Carbon isotopic dietary signatures of amino acids

Thesis

In an exploratory study, techniques were developed for isolating bulk plant proteins and measuring the ¹³C isotopic compositions of their constituent amino acids by HPLC-IRMS. Samples of plants expected to be of potential palaeodietary significance in northwestern Europe were selected for investigation.

Different tissues of plants, leaves and seeds, may be distinguished from each other by the relative ¹³C isotopic compositions (‘isotopic signatures’) of the amino acids of their constituent proteins. For each tissue type, different plant types may be distinguished in the same way. These signatures can vary slightly according to environment and season, but the variation among types is greater than this. For leaves, isotopic signatures can be used to differentiate (i) nettles, (ii) true grasses, (iii) reeds etc, (iv) trees, (v) legumes, (vi) maize, (vii) freshwater plants and (viii) marine algae. For seeds, these signatures are able to differentiate (i) wheat-type cereals, (ii) barley-type cereals, (iii) C4 cereals, (iv) pseudocereals, (v) legumes and (vi) tree nuts.

From investigations using a mixing model, it appears that these signals, particularly those of essential amino acids, are reflected in the tissues of their consumers. Freshwater plants are identified as the base of the food chain for dragonfly larvae, marine algae as the diet of marine molluscs and grass as the diet of archaeological cattle and aurochs. Isotopic ‘marine signals’ identified by previous researchers have been refined using these data and the isotopic signatures of fish muscle.

These findings are expected to be of particular value in the study of palaeodiets using proteins from archaeological tissues, especially bone and hair. This approach will also find application in the fields of plant physiology and biochemistry.

Authors: Lynch, A

• Publication date: 2011
• DOI: 10.5287/ora-0ndzxokzk
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: Oxford University, UK
• Language: English
• Keywords: 13C; archaeological science; Palaeodiet; Amino acid; HPLC; isotope
• Subjects: Molecular Plant Physiology; Archaeology