Selective Electroless Metallization of Patterned Ligand Surfaces

1992 ◽  
Vol 260 ◽  
Author(s):  
W. J. Dressick ◽  
C. S. Dulcey ◽  
J. M. Calvert ◽  
J. H. Georger ◽  
G. S. Calabrese ◽  
...  
Keyword(s):  
Metal Binding ◽  
Metal Ion ◽  
Ligand Interaction ◽  
Patterned Surface ◽  
Electroless Metallization ◽  
Catalytic Sites ◽  
Modified Surfaces ◽  
Deep Uv

ABSTRACTA process for creating patterns of metal-binding ligands on a variety of substrates is described. Deep UV patterning of chemisorbed ligand-bearing organosilane films creates modified surfaces that can selectively bind species such as Pd(II) via a covalent metal ion-ligand interaction. Patterned surface-bound Pd(II) is used to initiate additive electroless metallization at the catalytic sites. Metal adhesion to the substrate is controlled by the nature of the catalyst-ligand interaction.

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.

scholarly journals Acylated Anthocyanins from Red Cabbage and Purple Sweet Potato Can Bind Metal Ions and Produce Stable Blue Colors

2021 ◽  
Vol 22 (9) ◽  
pp. 4551
Author(s):  
Julie-Anne Fenger ◽  
Gregory T. Sigurdson ◽  
Rebecca J. Robbins ◽  
Thomas M. Collins ◽  
M. Mónica Giusti ◽  
...  
Keyword(s):  
Metal Ions ◽  
Sweet Potato ◽  
Metal Binding ◽  
Metal Ion ◽  
High Resolution Mass Spectrometry ◽  
Large Set ◽  
Water Addition ◽  
Red Cabbage ◽  
Aluminum Ions ◽  
Purple Sweet Potato

Red cabbage (RC) and purple sweet potato (PSP) are naturally rich in acylated cyanidin glycosides that can bind metal ions and develop intramolecular π-stacking interactions between the cyanidin chromophore and the phenolic acyl residues. In this work, a large set of RC and PSP anthocyanins was investigated for its coloring properties in the presence of iron and aluminum ions. Although relatively modest, the structural differences between RC and PSP anthocyanins, i.e., the acylation site at the external glucose of the sophorosyl moiety (C2-OH for RC vs. C6-OH for PSP) and the presence of coordinating acyl groups (caffeoyl) in PSP anthocyanins only, made a large difference in the color expressed by their metal complexes. For instance, the Al3+-induced bathochromic shifts for RC anthocyanins reached ca. 50 nm at pH 6 and pH 7, vs. at best ca. 20 nm for PSP anthocyanins. With Fe2+ (quickly oxidized to Fe3+ in the complexes), the bathochromic shifts for RC anthocyanins were higher, i.e., up to ca. 90 nm at pH 7 and 110 nm at pH 5.7. A kinetic analysis at different metal/ligand molar ratios combined with an investigation by high-resolution mass spectrometry suggested the formation of metal–anthocyanin complexes of 1:1, 1:2, and 1:3 stoichiometries. Contrary to predictions based on steric hindrance, acylation by noncoordinating acyl residues favored metal binding and resulted in complexes having much higher molar absorption coefficients. Moreover, the competition between metal binding and water addition to the free ligands (leading to colorless forms) was less severe, although very dependent on the acylation site(s). Overall, anthocyanins from purple sweet potato, and even more from red cabbage, have a strong potential for development as food colorants expressing red to blue hues depending on pH and metal ion.

scholarly journals Crystallographic and X-ray absorption spectroscopic characterization of Helicobacter pylori UreE bound to Ni2+ and Zn2+ reveals a role for the disordered C-terminal arm in metal trafficking

2012 ◽  
Vol 441 (3) ◽  
pp. 1017-1035 ◽  
Author(s):  
Katarzyna Banaszak ◽  
Vlad Martin-Diaconescu ◽  
Matteo Bellucci ◽  
Barbara Zambelli ◽  
Wojciech Rypniewski ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Metal Ions ◽  
Metal Binding ◽  
Metal Ion ◽  
Mutual Influence ◽  
Accurate Information ◽  
Metal Ion Binding ◽  
X Ray ◽  
X Ray Absorption

The survival and growth of the pathogen Helicobacter pylori in the gastric acidic environment is ensured by the activity of urease, an enzyme containing two essential Ni2+ ions in the active site. The metallo-chaperone UreE facilitates in vivo Ni2+ insertion into the apoenzyme. Crystals of apo-HpUreE (H. pylori UreE) and its Ni2+- and Zn2+-bound forms were obtained from protein solutions in the absence and presence of the metal ions. The crystal structures of the homodimeric protein, determined at 2.00 Å (apo), 1.59 Å (Ni2+) and 2.52 Å (Zn2+) resolution, show the conserved proximal and solvent-exposed His102 residues from two adjacent monomers invariably involved in metal binding. The C-terminal regions of the apoprotein are disordered in the crystal, but acquire significant ordering in the presence of the metal ions due to the binding of His152. The analysis of X-ray absorption spectral data obtained using solutions of Ni2+- and Zn2+-bound HpUreE provided accurate information of the metal-ion environment in the absence of solid-state effects. These results reveal the role of the histidine residues at the protein C-terminus in metal-ion binding, and the mutual influence of protein framework and metal-ion stereo-electronic properties in establishing co-ordination number and geometry leading to metal selectivity.

