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Analyses of the degraded mordant gilding on two early fourteenth-century paintings by Pietro Lorenzetti were undertaken at the UK synchrotron facility Diamond Light Source. Previous studies revealed a complex orpiment-tinted mordant and its application for adhering two separate layers of silver and gold leaf and demonstrated degradation of the original materials. A new study involving synchrotron radiation (SR) microfocus X-ray fluorescence (µ-XRF) maps on cross-sections of the discolored mordant allowed imaging of the extent of migration of mobile As-Ag-S bearing species and provided ideal positions from which to collect microfocus X-ray absorption near edge structure (µ-XANES) maps of As, Ag, and S for oxidation state analysis. SR µ-XANES indicates that arsenolite (As2O3) is present throughout the mordant suggesting light-induced photooxidation of orpiment. Both As3+ (as oxide) and As5+ have been detected and these are known signs for orpiment degradation. SR microfocus X-ray diffraction (µ-XRD) was used to reveal the nature of altered phases in the mordant layer and identified the presence of acanthite Ag2S, xanthoconite Ag3AsS3, and arsenolite As2O3. The analysis confirmed that the darkening of the mordant is most probably caused by finely dispersed grey-colored Ag + -bearing acanthite particles (Ag2S). The results are discussed in the context of analysis of contemporary paintings and recent studies on the alteration of orpiment. [ABSTRACT FROM AUTHOR]

Celery (Apium graveolens L.) is a kind of green leaf vegetable with a large consumption demand in the food industry. It is a commonly used material in quick-frozen food stuffing such as dumplings and steamed stuffed. Fresh celery leaf blades and petioles are rich in photosynthetic pigments including chlorophyll and carotenoid, their contents are closely related to the quality of celery and its products. In order to explore the effects of freezing and thawing temperature and thawing time on the degradation of photosynthetic pigments in celery leaf blades and petioles, the changes in photosynthetic pigments during thawing storage were measured under different freezing and thawing temperatures. The results showed that lower freezing and thawing temperatures were beneficial to the preservation of photosynthetic pigments in celery leaf blades and petioles, and the loss of photosynthetic pigments enhanced with the increase in thawing temperature and thawing time. Under the cold storage condition of −80 °C, the loss rate of pigment substances can be reduced by nearly 20% compared with that of −18 °C, and −80 °C and 4 °C could be the best temperature combination of freezing and thawing. The content and degradation rate of photosynthetic pigments in celery leaf blades were higher than that in petioles during thawing, with a total chlorophyll loss rate reaching 35% during 6 to 12 h after thawing. The increase in temperature difference between freezing and thawing could aggravate the damage to the cell structure and the degradation of the pigment, as chlorophyll is more sensitive to temperature changes, and the degradation rate is significantly higher than that of carotenoids. From the perspective of delaying the degradation of photosynthetic pigments, the results of this study will provide potential references for the reasonable configuration of freezing and thawing temperatures in the process of storage and transportation of celery products. [ABSTRACT FROM AUTHOR]

The petals of Paeonia lactiflora 'Coral Sunset' change color from coral pink to pale yellow after flower opening. Pigment-targeted metabolomic analysis showed that the carotenoid and anthocyanin contents rapidly decreased after petal fading. SMART-sequencing and next-generation-sequencing analyses were performed to identify differentially expressed transcripts to characterize the candidate genes involved in petal fading. The expression of certain genes associated with anthocyanin and carotenoid synthesis and degradation was correlated with the petal-fading phenotype. The anthocyanin synthesis (AS) structural genes, CHS, F3H, F3′H, DFR, and ANS, and the carotenoid synthesis genes, LCYB and LCYE, were strongly expressed before fading, but their expression significantly declined after fading. In contrast, the expression of certain genes associated with oxidase activity and light signaling significantly increased after fading. Therefore, inhibition of pigment synthesis and accelerated pigment degradation may be crucial for petal fading. A R2R3-MYB family member of subgroup 4 (MYBs-SG4) showed the same expression pattern as the AS structural genes and functioned in the positive regulation of anthocyanin synthesis by forming the MBW protein complex. This is the first report of a SG4 member with a positive regulatory function. This study provides a foundation for elucidation of the mechanisms of pigment synthesis and metabolism, and a theoretical basis for flower-color-directed breeding. [ABSTRACT FROM AUTHOR]

This paper presents the first results of a current interdisciplinary research project on the polychromy of Roman provincial stone artefacts in selected areas of the Danubian provinces (PolychroMon). The statuary group of Minerva and the Genius immunium from Carnuntum (Archaeological Museum Carnuntinum inv. CAR-S-48) is dated to the second half of the second century AD and still retains traces of the original polychromy. The aim was to focus on non-invasive techniques and to employ micro-invasive methods for necessary cross-checking and gaining information otherwise not accessible. The investigation revealed that paint was applied on a layer of white lime wash. Additionally, the object shows several traces of Egyptian blue, which was mainly detected in Minerva’s and the Genius’ clothes. Other pigments whose traces were found on the sculpture include green earth, yellow and red ochre, as well as red lead and carbon black. Microscopic analysis confirms the presence of modern-age compounds as well (barium sulphate and zinc oxide) used for modern retouches. Gas chromatography–mass spectrometry revealed the use of egg as the major proteinaceous binding medium in the red lead polychromy.

