1Group Earth System Science - Dpt Geography, Universidade de Santiago de Compostela, Spain, 2Archaeological Research Laboratory, Stockholm University, Sweden, 3Laboratory of Physical Anthropology, Universidad de Granada, Spain, 4Group Earth System Science - Dpt Edafoloxía e Química Agrícola, Universidade de Santiago de Compostela, Spain, 5Pyrolyscience, private company, Pyrolyscience, Santiago de Compostela, Spain
April 22, 2017 , Acadia
Bone remains from pre-industrial populations are suitable and accesible models to understand skeletal biology, including the presence of advanced chronic infections. In this case, bone and its proteins (collagen) could show modifications due to both pre-mortem (e.g. disease) and post-mortem processes. Our work pretend to characterize the skeletal molecular structure in healthy and unhealthy individuals using non-destructive spectroscopic techniques combined with multivariate statistics.
Non-pathological bone and extracted collagen (n=55, ribs) were characterized using FTIR-ATR spectroscopy. We also analyzed skeletal pieces (n=10) showing pathological signs compatible with chronic infections (tuberculosis, brucellosis and treponematosis). Samples were recovered in 9 necropoleis from Spain, representing a wide chronological period (~3,500 years). The second derivative were used to identify the most relevant absorption bands. Principal components analysis (PCA) and multiple regression models were developed to synthesize the spectroscopic information.
PCA in non-pathological bone enabled us to distinguish the main bone components: proteins (mainly collagen), carbonates and phosphates (bioapatite). The same analytical procedure was applied to collagen observing two main post-mortem changes: a preferential loss of α-helix with a residual increment in carbohydrates, and a secondary process related to the damage of β-sheets. Little changes in protein composition have been found in pathological bone with respect to non-affected (from the same individual); however, a preferential increase in carbonate rather than phosphate was detected. Our results show the potential of FTIR to explore skeletal structure and composition. The implications in the understanding of bone remodeling during chronic diseases encourage future studies.
OLC is funded by Plan Galego I2C mod.A. The research was supported by the projects GPC2014/009 (Xunta de Galicia), Rede Consiliencia and CSO2014-55816-P from Spanish Mnistry of Research