68847-70-1Relevant academic research and scientific papers
New calcium-selective smart contrast agents for magnetic resonance imaging
Verma, Kirti Dhingra,Forgacs, Attila,Uh, Hyounsoo,Beyerlein, Michael,Maier, Martin E.,Petoud, Stephane,Botta, Mauro,Logothetis, Nikos K.
, p. 18011 - 18026 (2014/01/17)
Calcium plays a vital role in the human body and especially in the central nervous system. Precise maintenance of Ca2+ levels is very crucial for normal cell physiology and health. The deregulation of calcium homeostasis can lead to neuronal cell death and brain damage. To study this functional role played by Ca2+ in the brain noninvasively by using magnetic resonance imaging, we have synthesized a new set of Ca2+-sensitive smart contrast agents (CAs). The agents were found to be highly selective to Ca 2+ in the presence of other competitive anions and cations in buffer and in physiological fluids. The structure of CAs comprises Gd3+-DO3A (DO3A=1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane) coupled to a Ca2+ chelator o-amino phenol-N,N,O-triacetate (APTRA). The agents are designed to sense Ca2+ present in extracellular fluid of the brain where its concentration is relatively high, that is, 1.2-0.8 mM. The determined dissociation constant of the CAs to Ca2+ falls in the range required to sense and report changes in extracellular Ca2+ levels followed by an increase in neural activity. In buffer, with the addition of Ca2+ the increase in relaxivity ranged from 100-157 %, the highest ever known for any T1-based Ca2+-sensitive smart CA. The CAs were analyzed extensively by the measurement of luminescence lifetime measurement on Tb 3+ analogues, nuclear magnetic relaxation dispersion (NMRD), and 17O NMR transverse relaxation and shift experiments. The results obtained confirmed that the large relaxivity enhancement observed upon Ca 2+ addition is due to the increase of the hydration state of the complexes together with the slowing down of the molecular rotation and the retention of a significant contribution of the water molecules of the second sphere of hydration. Smart Ca2+ sensing in the brain: To study Ca2+ in the brain noninvasively by magnetic resonance imaging, a new set of Ca2+-sensitive smart contrast agents (CAs) have been synthesized. The agents were found to be highly selective to Ca2+ in the presence of other competitive anions and cations in buffer and in physiological fluids. The determined dissociation constant of the CAs to Ca 2+ falls in the range required to sense and report changes in extracellular Ca2+ levels in response to neural activity (see figure). Copyright
Stabilization of unique valencies of cobalt, nickel and copper by complexation with the tridentate ligand 2-(2′-pyridyl)-8-hydroxyquinoline Dedicated to Prof. George Christou, on his 60th birthday, an extraordinary and enthusiastic inorganic chemist, and the most supportive mentor i could ever ask for (GM).
Maayan, Galia,Dayagi, Yohai,Arad-Yellin, Rina,Shimon, Linda J.W.,Shanzer, Abraham
, p. 365 - 370 (2013/10/08)
The complexes of cobalt, copper and nickel ions with the known tridentate ligand 2-(2′-pyridyl)-8-hydroxyquinoline (HQP) were prepared and characterized. The structures of the complexes with Co(II), Cu(II) and Ni(III) were corroborated by crystal structure analyses. The structures of the complexes with Co(III) and Cu(I) were realized from NMR measurements in solution. It was found that HQP stabilizes high oxidation states of the complexed metal ions. The results also suggest that HQP binds Cu(II) and Cu(I) in two different modes; Cu(II) forms an octahedral complex with the three elements of the ligand, namely, the 8-hydroxyl the two nitrogens of bipyridine, while Cu(I) binds only to two nitrogens of the bipyridine, yielding a tetra-coordinated complex.
