Artificial, Photoinduced Activation of Nitrogenase Using Directed and Mediated Electron Transfer Processes

2020 ◽  
Author(s):  
Matan Moshe Meirovich ◽  
Oren Bachar ◽  
Omer Yehezkeli
Keyword(s):  
Basic Research ◽  
Fold Increase ◽  
Redox Mediator ◽  
Cds Nanoparticles ◽  
Transmission Electron ◽  
Mediated Electron Transfer ◽  
Electron Transfer Processes ◽  
First Time ◽  
Atmospheric Nitrogen Fixation ◽  
Production Of Ammonia

Nitrogenase, a bacteria-based enzyme, is the sole enzyme able to generate ammonia by atmospheric nitrogen fixation. Thus, improved understanding of its mechanism and developing methods to artificially activate it may contribute greatly to basic research, as well as to the design of future artificial systems. Here, we present methods to artificially activate nitrogenase using photoinduced reactions. Two nitrogenase variants originating from Azotobecotor vinelinii were examined using photoactivated CdS nanoparticles (NPs) capped with thioglycolic acid (TGA) or 2-mercaptoethanol (ME) ligands. The effect of methyl viologen (MV) as a redox mediator of hydrogen and ammonia generation was tested and analyzed. We further determined the NPs conductive band edges and their effect on nitrogenase photo-activation. The nano-bio hybrid systems comprising CdS NPs and nitrogenase were further imaged by transmission electron microscopy, confirming their formation for the first time. Our results show that the ME-capped CdS NPs–nitrogenase enzyme biohybrid system with added MV as redox mediator, leads to a five-fold increase in the production of ammonia compared with the non-mediated biohybrid system.

scholarly journals Artificial, Photoinduced Activation of Nitrogenase Using Directed and Mediated Electron Transfer Processes

2020 ◽  
Author(s):  
Matan Moshe Meirovich ◽  
Oren Bachar ◽  
Omer Yehezkeli
Keyword(s):  
Basic Research ◽  
Fold Increase ◽  
Redox Mediator ◽  
Cds Nanoparticles ◽  
Transmission Electron ◽  
Mediated Electron Transfer ◽  
Electron Transfer Processes ◽  
First Time ◽  
Atmospheric Nitrogen Fixation ◽  
Production Of Ammonia

Nitrogenase, a bacteria-based enzyme, is the sole enzyme able to generate ammonia by atmospheric nitrogen fixation. Thus, improved understanding of its mechanism and developing methods to artificially activate it may contribute greatly to basic research, as well as to the design of future artificial systems. Here, we present methods to artificially activate nitrogenase using photoinduced reactions. Two nitrogenase variants originating from Azotobecotor vinelinii were examined using photoactivated CdS nanoparticles (NPs) capped with thioglycolic acid (TGA) or 2-mercaptoethanol (ME) ligands. The effect of methyl viologen (MV) as a redox mediator of hydrogen and ammonia generation was tested and analyzed. We further determined the NPs conductive band edges and their effect on nitrogenase photo-activation. The nano-bio hybrid systems comprising CdS NPs and nitrogenase were further imaged by transmission electron microscopy, confirming their formation for the first time. Our results show that the ME-capped CdS NPs–nitrogenase enzyme biohybrid system with added MV as redox mediator, leads to a five-fold increase in the production of ammonia compared with the non-mediated biohybrid system.

scholarly journals Artificial, Photoinduced Activation of Nitrogenase Using Directed and Mediated Electron Transfer Processes

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 979
Author(s):  
Matan M. Meirovich ◽  
Oren Bachar ◽  
Omer Yehezkeli
Keyword(s):  
Hydrogen Generation ◽  
Azotobacter Vinelandii ◽  
Basic Research ◽  
Fold Increase ◽  
Redox Mediator ◽  
Cds Nanoparticles ◽  
Transmission Electron ◽  
Mediated Electron Transfer ◽  
Electron Transfer Processes ◽  
First Time

