Determination of O and OH Adsorption Sites and Coverage in Situ on Pt Electrodes from Pt L23X-ray Absorption Spectroscopy

2005 ◽  
Vol 109 (16) ◽  
pp. 8076-8084 ◽  
Author(s):  
M. Teliska ◽  
W. E. O'Grady ◽  
D. E. Ramaker
Keyword(s):  
Absorption Spectroscopy ◽  
Adsorption Sites ◽  
Pt Electrodes

scholarly journals In Situ Structural Determination of a Homogeneous Ruthenium Racemization Catalyst and Its Activated Intermediates Using X‐Ray Absorption Spectroscopy

2020 ◽  
Vol 26 (15) ◽  
pp. 3411-3419 ◽  
Author(s):  
Karl P. J. Gustafson ◽  
Arnar Guðmundsson ◽  
Éva G. Bajnóczi ◽  
Ning Yuan ◽  
Xiaodong Zou ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Structural Determination ◽  
X Ray ◽  
X Ray Absorption

scholarly journals Sequential Collinear Photofragmentation and Atomic Absorption Spectroscopy for Online Laser Monitoring of Triatomic Metal Species

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 533 ◽  
Author(s):  
Jan Viljanen ◽  
Kim Kalmankoski ◽  
Victor Contreras ◽  
Jaakko K. Sarin ◽  
Tapio Sorvajärvi ◽  
...  
Keyword(s):  
Atomic Absorption ◽  
Gas Phase ◽  
Absorption Spectroscopy ◽  
Atomic Absorption Spectroscopy ◽  
Limit Of Detection ◽  
In Situ Monitoring ◽  
Metal Species ◽  
Chemical Reaction Kinetics

Industrial chemical processes are struggling with adverse effects, such as corrosion and deposition, caused by gaseous alkali and heavy metal species. Mitigation of these problems requires novel monitoring concepts that provide information on gas-phase chemistry. However, selective optical online monitoring of the most problematic diatomic and triatomic species is challenging due to overlapping spectral features. In this work, a selective, all-optical, in situ gas-phase monitoring technique for triatomic molecules containing metallic atoms was developed and demonstrated with detection of PbCl2. Sequential collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) enables determination of the triatomic PbCl2 concentration through detection of released Pb atoms after two consecutive photofragmentation processes. Absorption cross-sections of PbCl2, PbCl, and Pb were determined experimentally in a laboratory-scale reactor to enable calibration-free quantitative determination of the precursor molecule concentration in an arbitrary environment. Limit of detection for PbCl2 in the laboratory reactor was determined to be 0.25 ppm. Furthermore, the method was introduced for in situ monitoring of PbCl2 concentration in a 120 MWth power plant using demolition wood as its main fuel. In addition to industrial applications, the method can provide information on chemical reaction kinetics of the intermediate species that can be utilized in reaction simulations.

Actualizing In Situ X-ray Absorption Spectroscopy Characterization of PEMFC-Cycled Pt-Electrodes

2018 ◽  
Vol 165 (9) ◽  
pp. F597-F603 ◽  
Author(s):  
Todd E. Miller ◽  
Veronica Davies ◽  
Jingkun Li ◽  
Shraboni Ghoshal ◽  
Eli Stavitski ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
X Ray ◽  
Pt Electrodes ◽  
X Ray Absorption

scholarly journals Effect of ligands on HP-induced unfolding and oligomerization of β-lactoglobulin

2020 ◽  
Author(s):  
S. Minić ◽  
B. Annighöfer ◽  
A. Hélary ◽  
D. Hamdane ◽  
G. Hui Bon Hoa ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Protein Unfolding ◽  
Structural Changes ◽  
Bioactive Molecules ◽  
Visible Absorption ◽  
Hydrophobic Cavity ◽  
Β Lactoglobulin

ABSTRACTTo probe intermediate states during unfolding and oligomerization of proteins remains a major challenge. High pressure (HP) is a powerful tool for studying these problems, revealing subtle structural changes in proteins not accessible by other means of denaturation. Bovine β-lactoglobulin (BLG), the main whey protein, has a strong propensity to bind various bioactive molecules, such as retinol and resveratrol, two ligands with different affinity and binding sites. By combining in situ HP-small-angle neutron scattering (SANS) and HP-UV/visible absorption spectroscopy, we report the specific effects of these ligands on 3D conformational and local changes in BLG induced by HP. Depending on BLG concentration, two different unfolding mechanisms are observed in situ under pressures up to ~300 MPa, mediated by the formation of disulfide bonds: either a complete protein unfolding, from native dimers to Gaussian chains, or a partial unfolding with oligomerization in tetramers. Retinol, which has a high affinity for BLG hydrophobic cavity, significantly stabilizes BLG both in 3D and local environments, by shifting the onset of protein unfolding by ~100 MPa. Increasing temperature from 30 to 37°C enhances the hydrophobic stabilization effects of retinol. In contrast, resveratrol, which has a low binding affinity for site(s) on the surface of the BLG, does not induce any significant effect on the structural changes of BLG due to pressure. HP treatment back and forth up to ~300 MPa causes irreversible covalent oligomerization of BLG. Ab initio modeling of SANS shows that the oligomers formed from BLG/retinol complex are smaller and more elongated compared to BLG without ligand or in the presence of resveratrol. By combining HP-SANS and HP-UV/vis absorption spectroscopy, our strategy highlights the crucial role of BLG hydrophobic cavity and opens up new possibilities for the structural determination of HP-induced protein folding intermediates and irreversible oligomerization.STATEMENT OF SIGNIFICANCEHigh pressure (HP) is a powerful probe to access the intermediate states of proteins through subtle structural changes not accessible by other means of denaturation. Bovine β-lactoglobulin (BLG), the main whey protein, is able to bind various bioactive molecules, such as retinol and resveratrol, exhibiting different affinity and binding sites. By combining HP-small-angle neutron scattering and HP-UV/visible absorption spectroscopy, we highlight two different mechanisms during the unfolding and oligomerization of BLG depending on protein concentration. Above all, we show that retinol significantly prevents the unfolding and oligomerization of BLG, unlike resveratrol, emphasizing the crucial role of the hydrophobic cavity in BLG stabilization. Our strategy opens up new possibilities for the structural determination of protein intermediates and oligomers using HP.

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