CHAPTER 13: The Birth and Fate of Glycine: The the Interstellar Medium to Primitive Earth

Glycine (Gly) is a paradigmatic case to understand the molecular complexity in the interstellar medium (ISM) and planetary scenarios. On the one hand, Gly exhibits an enhanced complexity compared to interstellar complex organic molecules (COMs) and, accordingly, its formation represents one step beyond in the interstellar chemical evolution. On the other hand, it is the simplest proteinogenic amino acid and, accordingly, the simplest building block for the formation of biopolymers. The life's pathway of Gly can roughly be elucidated by joining different results from different approaches: (i) from laboratory experiments, showing Gly formation via processing of interstellar ice analogs; (ii) from chemical analysis of comets and meteorites; and (iii) from experimental measurements of Gly polymerization on minerals' surfaces. Therefore, life's pathway of Gly can be associated with its synthesis in the ISM, its transportation and delivery by micro-asteroidal bodies to the early Earth, and its polymerization under prebiotic conditions on a young Earth. However, the elucidation of the atomistic details and related energetics of these plausible Gly voyages are still incomplete and spread in the literature and, most of the time, difficult to be coherently harmonized due to the different approaches and methods adopted. This book chapter provides an overview of the atomistic interpretation of the birth and fate of Gly by means of what has been achieved through quantum chemical investigations.