Selective biodegradation in hair shafts derived from archaeological, forensic and experimental contexts

Using surface-enhanced Raman spectroscopy to probe artificial dye degradation on hair buried in multiple soils for up to eight weeks

The discovery of clandestine burials poses unique challenges for forensic specialists, requiring diverse expertise to analyze remains in various states. Bones, teeth, and hair often endure the test of time, with hair particularly exposed to the external environment. While existing studies focus on the degradation of virgin hair influenced by soil pH and decomposition fluids, the interaction between artificial dyes on hair and soil remains underexplored. This paper introduces a novel approach to forensic hair analysis that is based on high-throughput, nondestructive, and non-invasive surface-enhanced Raman spectroscopy (SERS) and machine learning. Using this approach, we investigated the reliability of the detection and identification of artificial dyes on hair buried in three distinct soil types for up to eight weeks. Our results demonstrated that SERS enabled the correct prediction of 97.9% of spectra for five out of the eight dyes used within the 8 weeks of exposure. We also investigated the extent to which SERS and machine learning can be used to predict the number of weeks since burial, as this information may provide valuable insights into post-mortem intervals. We found that SERS enabled highly accurate exposure intervals to soils for specific dyes. The study underscores the high achievability of SERS in extrapolating colorant information from dyed hairs buried in diverse soils, with the suggestion that further model refinement could enhance its reliability in forensic applications.

The rate and quality of post-mortem hair root changes in relation to melanin content

Hairs is a relatively environmentally resistant biological material that is often found at crime scenes. Human hair is more durable than other biological traces such as blood or urine, and its collection and storage does not require specific preservation procedures. Melanin is the hair pigment, which is the main determinant of hair colour. There are two pigments present in human hair: eumelanin, predominant in dark hair, and pheomelanin, responsible for red colour. Eumelanin is more resistant and has photoprotective properties, while pheomelanin is phototoxic and shows lower resistance to environmental factors. The differences in the properties of eu- and pheomelanin are the basis of the present study, which aimed to examine the rate and quality of taphonomic changes in hair roots in relation to the predominant melanin type, under the influence of selected environmental factors, such as soil pH, degree of exposure to solar radiation, temperature and water from a natural watercourse (river) and chemically pure water. Therefore, changes in blonde, dark, grey, red and dyed hair roots were microscopically documented for six months under the influence of the above factors. The results of the study indicated the strongest degradation potential among acidic soil and a riverine environment, as well as the protective role of eumelanin against environmental taphonomic factors. Degradation occurred most rapidly in the river environment, where microbial activity was additionally observed. Distilled water, exposure to sunlight and low temperature did not lead to decomposition changes. The results of our team's research provide the basis for an extended analysis of the changes occurring in hair under the influence of environmental factors in relation to melanin content.

Impact of hair type, hair sample weight, external hair exposures, and race on cumulative hair cortisol

The biomarker cortisol assesses the impact of biopsychosocial stressors that activate the stress response system. Hair has emerged as a valid and non-invasive means of gauging cumulative cortisol deposited over month-long periods of time. Established protocols for the extraction of hair cortisol are being validated and refined in humans, yet methodological information about hair characteristics on cortisol remains limited. In addition to external hair exposures (e.g. dye, time spent outside), we examined hair categorization or type (e.g. kinky, straight) by extending a hair typing methodology for scientific use that is currently popular among hair care professionals. We then examined the interaction between hair type and race on cortisol levels with a hair questionnaire. Three studies were pooled to investigate how sample weight, hair type, race, heat exposures, and hair treatments impacted cumulative hair cortisol concentrations. Study 1 consisted of Adult Kenyan Medical Workers (N = 44); Study 2 Mexican and Mexican Americans (N = 106); and Study 3 American Youth (N = 107). We found significantly higher cortisol in 5 mg of hair when compared to larger sample weights, and higher cortisol in those who spent more time outdoors. Cortisol concentrations differed between racial groups and varied by hair type; moreover, there were directional differences in cumulative cortisol from straighter to curlier hair types which depended on racial group. In addition to demonstrating the impact of relatively novel control factors like hair sample weight, outdoor exposure, and hair type, the present study illustrates the importance of disentangling hair type and race to understand variability in cumulative hair cortisol. These influences should be included in future studies that measure hair cortisol.

