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(Associate Professor)

Contact Information:
Dept of Biological Sciences
National University of Singapore
Science Drive 4
Singapore 117543
Tel: 65162857
Fax:67792486

email: dbssfs@nus.edu.sg

Research Interests:

Uncovering cellular and molecular bases of learning and memory

Higher brain functions such as learning and memory have been explained by the synaptic modulation in terms of electrophysiological models of long-term poterntiation (LTP) and long-term depression (LTD). In these models brief period of synaptic activity leads to sustained changes in synaptic transmission. The glutamate subtype receptor, NMDA receptor opening and rise in calcium concentration are critical events of these forms of plasticity. Calcium concentration in the neurons is under strict regulation and its changes can bring about such global responses. The involvement of the presynaptic neuron-specific protein kinase C (PKC) substrate Neuromodulin (Nm, aka GAP43) in transmitter release and the involvement of the postsynaptic substrate Neurogranin (Ng) in decoding the Ca 2+ spikes have been predicted due to their affinity with some crucial signaling molecules, very upstream in signaling cascade, namely calmodulin (CaM) and PKC. Given the important linkage of these neuronal proteins with synaptic plasticity in the literature, little is known about the structure of these proteins when complex with their known interaction protein CaM. How structural changes induced in protein complex help identify their roles in the nervous system? The other pressing question appears to identify other natural protein interaction targets of Ng to gain more insight of its functional role in neuronal signaling at the postsynaptic site. To these ends, we propose the present study of X-ray crystal structure determination of Ng-CaM and Nm-CaM protein complex and functional study focused on Ng Tet-On over expression system designed for LTP experiment and to study the Ng regulation over Ca 2+ spikes generation and to predict the interacting partners of Ng in addition to the well known CaM.

Current Projects:

1. Structural study of neuron-specific protein, Neurogranin (Ng) and the induced structural change of calmodulin (CaM) and Ng when they form protein complex in the absence of calcium ion: two focus molecular candidates of biomedical research for learning and memory.

2. Controlled regulation of the Ng expression that is reversible and quantitative to address the function of Ng in neurons.To explore the function of Ng in learning and memory formation, we try to insert Ng gene intothe Tet-On gene expression system that is a reversibly regulated, high-level gene expression system. Ng expression is turned on in the Tet-On system by the addition of Tc or Dox. Our goal in setting up a functional Tet system is to create a stable Tet cell line that contains both the regulatory and response plasmids to express Ng protein. When cells contain both the pTet-On and the pTRE-Ng gene vectors, Ng gene is expressed upon binding of the (r)tTA to the TRE. Hence, Ng transcription is turned on or off in response to Tc or Dox in a highly dose-dependent manner that is reversible and quantitative to address the function of Ng in cultured neuronal cell lines and eventually extended to transgenic mice model

3. Development of Electrochemical Biosensors Using Multi-walled Carbon Nanotubes
Sensors represent a most plausible and exciting application area for nanobiotechnology; and nanosensors based on advanced nanomaterials are expected to emerge in the marketplace in significant volumes over circa the next ten years. Sensors constructed at the molecular scale are promising and have achieved to be extremely sensitive, selective, and responsive. For example, the U.S. Defense Department has been interested in such sensors for rapidly and accurately detecting small amounts of chemical or biological agents to allow soldiers to defend against chemical or biological attacks. In the medical diagnostics arena, nanotechnology-based biosensors could be used, for example, to replace more costly and tedious laboratory methods for monitoring a patient's blood for proteins, chemicals, and pathogens.

Carbon nanotubes, consisting of only sp2 hybridized carbon atoms, are cylindrical nanostructures with nanometer diameter, high electrical conductivity, chemical stability, and extremely high mechanical strength and modulus. These special properties of both single-walled and multi-walled carbon nanotubes (SWNTs and MWNTs, respectively) have attracted much attention. Recently, significant advances have been made by using carbon nanotubes as sensors for the detection of biomolecules.

