nguanhs@gmail.com
Education
2013 Ph.D in Computational Chemistry, University of Malaya, Malaysia.
2009 M.Sc. in nuclear physics, University of Malaya, Malaysia.
2004 B.Sc. (Hon) in physics, University of Malaya, Malaysia.
Research Interests
Modeling of Liquid crystals phase transitions
Quantum chemistry study of Carbohydrates molecules
Molecular dynamics simulation of water, water-lipid interface, and water-air interface
Ongoing Research
1. Carbohydrate dissociation mechanism using enhanced sampling methods
Carbohydrates are not only as a source of energy for the living being, but also plays important roles in the numerous biological functions that sustain life. Glycome, i.e. the glycan sequencing, unlike the human genome and proteome, is still present a great puzzle. One common approach of glycan sequencing is using mass spectrometry, where carbohydrates were fragmented and studied to understand their structure and sequences. To understand how the fragments are produced, we study the reaction mechanism of carbohydrates oligomers fragmentation using the enhanced sampling method such as metadynamics and umbrella sampling. The enhanced sampling method is to account for the complexity raised from diverse structures of the carbohydrates oligomer.
2. Modeling of lipids self-assembly through molecular dynamics simulation
Molecular dynamics simulations can help to shade some lights on the water behavior at bilayers interface. Previous molecular dynamics (MD) simulation study shown that water at the lipid membranes interface has slower translational motion and rotational motions compared to that of in the bulk. The slower motions are attributed to the hydrogen bonding of water to the headgroups of the lipids and the formations of the inter-lipids water bridges. The water diffusion at the headgroup regions of lipid membranes are found to subdiffusion, which deviates from normal Einstein diffusion relations as found in the bulk water. Previous study suggested two mechanisms that are responsible to the origin of the interfacial water subdiffusion: 1. The power law distribution of time period when water is trapped at the head group regions, and 2. The motions of the viscoelastic lipids in the membranes. However, it is still not clear that this implies the physical picture that lipids are seemingly immobile from the interfacial water molecules point of view is not valid? If so, how does lipids influence the diffusion of their nearby water when hydrogen bonds are formed? To answer these questions, we model the diffusion behavior of water by the lipids shall take place in the picosecond time, i.e. the time range of energy transfer and dissipation in molecular system.
3. Understand the effect of the salt at water-air interface and lipids water interface
It is well recognized that ions has significant effects on the functioning of the biomembranes. Till now, the understanding of the interactions between ionics species to the biomembranes as still lacking. Here, we use the molecular simulation method to understand how ions modulate the physical behavior of biomembranes. Using the model lipids such as phospholipids and glycolipids as the model biomembranes, we will investigate in the effects of ions towards the lipid swelling, hydration forces, interfacial water behavior, hydrogen bonds networks and bending rigidity.
Publications
1. H.S. Nguan, T. Heidelberg, G.J.T. Tiddy and R. Hashim, 2010, Quantitative analysis of the packing of alkyl
glycosides: a comparison of linear and branched alkyl chains, Liquid Crystals, 37(9), 1205-1213.
2. Hockseng Nguan, Sara Ahmadi and Rauzah Hashim, 2012, DFT study of glucose based glycolipid crown
ethers and their complexes with alkali metal cations Na+ and K+, Journal of Molecualr Modeling, 18(12):5041-50.
3. Vijayan Manickam Achari, Hock-Seng Nguan, Thorsten Heidelberg, Richard A. Bryce and Rauzah Hashim, 2012, Molecular Dynamics Study of Anhydrous Bilayers of Synthetic Glycolipids: Effects of Chain Branching and Disaccharide Headgroup, Journal of Physical Chemistry B, 116(38), 11626-11634
4. Hock-Seng Nguan, Sara Ahmadi and Rauzah Hashim, Molecular Dynamics Simulation of Lyotropic Reverse
Hexagonal (HII) of Guerbet Branched-Chain β-D- Glucoside, Physical Chemistry Chemical Physics, 2014, 16,
324-334
5. Sara Ahmadi, Vijayan ManickamAchari, HockSeng Nguan and Rauzah Hashim. 2014. Atomistic simulation
studies of the α/β-glucoside and galactoside in anhydrous bilayers: effect of the anomeric and epimeric configurations. Journal of Molecular Modeling, 20(3):2165-2176
6. Velayutham, T. S., H. S. Nguan, B. K. Ng, W. C. Gan, V. Manickam Achari, N. I. Zahid, WH Abd Majid, C. Zannoni, and R. Hashim, Molecular dynamics of anhydrous glycolipid self-assembly in lamellar and hexagonal
phases, Physical Chemistry Chemical Physics 18, no. 22 (2016): 15182-15190.
7. Hashim, Rauzah, Akihiko Sugimura, Hock-Seng Nguan, Matiur Rahman, and Herbert Zimmermann, Anhydrous octyl-glucoside phase transition from lamellar to isotropic induced by electric and magnetic fields, The Journal of Chemical Physics 146, no. 8 (2017): 084702.
8. Huynh HT, Phan HT, Hsu PJ, Chen JL, Nguan HS, Tsai ST, Roongcharoen T, Liew CY, Ni CK, Kuo JL. Collision-induced dissociation of sodiated glucose, galactose, and mannose, and the identification of anomeric configurations. Physical Chemistry Chemical Physics (2018)