Direct Chemical Evidence Research Articles

Meals for the dead: investigating Romano-British accessory vessels in burials using organic residue analysis

Accessory vessels, including platters, dishes, beakers, flagons, jars, and amphorae, are a common feature of Romano-British burials, raising questions as to their provenance; for example, were such vessels recycled from the domestic sphere or made specially for funerary purposes? Furthermore, uncertainty surrounds their purpose: did they contain foods for the deceased, possibly for their final journey to the underworld? Interestingly, organic residue analysis of vessels from Baginton, a site adjacent to The Lunt fort, Coventry, an early (mid to late first century) Roman military cremation cemetery did not yield evidence for food offerings and may have reflected the use of seconds or damaged vessels in burials, perhaps to provide a symbolic meal. In contrast, here we provide, for the first time, direct chemical and isotopic evidence for ‘meals for the dead’, comprising mainly dairy products, often mixed with leafy plants, extracted from somewhat unusual accessory vessels found in a small, enclosed inhumation cemetery, perhaps associated with a family group, which dates to the late (third to late fourth century, or early fifth century A.D) in urban Canterbury. Thus, we can confirm that accessory vessels found in later Romano-British burials were, in this instance, used in the laying out of funerary meals, presumably to nourish the soul on the journey to the underworld. These preliminary insights on vessel use and burial practices across the span of the Roman occupation of Britain thus provide a strong hint at the diversity of Roman burial practices.

Investigation of electrostatic interactions in laponite-polyacrylic acid nanocomposites

Nanocomposites provides a unique opportunity to enhance thermal, mechanical, and waterproof resistance properties of polymer. The effectiveness of these enhancements typically depends on the optimal dispersion and interaction of nanofillers within the polymer matrix. The primary objective of this study is to provide direct chemical evidence for electrostatic interactions between Laponite nanofiller and polyacrylic acid. Samples were prepared by mixing Laponite dispersion and aqueous polyacrylic acid (PAA) that were adjusted to various pH conditions. We observed, an IR peak shift in the carbonyl peak of PAA and Si–O peak of Laponite to lower wave number in nanocomposite, with the maximum shift at pH 7. UV–Vis results also showed a hypsochromic shift in the carbonyl peak of PAA due to the interaction with Laponite. The extent of peak shift in IR, and UV–Vis region for the PAA-Laponite dispersion was found to be influenced by the molar mass of PAA used in the formulation of Laponite-PAA nanocomposite and pH of the medium. These results along with zeta potential measurements strongly suggest that electrostatic forces are in play between deprotonated PAA and the positively charged rim of Laponite in promoting electrostatic interactions between Laponite and PAA. The findings of the study can have a strong bearing on the design of next generation high performance coatings, sealants, and adhesives.

Integrating multiple spheres to identify the provenance and risk of urban dust and potentially toxic elements: Case study from central Mexico

This study aims to improve the current method of studying potentially toxic elements (PTEs) in urban dust using direct chemical evidence (from dust, rock, and emission source samples) and robust geochemical methods. The provenance of urban dust was determined using rare earth elements (REEs) and geochemical diagrams (V–Ni–Th*10, TiO2 vs. Zr, and Zr/Ti vs. Nb/Y). The geogenic or anthropogenic source of PTEs was determined using the enrichment factor (EF) and compositional data analysis (CoDA), while a PTE's point emission source was identified using a 3.1*La–1.54*Ce–Zn diagram, mineralogy, and morphology analyses. The spatiotemporal distribution of PTEs was determined using a geographic information system, and their health risk (by inhalation) was estimated using a lung bioaccessibility test and particle size distribution. We collected urban dust (n = 38), rock (n = 4), and zinc concentrate (n = 2) samples and determined PTEs and REEs in a city of 1.25 million inhabitants in central Mexico. Results showed that urban dust derived from the San Miguelito Range. REEs, Sc, and Zr were geogenic, while Mn, Cu, Zn, As, and Pb were anthropogenic. Due to the presente of sphalerite particles, a zinc refinery was identified as the point emission source of Zn, As, and Pb. High concentrations of Zn (5000–20,008 mg/kg), As (120–284 mg/kg), and Pb (350–776 mg/kg) were found in urban dust near the zinc refinery. Additionally, particles of PM2.5 (66–84%), PM5.0 (13–27%), PM10 (3–8%), and PM20 (0–2%) and lung bioaccessibility of Sr (48.5–72.4%), Zn (9.6–28.4%), Cu (10.5–27.0%), Fe (4.5–8.6%), Mn (2.9–9.2%), Cr (38.3%) and Pb (30.6%) demonstrated a latent risk to human health. These approaches improve our understanding of the provenance of urban dust and its PTE emission sources in urban areas.

