The Abiotic Nitrite Oxidation by Ligand-Bound Manganese (III): The Chemical Mechanism

2021 ◽  
Author(s):  
George W. Luther III ◽  
Jennifer S. Karolewski ◽  
Kevin M. Sutherland ◽  
Colleen M. Hansel ◽  
Scott D. Wankel
Keyword(s):  
Chemical Mechanism ◽  
Nitrite Oxidation

Graphene and Graphene Oxide Applications for SERS Sensing and Imaging

2019 ◽  
Vol 26 (38) ◽  
pp. 6878-6895 ◽  
Author(s):  
Anna Jabłońska ◽  
Aleksandra Jaworska ◽  
Mateusz Kasztelan ◽  
Sylwia Berbeć ◽  
Barbara Pałys
Keyword(s):  
Graphene Oxide ◽  
Surface Enhanced Raman Spectroscopy ◽  
Biological Species ◽  
Chemical Mechanism ◽  
Aromatic Molecules ◽  
Sers Enhancement ◽  
Reduced Graphene ◽  
Surface Enhanced Raman ◽  
Active Nanoparticles ◽  
Fluorescence Quencher

: Surface Enhanced Raman Spectroscopy (SERS) has a long history as an ultrasensitive platform for the detection of biological species from small aromatic molecules to complex biological systems as circulating tumor cells. Thanks to unique properties of graphene, the range of SERS applications has largely expanded. Graphene is efficient fluorescence quencher improving quality of Raman spectra. It contributes also to the SERS enhancement factor through the chemical mechanism. In turn, the chemical flexibility of Reduced Graphene Oxide (RGO) enables tunable adsorption of molecules or cells on SERS active surfaces. Graphene oxide composites with SERS active nanoparticles have been also applied for Raman imaging of cells. This review presents a survey of SERS assays employing graphene or RGO emphasizing the improvement of SERS enhancement brought by graphene or RGO. The structure and physical properties of graphene and RGO will be discussed too.

scholarly journals Comprehensive modeling of bloodstain aging by multivariate Raman spectral resolution with kinetics

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Ayari Takamura ◽  
Daisuke Watanabe ◽  
Rintaro Shimada ◽  
Takeaki Ozawa
Keyword(s):  
Spectral Resolution ◽  
Aging Process ◽  
Near Infrared ◽  
Biochemical Characterization ◽  
Forensic Analysis ◽  
Chemical Mechanism ◽  
Experimental Conditions ◽  
Spectral Components ◽  
Different Temperatures ◽  
Analytical Approaches

Abstract Blood, as a cardinal biological system, is a challenging target for biochemical characterization because of sample complexity and a lack of analytical approaches. To reveal and evaluate aging process of blood compositions is an unexplored issue in forensic analysis, which is useful to elucidate the details of a crime. Here we demonstrate a spectral deconvolution model of near-infrared Raman spectra of bloodstain to comprehensively describe the aging process based on the chemical mechanism, particularly the kinetics. The bloodstain spectra monitored over several months at different temperatures are decomposed into significant spectral components by multivariate calculation. The kinetic schemes of the spectral components are explored and subsequently incorporated into the developed algorithm for the optimal spectral resolution. Consequently, the index of bloodstain aging is proposed, which can be used under different experimental conditions. This work provides a novel perspective on the chemical mechanisms in bloodstain aging and facilitates forensic applications.

scholarly journals Structural effects in alkyl nitrite oxidation of human hemoglobin.

1984 ◽  
Vol 259 (1) ◽  
pp. 80-87
Author(s):  
M P Doyle ◽  
R A Pickering ◽  
J da Conceição
Keyword(s):  
Human Hemoglobin ◽  
Structural Effects ◽  
Nitrite Oxidation ◽  
Alkyl Nitrite

scholarly journals Microbial niche differentiation explains nitrite oxidation in marine oxygen minimum zones

2021 ◽  
Author(s):  
Xin Sun ◽  
Claudia Frey ◽  
Emilio Garcia-Robledo ◽  
Amal Jayakumar ◽  
Bess B. Ward
Keyword(s):  
Nitrogen Loss ◽  
Niche Differentiation ◽  
Nitrite Reduction ◽  
Nitrite Oxidation ◽  
Fixed Nitrogen ◽  
Anoxic Waters ◽  
Biogeochemical Models ◽  
Nitrite Oxidizing Bacteria ◽  
Oxygen Addition ◽  
Oxygen Minimum

AbstractNitrite is a pivotal component of the marine nitrogen cycle. The fate of nitrite determines the loss or retention of fixed nitrogen, an essential nutrient for all organisms. Loss occurs via anaerobic nitrite reduction to gases during denitrification and anammox, while retention occurs via nitrite oxidation to nitrate. Nitrite oxidation is usually represented in biogeochemical models by one kinetic parameter and one oxygen threshold, below which nitrite oxidation is set to zero. Here we find that the responses of nitrite oxidation to nitrite and oxygen concentrations vary along a redox gradient in a Pacific Ocean oxygen minimum zone, indicating niche differentiation of nitrite-oxidizing assemblages. Notably, we observe the full inhibition of nitrite oxidation by oxygen addition and nitrite oxidation coupled with nitrogen loss in the absence of oxygen consumption in samples collected from anoxic waters. Nitrite-oxidizing bacteria, including novel clades with high relative abundance in anoxic depths, were also detected in the same samples. Mechanisms corresponding to niche differentiation of nitrite-oxidizing bacteria across the redox gradient are considered. Implementing these mechanisms in biogeochemical models has a significant effect on the estimated fixed nitrogen budget.

scholarly journals Photochemically induced cyclic morphological dynamics via degradation of autonomously produced, self-assembled polymer vesicles