Nitrogenase, a bacteria-based enzyme, is the sole enzyme that is able to generate ammonia by atmospheric nitrogen fixation. Thus, improved understanding of its utilization and developing methods to artificially activate it may contribute to basic research, as well as to the design of future artificial systems. Here, we present methods to artificially activate nitrogenase using photoinduced reactions. Two nitrogenase variants originating from Azotobacter vinelandii were examined using photoactivated CdS nanoparticles (NPs) capped with thioglycolic acid (TGA) or 2-mercaptoethanol (ME) ligands. The effect of methyl viologen (MV) as a redox mediator of hydrogen and ammonia generation was tested and analyzed. We further determined the NPs conductive band edges and their effect on the nitrogenase photoactivation. The nano-biohybrid systems comprising CdS NPs and nitrogenase were further imaged by transmission electron microscopy, visualizing their formation for the first time. Our results show that the ME-capped CdS NPs–nitrogenase enzyme biohybrid system with added MV as a redox mediator leads to a five-fold increase in the production of ammonia compared with the non-mediated biohybrid system; nevertheless, it stills lag behind the natural process rate. On the contrary, a maximal hydrogen generation amount was achieved by the αL158C MoFe-P and the ME-capped CdS NPs.

scholarly journals Synthesis of nanomaterials using expired medicines: an eco-friendly option

2012 ◽  
Vol 2 (1) ◽  
pp. 7 ◽  
Author(s):  
Anal K. Jha ◽  
Kamal Prasad
Keyword(s):  
Single Step ◽  
Molecular Organization ◽  
Cds Nanoparticles ◽  
X Ray Diffraction ◽  
Green Approach ◽  
Transmission Electron ◽  
Novel Method ◽  
Molecular Forces ◽  
First Time ◽  
Expired Medicines

Expired medicines are a burden to the environment. In this paper, a novel method is suggested to reutilize expired medicines in order to assess the possibilities of synthesizing a variety of nanomaterials. To this end, expired flouroquinolone (norfloxacin) and tinidazole combinations were used to synthesize metal (Au), oxide (ZrO<sub>2</sub>) and chalcognide (CdS) nanoparticles using for the first time a green chemistry approach. Au, ZrO<sub>2</sub> and CdS nanoparticles are available in convenient sizes of 6 nm, 26 nm and 18 nm, respectively, and remain stable for at least six months. This novel procedure is possible thanks to their molecular organization and elements. The inclusion of a fluorine atom in a drug molecule may influence both the disposition of the drug and its interaction with its pharmacological target; for example, the effects of fluorine substitution on the inter- and intra-molecular forces that affect binding of ligands. The presence of sulfur in the tinidazole molecules may also have contributed towards synthesis through proton withdrawal. The nanomaterials synthesized in this way were characterized using X-ray diffraction analysis and transmission electron microscopy to identify the formation of the desired nanoparticles. This single-step green approach is very convenient, simple and can be extended to synthesize a variety of nanomaterials that might find new technological and pharmaceutical applications.

A Novel TEM Technique for Characterizing As-Grown CVD Diamond Films

1991 ◽  
Vol 49 ◽  
pp. 956-957 ◽  
Author(s):  
Z.L. Wang ◽  
J. Bentley ◽  
R.E. Clausing ◽  
L. Heatherly ◽  
L.L. Horton
Keyword(s):  
Diamond Films ◽  
Chemical Vapor ◽  
Growth Direction ◽  
Dark Field ◽  
Growth Surface ◽  
Specimen Preparation ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
First Time ◽  
Microstructural Studies

Microstructural studies by transmission electron microscopy (TEM) of diamond films grown by chemical vapor deposition (CVD) usually involve tedious specimen preparation. This process has been avoided with a technique that is described in this paper. For the first time, thick as-grown diamond films have been examined directly in a conventional TEM without thinning. With this technique, the important microstructures near the growth surface have been characterized. An as-grown diamond film was fractured on a plane containing the growth direction. It took about 5 min to prepare a sample. For TEM examination, the film was tilted about 30-45° (see Fig. 1). Microstructures of the diamond grains on the top edge of the growth face can be characterized directly by transmitted electron bright-field (BF) and dark-field (DF) images and diffraction patterns.