This paper presents the first results of a current interdisciplinary research project on the polychromy of Roman provincial stone artefacts in selected areas of the Danubian provinces (PolychroMon). The statuary group of Minerva and the Genius immunium from Carnuntum (Archaeological Museum Carnuntinum inv. CAR-S-48) is dated to the second half of the second century AD and still retains traces of the original polychromy. The aim was to focus on non-invasive techniques and to employ micro-invasive methods for necessary cross-checking and gaining information otherwise not accessible. The investigation revealed that paint was applied on a layer of white lime wash. Additionally, the object shows several traces of Egyptian blue, which was mainly detected in Minerva's and the Genius' clothes. Other pigments whose traces were found on the sculpture include green earth, yellow and red ochre, as well as red lead and carbon black. Microscopic analysis confirms the presence of modern-age compounds as well (barium sulphate and zinc oxide) used for modern retouches. Gas chromatography–mass spectrometry revealed the use of egg as the major proteinaceous binding medium in the red lead polychromy. [ABSTRACT FROM AUTHOR]

Cadmium sulfide (CdS) pigments have degraded in several well-known artworks, but the influence of pigment properties and environmental conditions on the degradation process have yet to be fully understood. Traditional non-destructive analysis techniques primarily focus on macroscopic degradation, whereas microscopic information is typically obtained with invasive techniques that require sample removal. Here, we demonstrate the use of pump-probe microscopy to nondestructively visualize the three-dimensional structure and degradation progress of CdS pigments in oil paints. CdS pigments, reproduced following historical synthesis methods, were reproduced as oil paints and artificially aged by exposure to high relative humidity and light. The degradation of CdS to CdSO _4 ·xH _2 O was confirmed by both FTIR (Fourier-transform infrared) and XPS (x-ray photoelectron spectroscopy) experiments. During the degradation process, optical pump-probe microscopy was applied to track the degradation progress in single grains, and volumetric imaging revealed early CdS degradation of small particles and on the surface of large particles. This indicates that the particle dimension influences the extent and evolution of degradation of historical CdS. In addition, the pump-probe signal decrease in degraded CdS is observable before visible changes to the eye, demonstrating that pump-probe microscopy is a promising tool to detect early-stage degradation in artworks.

The petals of Paeonia lactiflora ‘Coral Sunset’ change color from coral pink to pale yellow after flower opening. Pigment-targeted metabolomic analysis showed that the carotenoid and anthocyanin contents rapidly decreased after petal fading. SMART-sequencing and next-generation-sequencing analyses were performed to identify differentially expressed transcripts to characterize the candidate genes involved in petal fading. The expression of certain genes associated with anthocyanin and carotenoid synthesis and degradation was correlated with the petal-fading phenotype. The anthocyanin synthesis (AS) structural genes, CHS, F3H, F3′H, DFR, and ANS, and the carotenoid synthesis genes, LCYB and LCYE, were strongly expressed before fading, but their expression significantly declined after fading. In contrast, the expression of certain genes associated with oxidase activity and light signaling significantly increased after fading. Therefore, inhibition of pigment synthesis and accelerated pigment degradation may be crucial for petal fading. A R2R3-MYB family member of subgroup 4 (MYBs-SG4) showed the same expression pattern as the AS structural genes and functioned in the positive regulation of anthocyanin synthesis by forming the MBW protein complex. This is the first report of a SG4 member with a positive regulatory function. This study provides a foundation for elucidation of the mechanisms of pigment synthesis and metabolism, and a theoretical basis for flower-color-directed breeding.

Increased solar radiation on the Earth’s surface is expected due to global change. Mangrove macroalgae can be negatively affected by increased solar radiation, since some species, such as Bostrychia spp. have been characterized as typical “shade” plants. Thus, we investigated the effects of increasing photon flux densities (PFDs: 170, 267, 443, 638, and 1155 µmol photons m–2 s–1) on the physiological performance of Bostrychia calliptera and Bostrychia montagnei from a tropical mangrove. Several photosynthesis–related parameters indicated that both species decreased their photosynthetic performance under increasing PFDs, with photosynthesis of B. montagnei being more affected than that of B. calliptera. Bostrychia calliptera exhibited highest growth under 638 µmol photons m–2 s–1 while at 1155 µmol photons m–2 s–1 it was inhibited. The highest growth of Bostrychia montagnei was observed under 267 µmol photons m–2 s–1. Higher PFDs led to growth inhibition. The phycobiliprotein and chlorophyll a content of B. montagnei was degraded under increased PFDs. In B. calliptera only chlorophyll a degradation was observed. The mycosporine-like amino acid contents (photoprotective metabolites) of both species were degraded under increasing PFDs, which was more pronounced in B. montagnei. Our results demonstrated that increased solar radiation on estuarine tropical ecosystems will be detrimental to the physiological performance of B. calliptera and B. montagnei. Our results also demonstrated that B. montagnei was more negatively affected by increased light stress than B. calliptera. This can explain its preferential occurrence in more shaded microhabitats compared to B. calliptera. Our data document for the first time light acclimation in the studied macroalgae and the deleterious effects of increased light stress on the genus Bostrychia.