China
Africa
Explore chapters and articles related to this topic
Dictionary
Published in Mario P. Iturralde, Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990
Chelate compounds and chelating agents. When a metal ion combines with a group containing an electron donor, a coordination compound is formed. If the substance which combine with the metal contains two or more donor groups, or if the metal is already combined with another atom in the molecule containing the donor atom so that one or more rings are formed, the resulting structure is said to be a chelate and the attached molecule a chelating agent. Although a large number of chelating agents are known, the donor atoms are commonly restricted to nitrogen, oxygen, and sulfur.
Luminescent Lanthanide Probes as Diagnostic and Therapeutic Tools
Published in Astrid Sigel, Helmut Sigel, Metal Ions in Biological Systems, 2004
Luminescence has played an essential role in the discovery of the rare-earth elements and in their early uses, particularly as inorganic phosphors. The first report on the lanthanide-centered luminescence of a coordination compound was published in 1942 by Weissman [2]. Using the sun as a source of light, he noted that absorption of radiation with wavelengths in the range 320 to 440 nm by the organic part of several EuIII complexes resulted in the characteristic line luminescence from the f-f transitions of trivalent europium. Studying several anionic chelating agents such as β-diketonates, benzoates, salicylates or picrates, he observed that the efficiency of excitation varies greatly with the nature of the compounds, as well as with the temperature and the solvent, and speculated that in some cases a quantum yield of unity was obtained at low temperature. The intermolecular energy transfer process between an organic ligand and a luminescent metal ion is presently designated as the “antenna effect”. The discovery stirred interest but no immediate application was found and, moreover, coordination chemistry of the LnIII ions did not develop much until the 1960’s when it was finally recognized that these ions usually display a large coordination number [3,4], which inevitably influences the design of adequate receptors. The excited states of luminescent LnIII ions are populated by a fast intramolecular energy transfer process from a triplet state of the ligand (itself populated from the singlet state by intersystem crossing), as demonstrated for the first time by Crosby et al. [5]. Estimates for the transfer rate range between 106 and 109 s−1.
Combination of static magnetic field and cisplatin in order to reduce drug resistance in cancer cell lines
Published in International Journal of Radiation Biology, 2019
Amir Jalali, Jaber Zafari, Fatemeh Javani Jouni, Parviz Abdolmaleki, Farshad H. Shirazi, Mohammad Javad Khodayar
Cisplatin is a metallic coordination compound that is one of the most potent antitumor agents known (Siddik 2003; Dasari and Tchounwou 2014). This compound acts as a DNA damaging agent forming intra-strand DNA adducts that inhibit DNA synthesis (Chaney et al. 2005). Recent studies, show other mechanisms for cisplatin action include oxidative stress (Brozovic et al. 2010), the effect on calcium signaling (Florea and Büsselberg 2009) protein kinase C (Basu and Tu 2005), mitogen-activated protein kinase (MAPK) (Brozovic and Osmak 2007) and modulation of gene expression (Shen et al. 2012). Cisplatin is used for the treatment of solid tumors including ovarian, testicular and lung cancer (Kuo et al. 2012; Sullivan et al. 2014). Resistance is an important problem in reaching maximal therapeutic efficacy of cisplatin and many chemotherapy drugs. The decrease in drug resistance is essential for improving treatment outcomes. When cancer cells are resistant, effective treatment choices are restricted. Currently, there is no effective strategy for combatting cisplatin resistance in cancer therapy (Kuo et al. 2012).