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57 result(s) for "Reedijk, Jan"
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New Clues for Platinum Antitumor Chemistry: Kinetically Controlled Metal Binding to DNA
From the metal ions and metal compounds that are known to bind to DNA, many anticancer Pt(II) and Ru(II)/Ru(III) compounds are known to have ligand-exchange kinetics in the same order of magnitude as the division of tumor cells. The present article discusses this process in detail with special attention to cisplatin and related compounds and the cellular binding sites and processes of such compounds. Detailed platinated DNA structures are presented and discussed in light of the mechanistic studies of metal antitumor compounds. It is now known that platinum antitumor drugs eventually end up on the DNA. However, it remains a challenge to understand how (fast) they reach the DNA and how they are removed. The kinetics of ligand exchange around platinum appear to play a crucial role, and the possible role of other ligands as intermediates, especially those with S-donor sites, is of great interest. New types of Pt compounds with additional functionalities influencing DNA binding and kinetics are discussed in the context of steric and H-bonding properties. A comparison is made with more sterically crowded Ru complexes. The effects on activity and correlations with structural and kinetic properties are clues in understanding the biological activities of these classes of compounds.
Terminology of metal–organic frameworks and coordination polymers (IUPAC Recommendations 2013)
A set of terms, definitions, and recommendations is provided for use in the classification of coordination polymers, networks, and metal–organic frameworks (MOFs). A hierarchical terminology is recommended in which the most general term is coordination polymer. Coordination networks are a subset of coordination polymers and MOFs a further subset of coordination networks. One of the criteria an MOF needs to fulfill is that it contains potential voids, but no physical measurements of porosity or other properties are demanded per se. The use of topology and topology descriptors to enhance the description of crystal structures of MOFs and 3D-coordination polymers is furthermore strongly recommended.
Metal-Ligand Exchange Kinetics in Platinum and Ruthenium Complexes
Metal coordination compounds with ‘slow’ metal-ligand exchange rates, comparable to those of cell division processes, often appear to be highly active in killing cancer cell lines. This is particularly marked in platinum and ruthenium complexes. Classical examples such as cisplatin, as well as very recent examples from the author’s and other work, will be discussed in detail, and in the context of the current knowledge of the mechanism of antitumour action. It is shown that even though much is known about the molecular mechanism of action of cisplatin, many challenging questions are left for future research. For the ruthenium anticancer drugs molecular mechanistic studies are only at the beginning. Mechanistic studies on both platinum and ruthenium compounds have, however, opened many new avenues of research that may lead to the design of completely new drugs.
Names and symbols of the elements with atomic numbers 113, 115, 117 and 118 (IUPAC Recommendations 2016)
A joint IUPAC/IUPAP Working Party (JWP) has confirmed the discovery of the elements with atomic numbers ( ) 113, 115, 117 and 118. In accordance with the 2016 IUPAC guideline for naming new elements, the discoverers were invited to propose names and symbols for the elements. Claims have been assigned to them and the following are proposed: (a) nihonium and symbol Nh, for the element with =113, (b) moscovium with the symbol Mc, for the element with =115, (c) tennessine with the symbol Ts, for the element with =117, and oganesson with the symbol Og, for the element with =118. After careful deliberation on these names and symbols, considering the 2016 rules and a public review period, the Inorganic Chemistry Division recommended these proposals for acceptance by the IUPAC Council.
Coexistence of Spin Canting and Metamagnetism in a One-Dimensional Mn(II) Compound Bridged by Alternating Double End-to-End and Double End-On Azido Ligands and the Analog Co(II) Compound
Two new compounds of general formula [M(N3)2(dmbpy)] in which dmbpy = 5,5′-dimethyl-2,2′-bipyridine, and M = Mn(II) or Co(II), have been solvothermally synthesized and characterized structurally and magnetically. The structures consist of zig-zag polymeric chains with alternating bis-µ(azide-N1)2M and bis-µ(azide-N1,N3)2M units in which the cis-octahedrally based coordination geometry is completed by the N,N’-chelating ligand dmbpy. The molecular structures are basically the same for each metal. The Mn(II) compound has a slightly different packing mode compared to the Co(II) compound, resulting from their different space groups. Interestingly, relatively weak interchain interactions are present in both compounds and this originates from π–π stacking between the dmbpy rings. The magnetic properties of both compounds have been investigated down to 2 K. The measurements indicate that the manganese compound shows spin-canted antiferromagnetic ordering with a Néel temperature of TN = 3.4 K and further, a field-induced magnetic transition of metamagnetism at temperatures below the TN. This finding affords the first example of an 1D Mn(II) compound with alternating double end-on (EO) and double end-to-end (EE) azido-bridged ligands, showing the coexistence of spin canting and metamagnetism. The cobalt compound shows a weak ferromagnetism resulting from a spin-canted antiferromagnetism and long-range magnetic ordering with a critical temperature, TC = 16.2 K.
