scholarly journals Characterisation of the metal-ion-GDP complex at the active sites of transforming and nontransforming p21 proteins by observation of the 17O-Mn superhyperfine coupling and by kinetic methods

1987 ◽  
Vol 162 (1) ◽  
pp. 49-55 ◽  
Author(s):  
Jurgen FEUERSTEIN ◽  
Hans Robert KALBITZER ◽  
Jacob JOHN ◽  
Roger S. GOODY ◽  
Alfred WITTINGHOFER
Keyword(s):  
Metal Ion ◽  
Active Sites ◽  
Kinetic Methods ◽  
P21 Proteins

scholarly journals Bismuth/hydroxyapatite-modified carbon screen-printed electrode for heavy-metal ion detection in aqueous media

2019 ◽  
Vol 76 ◽  
pp. 02001
Author(s):  
Aamir Amanat Ali Khan ◽  
Huma Ajab ◽  
Asim Yaqub ◽  
Mohd Azmuddin Abdullah
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Active Sites ◽  
Anodic Stripping Voltammetry ◽  
Simultaneous Detection ◽  
Current Response ◽  
Screen Printed Electrode ◽  
Square Wave ◽  
Screen Printed

Square-wave voltammetric stripping analysis is attractive for environmental monitoring and trace metal ion determination. The sensitivity is a result of analytes preconcentration steps on the electrode and advanced measurement procedures, where metal analytes are stripped away from the electrode at appropriate potential scan. Screen-printed electrode (SPE) has great advantages for in situ assays of heavy metal ions. Modification of SPE with bismuth (Bi) film improves the amalgamation of metal ions and the addition of hydroxyapatite (HA) increases the ion sorption, and enhances the current response due to the large porous structure and surface active sites for the metal ion binding. The ionization of the functional groups on the electrode surface upon contact with the aqueous system further assists the cation binding. The analytical performance of Bi and HA-modified SPE for simultaneous detection of Cd(II) and Pb(II) ions by square wave anodic stripping voltammetry (SWASV) was evaluated. Under the optimized electrochemical working conditions, calibration graph is linear for 240 s deposition time, in 0.1 M acetate buffer at pH 7.6 with the detection limit of 16.8 ppb for Pb(II). Two peaks corresponding to Cd(II) at -0.8 V and Pb(II) at -0.6 V can be discerned suggesting that Bi-HA modification had increased the current responses.

scholarly journals Mechanistic study of Cd adsorption through esterification and acetylation of novel biosorbent Gallus Domesticus chemically modified biomaterial for heavy metal

2013 ◽  
Vol 4 (2) ◽  
pp. 76-84
Author(s):  
Aliya Fazal ◽  
Uzaira Rafique
Keyword(s):  
Metal Ion ◽  
Active Sites ◽  
Integrated Approach ◽  
Gallus Domesticus ◽  
Operating Conditions ◽  
Mechanistic Study ◽  
Removal Capacity ◽  
Aqueous Effluents ◽  
Base Matrix ◽  
Elovich Equation

The inevitable expansion of industries for development is at the cost of release of industrial pollutants into the natural reservoirs of the environment. Biosorption is becoming an important component in the integrated approach to the treatment of aqueous effluents. The adsorption properties of Gallus Domesticus are determined as a function of batch operating conditions including contact time, solution initial concentration and temperature. Metal ion fixed Fourier transform infrared spectroscopy spectrum depicted amine, alcohol, carboxyl, and carbonate ion as active sites for metal sorption. Augmentation of removal capacity to 5 and 17% is tailored by esterification and acetylation of different surface functional groups of the base matrix. Kinetics is dissected through diffusion-based kinetic models, and best fit was figured out for Elovich equation. The thermodynamic relationship draws that enthalpy (ΔH° 45.48 KJ/mol) and entropy (ΔS° 153.32 J/mol K) are positive and entropy of the system is much larger than enthalpy. Results propose alteration of domestic waste into economical adsorbent for commercialization with no processing in the efficient removal of cadmium from wastewater.

Metallophosphoesterases: structural fidelity with functional promiscuity

2015 ◽  
Vol 467 (2) ◽  
pp. 201-216 ◽  
Author(s):  
Nishad Matange ◽  
Marjetka Podobnik ◽  
Sandhya S. Visweswariah
Keyword(s):  
Active Site ◽  
Metal Ion ◽  
Active Sites ◽  
Dependent Manner ◽  
The Core ◽  
Repair Enzymes ◽  
Phosphoprotein Phosphatases ◽  
Purple Acid Phosphatases ◽  
Binuclear Metal ◽  
Regulatory Effects