Biodegradation of bio-sourced and synthetic organic electronic materials towards green organic electronics

Ubiquitous use of electronic devices has led to an unprecedented increase in related waste as well as the worldwide depletion of reserves of key chemical elements required in their manufacturing. The use of biodegradable and abundant organic (carbon-based) electronic materials can contribute to alleviate the environmental impact of the electronic industry. The pigment eumelanin is a bio-sourced candidate for environmentally benign (green) organic electronics. The biodegradation of eumelanin extracted from cuttlefish ink is studied both at 25 °C (mesophilic conditions) and 58 °C (thermophilic conditions) following ASTM D5338 and comparatively evaluated with the biodegradation of two synthetic organic electronic materials, namely copper (II) phthalocyanine (Cu-Pc) and polyphenylene sulfide (PPS). Eumelanin biodegradation reaches 4.1% (25 °C) in 97 days and 37% (58 °C) in 98 days, and residual material is found to be without phytotoxic effects. The two synthetic materials, Cu-Pc and PPS, do not biodegrade; Cu-Pc brings about the inhibition of microbial respiration in the compost. PPS appears to be potentially phytotoxic. Finally, some considerations regarding the biodegradation test as well as the disambiguation of "biodegradability" and "bioresorbability" are highlighted.

Reprint of: The effects of decomposition and environment on antemortem H-Pb-Sr isotope compositions and degradation of human scalp hair: Actualistic taphonomic observations

Multi-isotope analysis (e.g., Sr-Pb-O-H-C-N) of human scalp hair is routinely used in forensic investigations of human remains to constrain the geographic origin of unidentified bodies, and to investigate antemortem mobility patterns. However, while it is known that postmortem processes can affect the preservation of, or even overprint, the biogenic isotopic signatures in hair, the speed and nature of these processes have rarely been studied. This study investigates the effects of decomposition and environment on the H-Pb-Sr isotope compositions of human hair as well as the relationship between structural hair shaft degradation and isotopic signature change over time. Human scalp hair samples from four body donations were collected at different stages throughout gross body decomposition. The willed-donated bodies were placed to decompose outdoors at the Forensic Anthropology Research Facility (FARF) at Texas State University. Hair fibres from two of the donations were examined using scanning electron microscopy (SEM) and high-resolution light microscopy (HRLM). Chemical and microbiological degradation of hair fibres occurred rapidly after placement of the body outdoors. Measurements of scalp hair isotopic composition demonstrated that H-Pb-Sr isotope ratios were altered within days after environmental exposure, presumably by deposition, leaching and/or exchange with the local bioavailable soil, and vapour. The degree of physical hair degradation and changes in H-Pb-Sr isotope composition were not correlated. We conclude that antemortem isotopic H-Pb-Sr isotope ratios are difficult to recover in hairs derived from decomposing whole bodies.

The effects of decomposition and environment on antemortem H-Pb-Sr isotope compositions and degradation of human scalp hair: Actualistic taphonomic observations