In our laboratory, we have utilized high-density well-aligned carbon nanotubes, which are multi-walled and vertically aligned on a large area of substrates, such as Ta, that can be readily synthesized. In particular, Ta plate was used as a substrate and a thin cobalt (Co) layer of 8 to 50 nm was coated onto the substrate as catalyst by magnetron sputtering for the synthesis of MWNTs. The nanotubes prepared by this method have diameters of 200 nm to 400 nm and a length of about 10 µm depending on the Co layer thickness and growth time. MWNTs at Ta substrate can be easily attached to the surface of a planar electrode using conductive silver paint as biosensing electrode. Firstly, these MWNTs have high electrochemically accessible surface area, high electrical conductivity, and useful mechanical properties for developing electrochemical sensors in selectively detection of uric acid (UA) in the presence of L-ascorbic acid (L-AA). Secondly, MWNTs can be used as a nonenzymatic sensor to detect glucose with high sensitivity and stability in alkaline medium. Thirdly, we have successfully constructed a hemin-modified MWNTs electrode in the development of novel oxygen sensor for working at a relatively low potential.

Despite tremendous excitement has recently been generated by experimental breakthroughs that have led to realistic possibilities of using carbon nanotubes in electrochemical sensors, further experimental and theoretical research is still necessary. To actualize and optimize the full commercial potential of carbon nanotube-based electrochemical sensors, efforts must continue to be devoted to integrate the nanotube-arrays with power, miniaturized and easy-to-use electrochemical instruments for glucose sensing, genetic analysis, and drug discovery or screening.

Major Publications

• Chan, W.K., Wong, P.T.H., and Sheu, F.-S. (2007) Frontal cortical a7 and a4b2 nicotinic acetylcholine receptors in working and reference memory. Neuropharmacology 52: 1641-1649.

• Chong, K.F., Loh, K.P., Vedula, S.R., Lim, C.T., Sternschulte, H, Steinmuller, D., Sheu, F.-S., and Zhong, Y.L. (2007) Cell adhesion properties on photochemically functionalized diamond. Langmuir 23: 5615-5621.

• Han, N.-L.R., Wen, J., Lin, Q., Liou, Y.-C., Tan, P.L., and Sheu, F.-S. (2007) Proteomics analysis of the expression of neurogranin in murine neuroblastoma (neuron-2A) cells reveals a novel mechanism for cell differentiation. International Journal of Biological Sciences 3: 263-273.

• Gui, J., Song, Y., Han, N.-L.R., and Sheu, F.-S. (2007) Characterization of transcriptional regulation of neurogranin by nitric oxide and the role of neurogranin in SNP-induced cell death: implication of neurogranin in an increased neuronal susceptibility to oxidative stress. International Journal of Biological Sciences 3: 212-224.

• Ye, J.-S, and Sheu, F.-S. (2007) Carbon nanotube-based sensor. 'Nanotechnologies for the Life Sciences' Vol. 8 Nanomaterials for Biosensors, Edited by Challa S. S. R. Kumar, Wiley-VCH. Chap 2:27-55.

• Ye, J.-S, and Sheu, F.-S. (2006) Functionalization of CNTs: New routes towards the development of novel electrochemical sensors. Current Nanoscience 2 (4): 319-327.

• Cui, H.-F., Ye, J.-S., Chen, Y., Chong, S.-C., and Sheu, F.-S. (2006) Microelectrode array biochip: tool for in vitro drug screening based on the detection of a drug effect on dopamine release from PC12 cells . Analytical Chemistry 78(18):6347-6355.

• Gui, J., Song, Y., Han, N.-L.R., Zhou, S.-F., and Sheu, F.-S. (2006) Involvement of the GC-rich sequence and specific proteins (Sp1/Sp3) in the basal transcription activity of neurogranin gene. Biochemical and Biophysical Research Communications 345 (1): 124-132

• Paul J. S., Sheu, F.-S. , and Luft , A. R. (2006) Early adaptations in somatosensory cortex after focal ischemic injury to motor cortex. Experimental Brain Research 168: 178-185.

• Ye, J.-S., Cui, H.-F., Wen, Y., Zhang, W.D., Xu, G.Q, and Sheu, F.-S. (2006) Electrodeposition of platinum nanoparticles on multi-walled carbon nanotubes for electrocatalytic oxidation of methanol. Microchimica Acta 152: 267-275 (Invited paper).

• Paul J. S., Luft , A. R., Yew, E., and Sheu, F.-S. (2006) Imaging the development of an ischaemic core following photochemically induced cortical infarction in rats using Laser Speckle Contrast Analysis (LASCA). NeuroImage Jan 1; 29(1):38-45 .

