Molecular simulations of the dynamics of water in model cartilage

Overview

Topic status: We're looking for students to study this topic.

Articular cartilage is a unique biological tissue that protects our long bones from wear. It is based on a biopolymeric matrix that provides structural stiffness to the tissue and also serves as a molecular 'sponge' to retain water under compression. Interaction between water and the matrix biopolymers is key to understanding the biophysics behind load carriage in cartilage.

Understanding of this fundamental biophysics if the main aim of this project. The organisation of the cartilage biopolymeric matrix can be studied by magnetic resonance, most notably using diffusion-tensor imaging (DTI) and spin-relaxation imaging. A crucial step in the interpretation of MRI data is the translation of the measured MRI parameters into quantitative biophysical information. For example, the finding that the diffusion tensor of cartilage has a 10% anisotropy is not very useful in itself; however, it can become useful when translated into biopolymer content and quantitative descriptors of the order and alignment of the matrix.

We use a range of molecular simulation techniques to facilitate the interpretation of MRI properties of cartilage.

  • Monte Carlo simulations of water dynamics enable us to calculate the obstruction effect to water diffusion created by collagen fibres in the matrix; the outcome is 'calibration plots' of the diffusion tensor on the tissue composition and fibre alignment.
  • Langevin Dynamics simulations provide the next level of approximation and consider the interaction potential between water molecules and the matrix biopolymers. LD simulations enable us to study the role of interaction between water and biopolymers in the biomechanics of the tissue.
  • Molecular mechanics and molecular dynamics simulations provide the most detailed level of approximation and consider intermolecular interactions between water molecules as well as specific interactions between water and collagen. MM/MD simulations probe picosecond-timescale water dynamics, which is important for interpretation of spin relaxation images of cartilage.

The project will involve the use of the supercomputers at QUT's High-Performance Computing Centre (HPC) and specialised molecular modelling software. You will acquire extensive experience in molecular and physical modelling; computer programming skills; and a detailed understanding of the physics of magnetic resonance imaging. You will also contribute to understanding of the molecular mechanisms of osteoarthritis - a disease that involves degradation of the cartilage matrix and leads to loss of mobility in the affected knee or hip.

References:

  • SK de Visser, RW Crawford, JM Pope. Osteoarthr. Cartilage 16, 83-89 (2008)
  • KI Momot, JM Pope, RM Wellard. NMR in Biomed. 23, 313-324 (2010)
Study level
PhD
Supervisors
QUT
Organisational unit

Science and Engineering Faculty

Research area

Physics

Contact
Please contact the supervisor.