Multi-isotope analysis (e.g., Sr-Pb-O-H-C-N) of human scalp hair is routinely used in forensic investigations of human remains to constrain the geographic origin of unidentified bodies, and to investigate antemortem mobility patterns. However, while it is known that postmortem processes can affect the preservation of, or even overprint, the biogenic isotopic signatures in hair, the speed and nature of these processes have rarely been studied. This study investigates the effects of decomposition and environment on the H-Pb-Sr isotope compositions of human hair as well as the relationship between structural hair shaft degradation and isotopic signature change over time. Human scalp hair samples from four body donations were collected at different stages throughout gross body decomposition. The willed-donated bodies were placed to decompose outdoors at the Forensic Anthropology Research Facility (FARF) at Texas State University. Hair fibers from two of the donations were examined using scanning electron microscopy (SEM) and high-resolution light microscopy (HRLM). Chemical and microbiological degradation of hair fibers occurred rapidly after placement of the body outdoors. Measurements of scalp hair isotopic composition demonstrated that H-Pb-Sr isotope ratios were altered within days after environmental exposure, presumably by deposition, leaching and/or exchange with the local bioavailable soil, and vapor. The degree of physical hair degradation and changes in H-Pb-Sr isotope composition were not correlated. We conclude that antemortem isotopic H-Pb-Sr isotope ratios are difficult to recover in hairs derived from decomposing whole bodies.

Using evidence from hair and other soft tissues to infer the need for and receipt of health-related care provision

The Bioarchaeology of Care approach developed by Tilley is usually applied to skeletalized human remains, given the usual constraints of preservation bias that are seen with archaeological assemblages. However, other tissues, such as hair are sometimes preserved and can provide a wealth of information that can supplement the skeletal data. Archaeological hair has been analysed for drug compounds for almost thirty years. This article integrates data from hair analyses for coca metabolites, stable light isotope analysis and aDNA to expand the potential of the Bioarchaeology of Care approach using the example of a spontaneously mummified adult female from northern Chile.

A matter of months: High precision migration chronology of a Bronze Age female

Establishing the age at which prehistoric individuals move away from their childhood residential location holds crucial information about the socio dynamics and mobility patterns in ancient societies. We present a novel combination of strontium isotope analyses performed on the over 3000 year old “Skrydstrup Woman” from Denmark, for whom we compiled a highly detailed month-scale model of her migration timeline. When combined with physical anthropological analyses this timeline can be related to the chronological age at which the residential location changed. We conducted a series of high-resolution strontium isotope analyses of hard and soft human tissues and combined these with anthropological investigations including CT-scanning and 3D visualizations. The Skrydstrup Woman lived during a pan-European period characterized by technical innovation and great social transformations stimulated by long-distance connections; consequently she represents an important part of both Danish and European prehistory. Our multidisciplinary study involves complementary biochemical, biomolecular and microscopy analyses of her scalp hair. Our results reveal that the Skrydstrup Woman was between 17–18 years old when she died, and that she moved from her place of origin -outside present day Denmark- to the Skrydstrup area in Denmark 47 to 42 months before she died. Hence, she was between 13 to 14 years old when she migrated to and resided in the area around Skrydstrup for the rest of her life. From an archaeological standpoint, this one-time and one-way movement of an elite female during the possible “age of marriageability” might suggest that she migrated with the aim of establishing an alliance between chiefdoms. Consequently, this detailed multidisciplinary investigation provides a novel tool to reconstruct high resolution chronology of individual mobility with the perspective of studying complex patterns of social and economic interaction in prehistory.

Sulfitolytic and keratinolytic potential of Chryseobacterium sp. RBT revealed hydrolysis of melanin containing feathers

In black feathers, melanin is embedded in keratin matrix that makes feather more resistance to the microbial degradation. Chryseobacterium sp. RBT previously isolated from the poultry waste disposable site revealed strong sulfitolytic and keratinolytic activities. Maximum keratinase activity was observed at 48 h (89.12 U ml⁻¹) showed 83 % of native black feather degradation. The concentration of free sulfhydryl groups released during degradation was 0.648 × 10⁻⁴ M (12 h), 2.144 × 10⁻⁴ M (96 h), and however, declined on prolong incubation to 1.752 × 10⁻⁴ M (120 h). Melanin was released in the degradation medium after microbial exploitation of black feather. After purification, melanin was dark brown colored powder insoluble in water, 5 M HCL, ethanol, methanol, benzene, chloroform, and acetone; whereas, soluble in KOH and NaOH. On exposure to oxidizing and reducing reagents feather melanin showed decolorization, while formed a brown precipitate when reacted with FeCl₃. The spectroscopic characterization of isolated melanin demonstrated absorption at infra-red region. Similarly, UV–visible scan confirmed that increase in the wavelength progressively declined the absorbance of pigment. The crude keratinase enzyme (2 % v/v) produced during degradation showed complete dehairing of goat skin within 20 h.

