Manganese oxides are considered an essential component of natural geochemical barriers due to their redox and sorptive reactivity towards essential and potentially toxic trace elements. Despite the perception that they are in a relatively stable phase, microorganisms can actively alter the prevailing conditions in their microenvironment and initiate the dissolution of minerals, a process that is governed by various direct (enzymatic) or indirect mechanisms. Microorganisms are also capable of precipitating the bioavailable manganese ions via redox transformations into biogenic minerals, including manganese oxides (e.g., low-crystalline birnessite) or oxalates. Microbially mediated transformation influences the (bio)geochemistry of manganese and also the environmental chemistry of elements intimately associated with its oxides. Therefore, the biodeterioration of manganese-bearing phases and the subsequent biologically induced precipitation of new biogenic minerals may inevitably and severely impact the environment. This review highlights and discusses the role of microbially induced or catalyzed processes that affect the transformation of manganese oxides in the environment as relevant to the function of geochemical barriers.
- MeSH
- mangan * chemie MeSH
- minerály chemie MeSH
- oxidace-redukce MeSH
- oxidy * chemie MeSH
- sloučeniny manganu chemie MeSH
- životní prostředí MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Inhibition of the human O-linked β-N-acetylglucosaminidase (hOGA, GH84) enzyme is pharmacologically relevant in several diseases such as neurodegenerative and cardiovascular disorders, type 2 diabetes, and cancer. Human lysosomal hexosaminidases (hHexA and hHexB, GH20) are mechanistically related enzymes; therefore, selective inhibition of these enzymes is crucial in terms of potential applications. In order to extend the structure-activity relationships of OGA inhibitors, a series of 2-acetamido-2-deoxy-d-glucono-1,5-lactone sulfonylhydrazones was prepared from d-glucosamine. The synthetic sequence involved condensation of N-acetyl-3,4,6-tri-O-acetyl-d-glucosamine with arenesulfonylhydrazines, followed by MnO2 oxidation to the corresponding glucono-1,5-lactone sulfonylhydrazones. Removal of the O-acetyl protecting groups by NH3/MeOH furnished the test compounds. Evaluation of these compounds by enzyme kinetic methods against hOGA and hHexB revealed potent nanomolar competitive inhibition of both enzymes, with no significant selectivity towards either. The most efficient inhibitor of hOGA was 2-acetamido-2-deoxy-d-glucono-1,5-lactone 1-naphthalenesulfonylhydrazone (5f, Ki = 27 nM). This compound had a Ki of 6.8 nM towards hHexB. To assess the binding mode of these inhibitors to hOGA, computational studies (Prime protein-ligand refinement and QM/MM optimizations) were performed, which suggested the binding preference of the glucono-1,5-lactone sulfonylhydrazones in an s-cis conformation for all test compounds.
- MeSH
- antigeny nádorové chemie metabolismus MeSH
- beta-hexosaminidasa, beta řetězec chemie metabolismus MeSH
- histonacetyltransferasy chemie metabolismus MeSH
- hyaluronoglukosaminidasa chemie metabolismus MeSH
- hydrazony chemická syntéza chemie farmakologie MeSH
- inhibitory enzymů chemická syntéza chemie farmakologie MeSH
- laktony chemie MeSH
- lidé MeSH
- molekulární konformace MeSH
- molekulární modely MeSH
- oxidy chemie MeSH
- sloučeniny manganu chemie MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Nanostructured titanium(IV) oxide was used for the destructive adsorption and photocatalytic degradation of mitoxantrone (MTX), a cytostatic drug from the group of anthracycline antibiotics. During adsorption on a titania dioxide surface, four degradation products of MTX, mitoxantrone dicarboxylic acid, 1,4-dihydroxy-5-((2-((2-hydroxyethyl)amino)ethyl)amino)-8-((2-(methylamino)ethyl)amino)anthracene-9,10-dione, 1,4-dihydroxy-5,8-diiminoanthracene-9,10(5H,8H)-dione and 1,4-dihydroxy-5-imino-8-(methyleneamino)anthracene-9,10(5H,8H)-dione, were identified. In the case of photocatalytic degradation, only one degradation product after 15 min at m/z 472 was identified. This degradation product corresponded to mitoxantrone dicarboxylic acid, and complete mineralization was attained in one hour. Destructive adsorbent manganese(IV) oxide, MnO2, was used only for the destructive adsorption of MTX. Destructive adsorption occurred only for one degradation product, mitoxantrone dicarboxylic acid, against anatase TiO2.
