scholarly journals S-Layer protein fromLysinibacillus sphaericusJG-A12 as matrix for AuIIIsorption and Au-nanoparticle formation

2010 ◽  
Vol 24 (1-2) ◽  
pp. 177-181 ◽  
Author(s):  
Ulrike Jankowski ◽  
Mohamed L. Merroun ◽  
Sonja Selenska-Pobell ◽  
Karim Fahmy
Keyword(s):  
Metal Binding ◽  
Au Nanoparticle ◽  
Side Chain ◽  
Ir Absorption ◽  
Au Nanoclusters ◽  
Absorption Frequency ◽  
Lysinibacillus Sphaericus ◽  
Mining Site ◽  
Effect Of Pd ◽  
Exafs Spectra

The strainLysinibacillus sphaericusJG-A12, isolated from the uranium mining site at Haberland, Saxony (Germany) selectively and reversibly accumulates radionuclides and toxic metals. Metal binding occurs to its surface layer (S-layer) surrounding the cells. Here, we have studied by Fourier-transform infrared (FTIR) spectroscopy the protein structure and stability as a function of AuIIIbinding and the subsequent reductively induced formation of Au-nanoclusters. Similar to previously studied complexes with PdII, Au-treated S-layers become resistant to acid denaturation evidenced by little response of their amide I absorption frequency. However, the strong effect of PdIIexerted on the side chain carboxylate IR absorption intensity is not observed with gold. Particularly after reduction, the carboxyl absorption responds little to acidification and a fraction appears to be protonated already at neutral pH. We ascribe this to a hydrophobic environment of the carboxyl groups after formation of Au-nanoclusters. EXAFS spectra agree with the metallic Au–Au distance but the reduced coordination number indicates that the Au-nanoclusters do not exceed ~2 nm. Thus, the S-layer ofL. sphaericusJG-A12 provides a biotemplate for efficient Au-nanocluster formation in an acid-resistant matrix and independently of cysteins.

scholarly journals Synthesis of New Derivatives of BEDT-TTF: Installation of Alkyl, Ethynyl, and Metal-Binding Side Chains and Formation of Tris(BEDT-TTF) Systems

2021 ◽  
Vol 7 (8) ◽  
pp. 110
Author(s):  
Songjie Yang ◽  
Matteo Zecchini ◽  
Andrew Brooks ◽  
Sara Krivickas ◽  
Desiree Dalligos ◽  
...  
Keyword(s):  
Metal Binding ◽  
Tricarboxylic Acid ◽  
Metal Salts ◽  
Side Chain ◽  
Side Chains ◽  
Ethynyl Group ◽  
X Ray ◽  
Transition Metal Salts ◽  
Alkyl Side Chains ◽  
Derivatives Of

The syntheses of new BEDT-TTF derivatives are described. These comprise BEDT-TTF with one ethynyl group (HC≡C-), with two (n-heptyl) or four (n-butyl) alkyl side chains, with two trans acetal (-CH(OMe)2) groups, with two trans aminomethyl (-CH2NH2) groups, and with an iminodiacetate (-CH2N(CH2CO2−)2 side chain. Three transition metal salts have been prepared from the latter donor, and their magnetic properties are reported. Three tris-donor systems are reported bearing three BEDT-TTF derivatives with ester links to a core derived from benzene-1,3,5-tricarboxylic acid. The stereochemistry and molecular structure of the donors are discussed. X-ray crystal structures of two BEDT-TTF donors are reported: one with two CH(OMe)2 groups and with one a -CH2N(CH2CO2Me)2 side chain.

scholarly journals An Adaptive Geometric Search Algorithm for Macromolecular Scaffold Selection

2017 ◽  
Author(s):  
Tian Jiang ◽  
P. Douglas Renfrew ◽  
Kevin Drew ◽  
Noah Youngs ◽  
Glenn Butterfoss ◽  
...  
Keyword(s):  
Protein Design ◽  
Active Site ◽  
Metal Binding ◽  
Search Algorithm ◽  
Three Dimensional ◽  
Side Chain ◽  
Enzyme Design ◽  
Hydrogen Binding ◽  
Performance Improvements ◽  
Geometric Search