Provenancing Archaeological Wool Textiles from Medieval Northern Europe by Light Stable Isotope Analysis (δ13C, δ15N, δ2H)

We investigate the origin of archaeological wool textiles preserved by anoxic waterlogging from seven medieval archaeological deposits in north-western Europe (c. 700–1600 AD), using geospatial patterning in carbon (δ¹³C), nitrogen (δ¹⁵N) and non-exchangeable hydrogen (δ²H) composition of modern and ancient sheep proteins. δ¹³C, δ¹⁵N and δ²H values from archaeological wool keratin (n = 83) and bone collagen (n = 59) from four sites were interpreted with reference to the composition of modern sheep wool from the same regions. The isotopic composition of wool and bone collagen samples clustered strongly by settlement; inter-regional relationships were largely parallel in modern and ancient samples, though landscape change was also significant. Degradation in archaeological wool samples, examined by elemental and amino acid composition, was greater in samples from Iceland (Reykholt) than in samples from north-east England (York, Newcastle) or northern Germany (Hessens). A nominal assignment approach was used to classify textiles into local/non-local at each site, based on maximal estimates of isotopic variability in modern sheep wool. Light element stable isotope analysis provided new insights into the origins of wool textiles, and demonstrates that isotopic provenancing of keratin preserved in anoxic waterlogged contexts is feasible. We also demonstrate the utility of δ²H analysis to understand the location of origin of archaeological protein samples.

Demonstration of Protein-Based Human Identification Using the Hair Shaft Proteome

Human identification from biological material is largely dependent on the ability to characterize genetic polymorphisms in DNA. Unfortunately, DNA can degrade in the environment, sometimes below the level at which it can be amplified by PCR. Protein however is chemically more robust than DNA and can persist for longer periods. Protein also contains genetic variation in the form of single amino acid polymorphisms. These can be used to infer the status of non-synonymous single nucleotide polymorphism alleles. To demonstrate this, we used mass spectrometry-based shotgun proteomics to characterize hair shaft proteins in 66 European-American subjects. A total of 596 single nucleotide polymorphism alleles were correctly imputed in 32 loci from 22 genes of subjects' DNA and directly validated using Sanger sequencing. Estimates of the probability of resulting individual non-synonymous single nucleotide polymorphism allelic profiles in the European population, using the product rule, resulted in a maximum power of discrimination of 1 in 12,500. Imputed non-synonymous single nucleotide polymorphism profiles from European-American subjects were considerably less frequent in the African population (maximum likelihood ratio = 11,000). The converse was true for hair shafts collected from an additional 10 subjects with African ancestry, where some profiles were more frequent in the African population. Genetically variant peptides were also identified in hair shaft datasets from six archaeological skeletal remains (up to 260 years old). This study demonstrates that quantifiable measures of identity discrimination and biogeographic background can be obtained from detecting genetically variant peptides in hair shaft protein, including hair from bioarchaeological contexts.

Splitting hairs: differentiating between entomological activity, taphonomy, and sharp force trauma on hair

PURPOSE

The analysis of hair can provide useful information for the correct evaluation of forensic cases, but studies of trauma on hair are extremely rare. Hair may present lesions caused by traumatic events or by animals: in fact, signs of sharp force weapons on hair may provide important information for the reconstruction of the manner of death, and, for example, may suggest fetishist practice. This study stemmed from a judicial case where it was fundamental to distinguish between sharp force lesions and insect activity on hair.