Nano zero-valent iron (nZVI) is currently investigated as a stabilising amendment for contaminated soils. The effect of pH (4-8) and time (48 and 192 h) on the behaviour of nZVI-treated Pb-Zn and As-contaminated soil samples was assessed. Additionally, soil leachates were subsequently used to study the direct interaction between soil solution components and nZVI particles in terms of mineralogical changes and contaminant retention. A typical U-shaped leaching trend as a function of pH was observed for Cd, Pb and Zn, while As was released predominantly under alkaline conditions. Oxidising conditions prevailed, so pH was the key controlling parameter rather than redox conditions. Generally, longer contact time resulted in increased soluble concentrations of metal(loid)s. However, the stabilisation effect of nZVI was only observed after the direct soil leachate-nZVI interactions, showing enhanced redox and sorption processes for the studied metals. A significant decrease of dissolved As concentrations was observed for both experimental soils, but with different efficiencies depending on neutralisation capacity, organic matter content or solid fractionation of As related to the origin of the soils. Scorodite (FeAsO4·2H2O) was predicted as a potential solubility-controlling mineral phase for As. Sorption of metal(loid)s onto secondary Fe- and Al-(oxyhydr)oxides (predicted to precipitate at pH > 5) represents an important scavenger mechanism. Moreover, transmission electron microscopy confirmed the retention of Zn and Pb under near-neutral and alkaline conditions by newly formed Fe oxides or aluminosilicates. This study shows that the efficiency of nZVI application strongly depends not only on soil pH-Eh conditions and contaminant type, but also on the presence of organic matter and other compounds such as Al/Fe/Mn oxyhydroxides and clay minerals.
- MeSH
- arsen analýza chemie MeSH
- časové faktory MeSH
- kadmium analýza chemie MeSH
- koncentrace vodíkových iontů MeSH
- látky znečišťující půdu chemie MeSH
- minerály chemie MeSH
- nanostruktury chemie MeSH
- olovo analýza chemie MeSH
- oxid hlinitý chemie MeSH
- oxidy chemie MeSH
- regenerace a remediace životního prostředí MeSH
- silikáty hliníku MeSH
- sloučeniny manganu chemie MeSH
- těžké kovy analýza chemie MeSH
- železo chemie MeSH
- zinek analýza chemie MeSH
- znečištění životního prostředí MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Česká republika MeSH
An amorphous Mn oxide (AMO), nanomaghemite, and nanomagnetite were used as potential amendments reducing the mobility of As in three contrasting contaminated soils differing in origin of As contamination. Adsorption experiments and XPS analyses combined with incubation batch experiments and pH-static leaching tests were used. The AMO showed excellent adsorption capacity for As(V) reaching a maximum of 1.79 mmol g(-1) at pH 7 and 8. Interestingly, the adsorption capacity in this case decreases with decreasing pH, probably as a result of AMO dissolution at lower pH values. Chemical sorption of As(V) onto AMO was further confirmed with XPS. Both Fe nano-oxides proved the highest adsorption capacity at pH 4 reaching 11 mg g(-1) of adsorbed As(V). The AMO was also the most efficient amendment for decreasing As concentrations in soil solutions during 8 weeks of incubation. Additionally, pH-static leaching tests were performed at pH 4, 5, 6, 7, and natural pH (not adjusted) and AMO again proved the highest ability to decrease As content in leachate. On the other hand, strong dissolution of this amendment at lower pH values (especially pH 4) was observed. For that reason, AMO appears as a promising stabilizing agent for As, especially in neutral, alkaline, or slightly acidic soils, where As(V) species are expected to be more mobile.