AbstractA wide variety of protein and peptidomimetic design tasks require matching functional three-dimensional motifs to potential oligomeric scaffolds. Enzyme design, for example, aims to graft active-site patterns typically consisting of 3 to 15 residues onto new protein surfaces. Identifying suitable proteins capable of scaffolding such active-site engraftment requires costly searches to identify protein folds that can provide the correct positioning of side chains to host the desired active site. Other examples of biodesign tasks that require simpler fast exact geometric searches of potential side chain positioning include mimicking binding hotspots, design of metal binding clusters and the design of modular hydrogen binding networks for specificity. In these applications the speed and scaling of geometric search limits downstream design to small patterns. Here we present an adaptive algorithm to searching for side chain take-off angles compatible with an arbitrarily specified functional pattern that enjoys substantive performance improvements over previous methods. We demonstrate this method in both genetically encoded (protein) and synthetic (peptidomimetic) design scenarios. Examples of using this method with the Rosetta framework for protein design are provided but our implementation is compatible with multiple protein design frameworks and is freely available as a set of python scripts (https://github.com/JiangTian/adaptive-geometric-search-for-protein-design).

scholarly journals Thermodynamic and Structural Characterization of the Copper(II) Complexes of Peptides Containing Both Histidyl and Aspartyl Residues

2007 ◽  
Vol 2007 ◽  
pp. 1-9 ◽  
Author(s):  
Csilla Kállay ◽  
Zoltán Nagy ◽  
Katalin Várnagy ◽  
Gerasimos Malandrinos ◽  
Nick Hadjiliadis ◽  
...  
Keyword(s):  
Metal Binding ◽  
Significant Contribution ◽  
Binding Mode ◽  
Side Chain ◽  
Spectroscopic Techniques ◽  
Metal Binding Site ◽  
Carboxylate Groups ◽  
Protected Peptides

Terminally protected pentapeptides with 2 histidines (Ac-HHVGD-NH2and Ac-HVGDH-NH2) and the terminally free peptides containing both internal aspartyl and C-terminal histidyl residues (FDAH and VIDAH) have been synthesized, and copper(II) complexes studied by potentiometric, UV-Vis, CD, and EPR spectroscopic techniques in solution. Both thermodynamic and spectroscopic data reveal that side chain donor atoms of aspartyl and histidyl residues have a significant contribution to the metal binding affinity of peptide molecules. In the case of terminally protected peptides, the role of the imidazole-N donor functions is reflected in the enhanced stability of the 3N and 4N coordinated copper(II) complexes. The amino andβ-carboxylate groups of FDAH and VIDAH create a very effective metal binding site with the (NH2,N−,β-COO−) and (NH2,N−,N−,β-COO−) coordination modes including the N-termini, while the histidine sites are available for the formation of the (Nim,N−,N−) binding mode resulting in the preference of dinuclear complex formation.

scholarly journals High Efficiency Mercury Sorption by Dead Biomass of Lysinibacillus Sphaericus—New Insights into the Treatment of Contaminated Water

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1296 ◽  
Author(s):  
Vega-Páez ◽  
Rivas ◽  
Dussán-Garzón
Keyword(s):  
Metal Binding ◽  
High Efficiency ◽  
Immobilized Cells ◽  
Graphite Furnace ◽  
Toxic Metal ◽  
Bacterial Biomass ◽  
Sem Analysis ◽  
Mercury Chloride ◽  
Dead Cell ◽  
Lysinibacillus Sphaericus

Mercury (Hg) is a toxic metal frequently used in illegal and artisanal extraction of gold and silver which makes it a cause of environmental poisoning. Since biosorption of other heavy metals has been reported for several Lysinibacillus sphaericus strains, this study investigates Hg removal. Three L. sphaericus strains previously reported as metal tolerant (CBAM5, Ot4b31, and III(3)7) were assessed with mercury chloride (HgCl2). Bacteria were characterized by scanning electron microscopy coupled with energy dispersive spectroscopy (EDS-SEM). Sorption was evaluated in live and dead bacterial biomass by free and immobilized cells assays. Hg quantification was achieved through spectrophotometry at 508 nm by reaction of Hg supernatants with dithizone prepared in Triton X-114 and by graphite furnace atomic absorption spectroscopy (GF-AAS). Bacteria grew up to 60 ppm of HgCl2. Non-immobilized dead cell mixture of strains III(3)7 and Ot4b31 showed a maximum sorption efficiency of 28.4 µg Hg/mg bacteria during the first 5 min of contact with HgCl2, removing over 95% of Hg. This process was escalated in a semi-batch bubbling fluidized bed reactor (BFB) using rice husk as the immobilization matrix leading to a similar level of efficiency. EDS-SEM analysis showed that all strains can adsorb Hg as particles of nanometric scale that can be related to the presence of S-layer metal binding proteins as shown in previous studies. These results suggest that L. sphaericus could be used as a novel biological method of mercury removal from polluted wastewater.

