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Professor Athene Donald: Research

My early research focussed on synthetic polymers, but rather little of my current work is on this class of materials: currently there is an ongoing project on the study of polymer blends used in photovoltaic devices, and a recent project considered latex film formation in the ESEM. The bulk of my work is now directed at biological problems, using a range of techniques and spanning from studying individual molecules (protein aggregation), through cellular biophysics to recent work on whole tissues and organisms (bacteria and leaves in the ESEM).







Protein aggregation

Images of bovine insulin spherulites. All scalebars: 50 microns. A. Optical microscopy image, taken between crossed polars (aligned horizontally and vertically). B. Same image as in A. but with added waveplate (550 nm, fast axis oriented at 45degrees to the horizontal). C. ESEM image of a spherulite that split open due to dehydration.

Protein aggregation is relevant to both the texture of food (eg using the protein beta lactoglobulin) and disease (eg A beta aggregation). We seek to find generic behaviour, so that the factors that drive aggregation - particularly at the suprafibrillar level where spherulites are found to form (see image) - can be teased out. We are exploring the effect of electrostatic interactions and shear (as mediated by salt and pH) on the aggregates that form, and have a collaboration with Dr J Sharp and Professor C Roberts in Nottingham.

MRH Krebs, EHC Bromley and AM Donald - 2005. J Struct Biol, 149, 30-37. The binding of thioflavin T to amyloid fibrils: Localisation and implications.

MRH Krebs, ECH Bromley and AM Donald – 2005. Biophys J 88 2013-21. The mechanism of spherulite formation by bovine insulin amyloid fibrils.

EHC Bromley, MRH Krebs and AM Donald – 2006. EPJE 21 145-52. Mechanisms of structure formation in beta lactoglobulin near the isoelectric point.

MRH Krebs, KR Domike and AM Donald - 2009. Biochem Trans 37, 682-6. Protein aggregation: more than just fibrils.

C Exley, E House, JF Collingwood, MR Davidson, D Cannon and AM Donald - 2010. J Alzheimers Disease 20 1159-65. Spherulites in Abeta 42 in vitro and in Alzheimers Disease.

V Fodera and AM Donald - 2010. EPJE 33 273-82. Tracking the heterogeneous distribution of amyloid spherulites and their population balance with free fibrils.

MI Smith, V Fodera, JS Sharp, CJ Roberts and AM Donald – 2012. Coll and Surf B. 89, 216-222 Factors affecting the formation of insulin amyloid spherulites.

Cellular biophysics

cell motion

Sample snapshots of fibroblasts after seeding on ridge-groove patterned PDMS substrates (55 micron wide ridges, 10 micron wide and 15 micron deep grooves). The cells are stained with the membrane probe Rhodamine octadecyl ester delivered using CelLuminate (red, with the unstained nuclei as dark circles) while the green lines mark the grooves in the pattern.

The majority of our work on cellular biophysics has concentrated on how 3T3 cells behave on ridge-groove patterned substrates. We have examined their spreading across patterns of different sizes;we have looked at the anisotropy of their motion on the ridges (collaboration with Dr G Battaglia, Sheffield); and we are looking at how the pattern influences mitosis(collaboration with Dr V Draviam, Genetics). We are also using microrheology (see below) to characterise the viscoelastic response inside the cell.

PM Stevenson and AM Donald, - 2009. Langmuir 25 367-76. Identification of three regimes of behaviour for cell attachment on topographically patterned substrates.

C Picard and AM Donald – 2009. EPJE 30, 127-34. The impact of environmental changes on the microrheology of adherent cells.

C Picard, V Hearnden, M Massignani, S Achouri, G Battaglia, S MacNeil, and A Donald – 2010. BioTechniques 48, 135-138 A micro-incubator for cell and tissue imaging.

KS Kung, I Canton, M Massignani, G Battaglia, AM Donald – 2011.EPJE 34, 23-32. The development of anisotropic behaviours of 3T3 fibroblasts on microgrooved patterns.

Environmental scanning electron microscopy (ESEM)

cell

3T3 cell viewed in the ESEM after fixing in 4% glutaraldehyde (15 mins); no gold coating needs to be applied in the ESEM.

The Environmental Scanning Electron Microscope (ESEM), sometimes referred to as low vacuum SEM, is the latest version of one of the most powerful analytic tools available to scientists.The low vacuum environment in the sample chamber (up to 1500 Pa) permits examination of samples in their natural state (wet, hydrated, uncoated, etc) without the need for conventional preparation techniques. We have been developing the technique for the last 15 years, currently examining conditions to image a range of biological samples. We also use in situ focussed ion beam milling to cut sections both into a bulk sample and also to make ultra-thin sections suitable for TEM eg through photovoltaic devices.

