Strategic Utilization of the Photophysical and Photochemical Properties of Luminescent Transition Metal Complexes as Synthetic Substrates for Protein Tags

Project: Research

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In this project, we aim to develop new photofunctional transition metal complexes as novel synthetic substrates for protein tags including the SNAP-tag, CLIP-tag, and HaloTag. The analysis and evaluation of protein functions have been greatly assisted by the development of protein tag technology. In this strategy, the protein of interest is tagged with a low-molecular weight protein or polypeptide, which is subsequently modified with a synthetic label such as an organic fluorophore or other targeting molecules. Currently, the three most widely used protein tags are the SNAP-tag, CLIP-tag, and HaloTag. Although a number of fluorescent substrates for these tags have been developed, their use requires stringent washing after labeling because unlabeled probes remaining inside the cells can lead to strong background fluorescence. Thus, one of the current challenges is the development of fluorogenic probes that show fluorescence turn-on after bioconjugation. The protein tag technology has also facilitated the development of chromophore-assisted light inactivation (CALI). This technique employs a chromophore as a photosensitizer that produces reactive oxygen species (ROS) such as singlet oxygen upon irradiation; the latter can damage proteins in close vicinity of the chromophore. Although various protein tag substrates have been utilized, there is a lack of candidates that show high singlet oxygen production quantum yields and at the same time remain photostable upon irradiation. To date, nearly all of the fluorescent probes and photosensitizers developed as SNAP-tag, CLIP-tag, and HaloTag substrates are organic dyes. Although the interesting luminescence properties of transition metal complexes have been widely utilized in biosensing and bioimaging as demonstrated by us and other research groups, the idea of using metal complexes as substrates for protein tags has not been explored. In this project, we will design new substrates for the SNAP- tag, CLIP-tag, and HaloTag based on photofunctional transition metal complexes. The photophysical and photochemical properties of the complexes and their reactivity toward the protein tags will be investigated. Additionally, the cellular uptake, cytotoxicity, and bioimaging properties of the complexes, and their applications in CALI of proteins and intracellular biosensing will be examined. We believe that a combination of the specificity associated with the genetically encoded protein tags and the intriguing photophysical and photochemical properties of transition metal complexes will afford useful bioimaging, protein-inactivating, and biosensing reagents. Ultimately, we are very confident that the results generated from this project will lead to the development of biological and medical reagents with useful diagnostic and therapeutic applications.


Project number9042384
Grant typeGRF
Effective start/end date1/01/17 → …

    Research areas

  • bioimaging , luminescence , probes , protein tags , transition metal complexes