boron is an ultratrace element in animal cells and tissues. In this manuscript, we report on the sensing of biologically indispensable d-block metal cations such as zinc, copper, iron, cobalt, manganese, and nickel based on ¹¹B NMR signals of simple phenylboronic acid-pendant cyclen (cyclen = 1,4,7,10-tetraazacyclododecane), L⁶ and L⁷, in aqueous solution at physiological pH. The results indicate that the carbon鈥揵oron bond of L⁶ is cleaved upon the addition of Zn²⁺ and the broad ¹¹B NMR signal of L⁶ at 31 ppm is shifted upfield to 19 ppm, which corresponds to the signal of B(OH)₃. ¹H NMR, X-ray single crystal structure analysis, and UV absorption spectra also provide support for the carbon鈥揵oron bond cleavage of ZnL⁶. Because the cellular uptake of L⁶ was very small, a more cell-membrane permeable ligand containing the boronic acid ester L⁷ was synthesized and investigated for the sensing of d-block metal ions using ¹¹B NMR. Data on ¹¹B NMR sensing of Zn²⁺ in Jurkat T cells using L⁷ is also presented.