Jennifer Crowhurst's bursary placement
Jennifer Crowhurst from Sutton High School took a six week bursary placement in the Chemistry Department at Imperial College. Her bursary placement was titled 'Studies of the Phase Behaviour of Biological Amphiphiles'.
The aims of the project
The project aim was to investigate the phase behaviour of a system consisting of the phospholipid DOPC and its hydrolysis products lyso-PC and oleic acid. X-ray diffraction and light polarized microscopy were used to determine the phase of the system at different proportions of the lipids.
How the project was carried out
I prepared samples of the mixtures by lyophilising the compounds, then dissolving them in cyclohexane, mixing the solutions in the required ratios, and drying them. I added this buffer to the mixtures in a 1:1 mass ratio. These lipid-buffer mixtures were added to capillary tubes for investigation by X-ray diffraction: I operated the X-ray beamline under supervision and analysed the diffraction patterns obtained to work out the phase and the d-spacing. I also viewed the samples under the microscope, heating the samples to detect any phase changes.
What I found out
The system was in the lamella phase in all the mixtures investigated, from 100% DOPC to a 1:1:1 mole ration of DOPC, lyso-PC and oleic acid, as the rings on the diffraction patterns were evenly spaced. However, the rings became more blurred as the proportion of the lyso-PC and oleic acid increased, a sign of swelling between layers. Light-polarised microscopy confirmed that the system was in the lamella phase for all the mixtures studies, and that these remained in the same phase when heated, although the edge of the sample showed different patterns under the polarizer as the temperature increased, a sign of possible phase separation. These properties could be investigated further by X-ray diffraction as a function of temperature and by using DSC and NMR.
The most valuable thing about the bursary experience
I have become more aware of the depth of science - although the topic of lipid bilayers in cell membranes is only mentioned briefly at A-Level, it is the subject of much more research than I had imagined, and I have found out that understanding more about the behaviour of phospholipids can even lead to improvements in the efficiency of drug transport around the body. Taking part in academic research has confirmed my choice of studying science at university, and I am now keen to take part in another longer research project as part of my degree. I am also more informed about the possibilities afterwards, from MRes to PhD!