The original PDB format that was used for the first 100 or so
entries carried both fractional and orthogonal coordinates.
That format used 132 column lines which was awkward on some
computers. When we designed what is now known as PDB format
we decided to use 72 columns for data plus sequencing in 73 - 80
[for younger people - data was on punched cards and decks could
get dropped and there were sorters that could get them back in order
if the decks were sequenced].
So there were discussions about whether we should carry fractional
or orthogonal as there was not room for both. My argument was
that crystallographers would know how to go to fractional,
especially as we would provde the SCALE records, while other
users (i.e. biologists, chemists, etc.) might have a great
deal of difficulty understanding how to use fractional
coordinates.
Thirty seven years later I still think that this was the correct
decision, especially as the number of non-crystallographers
using the PDB has grown enormously.
Frances
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