Project:	Predicting biological traits from stable isotope ratios of amino acids
Disciplines:	Multidisciplinary, Biology, Chemistry, Geobiology, Geosciences, Data Science, Computer Science
Mentor:	Julia Tejada, Assistant Professor, (GPS), jtejada@caltech.edu
Background:	Nitrogen stable isotope of amino acids are used to infer trophic dynamics in modern and fossil ecosystems. Typically, only two amino acids out of the at least twelve consistently found in proteins —phenylalanine and glutamic acid — are employed. While these two amino acids are considered the canonical source and trophic amino acids, respectively, the predictive biological roles of the remaining amino acids have been largely overlooked.
Description:	The PI will provide the student with published and unpublished stable isotope data of keratin and collagen amino acids from modern and fossil mammals. The student’s tasks include collecting data on biological and life history traits for these mammal species and employing various mathematical models (e.g., generalized linear mixed models with AICc as the criterion for model selection) to infer these traits with the stable isotopic data. While the project is predominantly computer-based, there is also an opportunity for hands-on lab experience in stable isotope analysis of amino acids for students interested in learning about the isotopic measurement process.
References:	Boecklen et al. 2011. On the use of stable isotopes in trophic ecology. Annu. Rev. Ecological. Evolution. Syst. 42: 411-440 Lee-Thorp et al. 1989. Stable isotope ratio differences between bone collagen and bone apatite, and their relationship to diet. J. Archaeol. Sci. 16, 585-599 Clementz et al. 2009. Revisiting old bones: coupled carbon isotope analysis of bioapatite and collagen as an ecological and palaeoecological tool. Geol. J. 44, 605-620 McMahon et al., 2016. Embracing variability in amino acid d15N fractionation: mechanisms, implications, and applications for trophic ecology. Ecosphere 7, 1-26 Tejada et al. 2021. Isotope data from amino acids indicate Darwin's ground sloth was not an herbivore. Scientific Reports 11, 18944 O'Connell, 2017. 'Trophic' and 'Source' amino acids in trophic estimation: a likely metabolic explanation. Oecologia 184, 317-326 Larsen, et al. 2022. Reconstructing hominin diets with stable isotope analysis of amino acids: new perspectives and future directions. BioScience 72(7): 618-637
Student Requirements:	intro biology/chemistry/geosciences, basic experience and understanding of statistics.
Programs:	This AO can be done under the following programs:   Program    Available To        Amgen Scholars    Non-Caltech students only          SURF    both Caltech and non-Caltech students  Click on a program name for program info and application requirements.