Tetranuclear MnII /ZnII and Novel Azido-Bridged Chair-Shaped Heptanuclear CdII Compounds: The Effect of Metal Ion and Coordination Mode of the Azide Group on the Structure of the Products

2018 ◽  
Vol 2019 (2) ◽  
pp. 262-270 ◽  
Author(s):  
Farhad Akbari Afkhami ◽  
Ghodrat Mahmoudi ◽  
Ali Akbar Khandar ◽  
Antonio Franconetti ◽  
Ennio Zangrando ◽  
...  
Keyword(s):  
Metal Ion ◽  
Coordination Mode ◽  
Azide Group

Generic tags for Mn(ii) and Gd(iii) spin labels for distance measurements in proteins

2017 ◽  
Vol 19 (39) ◽  
pp. 26944-26956 ◽  
Author(s):  
Yin Yang ◽  
Yan-Jun Gong ◽  
Aleksei Litvinov ◽  
Hong-Kai Liu ◽  
Feng Yang ◽  
...  
Keyword(s):  
Spin Label ◽  
Metal Ion ◽  
Coordination Mode ◽  
Distance Distribution ◽  
Spin Labels ◽  
Distance Measurements

The coordination mode of the metal ion in the spin label affects the distance distribution determined by DEER distance measurements.

Metal ion size and coordination mode in complexes of a β-diketiminate ligand with pendant quinoline arms

2011 ◽  
Vol 369 (1) ◽  
pp. 173-179 ◽  
Author(s):  
Elodie E. Marlier ◽  
Daniel Sadowsky ◽  
Christopher J. Cramer ◽  
Kristopher McNeill
Keyword(s):  
Metal Ion ◽  
Coordination Mode ◽  
Ion Size

scholarly journals The first phosphoramide–mercury(II) complex with a Cl2Hg–OP[N(C)(C)]3segment

2016 ◽  
Vol 72 (3) ◽  
pp. 230-233 ◽  
Author(s):  
Anahid Saneei ◽  
Mehrdad Pourayoubi ◽  
Aurelien Crochet ◽  
Katharina M. Fromm
Keyword(s):  
Coordination Number ◽  
Lewis Acid ◽  
Metal Ion ◽  
Coordination Mode ◽  
Complex Molecule ◽  
Relativistic Effects ◽  
Asymmetric Unit ◽  
Coordination Environment ◽  
Bond Valence Sum ◽  
Linear Coordination

Mercury(II) exhibits a strong preference for linear coordination which has been attributed to relativistic effects splitting the 6porbitals and promotingsphybridization. If the two ligands attached to the mercury(II) ion are weak donors, the metal ion can act as a good Lewis acid and expand its coordination number. Moreover, mercury has a special affinity for softer bases, such as S and N atoms, and has much less affinity for hard bases, such as those including an O atom. The asymmetric unit of dichlorido[tris(piperidin-1-yl)phosphane oxide-κO]mercury(II)–dichloridomercury(II) (2/1), [HgCl2{(C5H10N)3PO}]2·[HgCl2], is composed of one HgCl2{(C5H10N)3PO} complex and one half of a discrete HgCl2entity located on an inversion centre. The coordination environment around the HgIIcentre in the complex component is a distorted T-shape. Bond-valence-sum calculations confirm the three-coordination mode of the HgIIatom of the complex molecule. The noncovalent nature of the Hg...Cl and Hg...O interactions in the structure are discussed.

scholarly journals Selective synthesis and crystal structures of manganese(I) complexes with a bi- or tridentate terpyridine ligand

2020 ◽  
Vol 76 (7) ◽  
pp. 1139-1142
Author(s):  
Kosei Wadayama ◽  
Tsugiko Takase ◽  
Dai Oyama
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Metal Ion ◽  
Coordination Mode ◽  
Selective Synthesis ◽  
Complex Molecules ◽  
Carbonyl Ligands ◽  
Octahedral Environment ◽  
Distorted Octahedral ◽  
Bromide Ion

The crystal structures of two manganese(I) complexes with a different coordination mode of the supporting ligand are reported: fac-bromidotricarbonyl(4′-phenyl-2,2′:6′,2′′-terpyridine-κ2 N,N′)manganese(I), [MnBr(C21H15N3)(CO)3], I, and cis-bromidodicarbonyl(4′-phenyl-2,2′:6′,2′′-terpyridine-κ3 N,N′,N′′)manganese(I), [MnBr(C21H15N3)(CO)2], II. In both complexes, the manganese(I) atom is coordinated by terminal carbonyl ligands, a bromide ion, and a 4′-phenyl-2,2′:6′,2′′-terpyridine ligand within a distorted octahedral environment. In I, the metal ion is facially coordinated by three carbonyl ligands and the terpyridine ligand binds in a bidentate fashion. The non-coordinating nitrogen atom in the terpyridine ligand is positioned on the side opposite to the bromido ligand. In II, the metal ion is coordinated by two carbonyl ligands in a cis configuration and the terpyridine ligand binds in a tridentate fashion; notably, one carbonyl and the trans bromido ligand are mutually disordered over two positions. In I, the complex molecules are linked by C—H...Br hydrogen bonds. In II, aromatic π–π contacts are present, as well as pairs of C—H...Br and C—H...O hydrogen bonds.