- MeSH
- adsorpce MeSH
- arsen analýza chemie MeSH
- kinetika MeSH
- koncentrace vodíkových iontů MeSH
- látky znečišťující půdu analýza chemie MeSH
- nanočástice chemie MeSH
- oxidy chemie MeSH
- půda chemie MeSH
- regenerace a remediace životního prostředí MeSH
- sloučeniny manganu chemie MeSH
- železité sloučeniny chemie MeSH
- znečištění životního prostředí analýza MeSH
- Publikační typ
- časopisecké články MeSH
Microporous Na-birnessite-type manganese oxides are synthesized by oxidation of Mn(OH)2 with K2S2O8 in strong alkaline environment. Subsequent ion-exchange reactions in aqueous solutions containing Sr, Ba promote their incorporation into the layered structural frameworks, which upon further hydration lead to the respective layered Buserites. Chemical composition and surface structure are assessed by X-ray powder diffraction, nitrogen- and argon- sorptiometry. Na-birnessites and Sr-buserites display good crystallinity. Ba-buserites consist mainly of nanocrystals. Their N2 adsorption/desorption isotherms of resemble IV-type isotherms. Integral and differential pore distribution curves obtained by N2-sorptiometry exhibit out-of-layers pores of 4-5 nm and 10-20 nm. Na-birnessites, Sr- and Ba-buserites possess external B.E.T surfaces of 75.6, 49.2 and 93.6 m2/g respectively. Considerable adsorption volumes of 14, 17 cm3/g for P/P0 = 0.05 for Na-birnessites and Ba-buserites are assessed by Ar-sorptiometry. Differential pore distribution curves confirm inner-layer micropores of 5 to 7 Å with a B.E.T specific area of 76.2 m²/g for Na-birnessites and 51.8 m²/g for Ba-buserites. Na-birnessites and Sr-, Ba-buserites possess enhanced ionic exchanging capacity, acting as a “sink” for heavy metal cations such as Fe2+, Fe3+, Co2+, Ni2+, As3+. The retention of U, Cs and Sr radioisotopes by them unfolds their salient anti-pollution potential for soil and subwater ecosystems.
- MeSH
- adsorpce MeSH
- baryum chemie MeSH
- difrakce rentgenového záření MeSH
- iontová výměna MeSH
- kationty MeSH
- minerály * chemie MeSH
- oxidy * chemická syntéza chemie MeSH
- povrchové vlastnosti MeSH
- sloučeniny manganu * chemie MeSH
- sodík chemie MeSH
- stroncium chemie MeSH
- Publikační typ
- práce podpořená grantem MeSH
Various low-molecular-weight organic acids (LMWOAs) play an important role in the mobilisation of contaminants and their subsequent uptake by plants. Nano-maghemite (NM) and an amorphous Mn oxide (AMO) were investigated for their stabilisation potential under simulated rhizosphere conditions in terms of their use during chemical stabilisation and aided phytostabilisation of metal(loid)s in contaminated soils. In order to understand the reactivity of these potential sorbents of contaminants in soils and subsequent mobility of metal(loid)s, a set of time-dependent batch leaching experiments was performed using a mix of acetic, lactic, citric, malic and formic acids simulating root exudates. Despite being relatively unstable under given conditions, the AMO proved to be an efficient amendment for rapid stabilisation of both metals and As compared to NM. Generally, low pH (∼ 4) and the presence of citrate complexes resulted in higher mobility of metals in the non- and NM-amended soil. In contrast, the presence of AMO in the soil accelerated the neutralisation reactions related to pH increase and (co-) precipitation of secondary Fe/Mn/Al oxyhydroxides. Mineralogical transformations of the AMO showed to be crucial for contaminant immobilisation.