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Chenyu Lin ◽  
Sai Krishna Katla ◽  
Juan Pérez-Mercader
Keyword(s):  
Morphological Evolution ◽  
Chemical Degradation ◽  
Chemical Mechanism ◽  
Giant Vesicles ◽  
Water Influx ◽  
Physico Chemical ◽  
Osmotic Water ◽  
Periodic Growth ◽  
Oxygen Conditions ◽  
Self Assembled

AbstractAutonomous and out-of-equilibrium vesicles synthesised from small molecules in a homogeneous aqueous medium are an emerging class of dynamically self-assembled systems with considerable potential for engineering natural life mimics. Here we report on the physico-chemical mechanism behind a dynamic morphological evolution process through which self-assembled polymeric structures autonomously booted from a homogeneous mixture, evolve from micelles to giant vesicles accompanied by periodic growth and implosion cycles when exposed to oxygen under light irradiation. The system however formed nano-objects or gelation under poor oxygen conditions or when heated. We determined the cause to be photoinduced chemical degradation within hydrated polymer cores inducing osmotic water influx and the subsequent morphological dynamics. The process also led to an increase in the population of polymeric objects through system self-replication. This study offers a new path toward the design of chemically self-assembled systems and their potential application in autonomous material artificial simulation of living systems.

scholarly journals Voltammetric sensor based on long alkyl chain tetraalkylammonium ionic liquids comprising ascorbate anion for determination of nitrite

2021 ◽  
Vol 188 (2) ◽  
Author(s):  
Tomasz Rębiś ◽  
Michał Niemczak ◽  
Patrycja Płócienniczak ◽  
Juliusz Pernak ◽  
Grzegorz Milczarek
Keyword(s):  
Ionic Liquids ◽  
Electrostatic Interactions ◽  
Film Surface ◽  
Modified Electrodes ◽  
Voltammetric Sensor ◽  
Nitrite Oxidation ◽  
Alkyl Chains ◽  
Modified Surface ◽  
Influence Of Ph

AbstractAn electrochemical sensor was fabricated utilizing ionic liquids possessing cations with long alkyl chains such as trimethyl octadecylammonium and behenyl trimethylammonium and ascorbate anion. The ionic liquids were drop-coated onto the electrode. Thin modifying layers were prepared. Cyclic voltammetric investigations revealed electrostatic interactions between the electrochemical probes and the modified surface, proving that a positive charge was established at the film surface. Hence, negatively charged species such as nitrite can be pre-concentrated on the surface of presented modified electrodes. The fabricated electrodes have been used as a voltammetric sensor for nitrite. Due to the electrostatic accumulation properties of long alkyl cation, the assay exhibits a remarkable improvement in the voltammetric response toward nitrite oxidation. The influence of pH on the electrode response was thoroughly investigated, and the mechanism of the electrode was established. The developed sensor showed a linear electrochemical response in the range 1.0–50 μM with a detection limit of 0.1 μM. The electrode revealed good storage stability, reproducibility, and anti-interference ability. The determination of nitrite performed in curing salts brought satisfactory results. Graphical abstract

scholarly journals Comparisons of observed and modeled OH and HO2concentrations during the ambient measurement period of the HOxComp field campaign

2012 ◽  
Vol 12 (5) ◽  
pp. 2567-2585 ◽  
Author(s):  
Y. Kanaya ◽  
A. Hofzumahaus ◽  
H.-P. Dorn ◽  
T. Brauers ◽  
H. Fuchs ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Chemical Mechanism ◽  
Ozone Production ◽  
High Yield ◽  
Base Case ◽  
Peroxy Radicals ◽  
Field Campaign ◽  
Mixing Ratios ◽  
Measurement Mode ◽  
Single Instrument

Abstract. A photochemical box model constrained by ancillary observations was used to simulate OH and HO2 concentrations for three days of ambient observations during the HOxComp field campaign held in Jülich, Germany in July 2005. Daytime OH levels observed by four instruments were fairly well reproduced to within 33% by a base model run (Regional Atmospheric Chemistry Mechanism with updated isoprene chemistry adapted from Master Chemical Mechanism ver. 3.1) with high R2 values (0.72–0.97) over a range of isoprene (0.3–2 ppb) and NO (0.1–10 ppb) mixing ratios. Daytime HO2(*) levels, reconstructed from the base model results taking into account the sensitivity toward speciated RO2 (organic peroxy) radicals, as recently reported from one of the participating instruments in the HO2 measurement mode, were 93% higher than the observations made by the single instrument. This also indicates an overprediction of the HO2 to OH recycling. Together with the good model-measurement agreement for OH, it implies a missing OH source in the model. Modeled OH and HO2(*) could only be matched to the observations by addition of a strong unknown loss process for HO2(*) that recycles OH at a high yield. Adding to the base model, instead, the recently proposed isomerization mechanism of isoprene peroxy radicals (Peeters and Müller, 2010) increased OH and HO2(*) by 28% and 13% on average. Although these were still only 4% higher than the OH observations made by one of the instruments, larger overestimations (42–70%) occurred with respect to the OH observations made by the other three instruments. The overestimation in OH could be diminished only when reactive alkanes (HC8) were solely introduced to the model to explain the missing fraction of observed OH reactivity. Moreover, the overprediction of HO2(*) became even larger than in the base case. These analyses imply that the rates of the isomerization are not readily supported by the ensemble of radical observations. One of the measurement days was characterized by low isoprene concentrations (∼0.5 ppb) and OH reactivity that was well explained by the observed species, especially before noon. For this selected period, as opposed to the general behavior, the model tended to underestimate HO2(*). We found that this tendency is associated with high NOx concentrations, suggesting that some HO2 production or regeneration processes under high NOx conditions were being overlooked; this might require revision of ozone production regimes.

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