METHODS

In order to highlight differences between sharp force lesions and insect feeding activity, different experiments were performed with high power microscopy: hair samples were subjected to several lesions by blunt and sharp force trauma; then samples were used as pabulum for two taxa of insects: the common clothes moth (Tineola bisselliella Lepidoptera, Tineidae) and the carpet beetle (Anthrenus sp., Coleoptera, Dermestidae). Hairs were examined from a macroscopic and microscopic point of view by stereomicroscopy and scanning electron microscopy (SEM): the morphological characteristics of the lesions obtained from the different experimental samples were compared.

RESULTS

Results show that sharp force trauma produces lesions with regular edges, whereas insects leave concave lesions caused by their "gnawing" activity. These two types of lesions are easily distinguishable from breaking and tearing using SEM.

CONCLUSIONS

This study demonstrates that insect activity leaves very specific indications on hair and sheds some light on different hair lesions that may be found in forensic cases.

Wet degradation of keratin proteins: linking amino acid, elemental and isotopic composition

RATIONALE

Archaeological keratin samples are increasingly the subject of palaeodietary, provenancing and dating studies. Keratin samples from wet archaeological contexts are microbiologically and chemically degraded, causing differential diagenesis of protein structures in hair fibres. The effects of these processes on the analytical parameters of interest are currently unknown.

METHODS

This study examined the impact of degradation of wool fibres on isotopic (δ(13)C, δ(15)N, un-exchangeable δ(2)H and δ(18)O values) composition. It compared two models of archaeological protein degradation in wet burial environments: (1) short term (up to 8 years) experimental burial in three contrasting soil environments; and (2) laboratory wet conditions, in which elevated temperature (80 °C, 110 °C, and 140 °C) and pressure simulated longer exposure. Elemental and amino acid (AA) composition were also measured.

RESULTS

In experimentally soil-buried samples, AA, elemental and isotopic composition changes were small, despite extensive macroscopic alteration. Isothermally heated samples showed preferential loss of hydrophilic AAs (Asx, Glx, Ser, Gly) from wool residues, with depletion in (2)H and (18)O at higher temperatures (up to -73‰ change in δ(2)H and -2.6‰ in δ(18)O values). The δ(13)C and δ(15)N values showed little change except in densely pigmented samples at low temperatures only. Samples dyed with madder/alum were better preserved than undyed samples.

CONCLUSIONS

Diagenesis in experimentally soil-buried wool textiles was consistent with microbiological, non-protein-selective activity, in contrast to highly AA-selective hydrolytic behaviour under laboratory wet conditions. Changes in δ(2)H and δ(18)O values were correlated with degree of AA change, but the δ(13)C and δ(15)N values were not. The results contribute to a baseline for interpreting analytical data from archaeological hair samples preserved by burial in wet environments.

Species identification of archaeological skin objects from Danish bogs: comparison between mass spectrometry-based peptide sequencing and microscopy-based methods

Denmark has an extraordinarily large and well-preserved collection of archaeological skin garments found in peat bogs, dated to approximately 920 BC - AD 775. These objects provide not only the possibility to study prehistoric skin costume and technologies, but also to investigate the animal species used for the production of skin garments. Until recently, species identification of archaeological skin was primarily performed by light and scanning electron microscopy or the analysis of ancient DNA. However, the efficacy of these methods can be limited due to the harsh, mostly acidic environment of peat bogs leading to morphological and molecular degradation within the samples. We compared species assignment results of twelve archaeological skin samples from Danish bogs using Mass Spectrometry (MS)-based peptide sequencing, against results obtained using light and scanning electron microscopy. While it was difficult to obtain reliable results using microscopy, MS enabled the identification of several species-diagnostic peptides, mostly from collagen and keratins, allowing confident species discrimination even among taxonomically close organisms, such as sheep and goat. Unlike previous MS-based methods, mostly relying on peptide fingerprinting, the shotgun sequencing approach we describe aims to identify the complete extracted ancient proteome, without preselected specific targets. As an example, we report the identification, in one of the samples, of two peptides uniquely assigned to bovine foetal haemoglobin, indicating the production of skin from a calf slaughtered within the first months of its life. We conclude that MS-based peptide sequencing is a reliable method for species identification of samples from bogs. The mass spectrometry proteomics data were deposited in the ProteomeXchange Consortium with the dataset identifier PXD001029.