Enhancement of enzymatic activity for myoglobins by modification of heme-propionate side chains

2004 ◽  
Vol 08 (03) ◽  
pp. 255-264 ◽  
Author(s):  
Takashi Hayashi ◽  
Hideaki Sato ◽  
Takashi Matsuo ◽  
Takaaki Matsuda ◽  
Yutaka Hitomi ◽  
...  
Keyword(s):  
Binding Site ◽  
Metal Binding ◽  
Protein Function ◽  
Site Directed Mutagenesis ◽  
Side Chain ◽  
Side Chains ◽  
Cytochrome P450 Enzyme ◽  
Prosthetic Group ◽  
Heme Pocket ◽  
P450 Enzyme

The modification of myoglobin is an attractive process not only for understanding its molecular mechanism but also for engineering the protein function. The strategy of myoglobin functionalization can be divided into at least two approaches: site-directed mutagenesis and reconstitution with a non-natural prosthetic group. The former method enables us to mainly modulate the physiological function, while the latter has the advantage of introducing a new function on the protein. Particularly, replacement of the native hemin with an artificially created hemin having hydrophobic moieties at the terminal of the heme-propionate side chains serves as an appropriate substrate-binding site near the heme pocket, and consequently enhances the peroxidase and peroxygenase activities for the reconstituted myoglobin. In addition, the incorporation of the synthetic hemin bearing modified heme-propionates into an appropriate apomyoglobin mutant drastically enhances the peroxidase activity. In contrast, to convert myoglobin into a cytochrome P450 enzyme, a flavin moiety as an electron transfer mediator was introduced at the terminal of the heme-propionate side chain. The flavomyoglobin catalyzes the deformylation of 2-phenylpropanal in the presence of NADH under aerobic conditions through the peroxoanion formation from the oxygenated species. In addition, modification of the heme-propionate side chains has an significant influence on regulating the reactivity of the horseradish peroxidase. Furthermore, the heme-propionate side chain can form a metal binding site with a carboxylate residue in the heme pocket. These studies indicate that modification of the heme-propionate side chains can be a new and effective way to engineer functions for the hemoproteins.

Au Nanoparticle-Decorated TiO2 Nanospheres Produced by Laser Reshaping in Water

2020 ◽  
Vol 312 ◽  
pp. 113-120
Author(s):  
Stanislav O. Gurbatov ◽  
Sergei A. Kulinich ◽  
Aleksandr A. Kuchmizhak
Keyword(s):  
Hybrid Nanostructures ◽  
Hybrid Nanoparticles ◽  
Au Nanoparticle ◽  
Chloroauric Acid ◽  
Au Nanoclusters ◽  
X Ray ◽  
Nanoparticle Surface ◽  
Average Size ◽  
New Generation ◽  
532 Nm

Here, we demonstrate formation of spherical-shaped amorphous titania (TiO2) nanoparticles decorated with Au nanoclusters via nanosecond pulse ablation (7-ns, 532-nm wavelength) of commercially available TiO2 nanopowders dispersed in an aqueous solution of chloroauric acid (HAuCl4). Generation of such hybrid nanostructures was found to be caused by laser-induced remelting of the initial TiO2 nanoparticles, stimulated by Au nanoclusters that can adsorbed on their surface and boost light-to-heat conversion process in optically transparent titania. The morphology and chemical composition of the obtained hybrid nanomaterials were studied in detail via scanning electron microscopy, Raman spectroscopy and Energy Dispersive X-ray spectroscopy. The average size and number of Au nanoclusters reduced on the TiO2 nanoparticle surface was shown to be tuned by varying the initial nanoparticles/HAuCl4 concentration ratio. Spectroscopic measurements of single hybrid nanoparticles scattering, as well as the corresponding numerical calculations of electromagnetic fields structure near their surface indicate synthesized functional nanomaterials as extremely promising for numerous applications of modern optics, optoelectronics and nanophotonics, e.g., realization of advanced chemo-and biosensing platforms, as well as of new-generation solar cells.

scholarly journals Effect of O-Side-Chain-Lipopolysaccharide Chemistry on Metal Binding

1999 ◽  
Vol 65 (2) ◽  
pp. 489-498 ◽  
Author(s):  
S. Langley ◽  
T. J. Beveridge
Keyword(s):  
Cell Surface ◽  
Metal Binding ◽  
Inductively Coupled Plasma ◽  
Iron Hydroxide ◽  
Repeat Unit ◽  
Dry Weight ◽  
Side Chain ◽  
Metallic Ions ◽  
Gram Negative ◽  
A Cell