Cuisine in transition? Organic residue analysis of domestic containers from 9th-14th century Sicily.

From the 9th to 14th centuries AD, Sicily experienced a series of rapid and quite radical changes in political regime, but the impact of these regime changes on the lives of the people that experienced them remains largely elusive within the historical narrative. We use a multi-faceted lipid residue approach to give direct chemical evidence of the use of 248 everyday domestic ceramic containers from Islamic and post-Islamic contexts in western Sicily to aid our understanding of daily habits throughout this period of political change. A range of commodities was successfully identified, including animal fats, vegetable products, fruit products (potentially including wine) and plant resins. The study highlights the complexity of residues in early medieval Mediterranean society as, in many cases, mixtures of commodities were observed reflecting sequential cooking events and/or the complex mixtures reflective of medieval recipes. However, overall, there were no clear changes in the composition of the residues following the imposition of Norman control over the island and through subsequent periods, despite some differences between urban centres and rural sites. Thus, lending to the idea that post-Islamic populations largely flourished and benefited from the agricultural systems, resources and recipes left by their predecessors.

Chemical evidence for milk, meat, and marine resource processing in Later Stone Age pots from Namaqualand, South Africa

The subsistence practices of Later Stone Age (LSA) foragers and herders living in Namaqualand South Africa are often difficult to differentiate based on their archaeological signatures but characterizing their dietary choices is vital to understand the economic importance of domesticates. However, ethnohistoric accounts have provided information on the cooking/boiling of marine mammal fat, mutton, plants, and milk by early herders and foragers across the Western Cape. To further investigate these reports, we use lipid residue analysis to characterize 106 potsherds from four open-air LSA sites, spanning in time from the early first millennium to the late second millennium AD. Two sites (SK2005/057A, SK2006/026) are located on the Atlantic coast whereas sites Jakkalsberg K and Jakkalsberg M are located further inland on the southern bank of the Orange River. Notably, at the coastal sites, the presence of marine biomarkers suggests the intensive and/or specialized processing of marine products in many vessels. The dominance of ruminant carcass products at inland sites and probable sheep remains confirms the importance of stockkeeping. Furthermore, and in good agreement with ethnohistoric accounts for its use, our results provide the first direct chemical evidence for the use of dairy products in LSA western South Africa.

Biosynthesis of D/L-lactate from methylglyoxal

Lactate is a common metabolite generated during anaerobic glycolysis from all three domains of life, which plays significant biological roles in health and disease states, especially cancer development. The most well-established biosynthetic pathway of lactate is the reduction of pyruvate mediated by lactate dehydrogenase (LDH). Here, we report another lactate source – the conversion of methylglyoxal (MGO) by an epigenetic eraser enzyme, DJ-1. In this study, we have uncovered that DJ-1 converts MGO to D- and l-lactate in two different manners. First, as a glyoxalase, DJ-1 stereoselectively transfers MGO to d-lactate in the presence of its cofactor, glutathione (GSH). On the other hand, as a protein deglycase, DJ-1 is able to rescue MGO-modified peptides/proteins (including itself) in the absence of GSH, resulting in the production of both D- and l-lactate. Our discoveries in this work distinguished the glyoxalase and deglycase activities of DJ-1 by tracking the stereochemistry of its product, lactate; thus, this study provides direct chemical evidence to confirm DJ-1 as a bona fide deglycase and new insights into the pathological effects of DJ-1 in carcinogenesis.

