Diagnostic features of EPR spectra of superoxide intermediates on catalytic surfaces and molecular interpretation of their g and A tensors

The use of electron paramagnetic resonance spectroscopy to study the superoxide intermediates, generated by end-on and side-on adsorption of the naturally abundant and 17O-enriched dioxygen on catalytic surfaces is discussed. Basic mechanisms of O2 − radical formation via a cationic redox mechanism, an anionic redox mechanism, and an electroprotic mechanism are illustrated with selected oxide-based systems of catalytic relevance. Representative experimental spectra of various complexities are analyzed and their diagnostic features have been identified and interpreted. The molecular nature of the g and A tensors of the electrostatic and covalent superoxide adducts is discussed in detail within the classic and density functional theory based approaches

Interaction of hydrogen peroxide with amorphous oxides of d0 metals

Celem pracy była identyfikacja reaktywnych form tlenu powstających podczas rozkładu nadtlenku wodoru katalizowanego na powierzchniach amorficznych materiałów tlenkowych. Do badań wybrano tlenki Nb2O5, Ta2O5, TiO2, ZrO2, które zsyntezowano w procesie zol-żel. Otrzymane materiały zbadano pod kątem składu chemicznego (XRF), fazowego (XRD, Raman) oraz potencjału dzeta. Amorficzne formy tlenków poddano reakcji z H2O2 w warunkach kontrolowanego pH. Produkty reakcji badano metodami EPR i Ramana. Ustalono, że w zależności od pH roztworu rozkład H2O2 na amorficznych tlenkach prowadzi do utworzenia rodników ponadtlenkowych (pH zbliżone do wartości punktu izoelektrycznego) lub grup nadtlenowych (pH powyżej punktu izoelektrycznego). Powierzchniowe rodniki ponadtlenkowe charakteryzują się dużą trwałością kinetyczną z czasem połowicznego zaniku rzędu kilku dni. Zastosowanie pułapki spinowej DMPO pozwoliło na identyfikację rodników O2-• i OH• w roztworze nad katalizatorem. Krystaliczne formy badanych tlenków okazały się nieaktywne w procesie rozkładu. Ustalono, że opisywany rozkład H2O2 zachodzi na drodze reakcji elektroprotycznych, w których kluczową rolę odgrywają kwasowo-zasadowe właściwości powierzchni amorficznych tlenków.The aim of this study was to identify the reactive oxygen species generated during the decomposition of hydrogen peroxide catalyzed on the surface of amorphous oxide materials. Selected oxides including Nb2O5, Ta2O5, TiO2, and ZrO2 were synthesized by the sol-gel method. The resulting materials were tested for chemical composition (XRF), phase composition (XRD, Raman), and zeta potential. The amorphous forms of the oxides were examined in the reaction with H2O2 under controlled pH. The reaction products were studied by EPR and Raman spectroscopies. It was found that depending on the pH of the solution, H2O2 decomposition led to the formation of superoxide radicals (pH close to the isoelectric point) or peroxide groups (pH above the isoelectric point). Surface superoxide radicals exhibited high kinetic stability with a half-life time of several days. The use of the DMPO spin trap allowed for identification of the O2-• and OH• radicals in the solution. Crystalline forms of the studied oxides proved to be inactive in the process of H2O2 decomposition. It was found that the decomposition of H2O2 occurred via electroprotic reactions, in which the key role played the acid-base properties of the surface of the amorphous oxides

The Role of ERG11 Point Mutations in the Resistance of Candida albicans to Fluconazole in the Presence of Lactate

Candidiasis refers to both superficial and deep-tissue fungal infections often caused by Candida albicans. The treatment of choice for these infections is the use of azoles, such as fluconazole (FLC). However, the increased use of antifungal agents has led to the emergence of azole-resistant isolates of C. albicans. Thus, the development of alternative drugs that are more efficient and with a better toxicological profile is necessary. This study aimed to determine the susceptibility profile of C. albicans CAF2-1 strain to FLC in the presence of glucose or lactate. The research was also focused on single nucleotide polymorphism (SNP) and the determination of the effect of the identified point mutations on the amino acid sequence of the Erg11 protein. The results show the growth of C. albicans CAF2-1 in the presence of FLC was significantly lower in the presence of lactate than in glucose. As a result, among recorded 45 amino acid mutations, the following mutations may be associated with the reduced susceptibility of C. albicans to FLC: G10D, G10V, I11M, I11R, Y13N, F31V, L35F, A249D, Q250H, E266G, R267G, N273K, D275C, D275G, D275R. Moreover, a twice higher number of hot-spot mutations was found in the presence of glucose as a sole carbon source compared to cells grown on lactate

New Insights into Psoriasis

Psoriasis is a chronic inflammatory skin disease with many comorbidities resulting from not only local but also systemic inflammation [...