- MeSH
- arsen chemie MeSH
- kovové nanočástice chemie MeSH
- kovy chemie MeSH
- kyseliny karboxylové chemie MeSH
- látky znečišťující půdu chemie MeSH
- molekulová hmotnost MeSH
- oxidy chemie MeSH
- sloučeniny manganu chemie MeSH
- železité sloučeniny chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
An amorphous manganese oxide (AMO) and a Pb smelter-polluted agricultural soil amended with the AMO and incubated for 2 and 6 months were subjected to a pH-static leaching procedure (pH 3-8) to verify the chemical stabilization effect on metals and metalloids. The AMO stability in pure water was pH-dependent with the highest Mn release at pH 3 (47% dissolved) and the lowest at pH 8 (0.14% dissolved). Secondary rhodochrosite (MnCO3) was formed at the AMO surfaces at pH>5. The AMO dissolved significantly less after 6 months of incubation. Sequential extraction analysis indicated that "labile" fraction of As, Pb and Sb in soil significantly decreased after AMO amendment. The pH-static experiments indicated that no effect on leaching was observed for Cd and Zn after AMO treatments, whereas the leaching of As, Cu, Pb and Sb decreased down to 20%, 35%, 7% and 11% of the control, respectively. The remediation efficiency was more pronounced under acidic conditions and the time of incubation generally led to increased retention of the targeted contaminants. The AMO was found to be a promising agent for the chemical stabilization of polluted soils.
- MeSH
- arsen chemie MeSH
- hutnictví MeSH
- koncentrace vodíkových iontů MeSH
- látky znečišťující půdu chemie MeSH
- nakládání s odpady MeSH
- oxidy chemie MeSH
- průmyslový odpad MeSH
- regenerace a remediace životního prostředí MeSH
- sloučeniny manganu chemie MeSH
- těžké kovy chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The potential of three Fe- and Mn-(nano)oxides for stabilizing Cd, Cu and Pb in contaminated soils was investigated using batch and column experiments, adsorption tests and tests of soil microbial activity. A novel synthetic amorphous Mn oxide (AMO), which was recently proposed as a stabilizing amendment, proved to be the most efficient in decreasing the mobility of the studied metals compared to nano-maghemite and nano-magnetite. Its application resulted in significant decreases of exchangeable metal fractions (92%, 92% and 93% decreases of Cd, Cu and Pb concentrations, respectively). The adsorption capacity of the AMO was an order of magnitude higher than those recorded for the other amendments. It was also the most efficient treatment for reducing Cu concentrations in the soil solution. No negative effects on soil microorganisms were recorded. On the other hand, the AMO was able to dissolve soil organic matter to some extent.
- MeSH
- adsorpce MeSH
- dekontaminace MeSH
- kadmium chemie MeSH
- látky znečišťující půdu chemie MeSH
- lidé MeSH
- měď chemie MeSH
- olovo chemie MeSH
- oxidy chemie MeSH
- sloučeniny manganu chemie MeSH
- těžké kovy chemie MeSH
- znečištění životního prostředí prevence a kontrola MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- hodnotící studie MeSH
- práce podpořená grantem MeSH
Three magnetic resonance (MR)/fluorescence imaging probes were tested for visualization, cellular distribution, and survival of labeled pancreatic islets in vitro and following transplantation. As T(1) contrast agents (CAs), gadolinium(III) complexes linked to β-cyclodextrin (Gd-F-βCD) or bound to titanium dioxide (TiO2 @RhdGd) were tested. As a T(2) CA, perovskite manganite nanoparticles (LSMO@siF@si) were examined. Fluorescein or rhodamine was incorporated as a fluorescent marker in all probes. Islets labeled with gadolinium(III) CAs were visible as hyperintense spots on MR in vitro, but detection in vivo was inconclusive. Islets labeled with LSMO@siF@si CA were clearly visible as hypointense spots or areas on MR scans in vitro as well as in vivo. All CAs were detected inside the islet cells by fluorescence. Although the vitality and function of the labeled islets was not impaired by any of the tested CAs, results indicate that LSMO@siF@si CA is a superior marker for islet labeling, as it provides better contrast enhancement within a shorter scan time.
- MeSH
- beta-cyklodextriny chemie MeSH
- fluorescenční barviva chemie MeSH
- fluorescenční mikroskopie MeSH
- gadolinium chemie MeSH
- kontrastní látky chemie diagnostické užití MeSH
- kovové nanočástice chemie diagnostické užití MeSH
- krysa rodu rattus MeSH
- kultivované buňky MeSH
- Langerhansovy ostrůvky cytologie metabolismus radiografie MeSH
- magnetická rezonanční tomografie MeSH
- potkani inbrední LEW MeSH
- sloučeniny manganu chemie MeSH
- titan chemie MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