Accurate non-invasive image-based cytotoxicity assays for cultured cells
Background The CloneSelect™ Imager system is an image-based visualisation system for cell growth assessment. Traditionally cell proliferation is measured with the colorimetric MTT assay. Results Here we show that both the CloneSelect Imager and the MTT approach result in comparable EC 50 values when assaying the cytotoxicity of cisplatin and oxaliplatin on various cell lines. However, the image-based technique was found non-invasive, considerably quicker and more accurate than the MTT assay. Conclusions This new image-based technique has the potential to replace the cumbersome MTT assay when fast, unbiased and high-throughput cytotoxicity assays are requested.
Structure-dependent in vitro cytotoxicity of the isomeric complexes Ru(L)2Cl2 (L=o-tolylazopyridine and 4-methyl-2-phenylazopyridine) in comparison to Ru(azpy)2Cl2
The dichlorobis(2-phenylazopyridine)ruthenium(II) complexes, [Ru(azpy)2Cl2], are under renewed investigation due to their potential anticancer activity. The three most common isomers α-, β- and γ-[RuL2Cl2] with L=o-tolylazopyridine (tazpy) and 4-methyl-2-phenylazopyridine (mazpy) (α indicating the coordinating Cl, N(pyridine) and Nazo atoms in mutual cis, trans, cis positions, β indicating the coordinating Cl, N(pyridine) and Nazo atoms in mutual cis, cis, cis positions, and γ indicating the coordinating Cl, N(pyridine) and Nazo atoms in mutual trans, cis, cis positions) are synthesized and characterized by NMR spectroscopy. The molecular structures of γ-[Ru(tazpy)2Cl2] and α-[Ru(mazpy)2Cl2] are determined by X-ray diffraction analysis. The IC50 values of the geometrically isomeric [Ru(tazpy)2Cl2] and [Ru(mazpy)2Cl2] complexes compared with those of the parent [Ru(azpy)2Cl2] complexes are determined in a series of human tumour cell lines (MCF-7, EVSA-T, WIDR, IGROV, M19, A498 and H266). These data unambiguously show for all complexes the following trend: the α isomer shows a very high cytotoxicity, whereas the β isomer is a factor 10 less cytotoxic. The γ isomers of [Ru(tazpy)2Cl2] and [Ru(mazpy)2Cl2] display a very high cytotoxicity comparable to that of the γ isomer of the parent compound [Ru(azpy)2Cl2] and to that of the α isomer. These biological data are of the utmost importance for a better understanding of the structure–activity relationships for the isomeric [RuL2Cl2] complexes.
