NMR Studies of the Early Stages of Aggregation Phenomena

Aggregation phenomena are the coming together of small molecular fragments to form larger, often non-covalent, structures and are important across a wide range of physical and biological sciences. For example, polymer aggregates are being developed as novel drug delivery platforms, designed to release a drug under certain predetermined physiological conditions, or the formation of insoluble protein and peptide assemblies is implicated in a number of diseases.Nuclear magnetic resonance spectroscopy is ubiquitous in its application across chemistry and has found great application in structural biology. Its success has been more limited in the investigation of aggregation phenomena, mainly being applied to the determination of thermodynamic parameters, with few examples of its use to study the kinetics of the aggregation process. The high degree of resonance overlap observed for molecular aggregates tends to preclude the use of high resolution methods, however, the determination of molecular sizes via the distribution of diffusion coefficients is still potentially tractable. For instance, polymer molecular weight distribution profiles have been determined using these NMR spectroscopic techniques.This proposal seeks to develop a time-resolved diffusion NMR methodology suitable for probing changes in aggregation state as a function of time. The proposal will focus on two complimentary aims. The first developing data analysis techniques suitable for the extraction of time-dependent distributions of diffusion coefficients during the aggregation process. This will allow information to be gained on the kinetics of the aggregation process in addition to the diffusion coefficient information. The second approach will extend the idea of chromatographic NMR to size-exclusion chromatography. The aim here is to improve the diffusion resolution by application of a in-situ chromatographic stationary phase to spread-out the distribution of diffusion coefficients. The combination of both methods should prove a powerful technique for probing aggregation phenomena in solution.

The research described in this proposal will be of wide interest both within the NMR community and to a wider audience, interested in aggregation phenomena. While the nature of the research is in essence blue skies , a number of potential beneficiaries outside of the immediate academic magnetic resonance community are envisaged. The formation of molecular aggregates has implications in a variety of scientific and engineering fields, including nano-scale engineering in terms of (self) assembly, synthetic biology, peptide and protein assembly, aggregation and flocculation in water treatment and polymer science, and many others. The research described in this proposal will add to the analytical tools available for the investigation of aggregating systems, by providing information which is complementary to that obtained by other methods, for example laser light scattering. Potential beneficiaries include the polymer industry and water treatment companies. Links with industrial partners will be explored in conjunction with the university's Regional Research and Development office and through discussions with the departmental London Technology Network fellow. The major results will be published in leading high-impact journals, read by a variety of potential beneficiaries along with the more technical aspects being published in detail in more specialist journals. The methods developed and results obtained will be presented at national and international conferences both by the PI and other members of his research group. The wider audiences will be engaged through the schools outreach activities undertaken within the department, and as talks and demonstrations within the further outreach work of the department.