Wild Food: Plants, Fish and Small Animals on the Menu for Early Holocene Populations at al-Khiday, Central Sudan

AbstractAl-Khiday, located on the bank of the White Nile in Sudan, offers an exceptionally preserved stratigraphic sequence, providing a unique opportunity to use organic residue analysis to investigate diet and subsistence during the Khartoum Mesolithic and the Early Neolithic, a period of nearly 3500 years (7000–4500 cal BC). While the vast and diverse Mesolithic fish assemblage indicates a strong reliance on products from aquatic habitats, floodplains, vegetated marshes, and open water, results from the lipid residue analysis suggest that the fish were not cooked in ceramic pots, but consumed in other ways. Rather, pots were more specialized in processing plants, including wild grasses, leafy plants, and sedges. These results, confirmed by experimental analysis, provide, for the first time, direct chemical evidence for plant exploitation in the Khartoum Mesolithic. Non-ruminant fauna (e.g., warthog) and low lipid-yielding reptiles (e.g., Adanson’s mud turtle and Nile monitor lizard), found in significant numbers at al-Khiday, were likely also cooked in pots. There is little evidence for the processing of wild ruminants in the Mesolithic pots, suggesting either that ruminant species were not routinely hunted or that large wild fauna may have been cooked in different ways, possibly grilled over fires. These data suggest sophisticated economic strategies by sedentary people exploiting their ecological niche to the fullest. Pottery use changed considerably in the Early Neolithic, with ruminant products being more routinely processed in pots, and while the exploitation of domesticates cannot be confirmed by a small faunal assemblage, some dairying took place. The results provide valuable information on Early and Middle Holocene lifeways in central Sudan.

Prehistoric Fermentation, Delayed-Return Economies, and the Adoption of Pottery Technology

Pottery production, like fermentation, is a highly skilled technology that requires the careful selection and transformation of raw ingredients under controlled conditions. Although the precise drivers for the invention and dispersal of ceramic containers are uncertain, it is clear that even the earliest pottery had a culinary role for processing foods. We now know from organic residue analysis that early pottery was used to process only a relatively limited range of the foodstuffs available, with biases, for example, toward fish among some hunter-gatherers or dairy products by early farmers. One reason for such selection might have been that pottery is well suited for the transformation of perishable fresh produce, such as milk and fish, to long(er)-life products that could be stored, exchanged, or accumulated. Such fermented products would be particularly useful for maximizing the return from seasonally abundant foods, thereby facilitating sedentism and greater investment in pottery production. Notwithstanding the fact that direct chemical evidence for fermentation is difficult to obtain, here it is proposed that the early uses of pottery and fermentation and the accumulation of storable surpluses are interrelated technologies that emerged in early sedentary or semi-sedentary societies during the final Pleistocene and start of the Holocene.

Honey-collecting in prehistoric West Africa from 3500 years ago

Honey and other bee products were likely a sought-after foodstuff for much of human history, with direct chemical evidence for beeswax identified in prehistoric ceramic vessels from Europe, the Near East and Mediterranean North Africa, from the 7th millennium BC. Historical and ethnographic literature from across Africa suggests bee products, honey and larvae, had considerable importance both as a food source and in the making of honey-based drinks. Here, to investigate this, we carry out lipid residue analysis of 458 prehistoric pottery vessels from the Nok culture, Nigeria, West Africa, an area where early farmers and foragers co-existed. We report complex lipid distributions, comprising n-alkanes, n-alkanoic acids and fatty acyl wax esters, which provide direct chemical evidence of bee product exploitation and processing, likely including honey-collecting, in over one third of lipid-yielding Nok ceramic vessels. These findings highlight the probable importance of honey collecting in an early farming context, around 3500 years ago, in West Africa.

Unfolding beeswax use in Neolithic and Chalcolithic Cyprus through molecular analysis of lipids extracted from ceramic containers

During the past 30 years, molecular analyses have provided an important corpus of evidence for the exploitation of Apis mellifera products, honey and beeswax, since the Neolithic. In this paper, we report the earliest, to our knowledge, evidence of bee product exploitation in Cyprus dated to the Ceramic Neolithic (5th millennium BC) and the Chalcolithic periods (4th–mid 3rd millennia BC). Systematic sampling and analysis of organic remains absorbed in the walls of ceramic containers from the Ceramic Neolithic sites of Sotira Teppes and Kantou Kouphovounos and also the Middle Chalcolithic site of Erimi Pamboula, located to the central and southern part of Cyprus, were undertaken. We conducted lipid residue analysis in seventy-nine sherd samples, using gas chromatography–mass spectrometry that provided direct chemical evidence for the presence of beeswax residues in twelve vessels from Erimi Pamboula and one vessel from Sotira Teppes. These findings bring new light on the use of beeswax in Cyprus, pushing back the date for the exploitation of Apis mellifera on the island to the second half of the 5th millennium BC. The sampled vessels do not imply a pattern in pottery types where beeswax was preserved, although its extensive presence at Erimi Pamboula ceramics suggests the diachronic use of bee products in the area.

