Raman spectroscopic analyses of preserved historical specimens of human hair attributed to Robert Stephenson and Sir Isaac Newton{ Howell G. M. Edwards,* a Nik F. N. Hassan a and Andrew S. Wilson b a Chemical and Forensic Sciences, The School of Pharmacy, University of Bradford, Bradford, UK BD7 1DP b Department of Archaeological Sciences/Biomedical Sciences, University of Bradford, Bradford, UK BD7 1DP. E-mail: h.g.m.edwards@bradford.ac.uk Received 16th June 2004, Accepted 2nd August 2004 First published as an Advance Article on the web 23rd August 2004 The Raman spectra of two historical specimens of human hair attributed to the engineer Robert Stephenson and scientist Sir Isaac Newton, preserved in private collections are reported. Comparisons are made with the Raman spectra of modern hair specimens and with hair from archaeological excavations. The hair spectra collected with a laser excitation of 785 nm are of a better quality than those collected using 1064 nm. The historical hair specimens are remarkably well-defined spectroscopically in terms of the amide I vibrational mode and the n(SS), ascribed to a predominantly gauche–gauche–gauche CSSC conformation. The contrast with degraded hair specimens recovered from archaeological excavations is striking. The presence of a weak feature near 2590 cm 21 in the hair samples attributed to a n(SH) vibration could be indicative of a reduction process operative on the CSSC cystine keratotic linkages and a possible origin of this is bacterial biodegradation identified histologically. This study demonstrates the molecular information available from non-destructive Raman spectroscopic analysis from single hair shafts or small bundles of fibres which complements information available from histological and destructive analytical techniques for rare biological specimens subjected to conservation or curation procedures in museums or private collections. Introduction The preservation of historical artefacts in museum collections and the conservation of artefacts and ecofacts from archaeo- logical excavations are important tasks facing curators of national heritage; this is even further complicated when the specimens are biological and subject to degradation processes including bacterial or fungal attack exacerbated by fluctuations in temperature and humidity on storage. Firstly, there are particular issues relating to the condition of curated tissues, such as hair, where the influence of low-wavelength radiation (v350 nm) and contact with packaging materials such as paper, which can have variable residual moisture and acidity levels, can initiate a complex sequence of chemical reactions. Colonisation by microorganisms is particularly affected through moisture change and atmospheric exposure. Secondly, modern conservation is critically dependent upon knowledge of curation procedures carried out hitherto and there are few non-destructive analytical methods which can be employed to monitor the status of biological samples which are potentially ‘‘at risk’’. Raman spectroscopy has been applied successfully to the characterisation of human tissues from a range of archaeo- logical and depositional environments including hot desert burials, ice-tombs and waterlogged soil. Specimens of skin, bone, hair, nail and teeth from prehistoric to recent times have yielded information about the taphonomy and diagenesis of the keratotic components of hard and soft tissue in frozen and naturally freeze-dried mummies 1–3 (from 5300 years ago), Egyptian mummies 4 (from 4000 years ago), early Amer-Indian cultures 5 (from 3000 years ago), Roman and early mediaeval burials (from 1000–2000 years ago) to comparatively recent interments (ca. 2–3 years ago). 6,7 The assembly of spectroscopic data from a wide variety of tissue specimens in different states of degradation is relevant for the evaluation of applica- tions of Raman techniques to forensic science and crime-scene investigation. In particular, the successful recording of Raman spectra from naturally desiccated human tissue specimens preserved under frozen conditions 1–3 has drawn attention to the effects on the vibrational bands of the proteins at the onset of deteriora- tion; the reduction in band intensity and disappearance of the n(SS) mode near 500 cm 21 arising from the cystine disulfide cross-links, followed by the broadening of the amide I band near 1660 cm 21 due to the a-helical to b-sheet and random coil conformational changes are clear biomarkers of specimen deterioration. More complex relative band intensity changes also occur in the d(CH 2 ) and d(NH) regions between 1200 and 1500 cm 21 . In contrast to these studies of relatively well- preserved human biomaterials, the chemical and biological degradation suffered by hair specimens in a variety of natural and simulated burial environments 7 seriously affects the Raman spectral quality. Hence, even after only a few months’ in a natural depositional environment, exhumations of hair specimens already show an advanced state of decomposi- tion spectroscopically in comparison with their cryogenically- preserved analogues, and the spectral interpretation of the degradation processes is thereby compromised. The absorption of potentially fluorescent materials, such as humic acids, from the surrounding burial environment also makes the recording of the Raman spectra of these samples very difficult. In the current study, an opportunity has arisen to examine spectroscopically two important historical human hair speci- mens from a museum archive and a private collection which { Electronic supplementary information (ESI) available: Profiles on Robert Stephenson and Sir Isaac Newton. See http://www.rsc.org/ suppdata/an/b4/b409224b/ DOI: 10.1039/b409224b 956 Analyst , 2004, 129 , 956–962 This journal is ß The Royal Society of Chemistry 2004 Published on 23 August 2004. 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