Characterisation of two calmodulin-like proteins from the liver fluke, Fasciola hepatica

2007 ◽  
Vol 388 (6) ◽  
pp. 593-599 ◽  
Author(s):  
Sean L. Russell ◽  
Neil V. McFerran ◽  
Elizabeth M. Hoey ◽  
Alan Trudgett ◽  
David J. Timson
Keyword(s):  
Metal Binding ◽  
Metal Ion ◽  
Liver Fluke ◽  
Fasciola Hepatica ◽  
Expression Vectors ◽  
Metal Ion Binding ◽  
Ion Sensing ◽  
Calcium Magnesium ◽  
Ion Binding Sites ◽  
Liver Flukes

Abstract Calmodulin is a calcium ion-sensing signalling protein found in eukaryotics. Two calmodulin-like gene sequences were identified in an EST library from adult liver flukes. One codes for a protein (FhCaM1) homologous to mammalian calmodulins (98% identity), whereas the other protein (FhCaM2) has only 41% identity. These genes were cloned into expression vectors and the recombinant proteins were expressed in Escherichia coli. Gel shift assays showed that both proteins bind to calcium, magnesium and zinc ions. Homology models have been built for both proteins. As expected, FhCaM1 has a highly similar structure to other calmodulins. Although FhCaM2 has a similar fold, its surface charge is higher than FhCaM1. One of the potential metal ion-binding sites has lower metal-ion co-ordination capability, while another has an adjacent lysine residue, both of which may decrease the metal-binding affinity. These differences may reflect a specialised role for FhCaM2 in the liver fluke.

Na+/K+exchange switches the catalytic apparatus of potassium-dependent plantL-asparaginase

2014 ◽  
Vol 70 (7) ◽  
pp. 1854-1872 ◽  
Author(s):  
Magdalena Bejger ◽  
Barbara Imiolczyk ◽  
Damien Clavel ◽  
Miroslaw Gilski ◽  
Agnieszka Pajak ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Active Site ◽  
Metal Binding ◽  
Metal Ion ◽  
Catalytic Mechanism ◽  
Structural Data ◽  
Activation Loop ◽  
Plant Type ◽  
Substrate Preferences ◽  
Autocatalytic Cleavage

Plant-type L-asparaginases, which are a subclass of the Ntn-hydrolase family, are divided into potassium-dependent and potassium-independent enzymes with different substrate preferences. While the potassium-independent enzymes have already been well characterized, there are no structural data for any of the members of the potassium-dependent group to illuminate the intriguing dependence of their catalytic mechanism on alkali-metal cations. Here, three crystal structures of a potassium-dependent plant-type L-asparaginase fromPhaseolus vulgaris(PvAspG1) differing in the type of associated alkali metal ions (K+, Na+or both) are presented and the structural consequences of the different ions are correlated with the enzyme activity. As in all plant-type L-asparaginases, immature PvAspG1 is a homodimer of two protein chains, which both undergo autocatalytic cleavage to α and β subunits, thus creating the mature heterotetramer or dimer of heterodimers (αβ)2. The αβ subunits of PvAspG1 are folded similarly to the potassium-independent enzymes, with a sandwich of two β-sheets flanked on each side by a layer of helices. In addition to the `sodium loop' (here referred to as the `stabilization loop') known from potassium-independent plant-type asparaginases, the potassium-dependent PvAspG1 enzyme contains another alkali metal-binding loop (the `activation loop') in subunit α (residues Val111–Ser118). The active site of PvAspG1 is located between these two metal-binding loops and in the immediate neighbourhood of three residues, His117, Arg224 and Glu250, acting as a catalytic switch, which is a novel feature that is identified in plant-type L-asparaginases for the first time. A comparison of the three PvAspG1 structures demonstrates how the metal ion bound in the activation loop influences its conformation, setting the catalytic switch to ON (when K+is coordinated) or OFF (when Na+is coordinated) to respectively allow or prevent anchoring of the reaction substrate/product in the active site. Moreover, it is proposed that Ser118, the last residue of the activation loop, is involved in the potassium-dependence mechanism. The PvAspG1 structures are discussed in comparison with those of potassium-independent L-asparaginases (LlA, EcAIII and hASNase3) and those of other Ntn-hydrolases (AGA and Tas1), as well as in the light of noncrystallographic studies.

scholarly journals Metal ion recognition of the metal-binding motif in hammerhead ribozymes

2003 ◽  
Vol 43 (supplement) ◽  
pp. S28
Author(s):  
Y. Tanaka ◽  
Y. Kasai ◽  
C. Kojima ◽  
K. Yamasaki ◽  
H. Morita ◽  
...  
Keyword(s):  
Metal Binding ◽  
Metal Ion ◽  
Binding Motif ◽  
Hammerhead Ribozymes ◽  
Ion Recognition ◽  
Metal Binding Motif

