Radiocarbon Dating of the Human Eye Lens Crystallines Reveal Proteins without Carbon Turnover throughout Life

BACKGROUND: Lens crystallines are special proteins in the eye lens. Because the epithelial basement membrane (lens capsule) completely encloses the lens, desquamation of aging cells is impossible, and due to the complete absence of blood vessels or transport of metabolites in this area, there is no subsequent remodelling of these fibers, nor removal of degraded lens fibers. Human tissue ultimately derives its (14)C content from the atmospheric carbon dioxide. The (14)C content of the lens proteins thus reflects the atmospheric content of (14)C when the lens crystallines were formed. Precise radiocarbon dating is made possible by comparing the (14)C content of the lens crystallines to the so-called bomb pulse, i.e. a plot of the atmospheric (14)C content since the Second World War, when there was a significant increase due to nuclear-bomb testing. Since the change in concentration is significant even on a yearly basis this allows very accurate dating. METHODOLOGY/PRINCIPAL FINDINGS: Our results allow us to conclude that the crystalline formation in the lens nucleus almost entirely takes place around the time of birth, with a very small, and decreasing, continuous formation throughout life. The close relationship may be further expressed as a mathematical model, which takes into account the timing of the crystalline formation. CONCLUSIONS/SIGNIFICANCE: Such a life-long permanence of human tissue has hitherto only been described for dental enamel. In confront to dental enamel it must be held in mind that the eye lens is a soft structure, subjected to almost continuous deformation, due to lens accommodation, yet its most important constituent, the lens crystalline, is never subject to turnover or remodelling once formed. The determination of the (14)C content of various tissues may be used to assess turnover rates and degree of substitution (for example for brain cell DNA). Potential targets may be nervous tissues in terms of senile or pre-senile degradation, as well as other highly specialised structures of the eyes. The precision with which the year of birth may be calculated points to forensic uses of this technique

Optimisation of the radiocarbon dating process of mortar samples. A case study in the Colosseum, Rome (Italy)

This project highlights the importance of an integrated planning of field and laboratory procedures for the success of the radiocarbon dating of mortar samples. In this research bulk mortar analysis was complemented with lime lump analysis. The two materials were dated at different laboratories. Results are discussed considering the historic and archaeological information available on the building and on the structure where the sample was collected

Projektet Ålands kyrkor och murbruksdatering – rapport från en metodutveckling

The Åland Churches and Mortar Dating – State of Research from the Development of a Method. By Åsa Ringbom, Jan Heinemeier, Alf Lindroos & Àrny Sveinbjörnsdottir. Why mortar dating? The project the Åland Churches was initiated with the aim to finally reach a reliable chronology for a group of stone churches upon which there had been deep disagreement. Since there are no contemporary sources to shed light on the matter, and since coins and artefacts cannot date buildings, there was an obvious need for objective scientific methods on a larger scale. The method of dendrochronology was widely applied on wooden structures in the churches in 1991-1992. Even if dendrochronology could not date the first building stages of the churches, due to repairs and fires, this method was very important in providing firm dates for secondary structures, and for comparative research. Mortar is not an organic material. Yet, absorbing CO2 from the atmosphere during the hardening process, makes mortar an ideal material for 14C dating. Compared to all other datable materials, mortar has the advantage of being found in the original in large quantities, from all the different building stages. Thus, the project focused on developing the method of mortar dating. Since 1994, reliable results have been reached, thanks to the introduction 14C AMS (Accelerator Mass Spectrometry) analysis. To begin with the analysis took place in the 14C AMS Dating Centre at Aarhus University, Denmark. The project turned international in 1997 when the method was tested in classical archaeology, upon mortars from the margins of the Roman Empire, and on hydraulic pozzolana mortars from Rome itself. Since 2005 the collaboration for the analysis includes the Oxford Radiocarbon Accelerator Unit, and the NSF-Arizona AMS Laboratory, in Tucson. Our conclusion today is that non hydraulic lime mortars, whether medieval or classical, are well suited for mortar dating. From Åland, 96% of all the mortars with age control, have yielded convincing results (for further information see www.kyrkor.ax). It is hardly surprising that hydraulic pozzolana concrete, with an entirely different chemistry, is more difficult. But even so, several important structures in Rome have yielded an age well known from historical sources and brick stamps. From our vast experience we have been able to identify different criteria of reliability for interpreting results where mortar dating is the only method available