The Natural History and Science Museum of the University of Porto houses a collection of 45 models of fungi in papier-mâché from the 19th-century, which were used at the university until 2015 as ...didactic models. For the first time, the materials and techniques used in the production of a
model were studied (vernacular name: cep, porcini). These sculptures, made to life-size scale, are painted in colors similar to those of the represented species (white, brown, and light brown). They are fixed to a rectangular base, which is painted black, and to which moss has been pasted. To fully characterize each color, at the molecular level, a multi-analytical approach was used, combining energy-dispersive x-ray fluorescence spectroscopy (micro-XRF) with fingerprinting techniques of Raman microscopy (microRaman and handheld Raman) spectroscopy and microFourier transform infrared spectroscopy (microFTIR). The papier-mâché was prepared with a groundwood paper to which kaolin and a quartz-based material have been added to reinforce the structure. Raman microscopy also identified carbon black in it, which is possibly responsible for its grey color. The white color was unequivocally identified as lithopone by microRaman. This white paint was prepared in a proteinaceous tempera, with calcium carbonate having been identified as filler (by microFTIR). In the brown color, iron was identified by microXRF, pointing to the use of ocher, which was not possible to identify by microRaman and microFTIR. Regarding the black rectangular base, the moss was fixed using a collagen-based glue. The binding medium in this black is possibly a mixture of drying oil and protein. Again, XRF detected iron as the main element, but it was not possible to acquire a Raman spectrum due to the high fluorescence of the binder/varnish. Others, such as the writing inks, will also be discussed. The colors identified are in line with the best materials available for use by artists of that time. This new knowledge is fundamental to informing the choice of the best conservation strategies for the preservation of these extraordinary models.
Antimicrobial resistance (AMR) is considered one of the greatest threats to global health. Methicillin-resistant
(MRSA) remains at the core of this threat, accounting for about 90% of
infections ...widespread in the community and hospital settings. In recent years, the use of nanoparticles (NPs) has emerged as a promising strategy to treat MRSA infections. NPs can act directly as antibacterial agents via antibiotic-independent activity and/or serve as drug delivery systems (DDSs), releasing loaded antibiotics. Nonetheless, directing NPs to the infection site is fundamental for effective MRSA treatment so that highly concentrated therapeutic agents are delivered to the infection site while directly reducing the toxicity to healthy human cells. This leads to decreased AMR emergence and less disturbance of the individual's healthy microbiota. Hence, this review compiles and discusses the scientific evidence related to targeted NPs developed for MRSA treatment.
The high rates of morbidity and mortality caused by fungal infections are associated with the current limited antifungal arsenal and the high toxicity of the compounds. Additionally, identifying ...novel drug targets is challenging because there are many similarities between fungal and human cells. The most common antifungal targets include fungal RNA synthesis and cell wall and membrane components, though new antifungal targets are being investigated. Nonetheless, fungi have developed resistance mechanisms, such as overexpression of efflux pump proteins and biofilm formation, emphasizing the importance of understanding these mechanisms. To address these problems, different approaches to preventing and treating fungal diseases are described in this review, with a focus on the resistance mechanisms of fungi, with the goal of developing efficient strategies to overcoming and preventing resistance as well as new advances in antifungal therapy. Due to the limited antifungal arsenal, researchers have sought to improve treatment via different approaches, and the synergistic effect obtained by the combination of antifungals contributes to reducing toxicity and could be an alternative for treatment. Another important issue is the development of new formulations for antifungal agents, and interest in nanoparticles as new types of carriers of antifungal drugs has increased. In addition, modifications to the chemical structures of traditional antifungals have improved their activity and pharmacokinetic parameters. Moreover, a different approach to preventing and treating fungal diseases is immunotherapy, which involves different mechanisms, such as vaccines, activation of the immune response and inducing the production of host antimicrobial molecules. Finally, the use of a mini-host has been encouraging for
testing because these animal models demonstrate a good correlation with the mammalian model; they also increase the speediness of as well as facilitate the preliminary testing of new antifungal agents. In general, many years are required from discovery of a new antifungal to clinical use. However, the development of new antifungal strategies will reduce the therapeutic time and/or increase the quality of life of patients.