Photo-Degradation of Methamidophos (An Insecticide) in Water Using Dye-Modified Nano-Crystalline TiO2 Supported onto Activated Carbon Surfaces

2020 ◽  
Vol 8 (2) ◽  
pp. 100-111
Author(s):  
Lamees Majad ◽  
Nidal Zatar ◽  
Sameer Amereih ◽  
Hikmat Hilal
Keyword(s):  
Activated Carbon ◽  
Uv Degradation ◽  
Photo Degradation ◽  
New Class ◽  
Nano Crystalline ◽  
Catalytic Sites ◽  
Modified Surfaces ◽  
Significant Temperature ◽  
A Charge ◽  
Catalyst Efficiency

Anatase TiO2 surfaces have been treated with 2, 4, 6-triphenylpyrylium hydrogen sulfate (TPPHS) or tripyridylporhpyrinatomanganese(II) (MnP) dyes to yield the modified TiO2/ dye surfaces. The modified TiO2/dye surface was then supported onto activated carbon (AC) surfaces to yield a new class of catalytic system AC/TiO2/dye. The catalytic activities of naked TiO2, dye solution, TiO2/dye, and AC/TiO2/dye systems were examined in photo-degradation of Methamidophos (insecticide) in water, using both UV and visible light. All examined systems showed catalytic activity when used either in the UV or the visible regions, but the AC/TiO2/ dye showed the highest activity. The dye role, in enhancing activity of modified surfaces in UV degradation of the examined contaminants, is understandable by a charge-transfer catalytic effect. AC role can be explained by its ability to adsorb contaminant molecules and bringing them closer to catalytic sites. There was no significant temperature effect on catalyst efficiency in Methamidophos photo-degradation. Oxygen is essential for semiconductor photocatalytic degradation of Methamidophos, but higher oxygen concentrations lead to a downturn of the reaction rate.

Metal ion binding by humic substances as emergent functions of labile supramolecular assemblies

2020 ◽  
Vol 17 (3) ◽  
pp. 252 ◽  
Author(s):  
Elena A. Vialykh ◽  
Dennis R. Salahub ◽  
Gopal Achari
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Humic Substances ◽  
Metal Binding ◽  
Metal Ion ◽  
Computational Modelling ◽  
Intermolecular Forces ◽  
Metal Complexation ◽  
Emergent Properties ◽  
Metal Availability

Environmental contextThe fundamental basis for the high flexibility of humic substances is still unclear, though it is crucial for the understanding of metal bioavailability and toxicity in soil and aqueous environments. We show at the molecular level how characteristics of organic matter affect metal binding depending on the environmental conditions. Such understanding will help in the modulation of metal availability in soil and water in changing environmental situations. AbstractIn this work, we explore the hypothesis that humic substances (HS) can be perceived as labile supramolecular assemblages, the functioning of which is mainly determined by chemical composition and characteristics, the size of molecular units and weak intermolecular forces, rather than the exact primary structure of molecular moieties and their spatial configuration. To test the hypothesis, 72 computational models of three different organic mixtures were composed. The formation of inner and outer sphere metal–ligand complexes, metal binding sites, complex configurations, binding energies and aggregation/dissolution as emergent properties of HS were determined under various conditions. The results of computational modelling revealed that: (i) the highest Cu2+ binding (55.6%) was by the SRFA-22 organic model, which represents low-molecular-weight fulvic acids. In contrast, the highest amount of inner-sphere Mg–organic matter complex (63.4%) was formed in SRHA-6, which has higher-molecular-weight constituents. Therefore, a correlation between the type of cation, the system aromaticity and the extent of metal complexation is proposed. (ii) Increase of metal ion concentration and decrease of water content resulted in an increase in the number of hydrogen bonds and more compact and stable aggregates with lower hydrophilic and higher hydrophobic surface areas in SRFA-22. However, in SRHA-6, the results varied owing to the competition between metal binding, H-bonding and non-polar interactions in the structural arrangement of the aggregates. In general, the aggregation process, driven by metal complexation and water removal, resulted in the formation of more stable conformers, with lower potential energy, with the only exception of SRHA-6–Cu.

Efficient localization of a native metal ion within a protein by Cu2+-based EPR distance measurements

2019 ◽  
Vol 21 (20) ◽  
pp. 10238-10243 ◽  
Author(s):  
Austin Gamble Jarvi ◽  
Timothy F. Cunningham ◽  
Sunil Saxena
Keyword(s):  
Binding Site ◽  
Long Range ◽  
Metal Binding ◽  
Metal Ion ◽  
Native Metal ◽  
Distance Measurements ◽  
Metal Binding Site ◽  
Paramagnetic Metal

A native paramagnetic metal binding site in a protein is located with less than 2 Å resolution by a combination of double histidine (dHis) based Cu2+ labeling and long range distance measurements by EPR.

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