| 1. |
- Chelban, V., et al.
(författare)
-
PDXK mutations cause polyneuropathy responsive to pyridoxal 5′-phosphate supplementation
- 2019
-
Ingår i: Annals of Neurology. - : Wiley. - 0364-5134 .- 1531-8249. ; 86:2, s. 225-240
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: To identify disease-causing variants in autosomal recessive axonal polyneuropathy with optic atrophy and provide targeted replacement therapy. Methods: We performed genome-wide sequencing, homozygosity mapping, and segregation analysis for novel disease-causing gene discovery. We used circular dichroism to show secondary structure changes and isothermal titration calorimetry to investigate the impact of variants on adenosine triphosphate (ATP) binding. Pathogenicity was further supported by enzymatic assays and mass spectroscopy on recombinant protein, patient-derived fibroblasts, plasma, and erythrocytes. Response to supplementation was measured with clinical validated rating scales, electrophysiology, and biochemical quantification. Results: We identified biallelic mutations in PDXK in 5 individuals from 2 unrelated families with primary axonal polyneuropathy and optic atrophy. The natural history of this disorder suggests that untreated, affected individuals become wheelchair-bound and blind. We identified conformational rearrangement in the mutant enzyme around the ATP-binding pocket. Low PDXK ATP binding resulted in decreased erythrocyte PDXK activity and low pyridoxal 5′-phosphate (PLP) concentrations. We rescued the clinical and biochemical profile with PLP supplementation in 1 family, improvement in power, pain, and fatigue contributing to patients regaining their ability to walk independently during the first year of PLP normalization. Interpretation: We show that mutations in PDXK cause autosomal recessive axonal peripheral polyneuropathy leading to disease via reduced PDXK enzymatic activity and low PLP. We show that the biochemical profile can be rescued with PLP supplementation associated with clinical improvement. As B6 is a cofactor in diverse essential biological pathways, our findings may have direct implications for neuropathies of unknown etiology characterized by reduced PLP levels. ANN NEUROL 2019;86:225–240. © 2019 The Authors. Annals of Neurology published by Wiley Periodicals, Inc. on behalf of American Neurological Association.
|
|
| 2. |
- Ayagou, Martien, et al.
(författare)
-
Corrosion and hydrogen permeation in H 2 S environments with O 2 contamination, Part 2 : Impact of H 2 S partial pressure
- 2019
-
Ingår i: Corrosion. - : National Assoc. of Corrosion Engineers International. - 0010-9312 .- 1938-159X. ; 75:4, s. 389-397
-
Tidskriftsartikel (refereegranskat)abstract
- Materials selection in the oil and gas industry relies on engineering standards, such as NACE TM0177 and NACE TM0284, which stipulate that oxygen contamination should be avoided during materials testing in H 2 S-containing media. In this second paper, as part of a series of articles that evaluates how traces of oxygen modify the corrosion of pure iron and hydrogen permeation across iron membranes in H 2 S-containing solutions, the impact of changing the H 2 S partial pressure from 100 kPa to 0.1 kPa was investigated. It was found that bulk solution chemistry for all H 2 S partial pressures changes with time, due to the formation of H 2 S–O 2 reaction products (sulfates, sulfites, and thiosulfates), which results in bulk solution acidification. Electrochemical and weight-loss measurements confirm that Fe corrosion rates in baseline well-deaerated H 2 S-containing solutions decrease with decreasing H 2 S partial pressure, although these are observed to be much higher under continuous oxygen contamination. With decreasing H 2 S partial pressure, hydrogen uptake in Fe also decreases, due to lower and lower concentrations of dissolved H 2 S and the associated increase in pH. However, even at 1 kPa and 0.1 kPa H 2 S, permeation effciencies remain close to 100% when no O 2 contamination is present. The hydrogen uptake is always relatively lower in Fe exposed to oxygen-polluted H 2 S solutions. Permeation efficiencies decrease continuously. From electrochemical data and surface characterization, these observations at lower H 2 S partial pressures are attributed to the disruptive effect of oxygen on the nature of sulfide corrosion products, and hydrogen entry promotion, along with the contribution of an additional cathodic reaction that does not result in hydrogen entry into the metal
|
|
| 3. |
- Ayagou, Martien, et al.
(författare)
-
Corrosion and hydrogen permeation in h2S environments with o2 contamination, 1 : Tests on pure iron at high h2S concentration
- 2018
-
Ingår i: Corrosion. - : National Assoc. of Corrosion Engineers International. - 0010-9312 .- 1938-159X. ; 74:11, s. 1192-1202
-
Tidskriftsartikel (refereegranskat)abstract
- Materials selection in the oil and gas industry relies on engineering standards, such as NACE TM0177 and NACE TM0284, which stipulate that oxygen pollution should be avoided during materials testing in H2S-containing media. In this paper, we explore the manner in which traces of oxygen can modify the test solution chemistry and the corrosion of/hydrogen permeation across iron membranes in H2S-containing solutions. Oxygen pollution is shown to strongly influence solution chemistry, through the introduction of sulfur-oxygen reaction products resulting in bulk acidification. Weight loss, electrochemical methods, and solution chemistry measurements conclude that iron corrosion rates in the presence of oxygen pollution are doubled, when compared against the control system (without oxygen pollution). Unexpectedly, despite a lower pH and higher corrosion rates in the oxygen-polluted H2S-containing solutions, the hydrogen permeation rate decreases monotonically, relative to the control. We discuss how this observation is most likely related to a disruption of sulfur adsorbates involved in hydrogen entry promotion.
|
|
| 4. |
- Martien, Daffo, et al.