The use of ion-selective membranes to study cation transport in hybrid organic-inorganic perovskites.

Using a methylammonium selective membrane in conjunction with electrochemical impedance spectroscopy, we measured ion migration in methylammonium lead triiodide (MAPbI3) with a millisecond (ms) time constant under illumination. These values were consistent with the reported values of ionic conduction in thin-film perovskite solar cells. We monitored an electrochemical impedance response arising from ionic conductivity through MAPbI3 and a methylammonium selective layer. We could fit this complex impedance response to an intuitive circuit model, which revealed an ionic species moving on a ms time scale. Electrospray ionization mass spectrometry (ESI-MS) revealed direct chemical evidence of methylammonium diffusion into the ion-selective layer. We found no experimental evidence indicating the mobility of lead ions or protons, suggesting that the mobile species observed under illumination is likely methylammonium.

In vivo cross-linking supports a head-to-tail mechanism for regulation of the plant plasma membrane P-type H+-ATPase

In higher plants, a P-type proton-pumping ATPase generates the proton-motive force essential for the function of all other transporters and for proper growth and development. X-ray crystallographic studies of the plant plasma membrane proton pump have provided information on amino acids involved in ATP catalysis but provided no information on the structure of the C-terminal regulatory domain. Despite progress in elucidating enzymes involved in the signaling pathways that activate or inhibit this pump, the site of interaction of the C-terminal regulatory domain with the catalytic domains remains a mystery. Genetic studies have pointed to amino acids in various parts of the protein that may be involved, but direct chemical evidence for which ones are specifically interacting with the C terminus is lacking. In this study, we used in vivo cross-linking experiments with a photoreactive unnatural amino acid, p-benzoylphenylalanine, and tandem MS to obtain direct evidence that the C-terminal regulatory domain interacts with amino acids located within the N-terminal actuator domain. Our observations are consistent with a mechanism in which intermolecular, rather than intramolecular, interactions are involved. Our model invokes a "head-to-tail" organization of ATPase monomers in which the C-terminal domain of one ATPase molecule interacts with the actuator domain of another ATPase molecule. This model serves to explain why cross-linked peptides are found only in dimers and trimers, and it is consistent with prior studies suggesting that within the membrane the protein can be organized as homopolymers, including dimers, trimers, and hexamers.

Biochemistry and adaptive colouration of an exceptionally preserved juvenile fossil sea turtle

The holotype (MHM-K2) of the Eocene cheloniine Tasbacka danica is arguably one of the best preserved juvenile fossil sea turtles on record. Notwithstanding compactional flattening, the specimen is virtually intact, comprising a fully articulated skeleton exposed in dorsal view. MHM-K2 also preserves, with great fidelity, soft tissue traces visible as a sharply delineated carbon film around the bones and marginal scutes along the edge of the carapace. Here we show that the extraordinary preservation of the type of T. danica goes beyond gross morphology to include ultrastructural details and labile molecular components of the once-living animal. Haemoglobin-derived compounds, eumelanic pigments and proteinaceous materials retaining the immunological characteristics of sauropsid-specific β-keratin and tropomyosin were detected in tissues containing remnant melanosomes and decayed keratin plates. The preserved organics represent condensed remains of the cornified epidermis and, likely also, deeper anatomical features, and provide direct chemical evidence that adaptive melanism – a biological means used by extant sea turtle hatchlings to elevate metabolic and growth rates – had evolved 54 million years ago.

Probing Grain-Boundary Chemistry and Electronic Structure in Proton-Conducting Oxides by Atom Probe Tomography.