Brazilwood Reds: The (Photo)Chemistry of Brazilin and Brazilein Rondão, Raquel; Seixas de Melo, J. Sérgio; Pina, João ...
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
10/2013, Letnik:
117, Številka:
41
Journal Article
Recenzirano
The ground and excited state (in the singlet state, S1) acid–base equilibria, together with the photophysical properties of the two main constituents of brazilwood, brazilin and brazilein, have been ...investigated in aqueous solutions in the pH range: −1 < pH < 10. Brazilin is the colorless reduced form of brazilein where three ground and three excited state species (BredH n , with n = 2–4 representing the protonated hydroxyl groups) are observed with two corresponding acidity constants: pK a1 = 6.6 and pK a2 = 9.4 (pK a1 * = 4.7 and pK a2 * = 9.9, obtained from the Förster cycle). In the case of brazilein, three ground species (pK a1 = 6.5 and pK a2 = 9.5) and four excited state species were identified (again from the Förster cycle: pK a1 * = 3.9 and pK a2 * = 9.8). The colorless species (brazilin) presents a high fluorescence quantum yield (ϕF = 0.33) and competitive radiative channel (k F = 1.3 × 109 s–1) over radiationless processes (k NR = 2.6 × 109 s–1). In contrast to this behavior, brazilein displays a ϕF value 2 orders of magnitude lower and a dominance of the radiationless decay pathways, which is suggested to be linked to an excited state proton transfer leading to a quinoidal-like structure. This is further supported by time-resolved data (obtained in a ps time domain). The overall data indicates that brazilin is more prone to degradation than brazilein, mainly due to the high efficiency of the radiationless decay channel (likely through internal conversion), which confers a stabilizing inherent characteristic to the latter. In the case of brazilein, the efficiency of the radiationless channel is linked to an excited state intramolecular proton transfer resulting from an excited state equilibrium involving neutral and zwitterionic tautomeric species of this compound. Furthermore, a theoretical study has been performed with the determination of the optimized ground-state and excited molecular geometries for the two compounds together with the prediction of the lowest vertical one-electron excitation energy and the relevant molecular orbital contours and charge densities changes using density functional theory calculations. These were found to corroborate differences in acidity in the ground and excited states.
A careful analytical study of the paint materials used in medieval illuminated manuscripts and their respective formulations is critical to their preservation. Due to their high value and fragile ...nature, access to these objects is often limited. Therefore, the development of ad‐hoc methodologies allowing researchers to collect data in the least invasive way possible is an essential task in conservation science. This article shows the potential of a combined approach that complements handheld Raman spectroscopy with micro‐SORS for the characterization of medieval paints. This methodology was tested on a reference collection of mock‐up samples prepared as pure, mixture, and layered paints on parchment, based on historical information regarding paint formulations from Iberian scriptoria. Conventional Raman analysis, carried out by means of two handheld spectrometers, was found particularly effective for materials identification in pure paints and multi‐component formulations of increasing complexity. Complementing this data, micro‐SORS proved decisive in differentiating between mixture and layered paints in most mock‐ups examined, yielding detailed information about the stratigraphy of reference samples produced through the overlaying of different paints. This combined methodology may be helpful to researchers who would like to approach the vibrational characterization of paints applied onto fragile artifacts and supports in a totally non‐invasive manner.
SESN1 mitigates sevoflurane‐induced cognitive dysfunction, inflammation, and mitochondrial dysfunction in rats. SESN1 upregulates SIRT1, which subsequently promotes mitochondrial autophagy, suggesting a protective mechanism against anesthesia‐related neurodegeneration.