(författare)
-
Corrosion of pure iron and hydrogen permeation in the presence of H2S with O2 contamination
- 2018
-
Ingår i: NACE - International Corrosion Conference SeriesVolume 2018-April, 2018Corrosion Conference and Expo 2018; Phoenix; United States; 15 April 2018 through 19 April 2018. - : National Assoc. of Corrosion Engineers International. - 9781510864405
-
Konferensbidrag (refereegranskat)abstract
- This paper examines the influence of traces of oxygen on corrosion and hydrogen charging of steel in an H2S containing environment. It is well known that H2S promotes hydrogen entry into steels, that may result in many types of steel failures such as Hydrogen Induced Cracking (HIC), Sulfide Stress Cracking (SSC), and Stress-Oriented Hydrogen Induced Cracking (SOHIC). Since it is a huge concern for oil and gas industries, standard test methods have been developed and published as NACE technical methods (e.g. NACE TM0284 and NACE TM0177). Though it is recognized that oxygen pollution should be avoided during H2S cracking tests, there is still a lack of experimental data to illustrate the potential impacts of a small oxygen pollution. The aim of the present study is to check if oxygen traces can modify the mechanisms of corrosion and hydrogen charging of steel in H2S containing medium. Experiments consisted of hydrogen permeation measurements through a thin pure iron membrane. They were performed at free potential circuit in order to ensure more realistic environmental conditions. The corrosion rate was also evaluated and test solutions analyzed.
|
|
| 5. |
- Martien, Duffo, et al.
(författare)
-
EIS study of iron and steel corrosion in aqueous solutions at various concentrations of dissolved H2S : Impact of oxygen contamination
- 2019
-
Ingår i: NACE - International Corrosion Conference SeriesVolume 2019-March, 2019, Article number 13041Corrosion Conference and Expo 2019; Nashville; United States; 24 March 2019 through 28 March 2019. - : National Assoc. of Corrosion Engineers International.
-
Konferensbidrag (refereegranskat)abstract
- Mildly acidic water containing dissolved H2S presents a strong risk in the cracking of low-carbon steels. Several studies on H2S cracking mechanisms have shown that the main driving force is linked to the ability of H2S to promote hydrogen entry into the bulk material. Standard test methods have been developed and published as NACE technical standards (e.g. NACE TM0284 and NACE TM0177) to aid materials selection in the oil and gas sector. Though it is recognized that oxygen pollution should be avoided during H2S cracking tests, there is a lack of experimental data to illustrate the effects of a small oxygen pollution. Dissolved oxygen concentrations greater than the recommended upper limit (50 parts per billion) can easily be obtained in the case of poor laboratory practices. This paper will focus on the interactions between oxygen and H2S on electrochemical behavior of unalloyed steel. A continuous O2 injection at a level corresponding to 500 ppb is applied, together with H2S bubbling in our test solutions, for periods lasting the same order as SSC standard tests. Steel surface reaction phenomena/corrosion rates in H2S saturated solution, with or without oxygen pollution, are studied using electrochemical impedance spectroscopy. The evolution of corrosion rates obtained from impedance analysis was compared to two other independent methods: i/ weight loss measurements and, ii/ hydrogen permeation. Without O2 pollution, a permeation efficiency of 100% was obtained, as expected. Permeation current density was thus found to match precisely with the corrosion current density determined by impedance analysis at different times. On the other hand, when a continuous O2 pollution was added in the system, significantly higher corrosion rates were observed, associated with test solution acidification. At the same time, permeation efficiency was decreased by up to one order of magnitude.
|
|
| 6. |
- Martien Duvall, Deffo, et al.
(författare)
-
Impact of oxygen on corrosion and hydrogen permeation of pure iron in the presence of H2S
- 2017
-
Ingår i: EUROCORR 2017 - The Annual Congress of the European Federation of Corrosion, 20th International Corrosion Congress and Process Safety Congress 2017. - : Asociace koroznich inzenyru z.s.- AKI - Czech Association of Corrosion Engineers.
-
Konferensbidrag (refereegranskat)abstract
- This paper examines the influence of oxygen traces on corrosion and hydrogen charging of steel in H2S containing environment. It is well known that H2S is the driving force for many types of steel failures such as hydrogen induced cracking (HIC), sulfide stress cracking (SSC), and stress-oriented hydrogen induced cracking (SOHIC). Since it is a huge concern for oil and gas industries, standard test methods have been developed and published as NACE technical methods (e.g. NACE TM0284 and NACE TM0177). Though it is recognized that oxygen pollution shall be avoided during H2S cracking tests, there is still a lack of experimental data to illustrate the potential impacts of a small oxygen pollution. The aim of the present study was to check if oxygen traces can modify corrosion mechanisms and hydrogen charging of steel in H2S medium. Experiments consisted in hydrogen permeation measurements through thin pure iron membrane. They were performed at corrosion potential in order to be in realistic environmental conditions. Corrosion rate was also evaluated through weight loss measurements. Analysis of test solutions was performed in order to identify reaction products between H2S and O2
|
|
