Protein Structure - (Aug/15/2006 )
Why the protein structre is describe in Angstrom. what does it actually mean
I don't know if you mean same thing but Ångström is an unit of length.
*EDIT* That seemed to be obvious but I answered. I had no mean to insult you.
I donot feel any shame or insult for my stupid question. Your ansawer is right. but you did not uderstand my exact point. If the average distance between c-c is 1.5 A then why the structure of 1.3 A is of better resolution while the distance is 1.5 A. my intentions was to know this point. But i am grateful to you for your help. I donot mind even if you insult me for my questions.
regards
*EDIT* That seemed to be obvious but I answered. I had no mean to insult you.
You're speaking about resolution of some measurement or detection, like NMR or Roentgen crystallography, right? Maybe C-C distance (and other atom-atom) is more or less constant but other values may be different, eg. as a result of several forces. Well, in that case higher resolution is always better, but that's just my personal opinion. 
The resolution measure in Angstrom is basically an indication of the quality of the structural detail visible. A 5A resolution structure will not show as much fine detail as, say, a 1.2A structure. A really fine structure will enable you to see the "hole" in an aromatic ring, while a coarser structure will show the ring as a solid shape. The structure is only as good as the worst part, so a region of great flexibility is the limiting factor of the resolution of the whole structure.
If you go to higher Angstrom number (i.e., lower resolution) structures, you see less atomic detail, but you may see more global structural features. This is very useful for proteins (and especially complexes) that don't crystallise well. Cryo EM has lousy atomic detail, but it shows how large structures fit together.