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Interactions between cations andorganic molecules are found throughoutnature, from the functionality and structure of proteins in humansand animals to the exchange of ions in minerals in soil and oil reservoirswith the fluid phases. We have explored the behavior of the s-blockelements that are most common in the natural world, namely, Na, K, Mg2, and Ca2. Specifically,we investigated how these ions affect the interactions between surfacescovered by self-assembled monolayers (SAMs) terminated with benzenemolecules. We used a flat oxidized silicon substrate and an atomicforce microscopy (AFM) tip that were both functionalized with 11-phenoxyundecane-1-thioland measured the adhesion force between them in solutions of eachof the four chloride salts. We observed that the adhesion increasedin the order of the Hofmeister series: K< Na≈ Mg2< Ca2. Supplementary evidencefrom X-ray photoelectron spectroscopy (XPS) allowed us to concludethat K温 in the benzene layers, creating a positivesurface charge on the benzene-covered surfaces, thus leading to loweradhesion in KCl solutions than in pure water. Evidence suggested thatCa2皇 not bind to the surfaces but forms bridges betweenthe layers, leading to higher adhesion than in pure water. In Na橷 Mg2늉溶⨧, adhesion is quite similarto that in pure water, indicating a lack of interaction between thesetwo ions and the surfaces, or at least that the interaction is tooweak to be detected by our measurements. The results of our studiesclearly show that even a nonpolar, hydrophobic molecule, such as benzene,has a role to play in the behavior of aqueous solutions and that itinteracts differently depending on which ions are present. Even ionsfrom the same column in the periodic table behave differently. [ABSTRACT FROM AUTHOR]

Abstract: From an interplay between high-resolution scanning tunneling microscopy (STM) and density functional theory (DFT) we discuss the origin of various point defects on reduced rutile TiO2(110)-(1×1) surfaces. By means of adsorption and desorption experiments using water and oxygen as probe molecules we assign the different features observed in STM images to bridging oxygen vacancies, oxygen atoms on surface Ti atoms, and single as well as pairs of hydroxyls on bridging oxygen rows. These experimental results are discussed in comparison to previous STM reports where different assignments of the STM features were suggested. Based on DFT calculations we compare the interaction of water and oxygen with the reduced TiO2(110) surface with the situation when these molecules encounter a perfect, stoichiometric TiO2(110) surface. These DFT calculations strongly support the assignments of the features observed experimentally by STM. We report on how to produce clean, reduced TiO2(110) surfaces and address criteria to ascertain cleanliness by STM. [Copyright &y& Elsevier]

The water-TiO2 interaction is of paramount importance for many processes occurring on TiO2, and the rutile TiO2(110)-(1×1) surface has often been considered as a test case. Yet, no consensus has been reached whether the well-studied surface O vacancies on the terraces are the only active sites for water dissociation on rutile TiO2(110)-(1×1), or whether another channel for the creation of H adatoms exists. Here we use high-resolution scanning tunneling microscopy and density functional theory calculations to tackle this long-standing question. Evidence is presented that a second water dissociation channel exists on the surfaces of vacuum-annealed TiO2(110) crystals that is associated with the 〈1̄11〉 step edges. This second water dissociation channel can be suppressed by blocking of the 〈1̄11〉 step edges using ethanol. [ABSTRACT FROM AUTHOR]

We studied the nucleation of gold clusters on TiO2(110) surfaces in three different oxidation states by high-resolution scanning tunneling microscopy. The three TiO2(110) supports chosen were (i) reduced (having bridging oxygen vacancies), (ii) hydrated (having bridging hydroxyl groups), and (iii) oxidized (having oxygen adatoms). At room temperature, gold nanoclusters nucleate homogeneously on the terraces of the reduced and oxidized supports, whereas on the hydrated TiO2(110) surface, clusters form preferentially at the step edges. From interplay with density functional theory calculations, we identified two different gold-TiO2(110) adhesion mechanisms for the reduced and oxidized supports. The adhesion of gold clusters is strongest on the oxidized support, and the implications of this finding for catalytic applications are discussed. [ABSTRACT FROM AUTHOR]

Recently, two genes involved in amoebic liver abscess formation in a mouse model were identified by their differential expression of non-pathogenic (A1np) and pathogenic (B2p) clones of the Entamoeba histolytica isolate HM:1-IMSS. While overexpression of a gene encoding the metallopeptidase EhMP8-2 reduces the virulence of the pathogenic clone B2p, overexpression of the gene ehi&#95;127670 (ehhp127), encoding a hypothetical protein, increases the virulence of the non-pathogenic clone A1np, while silencing this gene in the pathogenic B2p reduces virulence. To understand the role of both molecules in determining the pathogenicity of E. histolytica, silencing, and overexpression transfectants were characterized in detail. Silencing of ehmp8-2, of the homologous gene ehmp8-1, or both in non-pathogenic A1np trophozoites significantly altered the transcript levels of 347, 216, and 58 genes, respectively. This strong change in the expression profiles caused by the silencing of ehmp8-1 and ehmp8-2 implies that these peptidases regulate the expression of numerous genes. Consequently, numerous phenotypic characteristics, including cytopathic, hemolytic, and cysteine peptidase activity, were altered in response to their silencing. Silencing of ehhp127 in pathogenic B2p trophozoites did not affect the expression of other genes, whereas its overexpression in non-pathogenic A1np trophozoites results in an altered expression of approximately 140 genes. EhHP127 is important for trophozoite motility, as its silencing reduces, while its overexpression enhances movement activity. Interestingly, the specific silencing of ehhp127 also significantly affects cytopathic, cysteine peptidase, and hemolytic activities. All three molecules characterized in this study, namely EhMP8-1, EhMP8-2, and EhHP127, are present in amoeba vesicles. The results show that ehmp8-2 and ehhp127 are not only differentially expressed between pathogenic and non-pathogenic amoebae, but that they also significantly affect amoeba pathogenicity-associated phenotypes by completely different mechanisms. This observation suggests that the regulation of amoeba pathogenicity is achieved by a complex network of molecular mechanisms rather than by single factors., Competing Interests: The authors have declared that no competing interest exist., (Copyright: © 2023 Anders et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Recently, a putative alcohol dehydrogenase 3, termed EhADH3B of the Entamoeba histolytica isolate HM-1:IMSS was identified, which is expressed at higher levels in non-pathogenic than in pathogenic amoebae and whose overexpression reduces the virulence of pathogenic amoebae. In an in silico analysis performed in this study, we assigned EhADH3B to a four-member ADH3 family, with ehadh3b present as a duplicate ( ehadh3b a / ehadh3b b ). In long-term laboratory cultures a mutation was identified at position 496 of ehadh3b a , which codes for a stop codon, which was not the case for amoebae isolated from human stool samples. When using transfectants that overexpress or silence ehadh3b b , we found no or little effect on growth, size, erythrophagocytosis, motility, hemolytic or cysteine peptidase activity. Biochemical characterization of the recombinant EhADH3B b revealed that this protein forms a dimer containing Ni 2+ or Zn 2+ as a co-factor and that the enzyme converts acetaldehyde and formaldehyde in the presence of NADPH. A catalytic activity based on alcohols as substrates was not detected. Based on the results, we postulate that EhADH3B b can reduce free acetaldehyde released by hydrolysis from bifunctional acetaldehyde/alcohol dehydrogenase-bound thiohemiacetal and that it is involved in detoxification of toxic aldehydes produced by the host or the gut microbiota.