Calcineurin-like metallophosphoesterases (MPEs) form a large superfamily of binuclear metal-ion-centre-containing enzymes that hydrolyse phosphomono-, phosphodi- or phosphotri-esters in a metal-dependent manner. The MPE domain is found in Mre11/SbcD DNA-repair enzymes, mammalian phosphoprotein phosphatases, acid sphingomyelinases, purple acid phosphatases, nucleotidases and bacterial cyclic nucleotide phosphodiesterases. Despite this functional diversity, MPEs show a remarkably similar structural fold and active-site architecture. In the present review, we summarize the available structural, biochemical and functional information on these proteins. We also describe how diversification and specialization of the core MPE fold in various MPEs is achieved by amino acid substitution in their active sites, metal ions and regulatory effects of accessory domains. Finally, we discuss emerging roles of these proteins as non-catalytic protein-interaction scaffolds. Thus we view the MPE superfamily as a set of proteins with a highly conserved structural core that allows embellishment to result in dramatic and niche-specific diversification of function.

Photochemical mapping of the active site of myosin

1992 ◽  
Vol 336 (1276) ◽  
pp. 55-61 ◽  
Keyword(s):  
Active Site ◽  
Metal Ion ◽  
Active Sites ◽  
Cross Linking ◽  
Detailed Structure ◽  
Atp Binding Site ◽  
Adenine Ring ◽  
Skeletal Myosin ◽  
Key Residues ◽  
Specific Labelling

The active sites of myosin from skeletal, smooth and scallop muscle have been partly characterized by use of a series of photoreactive analogues of ATP. Specific labelling was attained by trapping these analogues in their diphosphate forms at the active sites by either cross-linking two reactive thiols (skeletal myosin) or by formation of stable vanadate-metal ion transition state-like complexes (smooth muscle and scallop myosin). By use of this approach combined with appropriate chemistry, several key residues in all three myosins have been identified which bind at or near the adenine ring, the ribose ring and to the γ-phosphate of ATP. This information should aid in the solution of the crystal structure of the heads of myosin and in defining a detailed structure of the ATP binding site.

scholarly journals Nanostructured faujasite zeolite as metal ion adsorbent: kinetics, equilibrium adsorption and metal recovery studies

2020 ◽  
Author(s):  
Mariana B. Goncalves ◽  
Djanyna V. C. Schmidt ◽  
Fabiana S. dos Santos ◽  
Daniel F. Cipriano ◽  
Gustavo R. Gonçalves ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Metal Ions ◽  
Metal Ion ◽  
Active Sites ◽  
Metal Removal ◽  
High Surface ◽  
High Surface Area ◽  
Kinetic Studies ◽  
Crystallization Time ◽  
X Ray

Abstract The hydrothermal synthesis of nano-faujasite has been successfully performed and the effects of some crystallization parameters were investigated, along with the use of this material as a heavy-metal ion adsorbent. X-ray diffraction patterns have shown that the structure of the nano-faujasite is strongly dependent on both the crystallization time and the alkalinity of the synthesis medium. According to N2 physisorption, X-ray fluorescence, SEM/EDS, and solid state 29Si and 27Al NMR data, the produced nano-faujasite consists of a solid with low molar Si/Al ratio (1.7), with high availability of ion exchange sites and high surface area/small particle size, allowing easy diffusion of metal ions to adsorbent active sites. As a consequence, an excellent performance on removal of Cd2+, Zn2+ and Cu2+ ions was found for this solid. The adsorption capacity followed the order Cd2+ (133 mg·g−1) > Zn2+ (115 mg·g−1) > Cu2+ (99 mg·g−1), which agrees with the order of increasing absolute values of the hydration energy of the metal ions. Kinetic studies and adsorption isotherms showed that the metal ion removal takes place by ion exchange on the monolayer surface of the nano-faujasite. The electrochemical recovery of copper in metallic form exhibited an efficiency of 80.2% after 120 min, which suggests that this process can be adequately implemented for full-scale metal removal.

scholarly journals Oxygen Evolution Reaction: Boosting Oxygen Evolution Reaction by Creating Both Metal Ion and Lattice‐Oxygen Active Sites in a Complex Oxide (Adv. Mater. 1/2020)

2020 ◽  
Vol 32 (1) ◽  
pp. 2070001
Author(s):  
Yinlong Zhu ◽  
Hassan A. Tahini ◽  
Zhiwei Hu ◽  
Zhi‐Gang Chen ◽  
Wei Zhou ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Metal Ion ◽  
Active Sites ◽  
Complex Oxide ◽  
Lattice Oxygen

scholarly journals Synthesis of Hematite Nanodiscs from Natural Laterites and Investigating Their Adsorption Capability of Removing Ni2+ and Cd2+ Ions from Aqueous Solutions