• Cui, H.-F., Ye, J.-S., Chen, Y., Chong, S.-C., Liu, X., Lim, T.-M., and Sheu, F.-S. (2006) In situ temporal detection of dopamine exocytosis from L-dopa incubated MN9D cells using microelectrode array-integrated biochip. Sensors and Actuators B: Chemistry, 115 (2): 634-641

• Han, N.-L.R., Ye, J.-S., Yu, A.C.H., and Sheu, F.-S. (2006) Differential mechanisms underlying the modulation of delayed-rectifier K + channel in mouse neocortical neurons by nitric oxide. Journal of Neurophysiology, 95 (4) 2167-2178

• Cui, H.-F., Ye, J.-S., Liu, X., Zhang, W.-D., and Sheu, F.-S. (2006) Pt-Pb alloy nanoparticle/carbon nanotube nanocomposite: a strong electrocatalyst toward glucose oxidation. Nanotechnology 17 (2006) 2334-2339.

• Ye, J.-S., Wen, Y., Zhang, W.D., Cui, H.-F., Gan, L.M., Xu, G.Q and Sheu, F.-S. (2005) Electrochemical biosensing platforms using phthalocyanine-functionalized carbon nanotube electrode. Electroanalysis 17: 89-96.

• Cui, H.-F., Ye, J.-S., Zhang, W.-D., John Wang, and Sheu, F.-S. (2005) Electrocatalytic Reduction of Oxygen by Platinum Nanoparticles/Carbon Nanotubes Composite Electrode. Journal of Electroanalytical Chemistry 577:295-302.

• Ye, J.-S., Cui, H.-F., Liu, X., Lim, T.-M., Zhang, W.-D., and Sheu, F.-S. (2005) Preparation and characterization of well-aligned carbon nanotubes-ruthenium oxide nanocomposites for supercapacitors. Small 1: 560-565.

• Weng, J., Xue, J., Wang, J., Ye, J.-S., Cui, H., Sheu, F.-S., and Zhang, Q. (2005) Gold cluster sensors formed electrochemically at boron-doped-diamond electrodes: detection of dopamine in the presence of ascorbic acid and thiols. Advanced Functional Materials, 15: 639-647.

• Ye, J.-S., Liu, X., Cui, H.-F., Zhang, W.-D., Sheu, F.-S., and Lim, T.-M. (2005) Electrochemical oxidation of multi-walled carbon nanotubes and its application to electrochemical double layer capacitors. Electrochemistry Communications 7: 249-255.

• Ye, J.-S., Zheng, X.-J., Leung, K.-W. Chen, H.-M., and Sheu, F.-S. (2004) Induction of transient ion channel-like pores in a cancer cell by antibiotic peptide. Journal of Biochemistry 136: 255-259.

• Choo, W.-C., Lee, W.-W., Sheu, F.-S. and Chee, M.WL (2005) Dissociation of cortical regions modulated by both working memory load and sleep deprivation and by sleep deprivation alone. Neuroimage 25(2):579-87.

• Ye, J.-S., Cui, H.-F., Wen, Y., Zhang, W.D., Gan, L.M., Xu, G.Q, Tien, H.T., Ottova, A. and Sheu, F.-S. (2005) Self-assembly of bilayer lipid membrane at multiwalled carbon nanotubes towards the development of photo-switched functional devices. Electrochemistry Communications 7: 81-86.

• Yang, H.-M., Lee, P.H.-H., Lim, T.M. and Sheu, F.-S. (2004) Neurogranin expression affects cytosolic calcium level by nitric oxide stimulation. Molecular Brain Research 129:171-178

• Poh, W.C., Loh, K.P., Zhang, W.D., Sudhiranjan, T., Ye, J.-S., and Sheu, F.-S. (2004) Biosensing properties of diamond and carbon nanotubes. Langmuir 20: 5484-5492.

• Tay, Y.M.S., Lim, K.S, Sheu, F.-S., Jenner, A., Whiteman, M., Wong, K.P., and Halliwell, B (2004) Do mitochondria make nitric oxide? No? Free Radical Research 38: 591-599.

