Fungi with history: Unveiling the mycobiota of historic documents of Costa Rica.

We studied the physicochemical characteristics and mycobiota associated to five key historic documents from Costa Rica, including the Independence Act of Costa Rica from 1821. We used nondestructive techniques (i.e., ATR-FTIR and XRF) to determine paper and ink composition. Results show that some documents are composed of cotton-based paper, whereas others were made of wood cellulose with an increased lignin content. We also determined that the ink employed in some of the documents is ferrogallic. Cultivation and molecular techniques were used to characterize the fungi inhabiting the documents. In total, 22 fungal isolates were obtained: 15 from the wood-cellulose-based documents and seven from the other three cotton-based. We also tested the cellulolytic activity of the recovered fungi; 95% of the fungi presented cellulolytic activity correlated to their ability to cause deterioration of the paper. Results suggest that cotton-based paper is the most resistant to fungal colonization and that most of the isolates have cellulolytic activity. This work increases the knowledge of the fungal diversity that inhabits historic documents and its relationship with paper composition and provides valuable information to develop strategies to conserve and restore these invaluable documents.

Influence of surface roughness on the spectroscopic characterization of jadeite and greenstones archaeological artifacts: The axe-god pendants case study.

Spectroscopic techniques are commonly used for the non-invasive characterization of the molecular and elemental composition of greenstone archaeological artifacts. The surface topography of these artifacts is greatly influenced by the crafting and polishing techniques employed in their making. However, no study of the effect of roughness on spectra has ever been reported for greenstones. Here we show that infrared, Raman and X-ray fluorescence spectra are strongly influenced by the sample's surface roughness. Spectral changes were seen in both geological (45 jadeite and green stone samples) and archaeological artifacts (12 axe-God pendants); in every case, the variations were more prominent in samples with higher arithmetic average height values. The results show that these changes can affect the interpretation of the spectroscopic data and limit the efficacy of statistical analysis. Consequently, any spectroscopic characterization of this type of samples should be performed preferably in areas with lower values of roughness parameters. Overall, FT-IR appears to be the most advantageous technique to distinguish the differences in mineral composition of this type of samples during in situ studies; its performance was evaluated with an innovative statistical analysis that treats the spectra as functional data. Additionally, the results suggest that confocal Raman spectroscopy is an ideal complementary technique that enhances mineralogical characterization, nevertheless its applicability is limited to laboratory settings.

Structural and functional role of anions in electrochemical water oxidation probed by arsenate incorporation into cobalt-oxide materials.

Direct (photo)electrochemical production of non-fossil fuels from water and CO2 requires water-oxidation catalysis at near-neutral pH in the presence of appropriate anions that serve as proton acceptors. We investigate the largely enigmatic structural role of anions in water oxidation for the prominent cobalt-phosphate catalyst (CoCat), an amorphous and hydrated oxide material. Co3([(P/As)O]4)2·8H2O served, in conjunction with phosphate-arsenate exchange, as a synthetic model system. Its structural transformation was induced by prolonged operation at catalytic potentials and probed by X-ray absorption spectroscopy not only at the metal (Co), but for the first time also at the anion (As) K-edge. For initially isostructural microcrystals, anion exchange determined the amorphization process and final structure. Comparison to amorphous electrodeposited Co oxide revealed that in CoCat, the arsenate binds not only at oxide-layer edges, but also arsenic substitutes cobalt positions within the layered-oxide structure in an unusual AsO6 coordination. Our results show that in water oxidation catalysis at near-neutral pH, anion type and exchange dynamics correlate with the catalyst structure and redox properties.

Comparison of the adjuvant activity of aluminum hydroxide and calcium phosphate on the antibody response towards Bothrops asper snake venom.

The adjuvanticity of aluminum hydroxide and calcium phosphate on the antibody response in mice towards the venom of the snake Bothrops asper was studied. It was found that, in vitro, most of the venom proteins are similarly adsorbed by both mineral salts, with the exception of some basic phospholipases A2, which are better adsorbed by calcium phosphate. After injection, the adjuvants promoted a slow release of the venom, as judged by the lack of acute toxicity when lethal doses of venom were administered to mice. Leukocyte recruitment induced by the venom was enhanced when it was adsorbed on both mineral salts; however, venom adsorbed on calcium phosphate induced a higher antibody response towards all tested HPLC fractions of the venom. On the other hand, co-precipitation of venom with calcium phosphate was the best strategy for increasing: (1) the capacity of the salt to couple venom proteins in vitro; (2) the venom ability to induce leukocyte recruitment; (3) phagocytosis by macrophages; and (4) a host antibody response. These findings suggest that the chemical nature is not the only one determining factor of the adjuvant activity of mineral salts.