2020 ◽  
Vol 4 (2) ◽  
pp. 57
Author(s):  
B. P. N. Gunawardhana ◽  
C. A. Gunathilake ◽  
K. E. D. Y. T. Dayananda ◽  
D. M. S. N. Dissanayake ◽  
M. M. M. G. P. G. Mantilaka ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Inductively Coupled Plasma ◽  
Metal Ion ◽  
Active Sites ◽  
Low Cost ◽  
High Surface ◽  
High Surface Area ◽  
Nitrogen Adsorption ◽  
Batch Adsorption ◽  
Hematite Nanoparticles

In this work, disc-like hematite (Fe2O3) nanoparticles were prepared using a readily available inexpensive earth material, ferruginous laterite, via a low-cost synthesis route. Prepared hematite nanoparticles were characterized using X-Ray diffraction (XRD), inductively coupled plasma mass spectroscopy (ICP-MS), particle size analyzer (PSA), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and nitrogen adsorption-desorption analyzer. The performance of hematite nanoparticles was evaluated as a heavy metal ion adsorbent. Batch adsorption experiments were conducted to study the adsorption behaviour of Ni2+ and Cd2+ ions as a function of the amount of adsorbent, contact time, and pH. Adsorption data fitted to the linearized Langmuir and Freundlich kinetic models were compared and discussed. The correlation coefficient (R2) was used to determine the best fit kinetic model. Our data fitted the Langmuir kinetic model well and the highest adsorption efficiencies were found to be 62.5 mg/g for Ni2+ and 200 mg/g for Cd2+, respectively. Due to high surface area, pore volume with active sites, and sorption capabilities, hematite nanoparticles can be used as efficient and economical nano-adsorbents for the removal of Ni2+ and Cd2+ ions from industrial wastewater.

Improved Ni and Cd Rejection in Cellulose Acetate Mixed Matrix Membranes Coated with PVA/Fe3O4

2018 ◽  
Vol 43 (3) ◽  
pp. 237-243
Author(s):  
Mohammad Nouri ◽  
Azam Marjani ◽  
Majid Tajdari ◽  
Farhad Heidary ◽  
Mahmoud Salimi
Keyword(s):  
Cellulose Acetate ◽  
Metal Ion ◽  
Active Sites ◽  
Coating Layer ◽  
Mean Square Displacement ◽  
Mixed Matrix Membranes ◽  
Mixed Matrix ◽  
Ion Rejection ◽  
Substrate Layer ◽  
Matrix Membranes

AbstractA series of polyvinyl alcohol (PVA)/Fe3O4-coated cellulose acetate mixed matrix membranes were analyzed for Cd and Ni removal, both experimentally and theoretically. The effect of the coating layer on the metal ion rejection performance was investigated using molecular modeling approaches. Lower energy requirements for the detachment of ions from the coating layer were calculated. Our results imply that the coating layer interacts with metal ions to a much lower extent than the substrate layer does. Smaller mean square displacement data were calculated in the coating layer than in the substrate layer, which indicates a lower diffusivity of ions in the coating layer. This in turn shows the coating layer efficiently prevents ion transfer and provides higher retention/rejection. We conclude that applying a coating layer with lower Fe3O4 content would enhance the ion rejection performance of cellulose acetate mixed matrix membranes. The addition of Fe3O4 particles increases the number of active sites and the surface area, while a high content of these particles must be avoided as they may surround functional groups of polymer chains and also increase the porosity, which decreases the rejection performance of membranes.

Synthesis of zeolites with different chemical and textural properties for metal ions removal from aqueous solutions

2017 ◽  
Vol 76 (12) ◽  
pp. 3441-3451 ◽  
Author(s):  
Danielle França de Oliveira ◽  
Jefferson Antoniol Mendes Neri ◽  
Jonas Alves de Almeida Ribeiro ◽  
Fabiana Soares dos Santos ◽  
Mendelssolm Kister de Pietre
Keyword(s):  
Aqueous Solutions ◽  
Metal Ions ◽  
Surface Area ◽  
Metal Ion ◽  
Active Sites ◽  
Chemical Interaction ◽  
Textural Properties ◽  
Lead Ion ◽  
Metal Ion Removal ◽  
Β Zeolite

Abstract In this study β-zeolite, ferrierite and partially delaminated PREFER (precursor of ferrierite) zeolites with several chemical and textural properties were synthesized for the removal of zinc and lead ion metals from their respective solutions. Adsorption experiments involving the suspension of tiny amounts of these solids in aqueous solutions containing either Zn2+ or Pb2+ showed that the removal of these metals at a considerable extent may be attained. Among the studied materials, β-zeolite displayed the better performance in metal ion removal, which may be ascribed to its higher aluminum content, surface area and external surface area, that allows a greater density and availability of ion adsorption active sites. Kinetic data from a pseudo-second-order model indicate that the chemical interaction among metal ions and active sites is the rate-limiting step. Furthermore, the better performance of the β-zeolite displayed in reusability testing makes it a potential adsorbent for future applications in the treatment of effluents containing toxic metals.

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