Ken Holmes was working to solve the structure of the whole virus.

[Q] Yes.

And I wondered if it was going to be possible to get to a high resolution. So as a companion I thought that we would be trying to crystallise some of the substructures that are found when you try to extract TMV protein, that is the sub-unit protein on its own. And I thought that might be possible to crystallise what was thought to be a trimer... this is a trimer of the TMV protein, the so called 'A protein'. The... so I... Reuben Leberman was with us and he was preparing large quantities of virus for... for the X-ray work on the intact virus. But the... I... I found... I... I read all the original papers of Schramm that started off the early work on viruses in Tübingen in Germany and saw that under certain conditions you'd got quite a large proportion of so-called A protein, which was thought to be a trimer, in fact its aggregate with something between two and five or two and five units. And I thought that that might crystallise, so... I asked Reuben... Reuben Lieberman to... to make large quantities of this and set up a crystallisation. And he produced the... indeed it did form crystals, but, the crystals had very large unit cells, several hundred angstroms. And before, we knew what it was; it was clearly some large aggregate. Now, Don Caspar, who we mentioned before, had talked a great deal about... sub... he'd written a paper about sub-assemblies of TMV which is rather an exercise theoretical physical chemistry. There wasn't much data in what he analysed but it was... he had some idea that the sub-assemblies may be important in the assembly of TMV. So what happened was that the crystal structure was... we found, in the early '60s, I've forgotten when it was, that the fact that this... this was a crystal not of the... not of the trimer of the TMV protein but the crystal of a ring-shaped unit. And you could see from the X-ray diffraction pictures which were obtained by yourself, John, and also by Chang, who was visiting... from China, that they had 17-fold symmetry. And these... these clearly consisted... so the crystals, the unit cell was huge... it contained... rings of protein, 17 units in the ring and two rings stacked together which we called the disc, the two-layered disc. Now, this was... something like this had been described by Norman Simmons and other people working with the chemistry of the TMV proteins, quite a lot of people were working... TMV was used by many different people for different objects and TMV was a hard source of protein. So you'd do physical chemistry and Lauffer for example was measuring the specific volume and finding out the hydration of protein. TMV was a work horse in many different parts that we now call structural molecular biology, including the genetic code as far as the TMV RNA is concerned.