Multi-element stable isotope analysis of H, C, N and S in hair and nails of contemporary human remains

Abstract

This paper presents a comparison of the isotopic ratios of hydrogen, carbon, nitrogen and sulphur of three pairings of hair and nail tissue taken from contemporary human remains. Our aim was to examine the possibility of a direct comparison of isotopic data in hair with that of nail tissue for forensic purposes. The results indicate that stable isotope ratios of the elements were best comparable between human scalp hair longer than 3 cm and the distal end of the nails. There were no distinct variations between finger and toenails. Our isotopic data for bulk hair and nail confirmed that hair samples were slightly enriched in (13)C but depleted in (15)N compared to nail samples. Furthermore, our data reveal that δ(34)S values in nail samples were more variable than in hair samples. Direct comparison of the corresponding segments of hair and nail samples may be difficult due to individual differences especially for δ(15)N and δ(2)H. Hair may have an isotopic composition more consistent with the ingested food within a specific time than is provided by nail. It can be concluded that once a hair is formed, no further metabolic changes of the isotopic pattern should occur. Nevertheless, our data suggest that there was a change in isotope ratios particularly for δ(2)H along the hair shaft. Interpretation of the isotope data in corresponding segments of hair and nail for forensic purposes must consider particular variations, especially for chronological considerations.

Global spatial distributions of nitrogen and carbon stable isotope ratios of modern human hair

“…[20,21] In order to incorporate nail samples in the global dataset, correction factors for nail carbon and nitrogen isotope ratios were determined. Using paired samples of hair and nail from the same individuals the offsets between the hair and nail isotope ratios could be determined.…”

“…[17] In general, the δ 13 C values are lower in Europe than in the rest of the world. The highest δ 13 [20,21] as well as unpublished data. The dotted line represents the 1:1 correlation, the black solid line represents the linear regression.…”

“…Our results confirm that the δ 13 C values of human nail are lower than those of hair and that nail δ 15 N values are higher than those of hair. [20,21] The differences in isotope ratios between hair and nail are attributed to differing amino acid compositions as well as to potentially different amino acid turnover in hair follicles and the nail matrix, although the exact mechanisms remain unclear. [20] Because most of the published carbon and [4] Portugal, Spain -19.9 ±0.6 (49) (1,3); [4,17] Bulgaria, Moldova, Romania* -20.0 ±0.5 (36) (2,3); [4] Czech Rep., Hungary, Slovakia* -20.1 ±0.8 (70) [4,29] France -20.3 ±0.6 (≥61) + (3); [4,17,26,36] Italy incl.…”

Multi-factorialin vivostable isotope fractionation: causes, correlations, consequences and applications

“…The isotope data of sulphur are related to geographical peculiarities of the sample's origin [265,266] and can be especially efficient and informative in the context of multi-element multi-compound isotope ratio analysis [3,11,267]. This is not only of advantage in food origin assignment but also for forensic analysis [268]. Recently, the isotope ratio measurement of further elements has been integrated into the identification of meat origin [11,269].…”

Mechanical Properties of Healthy and ex vivo Onychomycosis Nails and the Influence of a Porphyrin-propylene Glycol Antifungal Formulation

“…1) of which the strength is determined by the number of -S-S-disulphide cross links in this structure mediated by sulphur-containing amino acids. In case of nail keratin, the number of SH-containing cysteine amino acid units is large [4] and apart from disulphide bridges within single keratin protein there is a large number of intermolecular disulphide bridges. Both factors cause the increased strength of nail compared to hair and skin keratin.…”