A laser-assisted atom-probe-tomographic (LAAPT) method has been developed and applied to measure and characterize the three-dimensional atomic and electronic nanostructure at an yttrium-doped barium zirconate (BaZr0.9Y0.1O3-δ, BZY10) grain boundary. Proton-conducting perovskites, such as BZY10, are attracting intense interest for a variety of energy conversion applications. However, their implementation has been hindered, in part, because of high grain-boundary (GB) resistance that is attributed to a positive GB space-charge layer (SCL). In this study, LAAPT is used to analyze BZY10 GB chemistry in three dimensions with subnanometer resolution. From this analysis, maps of the charge density and electrostatic potential arising at the GBs are derived, revealing for the first time direct chemical evidence that a positive SCL indeed exists at these GBs. These maps reveal new insights on the inhomogeneity of the SCL region and produce an average GB potential barrier of approximately 580 mV, agreeing with previous indirect electrochemical measurements.

A "White" Anthocyanin-less Pomegranate (Punica granatum L.) Caused by an Insertion in the Coding Region of the Leucoanthocyanidin Dioxygenase (LDOX; ANS) Gene.

Color is an important determinant of pomegranate fruit quality and commercial value. To understand the genetic factors controlling color in pomegranate, chemical, molecular and genetic characterization of a "white" pomegranate was performed. This unique accession is lacking the typical pomegranate color rendered by anthocyanins in all tissues of the plant, including flowers, fruit (skin and arils) and leaves. Steady-state gene-expression analysis indicated that none of the analyzed "white" pomegranate tissues are able to synthesize mRNA corresponding to the PgLDOX gene (leucoanthocyanidin dioxygenase, also called ANS, anthocyanidin synthase), which is one of the central structural genes in the anthocyanin-biosynthesis pathway. HPLC analysis revealed that none of the "white" pomegranate tissues accumulate anthocyanins, whereas other flavonoids, corresponding to biochemical reactions upstream of LDOX, were present. Molecular analysis of the "white" pomegranate revealed the presence of an insertion and an SNP within the coding region of PgLDOX. It was found that the SNP does not change amino acid sequence and is not fully linked with the "white" phenotype in all pomegranate accessions from the collection. On the other hand, genotyping of pomegranate accessions from the collection and segregating populations for the "white" phenotype demonstrated its complete linkage with the insertion, inherited as a recessive single-gene trait. Taken together, the results indicate that the insertion in PgLDOX is responsible for the "white" anthocyanin-less phenotype. These data provide the first direct molecular, genetic and chemical evidence for the effect of a natural modification in the LDOX gene on color accumulation in a fruit-bearing woody perennial deciduous tree. This modification can be further utilized to elucidate the physiological role of anthocyanins in protecting the tree organs from harmful environmental conditions, such as temperature and UV radiation.

‘Choicest unguents’: molecular evidence for the use of resinous plant exudates in late Roman mortuary rites in Britain

Resinous substances were highly prized in the ancient world for use in ritual contexts. Details gleaned from classical literature indicate that they played a significant role in Roman mortuary rites, in treatment of the body and as offerings at the tomb. Outside of Egypt, however, where research has shown that a range of plant exudates were applied as part of the mummification process, resins have rarely been identified in the burial record. This is despite considerable speculation regarding their use across the Roman Empire.Focusing on one region, we investigated organic residues from forty-nine late Roman inhumations from Britain. Using gas chromatography–mass spectrometry and the well-attested biomarker approach, terpenic compounds were characterized in fourteen of the burials analysed. These results provided direct chemical evidence for the presence of exudates from three different plant families: coniferous Pinaceae resins, Mediterranean Pistacia spp. resins (mastic/terebinth) and exotic Boswellia spp. gum-resins (frankincense/olibanum) from southern Arabia or beyond. The individuals accorded this rite had all been interred with a package of procedures more elaborate than the norm.These findings illuminate the multiplicity of roles played by resinous substances in Roman mortuary practices in acting to disguise the odour of decomposition, aiding temporary soft-tissue preservation and signifying the social status of the deceased. Nevertheless, it was their ritual function in facilitating the transition to the next world that necessitated transportation to the most remote outpost of the late Roman Empire, Britain.

Pulque production from fermented agave sap as a dietary supplement in Prehispanic Mesoamerica.