ABSTRACT Pseudomonas aeruginosa PAO1 produces two chemically distinct types of lipopolysaccharides (LPSs), termed A-band LPS and B-band LPS. The A-band O-side chain is electroneutral at physiological pH, while the B-band O-side chain contains numerous negatively charged sites due to the presence of uronic acid residues in the repeat unit structure. Strain PAO1 (A+ B+) and three isogenic LPS mutants (A+ B−, A−B+, and A− B−) were studied to determine the contribution of the O-side-chain portion of LPS to metal binding by the surfaces of gram-negative cells. Transmission electron microscopy with energy-dispersive X-ray spectroscopy was used to locate and analyze sites of metal deposition, while atomic absorption spectrophotometry and inductively coupled plasma-mass spectrometry were used to perform bulk quantitation of bound metal. The results indicated that cells of all of the strains caused the precipitation of gold as intracellular, elemental crystals with a d-spacing of 2.43 Å. This type of precipitation has not been reported previously for gram-negative cells and suggests that in the organisms studied gold binding is not a surface-mediated event. All four strains bound similar amounts of copper (0.213 to 0.222 μmol/mg [dry weight] of cells) at the cell surface, suggesting that the major surface metal-binding sites reside in portions of the LPS which are common to all strains (perhaps the phosphoryl groups in the core-lipid A region). However, significant differences were observed in the abilities of strains dps89 (A− B+) and AK1401 (A+B−) to bind iron and lanthanum, respectively. Strain dps89 caused the precipitation of iron (1.623 μmol/mg [dry weight] of cells) as an amorphous mineral phase (possibly iron hydroxide) on the cell surface, while strain AK1401 nucleated precipitation of lanthanum (0.229 μmol/mg [dry weight] of cells) as apiculate, surface-associated crystals. Neither iron nor lanthanum precipitates were observed on the cells of other strains, which suggests that the combination of A-band LPS and B-band LPS produced by a cell may result in a cell surface which promotes the formation of metal-rich precipitates. We therefore propose that the negatively charged sites located in the O-side chains are not directly responsible for the binding of metallic ions; however, the B-band LPS molecule as a whole may contribute to overall cell surface properties which favor the precipitation of distinct metal-rich mineral phases.

Optical Properties of Poly[(3-Pentyl-5-Oxyazobenzene) Thiophene]

1995 ◽  
Vol 413 ◽  
Author(s):  
S. Luzzati ◽  
W. Viera ◽  
M. Catellani
Keyword(s):  
Optical Properties ◽  
Raman Scattering ◽  
Steric Hindrance ◽  
Uv Light ◽  
Electron Delocalization ◽  
Side Chain ◽  
Ir Absorption ◽  
Spectral Features ◽  
Photoinduced Absorption ◽  
Azo Chromophore

ABSTRACTWe report a study of the optical and photoexcitation properties of a new polyalkylthiophene:poly[(3-pentyl-5-oxoazobenzene)thiophene]. UV-Vis absorption and emission, IR absorption, Raman scattering, indicate that the steric hindrance of the side chain induces some rotational disorder of the backbone but the π electron delocalization is not substantially differing from other polyalkylthiophenes. Long lived photoexcitations have been characterized by photoinduced absorption. The spectral features are intrinsic to the polyconjugated thiophene chain, even when the backbone and the azo chromophore are both photoexcited by UV light.

Preparation and Characterization of the Blended Film from Silk Fibroin and Regenerated Cellulose Fiber Residue

2011 ◽  
Vol 332-334 ◽  
pp. 1666-1669 ◽  
Author(s):  
Laksanawadee Saikhao ◽  
Potjanart Suwanruji ◽  
Suesat Jantip ◽  
Sae Be Porntip
Keyword(s):  
Silk Fibroin ◽  
Cellulose Fiber ◽  
Regenerated Cellulose ◽  
Ir Absorption ◽  
Cellulose Content ◽  
Absorption Frequency ◽  
Oh Groups ◽  
Bombyx Mori Silk ◽  
Regenerated Cellulose Fiber ◽  
Blended Film

This research studied the preparation of the blended film from Bombyx mori silk fibroin with the regenerated cellulose obtained from rayon fiber residue, the industrial waste fiber. The β-sheet structure of silk fibroin was observed while the regenerated cellulose possessed cellulose II crystalline form. The infrared spectra of the blends showed changes in shape and intensity of IR absorption frequency characteristics in the region of 3500-3300 cm-1 as compared with those of the starting materials, pure silk fibroin and cellulose. This indicates the occurrence of the intermolecular interactions between the –OH groups of cellulose and silk fibroin by forming hydrogen bond. The tensile properties of the blends with cellulose content lower than 50 % could not be measured due to the weakness of the prepared film. The stronger and more flexible film was obtained with increasing the regenerated cellulose content. The study on the effect of NaCl and CaCl2 salt addition aiming to establish a porous structure to the blends was also investigated.

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