Isopotential points in square-wave voltammetry of reversible electrode reactions

2009 ◽  
Vol 74 (10) ◽  
pp. 1489-1501 ◽  
Author(s):  
Marina Zelić ◽  
Milivoj Lovrić
Keyword(s):  
Square Wave Voltammetry ◽  
Electrode Reaction ◽  
Time Model ◽  
Model Calculations ◽  
Square Wave ◽  
Electrode Reactions ◽  
Wave Voltammetry ◽  
Electron Transfer Processes ◽  
Diagnostic Criterion ◽  
First Time

Isopotential points in square-wave voltammetry are described for the first time. Model calculations and real measurements (performed with UO22+ and Eu3+ in perchlorate and bromide solutions, respectively) indicate that such an intersection could be observed when backward components of the net response, resulting from an increase in frequency or reactant concentration, are presented together. The electrode reaction should be fully reversible because quasireversible or slower electron transfer processes give the isopoints only at increasing reactant concentrations but not at increasing square-wave frequencies. The effect could be used as an additional diagnostic criterion for recognition of reversible electrode reactions where products remain dissolved in the electrolyte solution.

scholarly journals Quartz Crystallite Size and Moganite Content as Indicators of the Mineralogical Maturity of the Carboniferous Chert: The Case of Cherts from Eastern Asturias (Spain)

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 611
Author(s):  
Celia Marcos ◽  
María de Uribe-Zorita ◽  
Pedro Álvarez-Lloret ◽  
Alaa Adawy ◽  
Patricia Fernández ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Crystallite Size ◽  
Archaeological Sites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Infrared And Raman Spectroscopy ◽  
First Time ◽  
Geological Formations

Chert samples from different coastal and inland outcrops in the Eastern Asturias (Spain) were mineralogically investigated for the first time for archaeological purposes. X-ray diffraction, X-ray fluorescence, transmission electron microscopy, infrared and Raman spectroscopy and total organic carbon techniques were used. The low content of moganite, since its detection by X-ray diffraction is practically imperceptible, and the crystallite size (over 1000 Å) of the quartz in these cherts would be indicative of its maturity and could potentially be used for dating chert-tools recovered from archaeological sites. Also, this information can constitute essential data to differentiate the cherts and compare them with those used in archaeological tools. However, neither composition nor crystallite size would allow distinguishing between coastal and inland chert outcrops belonging to the same geological formations.

scholarly journals In vitro biological activity of Hydroclathrus clathratus and its use as an extracellular bioreductant for silver nanoparticle formation

2020 ◽  
Vol 9 (1) ◽  
pp. 416-428 ◽  
Author(s):  
Raghad R. Alzahrani ◽  
Manal M. Alkhulaifi ◽  
Nouf M. Al-Enazi
Keyword(s):  
Biological Activity ◽  
Unsaturated Fatty Acids ◽  
Multidrug Resistant ◽  
Chemical Components ◽  
Resistant Bacteria ◽  
Transmission Electron ◽  
Hydroclathrus Clathratus ◽  
Adaptive Nature ◽  
First Time

AbstractThe adaptive nature of algae results in producing unique chemical components that are gaining attention due to their efficiency in many fields and abundance. In this study, we screened the phytochemicals from the brown alga Hydroclathrus clathratus and tested its ability to produce silver nanoparticles (AgNPs) extracellularly for the first time. Lastly, we investigated its biological activity against a variety of bacteria. The biosynthesized nanoparticles were characterized by UV-visible spectroscopy, Fourier-transform infrared spectroscopy, dynamic light scattering, transmission electron microscopy, and energy-dispersive spectroscopy. The biological efficacy of AgNPs was tested against eighteen different bacteria, including seven multidrug-resistant bacteria. Phytochemical screening of the alga revealed the presence of saturated and unsaturated fatty acids, sugars, carboxylic acid derivatives, triterpenoids, steroids, and other components. Formed AgNPs were stable and ranged in size between 7 and 83 nm and presented a variety of shapes. Acinetobacter baumannii, Staphylococcus aureus, Methicillin-resistant S. aureus (MRSA), and MDR A. baumannii were the most affected among the bacteria. The biofilm formation and development assay presented a noteworthy activity against MRSA, with an inhibition percentage of 99%. Acknowledging the future of nano-antibiotics encourages scientists to explore and enhance their potency, notably if they were obtained using green, rapid, and efficient methods.

