Hong - Fluorescent probes, cell imaging, protein misfolding and neurodegenerative diseases
Our group develops organic luminescent molecules as probes and imaging tools for understanding fundamental biological processes associated with ageing and diseases.
Fluorescence is a powerful technique that could provide spatiotemporal information with exquisite sensitivity. The primary goal of our research is to develop fluorescence-based tools for understanding and manipulating fundamental biological processes. Efforts will be directed towards the design and synthesis of new luminescent molecules in combination with advanced fluorescence spectroscopy and microscopy for monitoring protein conformational transitions associated with neurodegenerative diseases and for tracing biological events in living context.
Molecular reporters for measuring proteostasis capacity in cell
Protein homeostasis (proteostasis) describes the maintenance of the proteome in a proper folded state by an extensive quality control network. Under normal proteostasis conditions, protein synthesis, proper folding and localisation, as well as the timely degradation and disassembly of abundant proteins are in balance. Perturbation of proteostasis often leads to the accumulation of misfolded proteins and aggregates, which has been linked to many neurodegenerative diseases such as Alzheimer’s, Parkinson’s and Huntington’s Diseases. Pharmacologic manipulation of the proteostasis network to improve its capacity is emerging as a new therapeutic strategy for these conditions.
Given the importance of proteostasis in protein folding in cells and their association with diseases, we are interested to develop chemical tools to quantitatively measure the proteostasis capacity at the population and individual cell level. We have recently developed a general-purpose probe scheme based on a unique small molecule fluorogen (fluorescence turn-on sensor) to measure the unfolded protein load, which reflects on the proteome stress, in cells. In this project, a series of new probes are synthesized and will be used in combination with other techniques to study how the proteome unfolds under stress conditions and how the key quality control system deals with the unfolded proteins in these conditions.
Capturing early-stage protein aggregations and the role of misfolded proteins
Highly ordered protein aggregates termed amyloid fibrils are associated with a wide range of diseases including neurodegenerative diseases and amyloidosis. The transition from soluble functional protein into insoluble amyloid fibril occurs via a complex process involving the initial generation of highly dynamic early-stage aggregates or pre-fibrillar species. Traditional amyloid probes, for example, thioflavin T and Congo red, have been used for decades as “gold standard” for detecting amyloid fibrils in solution and in tissue section, respectively. However, these well-established dyes can hardly detect the presence of prefibrillar species in the early stage of protein aggregation process, which have been proposed to play a key role in the cytotoxicity of amyloid proteins and pathogenesis of neurodegenerative diseases. Our focus will be on the fluorescent dyes that are able to detect the emergence of prefibrillar species in the early stage of protein aggregation. This project will use this new probe as well as other biochemical and biophysical techniques to study the aggregation behavior of a wide range of amyloid proteins, investigate the toxicity of different aggregated species, and evaluate the effect of inhibitors on these processes.
New fluorescent probes for visualising cell structures and function
Organic fluorogens with aggregation-induced emission (AIE) characteristics have demonstrated their potential to be ideal candidates for live cell imaging. Opposite to conventional organic dyes, the AIE luminogens are non-luminescent when molecularly dissolved but highly emissive upon aggregation. As small molecules, the AIE luminogens normally enter cells through diffusion, accumulate in the target location, and generate light emission. Inherently, they possess large Stokes shift (> 100 nm) with appreciable brightness and they are resistant to photo-bleaching and blinking, owing to the formation of aggregates inside the cells. In addition, they are structurally simple and synthetically accessible: the excitation/emission wavelengths as well as the functionalities can be fine-tuned via structural modification. In this study, we would like to synthesize new AIE dyes and explore their applications for specific imaging of different organelles, tracking dynamics of mitochondria as well as mapping intracellular environment in physiological and pathological conditions via advanced fluorescence imaging techniques.
Meet the team
Xavier Shouxiang Zhang
Tze Cin OwYong (co-supervised with Dr Wallace Wong, Bio21 Institute)
Karren Jiamin Zhao
Specific detection and quantification of cardiolipin and isolated mitochondria by positively charged AIE fluorogens and method of manufacturing thereof: US Patent 10,113,968.
Aggregation Induced Emission Active Cytophilic Fluorescent Bioprobes for Long-Term Cell Tracking: US Patent 9,409,928.
Aggregation induced emission of fluorescent bioprobes and methods of using the same: US Patent 9,618,453.
Photostable AIE luminogens for specific mitochondrial imaging and its method of manufacturing thereof: US Patent 9,315,465.
Water-soluble AIE luminogens for monitoring and retardation of fibrillation of amyloid proteins: US Patent 9,279,806.
Aggregation-induced emission luminogens for metal ion detection: US Patent 9,228,949.
Water-soluble AIE luminogens for monitoring and retardation of fibrillation of insulins: US Patent 8,679,738.
Fluorescent water-soluble conjugated polyene compounds that exhibit aggregation induced emission and methods of making and using same: US Patent 8,129,111.
Fluorescent water-soluble conjugated polyene compounds that exhibit aggregation induced emission and methods of making and using same: US Patent 7,939,613.