Small Molecule Aggregation

Small molecule aggregation is important across a wide range of fields. For example, drug delivery can be affected by the formation of assemblies of amphipathic molecules, which can alter solution behaviour and membrane permeability. Research in the Day lab is focussed on developing NMR approaches to probe these interactions and enable kinetic and thermodynamic information to be obtained.

 

Diffusion NMR

Through the use of pulsed-gradient spin echos, nuclear spins, and hence the NMR signal, are sensitive to both molecular and bulk motion within the sample. We are applying diffusion NMR methods to probe aggregation, and developing new data analysis approaches applicable to aggregating systems.

 

Sunset Yellow - a model system

We have been working with the azo-dye sunset yellow which is known to form large scale aggregates in solution, and above a certain concentration will undergo a phase change to a lyotropic liquid crystal.

We have applied diffusion-ordered spectroscopy (DOSY) to probe the self association of this molecule with the aim of utilising it, and similar compounds, as model systems in future work. Results to date have suggested that large scale aggregates comprising tens to hundreds of molecules are present at the concentrations investigated (typically >50 mM).

 

Key Publications

  1. J. R. Katz and I. J. Day. Using small molecule probes to investigate aggregation of sunset yellow FCF: what are the concentration limits? J. Phys. Chem. B 123(42):8987-8994, 2019
  2. R. Briffitt and I. J. Day. Influence of structural isomerism and fluorine atom substitution on the self-association of naphthoic acid. J. Phys. Chem. B 119(22):6703-6710, 2015
  3. J. R. Katz and I. J. Day. Investigating the interaction of sunset yellow aggregates and 6-fluoro-2-naphthoic acid: increasing probe molecule complexity. Magn. Reson. Chem. 52(8):435-439, 2014
  4. J. R. Katz, L. J. Day and I. J. Day. NMR investigations of the interaction between the azo-dye sunset yellow and fluorophenol. J. Phys. Chem. B 117(39):11793-11800, 2013
  5. I. J. Day. On the inversion of diffusion NMR data: Tikhonov regularization and optimal choice of the regularization parameter. J. Magn. Reson. 211(2):178-185, 2011
  6. M. P. Renshaw and I. J. Day. NMR characterisation of the aggregation state of sunset yellow in the isotropic phase. J. Phys. Chem. B 114(31):10032-10038, 2010