Rapid Quantification of Bone Collagen Content by ATR-FTIR Spectroscopy

Abstract

Expensive and time-consuming preparation procedures for radiocarbon and stable isotope analyses can be conducted on archaeological bone samples even if no collagen is preserved. Such unsuccessful preparation can lead to the partial destruction of valuable archaeological material. Establishing a rapid prescreening method for evaluating the amount of bone collagen while minimizing the impact of sampling constitutes a challenge for the preservation of archaeological collections. This study proposes and discusses a new methodology to detect and quantify collagen content in archaeological bone samples by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. A total of 42 Pleistocene to modern bone samples were selected according to their nitrogen content measured using an elemental analyzer. Comparison of collagen content estimation using ATR-FTIR and mass spectrometry reveals that some of the studied samples are contaminated by a nitrogen source coming from the burial environment. Two different FTIR calibration approaches were tested on the uncontaminated samples: peak-to-peak ratio and multivariate regression (PLS). The two approaches yield similar results with a good correlation of ATR-FTIR analyses and N wt% from 0.7 to 4wt% (R²=0.97–0.99; standard error of estimation ±0.22 to 0.25wt%). While collagen content remains difficult to detect in poorly preserved bones (less than ~3wt%), ATR-FTIR analysis can be a fast alternative for sample screening to optimize the sampling strategy and avoid partial destruction of valuable samples that do not contain enough collagen for further analysis.

Assessing bone transformation in late Miocene and Plio‐Pleistocene deposits of Kenya and South Africa

“…Amide bands related to the collagen matrix (Lebon et al . ) are not visible in the ATR‐FTIR spectra of fossil bones, attesting to the degradation of the bone organic fraction. Compared with that of modern bone, diamond ATR‐FTIR spectra of Bolt's Farm fossil bones containing < 1.2 wt.% F display two additional bands at 630 and 3572 cm –1 related to the OH bending and stretching modes, respectively (Figs and S1).…”

Macroscopic electrostatic effects in ATR-FTIR spectra of modern and archeological bones

“…For the more transformed sample BZ-PJ1-09, the estimated collagen content (~11 wt%) of which is about half that of a modern bone, a better agreement with the experimental spectra is achieved for a lower value of the dielectric constant of the host matrix (e h = 1.9), keeping the mineral fraction constant (40 vol%). The decrease in collagen content is correlated to a less pronounced broadening of the n 3 Lebon et al (2016), b Yi et al (2014). …”

“…1) display the usual absorption bands ascribed to the internal vibrations of apatitic orthophosphate groups, to structural carbonate impurities located at the A and B sites (hydroxyl and phosphate sites, respectively) of apatite structure, as well as to the amide bands related to the collagen matrix (e.g., Elliott 2002). Its collagen content is estimated to be ~23 wt% as assessed from nitrogen concentration and intensity of amide bands (Lebon et al 2016). A weak and broad feature at ~700 cm -1 Downloaded from https://pubs.geoscienceworld.org/msa/ammin/article-pdf/103/2/326/4045402/am-2018-6320ccbyncnd.pdf by guest on 07 June 2019 affects the intense phosphate bands of the diamond ATR spectra of bone samples but the similarities of Ge-ATR spectra suggest that this effect is not associated with a strong modification of the microscopic structure of apatitic crystallites.…”

“…Three archaeological animal bone and a modern ox bone samples (Table 1), previously investigated using ATR-FTIR spectroscopy by Lebon et al (2016), were chosen for their various states of collagen preservation as well as a modern tooth enamel sample previously investigated by Yi et al (2014). For each sample, about 50 mg of powder were finely ground with agate mortar and pestle.…”

“…Although most of these studies have biomedical goals, FTIR spectroscopy also allows efficient screening of the preservation state of skeleton remains prior to isotopic and chemical analysis for paleo-environmental reconstructions or radiocarbon dating (e.g. ; Trueman et al 2008;Roche et al 2010;Lebon et al 2016;Snoeck and Pellegrini 2015). Diagenetic transformation of bones and teeth following burial often leads to an increase in crystallinity as well as a decrease in organic fraction and structural carbonate contents (e.g., Hedges 2002;Trueman et al 2008).…”