The Dominant Role Of Oxygen In Modulating Tyrosine-containing Peptide Self-evolving Pathways

As a necessary component in the whole environment of our living planet,oxygen has played an important role in the evolution of life.Although the emergence of oxygen has fundamentally varied the evolution pathway of macro-organic organisms,there is little research on the regulation of oxygen on the chemical evolution of the peptides and proteins at the molecular level.It is still unclear how oxygen influences and changes the chemical evolution pathway of endogenous molecules and thus lead to materials with different assembled structures and biological functions.Inspired by the fact that tyrosine-containing proteins in nature have different evolution pathways of oxidation reactions,this thesis employs tyrosine-containing amino acid derivatives,peptides and casein to study the effects of oxygen on the chemical evolution pathway of tyrosine molecules and the key regulation of biological function.In this work,the vital role of oxygen has been demonstrated and these different materials with photothermal or luminescent effects have been obtained,respectively.These tyrosine residues tend to form dityrosine or melanin by controlling different oxygen concentrations.The pathway to melanin will be dominant when oxygen is rich.In the process,the product with photothermal effect can be obtained.However,the pathway to dityrosine will dictate the whole reaction when oxygen is really rare.And a kind of pH-responding material can be obtained eventually.This oxygen-controlled chemical evolution has ubiquitously been discovered from amino acid derivatives containing tyrosine residues to casein,a protein that contains many tyrosine residues.Besides,different pathways also lead to different self-assembly with distinctive structures.According to previous work involving the interactions between peptide molecules that lead to hierarchical structures,possible intermolecular interactions that dictate to the formation of different constructions have been proposed.Moreover,the photophysical behavior of dityrosine under different pH conditions also was studied.This work not only reveals the important role the oxygen is playing during the biomolecular evolution but also describes a blueprint in these area of drug delivery,photothermal therapy and novel bio-devices.