scholarly journals The Effect of Surfactant-Modified Montmorillonite on the Cross-Linking Efficiency of Polysiloxanes

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2623
Author(s):  
Monika Wójcik-Bania ◽  
Jakub Matusik
Keyword(s):  
Total Pore Volume ◽  
Cross Linking ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Cross ◽  
Chain Lengths ◽  
First Time ◽  
Substituent Influence ◽  
Benzyl Substituent

Polymer–clay mineral composites are an important class of materials with various applications in the industry. Despite interesting properties of polysiloxanes, such matrices were rarely used in combination with clay minerals. Thus, for the first time, a systematic study was designed to investigate the cross-linking efficiency of polysiloxane networks in the presence of 2 wt % of organo-montmorillonite. Montmorillonite (Mt) was intercalated with six quaternary ammonium salts of the cation structure [(CH3)2R’NR]+, where R = C12, C14, C16, and R’ = methyl or benzyl substituent. The intercalation efficiency was examined by X-ray diffraction, CHN elemental analysis, and Fourier transform infrared (FTIR) spectroscopy. Textural studies have shown that the application of freezing in liquid nitrogen and freeze-drying after the intercalation increases the specific surface area and the total pore volume of organo-Mt. The polymer matrix was a poly(methylhydrosiloxane) cross-linked with two linear vinylsiloxanes of different siloxane chain lengths between end functional groups. X-ray diffraction and transmission electron microscopy studies have shown that the increase in d-spacing of organo-Mt and the benzyl substituent influence the degree of nanofillers’ exfoliation in the nanocomposites. The increase in the degree of organo-Mt exfoliation reduces the efficiency of hydrosilylation reaction monitored by FTIR. This was due to physical hindrance induced by exfoliated Mt particles.

scholarly journals Morphological and Ultrastructural Characterization of Hemocytes in an Insect Model, the Hematophagous Dipetalogaster maxima (Hemiptera: Reduviidae)

Insects ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 640
Author(s):  
Natalia R. Moyetta ◽  
Fabián O. Ramos ◽  
Jimena Leyria ◽  
Lilián E. Canavoso ◽  
Leonardo L. Fruttero
Keyword(s):  
Cell Biology ◽  
Cell Types ◽  
Transmission Electron ◽  
Ultrastructural Characterization ◽  
Current Classification ◽  
Contrast Microscopy ◽  
First Time ◽  
Controversial Aspect

Hemocytes, the cells present in the hemolymph of insects and other invertebrates, perform several physiological functions, including innate immunity. The current classification of hemocyte types is based mostly on morphological features; however, divergences have emerged among specialists in triatomines, the insect vectors of Chagas’ disease (Hemiptera: Reduviidae). Here, we have combined technical approaches in order to characterize the hemocytes from fifth instar nymphs of the triatomine Dipetalogaster maxima. Moreover, in this work we describe, for the first time, the ultrastructural features of D. maxima hemocytes. Using phase contrast microscopy of fresh preparations, five hemocyte populations were identified and further characterized by immunofluorescence, flow cytometry and transmission electron microscopy. The plasmatocytes and the granulocytes were the most abundant cell types, although prohemocytes, adipohemocytes and oenocytes were also found. This work sheds light on a controversial aspect of triatomine cell biology and physiology setting the basis for future in-depth studies directed to address hemocyte classification using non-microscopy-based markers.

scholarly journals Direct TEM observation of the “acanthite α-Ag2S–argentite β-Ag2S” phase transition in a silver sulfide nanoparticle

2019 ◽  
Vol 1 (4) ◽  
pp. 1581-1588 ◽  
Author(s):  
S. I. Sadovnikov ◽  
E. Yu. Gerasimov
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transmission Electron Microscopy ◽  
Silver Sulfide ◽  
Transmission Electron ◽  
Silver Sulfide Nanoparticles ◽  
Microscopy Method ◽  
Electron Microscopy Method ◽  
First Time

For the first time, the α-Ag2S (acanthite)–β-Ag2S (argentite) phase transition in a single silver sulfide nanoparticles has been observed in situ using a high-resolution transmission electron microscopy method in real time.

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