The Role of Ergosterol and Sphingolipids in the Localization and Activity of <i>Candida albicans</i>’ Multidrug Transporter Cdr1p and Plasma Membrane ATPase Pma1p

Opportunistic pathogen Candida albicans causes systemic infections named candidiasis. Due to the increasing number of multi-drug resistant clinical isolates of Candida sp., currently employed antifungals (e.g., azoles) are insufficient for combating fungal infection. One of the resistance mechanisms toward azoles is increased expression of plasma membrane (PM) transporters (e.g., Cdr1p), and such an effect was observed in C. albicans clinical isolates. At the same time, it has been proven that a decrease in PMs sphingolipids (SLs) content correlates with altered sensitivity to azoles and diminished Cdr1p levels. This indicates an important role for SL in maintaining the properties of PM and gaining resistance to antifungal agents. Here, we prove using a novel spot variation fluorescence correlation spectroscopy (svFCS) technique that CaCdr1p localizes in detergent resistant microdomains (DRMs). Immunoblot analysis confirmed the localization of CaCdr1p in DRMs fraction in both the C. albicans WT and erg11Δ/Δ strains after 14 and 24 h of culture. We also show that the C. albicanserg11Δ/Δ strain is more sensitive to the inhibitor of SLs synthesis; aureobasidin A (AbA). AbA treatment leads to a diminished amount of SLs in C. albicans WT and erg11Δ/Δ PM, while, for C. albicanserg11Δ/Δ, the general levels of mannose-inositol-P-ceramide and inositol-P-ceramide are significantly lower than for the C. albicans WT strain. Simultaneously, the level of ergosterol in the C. albicans WT strain after adding of AbA remains unchanged, compared to the control conditions. Analysis of PM permeabilization revealed that treatment with AbA correlates with the disruption of PM integrity in C. albicanserg11Δ/Δ but not in the C. albicans WT strain. Additionally, in the C. albicans WT strain, we observed lower activity of H+-ATPase, correlated with the delocalization of both CaCdr1p and CaPma1p

Occurrence of plant hormones in composts made from organic fraction of agri-food industry waste

Abstract Utilizing the organic fraction of agri-food industry waste for fertilization represents one approach to waste management, with composting emerging as a popular method. Composts derived from this waste may contain plant hormones alongside primary macronutrients. This study aimed to evaluate the content of plant hormones in composts crafted from the organic fraction of agri-food industry waste. The presence of these substances was ascertained using liquid chromatography–mass spectrometry (LC-MS) analysis, applied to extracted samples from three composts produced in a bioreactor and three obtained from companies. The results indicate the presence of 35 compounds, which belong to six types of plant hormones: auxins, cytokinins, gibberellins, brassinosteroids, abscisic acid, and salicylic acid, in composts for the first time. The highest amount of plant hormones was noted in buckwheat husk and biohumus extract (35 compounds), and the lowest in hemp chaff and apple pomace (14 compounds). Brassinosteroids (e.g., brassinolide, 28-homobrassinolide, 24-epicastasterone, 24-epibrassinolide, and 28-norbrassinolide) and auxins (e.g., indolilo-3-acetic acid) are dominant. The highest concentration of total phytohormones was reported in biohumus extract (2026.42 ng g−1 dry weight), and the lowest in organic compost (0.18 ng g−1 dry weight)

Fluconazole and Lipopeptide Surfactin Interplay During Candida albicans Plasma Membrane and Cell Wall Remodeling Increases Fungal Immune System Exposure

Recognizing the &beta;-glucan component of the Candida albicans cell wall is a necessary step involved in host immune system recognition. Compounds that result in exposed &beta;-glucan recognizable to the immune system could be valuable antifungal drugs. Antifungal development is especially important because fungi are becoming increasingly drug resistant. This study demonstrates that lipopeptide, surfactin, unmasks &beta;-glucan when the C. albicans cells lack ergosterol. This observation also holds when ergosterol is depleted by fluconazole. Surfactin does not enhance the effects of local chitin accumulation in the presence of fluconazole. Expression of the CHS3 gene, encoding a gene product resulting in 80% of cellular chitin, is downregulated. C. albicans exposure to fluconazole changes the composition and structure of the fungal plasma membrane. At the same time, the fungal cell wall is altered and remodeled in a way that makes the fungi susceptible to surfactin. In silico studies show that surfactin can form a complex with &beta;-glucan. Surfactin forms a less stable complex with chitin, which in combination with lowering chitin synthesis, could be a second anti-fungal mechanism of action of this lipopeptide