• Ye, J.-S., Wen, Y., Zhang, W.D., Cui, H.-F., Gan, L.M., Xu, G.Q and Sheu, F.-S. (2004) Application of multi-walled carbon nanotubes functionalized with hemin for oxygen detection in neutral solution. Journal of Electroanalytical Chemistry 562: 241-246.

• Ye, J.-S., Wen, Y., Zhang, W.D., Gan, L.M., Xu, G.Q and Sheu, F.-S. (2003) Selective voltammetric detection of uric acid in the presence of ascorbic acid at well-aligned carbon nanotube electrode. Electroanalysis 15: 1693-1698.

• Ye, J.-S., Wen, Y., Zhang, W.D., Gan, L.M., Xu, G.Q. and Sheu, F.-S. (2004) Nonenzymatic glucose detection using multi-walled carbon nanotube electrodes. Electrochemistry Communications 6: 66-70.

• Ye, J.-S., Ottova, A., Tien, H.T. and Sheu, F.-S. (2003) Nanostructured platinum-lipid bilayer composite as biosensor. Bioelectrochemistry 59: 65-72.

• Ran, X., Miao, H.-H., Sheu, F.-S. and Yang D. (2003) Structural and dynamic characterization of a neuron-specific protein kinase C substrate, neurogranin. Biochemistry 42: 5143-5150.

• Colley, P.A., Sheu, F.-S., and Routtenberg, A., (1990) Inhibition of protein kinase C blocks two components of LTP persistent leaving initial potentiation intact. Journal of Neuroscience, 10: 3353-3360.

• Sheu, F.-S., Kasamatsu, T. and Routtenberg, A. (1990) Protein kinase C activity and substrate (F1/GAP-43) phosphorylation in developing cat visual cortex. Brain Research, 524: 144-148.

• Sheu, F.-S., Marais, R.M., Parker, P.J., Bazan, N.G., and Routtenebrg, A. (1990) Neuron-specific protein F1/GAP-43 shows substrate specificity for the beta subtype of protein kinase C. Biochemical and Biophysical Research Communications, 171: 1236-1243.

• Sheu, F.-S., McCabe, B.J., Horn, G., and Routtenberg, A. (1993) Learning selectively increases protein kinase C substrate phosphorylation in specific regions of the chick brain. Proceedings of the National Academy of Sciences, U.S.A, 90: 2705-2709.

• Sheu, F.-S., Azmitia, E.C., Marshak, D.R., Parker, P.J., and Routtenberg, A. (1994) Glial-derived S100b protein selectively inhibits recombinant b protein kinase C (PKC) phosphorylation of neuron-specific protein F1/GAP43. Molecular Brain Research, 21:62-66.

• Sheu, F.-S., Huang, F.L., and Huang, K.-P. (1995) Differential responses of protein kinase C substrates (MARCKS, Neuromodulin, and Neurogranin) phosphorylation to calmodulin and S100. Archives of Biochemistry and Biophysics, 316: 335-342.

• Seki, K., Sheu, F-S. & Huang, K-P. Binding of myristoylated alanine-rich protein kinase C substrate to phosphoinositides attenuates the phosphorylation by protein kinase C. Archives of Biochemistry and Biophysics (1996) 326:193-201.

• Sheu, F-S, Mahoney, C.W., Seki, K. & Huang, K-P. Nitric oxide modification of rat brain neurogranin affects its phosphorylation by protein kinase C and affinity for calmodulin. Journal of Biological Chemistry (1996) 271:22407-22413.

• Sheu, F-S, Zhu, W. & Fung, P. C. W. Direct observation of trapping and release of nitric oxide by glutathione and cysteine with electron paramagnetic resonance spectroscopy. Biophysical Journal (2000) 78:1216-1226.

• Miao, H-H, Ye, J-S, Wong, S.L.Y., Wang, B-X, Li, X-Y & Sheu, F-S. Oxidative modification of recombinant neurogranin by nitric oxide: an amperometric study. Bioelectrochemistry (2000) 51:163-173.

• Ye, J.-S. Ottova, A., Tien, H.T. and Sheu, F.-S. (2001) Nitric Oxide enhances the capacitance of self-assembled, supported bilayer lipid membranes. Electrochemistry Communications 3: 580-584.