New insights in the cellular processing of platinum antitumor compounds, using fluorophore-labeled platinum complexes and digital fluorescence microscopy
The cellular distribution and processing pathways of two platinum compounds, modeling the antitumor drug cisplatin (cDDP) in human osteosarcoma (U2-OS) cells is reported. A [Pt(en)Cl2] entity has been covalently linked to a carboxyfluorescein diacetate (CFDA) moiety and to a dinitrophenyl (DNP) moiety. The two different constructs were administered to living cell cultures that were analyzed using digital fluorescence microscopy. The non-fluorescent CFDA construct becomes fluorescent after cellular uptake and subsequent acetate hydrolysis by esterases, and is therefore suitable to monitor platinum in living cells; the DNP construct can be visualized by immunocytochemistry and consequently serves as a control. Both complexes were readily internalized by the cells, and localized throughout the whole cell. After 2–3 h the complex accumulated in the nucleus, but 6–8 h after incubation a punctuate staining of a cytoplasmic region was observed, that persisted and became more pronounced after 24 h. The overall fluorescence in the cell decreased over time, implying a secretion of the platinum complex. Surprisingly, the accumulation remained visible after 72 h. Co-localization experiments with a Golgi apparatus-selective stain indicate the involvement of Golgi vesicles in intracellular processing of cisplatin-derived complexes. Immunocytochemical studies, using the DNP derivative, resulted in very similar images as obtained with the CFDA construct. CFDA-boc (a non-platinum-containing fluorescein derivative) was used as control: a faint staining throughout the whole cell was observed. Cisplatin-resistant U2-OS/Pt cells showed staining patterns very similar to the U2-OS cells using both platinum constructs. This study illustrates that only a very small portion of the platinum complex eventually remains bound to DNA, as after 24 h no significant fluorescence could be observed in the nucleus. Cisplatin-derived complexes with fluorescent tags afford a new insight into the cellular processing of these complexes and therefore may contribute to further unraveling of the mechanism of platinum antitumor complexes.
The Versatility of the Dicyanamide Anion (Dca) as a Bridging Ligand: Synthesis, Structure and Theory of a Unique Ladder Chain Consisting of 2 µ1,5-dca Bridged Dinuclear Cu2(dca)2 Units with Additional µ1,3-dca Bridges Along the Chain
The synthesis and structural details of a mixed-ligand Cu(II) coordination compound, specifically catena -poly[bis(dicyanamido)(1,10-phenanthroline-5,6-dione)copper(II)] 1 , are reported. The title compound was synthesized utilizing a solvothermal method by employing dicyanamide, 1,10-phenanthroline-5,6-dione (phendione) and copper(II) sulfate pentahydrate (CuSO 4 •5H 2 O) as the starting materials. The title compound was characterized by standard analytical and spectroscopic methods. The 3D structure was determined by single-crystal X-ray diffraction. Examination of the supramolecular interaction patterns indicates that the stability of the ladder structure is achieved by the bridging dca anions and the presence of weak hydrogen-bonding contacts, specifically C-H···O and C-H···N bonds, as well as C-O/N···π interactions. These interactions together contribute to the formation of a ladder-type infinite chain structure. The generated structure has been theoretically investigated with Hirshfeld surface analysis, QTAIM and NCI analysis to reveal the interaction energies and bonds present inside and between molecules. The non-covalent interactions present in the crystal structure were further investigated theoretically, with particular attention to the cooperative C ≡ N···π(py) and N···π(hole) interactions involving the dicyanamide ligand and nitrile moieties in the compound. The solid-state stability of compound 1 appears to be strongly influenced by the cooperative effect of H-bonding interactions as well as the C ≡ N···π(py) and N···π(hole) contacts, as confirmed by theoretical calculations. Graphical Abstract Synthesis, Structure and Theoretical Calculations of a Unique Ladder Chain Containing the Dicyanamido Ligand (dca), Consisting of 2 µ 1,5 -dca Bridged Dinuclear Cu 2 (dca) 2 Units and Having µ 1,3 -dca Bridges along the Chain. One sentence essence: catena -poly[bis(dicyanamido)(1,10-phenanthroline-5,6-dione)copper(II)] is a unique ribbon ladder, infinite chain structure with two differently bridged dicyanamide anions
How to name new chemical elements (IUPAC Recommendations 2016)
A procedure is proposed to name new chemical elements. After the discovery of a new element is established by the joint IUPAC-IUPAP Working Group, the discoverers are invited to propose a name and a symbol to the IUPAC Inorganic Chemistry Division. Elements can be named after a mythological concept, a mineral, a place or country, a property or a scientist. After examination and acceptance by the Inorganic Chemistry Division, the proposal follows the accepted IUPAC procedure and is then ratified by the Council of IUPAC. This document is a slightly amended version of the 2002 IUPAC Recommendations; the most important change is that the names of all new elements should have an ending that reflects and maintains historical and chemical consistency. This would be in general “-ium” for elements belonging to groups 1–16, i.e. including the f-block elements, “-ine” for elements of group 17 and “-on” for elements of group 18.