Soft-sphere ionic radii for alkali and halogenide ions

Abstract Calcium (Ca2+) and manganese (Mn2+) are essential elements for plants and have similar ionic radii and binding coordination. They are assigned specific functions within organelles, but share many transport mechanisms to cross organellar membranes. Despite their points of interaction, those elements are usually investigated and reviewed separately. This review takes them out of this isolation. It highlights our current mechanistic understanding and points to open questions of their functions, their transport, and their interplay in the endoplasmic reticulum (ER), vesicular compartments [Golgi apparatus, trans-Golgi Network (TGN), prevacuolar compartment (PVC)], vacuoles, chloroplasts, mitochondria, and peroxisomes. Complex processes demanding these cations, such as Mn2+-dependent glycosylation or systemic Ca2+ signaling, are covered in some detail if they have not been reviewed recently or if recent findings add to current models. The function of Ca2+ as signaling agent released from organelles into the cytosol and within the organelles themselves is a recurrent theme of this review, again keeping the interference by Mn2+ in mind. The involvement of organellar channels [e.g., Glutamate-Receptor-Likes (GLRs), Cyclic-Nucleotide-Gated Channels (CNGCs), Mitochondrial Conductivity Units (MCUs), Two-Pore Channel1 (TPC1)], transporters [e.g., Natural-Resistance-Associated Macrophage Proteins (NRAMPs), Calcium Exchangers (CAXs), Metal-Tolerance Proteins (MTPs), Bivalent-Cation Transporters (BICATs)] and pumps [Autoinhibited Ca2+-ATPases (ACAs), ER Ca2+-ATPases (ECAs)] in the import and export of organellar Ca2+ and Mn2+ is scrutinized, whereby current controversial issues are pointed out. Mechanisms in animals and yeast are taken into account where they may provide a blueprint for processes in plants, in particular with respect to tunable molecular mechanisms of Ca2+-versus-Mn2+ selectivity.

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Extending Shannon's ionic radii database using machine learning

Physical Review Materials ◽

10.1103/physrevmaterials.5.043804 ◽

2021 ◽

Vol 5 (4) ◽

Author(s):

Ahmer A. B. Baloch ◽

Saad M. Alqahtani ◽

Faisal Mumtaz ◽

Ali H. Muqaibel ◽

Sergey N. Rashkeev ◽

...

Keyword(s):

Machine Learning ◽

Ionic Radii

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The influence of ionic radii on the incorporation of trivalent dopants into BaTiO3

Materials Science and Engineering B ◽

10.1016/0921-5107(88)90019-0 ◽

1988 ◽

Vol 1 (2) ◽

pp. 193-201 ◽

Cited By ~ 93

Author(s):

L.A. Xue ◽

Y. Chen ◽

R.J. Brook

Keyword(s):

Ionic Radii

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Interactions of tervalent lanthanide ions with bacterial collagenase (clostridiopeptidase A)

Biochemical Journal ◽

10.1042/bj1950677 ◽

1981 ◽

Vol 195 (3) ◽

pp. 677-684 ◽

Cited By ~ 15

Author(s):

Christopher H. Evans

Keyword(s):