Although in modern societies fermented beverages are associated with socializing, celebration, and ritual, in ancient times they were also importa`nt sources of essential nutrients and potable water. In Mesoamerica, pulque, an alcoholic beverage produced from the fermented sap of several species of maguey plants (Agavaceae; Fig. 1) is hypothesized to have been used as a dietary supplement and risk-buffering food in ancient Teotihuacan (150 B.C. to A.D. 650). Although direct archaeological evidence of pulque production is lacking, organic residue analysis of pottery vessels offers a new avenue of investigation. However, the chemical components of alcoholic beverages are water-soluble, greatly limiting their survival over archaeological timescales compared with hydrophobic lipids widely preserved in food residues. Hence, we apply a novel lipid biomarker approach that considers detection of bacteriohopanoids derived from the ethanol-producing bacterium Zymomonas mobilis for identifying pulque production/consumption in pottery vessels. Gas chromatography-mass spectrometry selected ion monitoring (m/z 191) of lipid extracts of >300 potsherds revealed characteristic bacteriohopanoid distributions in a subset of 14 potsherds. This hopanoid biomarker approach offers a new means of identifying commonly occurring bacterially fermented alcoholic beverages worldwide, including palm wine, beer, cider, perry, and other plant sap- or fruit-derived beverages [Swings J, De Ley J (1977) Bacteriol Rev 41(1):1-46].

Direct Evidence of Lithium-Induced Atomic Ordering in Amorphous TiO2 Nanotubes

In this paper, we report the first direct chemical and imaging evidence of lithium-induced atomic ordering in amorphous TiO2 nanomaterials and propose new reaction mechanisms that contradict the many works in the published literature on the lithiation behavior of these materials. The lithiation process was conducted in situ inside an atomic resolution transmission electron microscope. Our results indicate that the lithiation started with the valence reduction of Ti4+ to Ti3+ leading to a LixTiO2 intercalation compound. The continued intercalation of Li ions in TiO2 nanotubes triggered an amorphous to crystalline phase transformation. The crystals were formed as nano-islands and identified to be Li2Ti2O4 with cubic structure (a = 8.375 A). The tendency for the formation of these crystals was verified with density functional theory (DFT) simulations. The size of the crystalline islands provides a characteristic length scale (∼5 nm) at which the atomic bonding configuration has been changed within a short ti...

Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles

Throughout the animal kingdom, adaptive colouration serves critical functions ranging from inconspicuous camouflage to ostentatious sexual display, and can provide important information about the environment and biology of a particular organism. The most ubiquitous and abundant pigment, melanin, also has a diverse range of non-visual roles, including thermoregulation in ectotherms. However, little is known about the functional evolution of this important biochrome through deep time, owing to our limited ability to unambiguously identify traces of it in the fossil record. Here we present direct chemical evidence of pigmentation in fossilized skin, from three distantly related marine reptiles: a leatherback turtle, a mosasaur and an ichthyosaur. We demonstrate that dark traces of soft tissue in these fossils are dominated by molecularly preserved eumelanin, in intimate association with fossilized melanosomes. In addition, we suggest that contrary to the countershading of many pelagic animals, at least some ichthyosaurs were uniformly dark-coloured in life. Our analyses expand current knowledge of pigmentation in fossil integument beyond that of feathers, allowing for the reconstruction of colour over much greater ranges of extinct taxa and anatomy. In turn, our results provide evidence of convergent melanism in three disparate lineages of secondarily aquatic tetrapods. Based on extant marine analogues, we propose that the benefits of thermoregulation and/or crypsis are likely to have contributed to this melanisation, with the former having implications for the ability of each group to exploit cold environments.

Cephalosporolide B Serving as a Versatile Synthetic Precursor: Asymmetric Biomimetic Total Syntheses of Cephalosporolides C, E, F, G, and (4-OMe-)G

Cephalosporolide B (Ces-B) was efficiently synthesized and exploited for the first time as a versatile biomimetic synthetic precursor for the chemical syntheses of not only cephalosporolides C, G, and (4-OMe-) G via a challenging diastereoselective oxa-Michael addition but also the structurally unprecedented cephalosporolides E and F via a novel biomimetic ring-contraction rearrangement. These findings provide the first direct chemical evidence that Ces-B may be the true biosynthetic precursor of cephalosporolides.