KA Dragnevski and AM Donald - 2008. Coll and Surf A 317 551-6. Film formation mechanism of novel acrylic latex for solvent-free architectural coatings.

S Kirk, JN Skepper and AM Donald – 2009. J Micros 233, 205-24. Application of VPSEM to determine biological surface structure.

J Benawara and AM Donald – 2009. J Micros 234 89-94. Developing dual beam methodologies for the study of heterogeneous polymer-based systems.

T Zheng, K.W. Waldron, A. M. Donald – 2009. Planta 230 1105-13. Investigation of viability of onion epidermal tissue in the environmental scanning electron microscopy .

D Waller, DJ Stokes and AM Donald- 2010. EPJ App Phys 51, 10901. Investigating sublimation and the effect of an imaging gas in a VPSEM

J E McGregor and AM Donald – 2010. J Micros 239  135-141. ESEM imaging of dynamic biological processes: the closure of stomatal pores.

N Thomson, K Channon, N A Mokhtar, L Staniewicz, R Rai, I Roy, A MDonald, D Summer and E Sivaniah - 2011. Scanning 33 59-68. Imaging internal features of whole, unfixed bacteria.

Microrheology

master curve

Master curves produced by superposing Mean Squared Displacement data before (upper) and after the gel point for 6% beta lactoglobulin in 50:50 TFE/pH 7 phosphate buffer. For clarity, the gel curve has been given an arbitrary shift downward to separate it from the pregel curve. Colours represent datasets collected at different times.

We use (passive) particle tracking microrheology to characterise soft matter samples ranging from clays to protein networks. We are particularly interested in following gelation in real time: microrheology provides an excellent way to measure the gel time accurately without invasively changing the network structure. We are also interested in developing these approaches for intracellular studies (see above).

IA Hasnain and AM Donald – 2006. PRE 73 031901. Microrheological characterisation of anisotropic materials.

HA Houghton, IA Hasnain and AM Donald, - 2008. EPJE 25 119-127. Particle tracking to reveal gelation of hectorite dispersions.

AM Corrigan and AM Donald, 2009. EPJE 28 457-52 . Particle tracking microrheology of gel-forming amyloid fibril networks.

C Picard and AM Donald – 2009. EPJE 30, 127-34. The impact of environmental changes on the microrheology of adherent cells.

AM Corrigan and AM Donald – 2010. Soft Matter 6 4105-4111. Lengthscale Dependence of Apparent Critical Exponents Determined by Vibration-corrected Two-particle Microrheology.

Polymer morphology

F8BT

Cryo-fractured thin film of an F8BT-PFB blend imaged in the ESEM. The different phases and topography are clearly visible.

We have studied polymer morphology via ESEM and other microscopies. The main current project is part of the UKOPV consortium , continuing as a collaboration between Sheffield University and ourselves,which focuses on the model organic photovoltaic (OPV) polymer blend systems between conjugated polymers and PCBM, with a view to gaining a comprehensive understanding of the intrinsic physical and chemical mechanisms that determine the ultimate device performance. Our part of the project uses thermal analysis and electron microscopy for characterisation, as well as forming part of the team at Diamond for synchrotron studies.

SJ Williams, AM Donald, BL Thiel and DE Morrison – 2005. Scanning 27, 190-8. Imaging of semi-conducting polymer blend systems using ESEM and ESTEM.

T Wang, ADF Dunbar, PA Staniec, AJ Pearson, PE Hopkinson, S Lilliu, JE MacDonald, C Pizzey, NJ Rerrill, AM Donald, AJ Ryan, RAL Jones and DG Lidzey – 2010. Soft Matter 6 4128-4134.The development of nanoscale morphology in polymer:fullerene photovoltaic blends during solvent casting.

PA Staniec, AJ Parnell, ADF Dunbar, H Yi, AJ Pearson, T Wang, PE Hopkinson, C Kinane, RM Dalgleish, AM Donald, AJ Ryan, RAL Jones and DG Lidzey -2011. Adv Energy Mat 1 499-504. The nanoscale composition of a PCDTBT: PCBM photovoltaic blend.

PE Hopkinson, PA Staniec, AJ Pearson, ADF Dunbar, T Wang, AJ Ryan, RAL Jones, DG Lidzey and AM Donald – 2011. Macromols 44 2908-17. A phase diagram of the P3HT:PCBM organic photovoltaic system: Implications for device processing and performance.

AJ Parnell, AJ Cadby, OO Mykhaylyk, ADF Dunbar, PE Hopkinson, AM Donald and RAL Jones. Macromolecules 44, 6503-6508. The Nanoscale Phase Separation of P3HT PCBM Thick Films as measured by Small Angle X-ray Scattering.

© 2006 BSS

last updated October 2011