Ecto-secretions: A Comparative Study between Mucus, Venom and Silk

Animals have developed specific characteristics to facilitate a range of natural functions, from the chemical to the mechanical. One of these adaptations include producing ecto-secretions, materials secreted by specialised glands to be used outside the body. Three model ecto- secretions include gastropod locomotive mucus, used to facilitate animal’s locomotion; snake venom, to facilitate the immobilization and digestion of prey; and silk, which has a range of functions, from protection to reproduction. However, even now, there are no studies analysing these three model ecto-secretions together. To fill the gap in the study of ecto-secretions, the primary aim of this thesis was to investigate the structure-hydration-function relationship of gastropod locomotive mucus and snake venom for comparison to silk. To achieve this a set of experimental techniques was included, such as spectroscopy, electrophoresis, thermoanalytical techniques (differential scanning calorimetry and thermogravimetric analysis) and rheology. This project was the first to directly correlate ecto-secretions’ properties. Here, I have developed a novel scientific platform combining different experimental and analytical techniques. This approach has made it possible to compare and contrast the role of proteins in ecto-secretions and to use these materials as a novel grouping to explore the more general area of how proteins have been selected and optimised to perform outside the body. The compositional and thermal characterisation of these materials revealed that proteins in gastropod locomotive mucus and snake venom exhibit a higher thermal stability than silk, due to glycosylation, hydration state and main function. Moreover, rheology offered a unique answer to a question regarding the flow properties of snake venom, proving it is a Newtonian fluid. The developed Performance Map can be used as a guide to incorporate more and new ecto- secretions in the future. With my findings, I have a broader knowledge of these materials, which can be used during the industrial processing of materials inspired by ecto-secretions.