Different practical applications have emerged in the last few years, requiring periodic and detailed inspections to verify possible structural changes. Inspections using Unmanned Aerial Vehicles ...(UAVs) should minimize flight time due to battery time restrictions and identify the terrain's topographic features. In this sense, Coverage Path Planning (CPP) aims at finding the best path to coverage of a determined area respecting the operation's restrictions. Photometric information from the terrain is used to create routes or even refine paths already created. Therefore, this research's main contribution is developing a methodology that uses a metaheuristic algorithm based on point cloud data to inspect slope and dams structures. The technique was applied in a simulated and real scenario to verify its effectiveness. The results showed an increasing 3D reconstructions' quality observing optimizing photometric and mission time criteria.
The absorption of light gives a pigment its colour and its reason for being, but it also creates excited states, that is, new molecules with an energy excess that can be dissipated through ...degradation pathways. Photodegradation processes provoke long‐term, cumulative and irreversible colour changes (fading, darkening, blanching) of which the prediction and prevention are challenging tasks. Of all the environmental risks that affect heritage materials, light exposure is the only one that cannot be controlled without any impact on the optimal display of the exhibit. Light‐induced alterations are not only associated with the pigment itself but also with its interactions with support/binder and, in turn, are further complicated by the nature of the environmental conditions. In this Minireview we investigate how chemistry, encompassing multi‐scale analytical investigations of works of art, computational modelling and physical and chemical studies contributes to improve our prediction of artwork appearance before degradation and to establish effective preventive conservation strategies.
What light does to colours: Light may provoke irreversible colour changes of artworks due to chemical transformations of their constitutive materials. Chemistry, by exploiting multi‐scale analytical investigations, computational modelling and physical and chemical studies, contributes to improve our prediction of artwork appearance before degradation and to establish effective preventive conservation strategies.
This work provides new knowledge on natural yellows used in Iran. Seven biological sources were selected based on interviews with dye masters in Isfahan workshops (Iran).
,
,
,
,
,
, and
are ...currently used in these workshops. Aiming to study the dye composition of wool samples dyed with the extracts of the selected biological sources and the changes induced by the dyeing procedures in the original chemical composition of the plant extract, raw materials and dyed wool (by us and in the workshops) were analyzed by HPLC-DAD and UHPLC-HRMS/MS. The main yellows for
are luteolin-
-glycosides. In the other plant sources, the main chromophores are based on 3-
-glycosides of kaempferol, quercetin, and isorhamnetin. In pistachio hulls, myricitin derivatives were detected and we propose their use as markers. Generally, the solutions extracted from the wool displayed a higher amount of more polar compounds, but also a higher amount of aglycones. Importantly, the chromatographic profiles of the samples we prepared compared well with 17th c. yellows in Persian carpets, and therefore can be considered highly characterized references for the study of Persian yellows.
In this paper, the potential of confocal microfluorescence spectroscopy is explored for the characterization of selected red lake pigments and paints based on alizarin, purpurin and eosin (weak, ...medium and strong emitters). The anthraquinone pigments have been used since ancient times by artists, and eosin lakes were used by impressionist painters. Reconstructions of artists paints based on 19th century recipes are examined. The paints were made using the lake pigments bound in a range of binding media including gum arabic, collagen, a vinyl emulsion and linseed oil. The acquisition of the spectra is rapid, with high spatial resolution and the data reliable and reproducible. Together with full emission spectra, it was possible to acquire well-resolved excitation spectra for purpurin, alizarin and eosin based colors. The present investigation suggests that micro-emission fluorescence can also be used as a semi-quantitative method for madder lake pigments, enabling the determination of purpurin lake ratio in a mixture of purpurin and alizarin, which is important for provenance studies. The data obtained with microfluorescence emission with those acquired with fiber-optic fluorimetry are compared. The spatial resolution used, 8
μm, is appropriate for the analysis of individual pigments particles or aggregates in a paint film. Micro-emission molecular fluorescence proved to be a promising analytical tool to identify the presence of selected red lake pigments combined with a range of binding media.
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