ABSTRACT
At any stage of one’s career a crossroads, of larger or smaller importance, can occur. A big one for me was deciding which route to go for my PhD. This decision occurred in the final year of my undergraduate physics degree. I was undertaking an experimental final year project involving electron microscopy studies of thin metal films and imaging their dislocations. I got on well with my project academic supervisor, and his electron microscope technician, so that when I was offered a PhD to stay in that research group in the interesting area of surface physics I accepted. Meanwhile the final year physics option courses on astrophysics, biophysics and geophysics commenced in the spring term. The biophysics course lecturer was in Brazil on a research education exchange visit and was delayed in starting the biophysics course. I opted for astrophysics, looking forward to learning about cosmology, especially the origin of the universe. Six lectures in, we had covered in considerable detail the laws of planetary motion and so on. In this I did not find the excitement I was looking for and so when the biophysics course finally started I decided to attend a few of those as well. Both the astrophysics and biophysics course lecturers were outstanding teachers. But the biophysics quickly and fully engaged me. I decided to switch over to biophysics from astrophysics. It became steadily clearer to me that my interests and abilities in chemistry, which I had left behind in my school advanced level, were still very strong. I enjoyed biophysics enormously. One area that I found amazing was the protein crystallography and the work of Dr Max Perutz. My course lecturer handed out an article written by Dr Perutz for the magazine New Scientist entitled ‘Haemoglobin the molecular lung’ [1]. The article explained, with X-ray crystal structure analysis, the atomic level details of what happens when oxygen binds at each of the four successive haems in this protein, which is found in the blood. There is a cooperative action between the four haems mediated by the protein in which they are embedded. When one haem group has taken up oxygen, it becomes progressively easier for the second, third and fourth haems to do so. The cooperative action is superior to ordinary dissolution, where it is easy to dissolve a small quantity of oxygen in pure solvent but gets steadily more difficult as the dissolved oxygen concentration rises. This molecular level process takes place after inhaling oxygen in the lungs; each haemoglobin of 64,000 molecular weight carries its four oxygen molecules to the muscles of the body where the cooperative 24effect facilitates the release of all four oxygens. The use of this method of physics to understand a fundamental process in biology in terms of chemistry was, I thought, fantastic. It was mind-blowing, in fact. Max Perutz also had a marvellous way of explaining things. He described haemoglobin as both a chemical machine and as a molecular amplifier. For good measure he said: “How can the weak chemical reaction of the four tiny molecules of oxygen with the four iron atoms produce such a drastic rearrangement in this giant molecule, like four fleas that can make an elephant jump?”