Aspects of high-resolution imaging with a scanning ion microprobe

1986 ◽  
Vol 44 ◽  
pp. 750-751
Author(s):  
R. Levi-Setti ◽  
J. M. Chabala ◽  
Y. L. Wang
Keyword(s):  
Metal Ion ◽  
Secondary Ion Mass Spectrometry ◽  
Chromatic Aberration ◽  
Ion Source ◽  
Ion Microprobe ◽  
Emission Pattern ◽  
Intrinsic Resolution ◽  
Resolution Imaging ◽  
20 Nm ◽  
Secondary Ion

We have shown the feasibility of 20 nm lateral resolution in both topographic and elemental imaging using probes of this size from a liquid metal ion source (LMIS) scanning ion microprobe (SIM). This performance, which approaches the intrinsic resolution limits of secondary ion mass spectrometry (SIMS), was attained by limiting the size of the beam defining aperture (5μm) to subtend a semiangle at the source of 0.16 mr. The ensuing probe current, in our chromatic-aberration limited optical system, was 1.6 pA with Ga+ or In+ sources. Although unique applications of such low current probes have been demonstrated,) the stringent alignment requirements which they imposed made their routine use impractical. For instance, the occasional tendency of the LMIS to shift its emission pattern caused severe misalignment problems.

Scanning ion microscopy images

1987 ◽  
Vol 45 ◽  
pp. 180-181
Author(s):  
R. Levi-Setti ◽  
J.M. Chabala ◽  
Y.L. Wang
Keyword(s):  
Metal Ion ◽  
Secondary Emission ◽  
Scanning Method ◽  
Ion Channeling ◽  
Secondary Ions ◽  
High Resolution Images ◽  
Ion Microscopy ◽  
Z Contrast ◽  
Focused Beams ◽  
Microscopy Images

Finely focused beams extracted from liquid metal ion sources (LMIS) provide a wealth of secondary signals which can be exploited to create high resolution images by the scanning method. The images of scanning ion microscopy (SIM) encompass a variety of contrast mechanisms which we classify into two broad categories: a) Emission contrast and b) Analytical contrast.Emission contrast refers to those mechanisms inherent to the emission of secondaries by solids under ion bombardment. The contrast-carrying signals consist of ion-induced secondary electrons (ISE) and secondary ions (ISI). Both signals exhibit i) topographic emission contrast due to the existence of differential geometric emission and collection effects, ii) crystallographic emission contrast, due to primary ion channeling phenomena and differential oxidation of crystalline surfaces, iii) chemical emission or Z-contrast, related to the dependence of the secondary emission yields on the Z and surface chemical state of the target.

Freeze-etch TEM of aqueous polymer gel network morphology

1986 ◽  
Vol 44 ◽  
pp. 796-797
Author(s):  
J. A. N. Zasadzinski ◽  
R. K. Prud'homme
Keyword(s):  
Metal Ion ◽  
Polymer Network ◽  
Polymer Gels ◽  
Polymer Gel ◽  
Deformation History ◽  
Crosslinked Polymer ◽  
Aqueous Polymer ◽  
History Of ◽  
Gel Network ◽  
Network Morphology

The rheological and mechanical properties of crosslinked polymer gels arise from the structure of the gel network. In turn, the structure of the gel network results from: thermodynamically determined interactions between the polymer chain segments, the interactions of the crosslinking metal ion with the polymer, and the deformation history of the network. Interpretations of mechanical and rheological measurements on polymer gels invariably begin with a conceptual model of,the microstructure of the gel network derived from polymer kinetic theory. In the present work, we use freeze-etch replication TEM to image the polymer network morphology of titanium crosslinked hydroxypropyl guars in an attempt to directly relate macroscopic phenomena with network structure.

Structures of c-di-GMP/cGAMP degrading phosphodiesterase VcEAL: identification of a novel conformational switch and its implication

2019 ◽  
Vol 476 (21) ◽  
pp. 3333-3353 ◽  
Author(s):  
Malti Yadav ◽  
Kamalendu Pal ◽  
Udayaditya Sen
Keyword(s):  
Active Site ◽  
Metal Binding ◽  
Metal Ion ◽  
Triosephosphate Isomerase ◽  
Catalytic Mechanism ◽  
Degradation Mechanism ◽  
Structural Basis ◽  
Conserved Residues ◽  
Phosphodiester Bond ◽  
Cyclic Dinucleotides

Cyclic dinucleotides (CDNs) have emerged as the central molecules that aid bacteria to adapt and thrive in changing environmental conditions. Therefore, tight regulation of intracellular CDN concentration by counteracting the action of dinucleotide cyclases and phosphodiesterases (PDEs) is critical. Here, we demonstrate that a putative stand-alone EAL domain PDE from Vibrio cholerae (VcEAL) is capable to degrade both the second messenger c-di-GMP and hybrid 3′3′-cyclic GMP–AMP (cGAMP). To unveil their degradation mechanism, we have determined high-resolution crystal structures of VcEAL with Ca2+, c-di-GMP-Ca2+, 5′-pGpG-Ca2+ and cGAMP-Ca2+, the latter provides the first structural basis of cGAMP hydrolysis. Structural studies reveal a typical triosephosphate isomerase barrel-fold with substrate c-di-GMP/cGAMP bound in an extended conformation. Highly conserved residues specifically bind the guanine base of c-di-GMP/cGAMP in the G2 site while the semi-conserved nature of residues at the G1 site could act as a specificity determinant. Two metal ions, co-ordinated with six stubbornly conserved residues and two non-bridging scissile phosphate oxygens of c-di-GMP/cGAMP, activate a water molecule for an in-line attack on the phosphodiester bond, supporting two-metal ion-based catalytic mechanism. PDE activity and biofilm assays of several prudently designed mutants collectively demonstrate that VcEAL active site is charge and size optimized. Intriguingly, in VcEAL-5′-pGpG-Ca2+ structure, β5–α5 loop adopts a novel conformation that along with conserved E131 creates a new metal-binding site. This novel conformation along with several subtle changes in the active site designate VcEAL-5′-pGpG-Ca2+ structure quite different from other 5′-pGpG bound structures reported earlier.

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