A new helical crossed-fibre structure of β-keratin in flight feathers and its biomechanical implications

The feather aerofoil is unequalled in nature. It is comprised of a central rachis, serial paired branches or barbs, from which arise further branches, the barbules. Barbs and barbules arise from the significantly thinner lateral walls (the epicortex) of the rachis and barbs respectively, as opposed to the thicker dorsal and ventral walls (the cortex). We hypothesized a microstructural design of the epicortex that would resist the vertical or shearing stresses. The microstructures of the cortex and epicortex of the rachis and barbs were investigated in several bird species by microbe-assisted selective disassembly and conventional methods via scanning electron microscopy. We report, preeminent of the finds, a novel system of crossed fibres (ranging from ∼100-800 nm in diameter), oppositely oriented in alternate layers of the epicortex in the rachis and barbs. It represents the first cross-fibre microstructure, not only for the feather but in keratin per se. The cortex of the barbs is comprised of syncitial barbule cells, definitive structural units shown in the rachidial cortex in a related study. The structural connection between the cortex of the rachis and barbs appears uninterrupted. A new model on feather microstructure incorporating the findings here and in the related study is presented. The helical fibre system found in the integument of a diverse range of invertebrates and vertebrates has been implicated in profound functional strategies, perhaps none more so potentially than in the aerofoil microstructure of the feather here, which is central to one of the marvels of nature, bird flight.

Hair analysis as a biomonitor for toxicology, disease and health status

Hair analysis receives a large amount of academic and commercial interest for wide-ranging applications. However, in many instances, especially for elemental or 'mineral' analysis, the degree of success of analytical interpretation has been quite minimal with respect to the extent of such endeavors. In this critical review we address the questions surrounding hair analysis with specific intent of discovering what hair concentrations can actually relate to in a biogenic sense. This is done from a chemistry perspective to explain why and how elements are incorporated into hair and their meaning. This includes an overview of variables attributed to altering hair concentrations, such as age, gender, melanin content, and other less reported factors. Hair elemental concentrations are reviewed with regard to morbidity, with specific examples of disease related effects summarized. The application of hair analysis for epidemiology and etiology studies is enforced. A section is dedicated specifically to the area of population studies with regards to mercury, which highlights how endogenous and exogenous incorporation relies on species dependant metabolism and metabolic products. Many of the considerations are relevant to other areas of interest in hair analysis, such as for drug and isotopic analysis. Inclusion of a table of elemental concentrations in hair should act as a valuable reference (298 references).

DNA from keratinous tissue. Part I: hair and nail

Keratinous tissues such as nail, hair, horn, scales and feather have been used as a source of DNA for over 20 years. Particular benefits of such tissues include the ease with which they can be sampled, the relative stability of DNA in such tissues once sampled, and, in the context of ancient genetic analyses, the fact that sampling generally causes minimal visual damage to valuable specimens. Even when freshly sampled, however, the DNA quantity and quality in the fully keratinized parts of such tissues is extremely poor in comparison to other tissues such as blood and muscle - although little systematic research has been undertaken to characterize how such degradation may relate to sample source. In this review paper we present the current understanding of the quality and limitations of DNA in two key keratinous tissues, nail and hair. The findings indicate that although some fragments of nuclear and mitochondrial DNA appear to be present in almost all hair and nail samples, the quality of DNA, both in quantity and length of amplifiable DNA fragments, vary considerably not just by species, but by individual, and even within individual between hair types.