Linking structural and compositional changes in archaeological human bone collagen: an FTIR-ATR approach

Abstract

Collagen is the main structural and most abundant protein in the human body, and it is routinely extracted and analysed in scientific archaeology. Its degree of preservation is, therefore, crucial and several approaches are used to determine it. Spectroscopic techniques provide a cost-effective, non-destructive method to investigate the molecular structure, especially when combined with multivariate statistics (chemometric approach). In this study, we used FTIR-ATR spectroscopy to characterise collagen extracted from skeletons recovered from necropoleis in NW Spain spanning from the Bronze Age to eighteenth century AD. Principal components analysis was performed on a selection of bands and structural equation models (SEM) were developed to relate the collagen quality indicators to collagen structural change. Four principal components represented: (i) Cp1, transformations of the backbone protein with a residual increase in proteoglycans; (ii) Cp2, protein transformations not accompanied by changes in proteoglycans abundance; (iii) Cp3, variations in aliphatic side chains and (iv) Cp4, absorption of the OH of carbohydrates and amide. Highly explanatory SEM models were obtained for the traditional collagen quality indicators (collagen yield, C, N, C:N), but no relationship was found between quality and δ13C and δ15N ratios. The observed decrease in C and N content and increase in C:N ratios is controlled by the degradation of protein backbone components and the relative preservation of carbon-rich compounds, proteoglycans and, to a lesser extent, aliphatic moieties. Our results suggest that FTIR-ATR is an ideal technique for collagen characterization/pre-screening for palaeodiet, mobility and radiocarbon research.

A Collagen Basketweave from the Giant Squid Mantle as a Robust Scaffold for Tissue Engineering

“…The polypeptide backbone CO stretching vibration is found in the range of 1600-1700 cm −1 : bands at 1740 cm −1 due to carbonyl vibrations, and the one 1630 cm −1 due to Amide I. The spectrum shows bands at 2878 and 2927 cm −1 assigned to aliphatic chains (CH stretching and CH 3 stretching) an Amide B band at 3073 cm −1 (NH stretching), and a broad band at 3500-3300 cm −1 related to Amide A (NH stretching) and OH vibrations [56][57][58][59][60]. For comparison, the FTIR spectra of collagens Type I and Type II were examined [61].…”

Biological histories of an elite: Skeletons from the Royal Chapel of Lugo Cathedral (NW Spain)

“…All samples fulfilled the established quality criteria for well-preserved collagen for carbon, nitrogen, and sulfur ratios and bioapatite (according to Cortizas & L opez-Costas, 2020;Garvie-Lok et al, 2004;Nehlich 2015;Nehlich & Richards, 2009;Van Klinken, 1999). In addition to the standard quality indicators, pyrolysis GC/MS was used to assess the preservation of the extracted collagen in two samples…”

“…Samples were then frozen and freeze dried to remove any remaining liquid. The quality of bioapatite as well as absence of organic material was tested using FTIR-ATR (Agilent Cary 630 FTIR Spectrometer)-this means that there were no absorption bands that correspond with Amide I, I, II, A, and B in the samples (see Cortizas & L opez-Costas, 2020;Prieto G omez, 2018). Carbon and oxygen isotope ratios in bioapatite were measured at Iso-Analytic (Chenery et al, 2012;Daux et al, 2008).…”

Clinical applications of infrared and Raman spectroscopy in the fields of cancer and infectious diseases

“…The different experimental variants of IR and Raman, each with distinct benefits and limitations, are provided in Table 1 [1][2][3][4][5][6] . Vibrational spectroscopy has been successfully employed as an analytical tool for a number of applications in fields such as pharmacology [7] , archaeology [8] , forensic [9] , food [10] and environmental science [11] , homeland security [12] and biomedicine [13] .…”