Ionic Radius ◽

Substrate Inhibition ◽

Volume Ratio ◽

Binding Pocket ◽

Lanthanide Ions ◽

Ionic Radii ◽

Apparent Dissociation Constant ◽

Substrate Complex ◽

Bacterial Collagenase ◽

Hydrolysis Of

Tervalent cations of the lanthanide (rare-earth) elements reversibly inhibit bacterial collagenase (clostridiopeptidase A; EC 3.4.24.3). Sm3+, whose ionic radius is closest to that of Ca2+, is the most effective inhibitor, completely suppressing clostridiopeptidase activity at a concentration of 100μm in the presence of 5mm-Ca2+. Er3+ and Lu3+, which both have ionic radii smaller than either Ca2+ or Sm3+, inhibit less efficiently, and La3+, which is slightly larger than Ca2+ or Sm3+, inhibits only weakly. These findings indicate a closely fitting, stereospecific, Ca2+-binding pocket in clostridiopeptidase, which excludes ions that are only slightly larger than Ca2+ [ionic radius 0.099nm (0.99 Ȧ)]. By contrast, trypsin, an enzyme whose activity does not depend on Ca2+, requires lanthanide concentrations 50–100-fold greater for inhibition. Furthermore, the relative efficiency of inhibition of trypsin by lanthanides increases as the lanthanide ions become smaller and the charge/volume ratio increases. At a concentration of 50μm, Sm3+ lowers the apparent Km for the hydrolysis of Pz-peptide by clostridiopeptidase from 5.4mm to 0.37mm and the apparent Vmax. from 0.29 Wünsch–Heidrich unit to 0.018 unit. Thus Sm3+ enhances the affinity of this enzyme for its substrate; inhibition of hydrolysis of Pz-peptide may result from the excessive stability of the enzyme–Sm3+–substrate complex. Inhibition by Sm3+ is competitive with regard to Ca2+. The apparent dissociation constant, Kd, of Ca2+ is 0.27mm, where the Ki for Sm3+ is 12μm. Clostridiopeptidase is more thermolabile in the absence of Ca2+. With Sm3+, thermoinactivation of the enzyme at 53°C or 60°C is initially accelerated, but then becomes retarded as heating continues. Lanthanide ions bind to gelatin and collagen. In so doing, they appear to protect these substrates from lysis by clostridiopeptidase through mechanisms additional to supplanting Ca2+ at its binding site on the enzyme. Collagen and gelatin sequester sufficient lanthanide ions to gain partial protection from clostridiopeptidase in the absence of an extraneous source of these inhibitors.

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Influence of doping on crystal growth, structure and optical properties of nanocrystalline CaTiO3: a case study using small-angle neutron scattering

Journal of Applied Crystallography ◽

10.1107/s1600576715006664 ◽

2015 ◽

Vol 48 (3) ◽

pp. 836-843 ◽

Cited By ~ 6

Author(s):

Oindrila Mondal ◽

Manisha Pal ◽

Ripandeep Singh ◽

Debasis Sen ◽

Subhasish Mazumder ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Optical Properties ◽

Crystal Growth ◽

Small Angle Neutron Scattering ◽

Ionic Radius ◽

Ionic Radii ◽

Growth Structure ◽

Transmission Electron ◽

The Difference

The effect of dopant size (ionic radius) on the crystal growth, structure and optical properties of nanocrystalline calcium titanate, CaTiO3(CTO), have been studied using small-angle neutron scattering. X-ray diffraction, along with high-resolution transmission electron microscopy, confirms the growth of pure nanocrystalline CTO. Rietveld analysis reveals that the difference of ionic radii between dopant and host ions induces strain within the lattice, which significantly affects the lattice parameters. The induced strain, due to the difference of ionic radii, causes the shrinkage of the optical band gap, which is manifested by the redshift of the absorbance band. Mesoscopic structural analysis using scattering techniques demonstrates that the ionic radius of the dopant influences the agglomeration behaviour and particle size. A high-resolution transmission electron microscopy study reconfirms the formation of pure highly crystalline CTO nanoparticles.

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Anion packing density: a universal quantity for both dense and porous crystalline inorganic phases

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768102002689 ◽

2002 ◽

Vol 58 (3) ◽

pp. 457-462 ◽

Cited By ~ 1

Author(s):

F. Liebau ◽

H. Küppers

Keyword(s):

High Pressure ◽

Packing Density ◽

Three Dimensional ◽

Ionic Radii ◽

Generalized Framework ◽

Molal Volumes ◽

Definition Of ◽

Anion Packing ◽

Very High ◽

Framework Density

To compare densities of inorganic high-pressure phases their molal volumes or specific gravities are usually employed, whereas for zeolites and other microporous materials the so-called framework density, FD, is applied. The definition of FD, which refers only to phases with three-dimensional tetrahedron frameworks, is extended to a `generalized framework density' d f, which is independent of the dimensionality of the framework and the coordination number(s) of the framework cations. In this paper the anion packing density, d ap, is introduced as a new quantity which is not only applicable to any inorganic phase but, in contrast to FD and d f, also allows quantitative comparisons to be made for crystalline inorganic phases of any kind. The anion packing density can readily be calculated if the volume and content of the unit cell and the radii of the anions of a phase are known. From d ap values calculated for high-pressure silica polymorphs studied under very high pressure, it is concluded that Shannon–Prewitt effective ionic radii do not sufficiently take into account the compressibility of the anions.

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