Mechanism-inspired development of a chemoselective click-based bio-orthogonal reaction platform

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Background - The post-genomic era has provided biologists with a wealth of information and -omic sequencing tools to further our understanding of fundamental biology and disease. However, it is still exceedingly difficult to interrogate biological processes where the link between gene and protein expression is decoupled. A pertinent exemplar of this is changes in the glycosylation state between healthy and cancerous cells presented on the cell surface. An emerging tool used to interrogate these changes is the metabolic incorporation of 'chemical reporters' within a target biomolecule and access to highly specific 'bio-orthogonal' chemical reactions, which preferably react only with the chemical reporter group. Key to the success of this approach is the availability of bio-orthogonal reactions that are fast, biocompatible, and chemoselective.The incorporation of two chemical reporters followed by chemoselective bio-orthogonal labelling is an extension of this 'tag and modify' strategy, which offers the opportunity to label two different biomolecules in cellulo. Additionally, the incorporation of different chemical reporters within a single biomolecule followed by dual differential labelling is a nascent approach to probe the dynamics of a single biomolecule. At present, this is highly challenging to achieve with current bio-orthogonal strategies if discretely tagged products (i.e., without a mixture of products) are required.Previous work - Our collaborative team has recently identified the utility of aromatic ynamines as a superior reagent for Cu-catalyzed alkyne-azide cycloaddition (CuAAC) reactions. These alkyne surrogates require significantly less Cu catalyst are the only alkyne reagents reported to date which enable chemoselective control in a sequential two-step CuAAC process.Project Objective - The principal objective of this studentship is to develop aromatic ynamines into a powerful new bio-orthogonal reaction platform for the chemoselective tagging of glycoproteins in prostate cancer cells. The specific aims of the project are to:(i) gain a mechanistic understanding of the enhanced chemoselectivity of ynamines in CuAAC reactions, and potentially across other bio-orthogonal reaction classes.(ii) establish conditions for chemoselective modification of biomolecules.(iii) explore the utility of ynamines as glycoprotein tagging agents of prostate cancer cells.