Major Research Interests
Overview - The underlying common theme subserving a diverse range of Khoo's Lab is the development and applications of mass spectrometry (MS) and associated microscale separation techniques to protein and glycosylation analysis. Over the last decade, such analyses have gradually evolved into omic scale undertakings with emphasis on global comprehensiveness to enable a holistic approach. Yet, this grand vision is often belied by limitations inherent to the very techniques it relies on. In essence, our research focuses on addressing these shortcomings, be it applied to single protein glycosylation analysis, glycomics or glycoproteomics.
In conjunction with overseeing the operation of a state-of-the-art MS facilities for Proteomics at IBC, we first established a MALDI-MS and MS/MS-based analytical platform for facile glycomic mapping, and have since ventured further into attempts to uncover what is often missing from this initial survey picture. Among these are the larger glycans with polyLacNAcs, those carrying sulfates, and/or those occurring at very low abundance, normally suppressed or masked by signals contributed by the uninteresting, highly abundant, ubiquitous structures.
The solution in general relies on strategic enrichment, chemical derivatization and/or enzymatic cleavages. Increasingly, we further resort to LC-MS/MS based approach, taking advantages of various data dependent scan functions to effect targeted glycomic mapping at MS2 or MS3 level. Another issue commonly encountered is the follow-up to glycomic discovery, namely to locate the identified glycotope/ glycan of interest to particular carrier proteins, which entails a highly efficient targeted glycoproteomics workflow that would allow de novo protein identification based on glycopeptide sequencing.
Overall Long Term Goals -
To derive both a panoramic and close-up view of mammalian cell surface glycosylation and its dynamic modulation during programmed development, malignant transformation, and in response to external stimuli in the context of infection, inflammation, and immunity, through which to understand cel-cell interactions from the perspectives of glycosylation mediated recognition at the molecular and systems level. Also of interest is how glycosylation attenuates signal transduction through myriad membrane receptors including siglecs, receptor tyrosine kinases, and the tyrosine phosphatases that are regulated via redox-mediated cysteine modifications.
Towards this long term goal is the current focus on developing mass spectrometry techniques on one hand, whilst incorporating other analytical tools on the other, to enable both discovery and targeted mode analyses. Conscious efforts are also devoted to developing the functional sulfoglycomics of lymphoid and myeloid cells and tissues as the principal biological systems to be investigated in depth.
Current Focus -
To capitalize on recent rapid advances in mass spectrometry instrumentation to deliver the much needed improved sensitivity and selectivity in protein modification analysis, proteomics, glycomics and glycoproteomics, without compromising precision.
Enabling MS techniques to be developed include: