This is related to the "atomic resolution in NMR" question discussed earlier. I have encountered a paradox and I suspect that someone in the bb might have an answer, so help me not to invent the wheel. Also, if you strongly believe that ccp4bb is only to be used for CCP4(or crystallography)-related questions, read no further.
Spatial resolution of any observation method that uses electromagnetic field (in form of photons) is determined by the wavelength (frequency) of the radiation. AFAIK, NMR frequency depends on the constant magnetic field component, but the 600 MHz is a good ballpark estimate. This corresponds to the wavelength of ~50cm. The question is, how can NMR solve a protein structure which overall size is some 8 orders of magnitude smaller? The bottom line is that there does not seem to be enough energy here to probe the structure of the matter at such small scale. I consulted with one NMR spectroscopist and he was not sure of exact answer, but pointed out that the distance between peaks in NMR may be as small as ten ppb - exactly the eight orders of magnitude I am looking for. But so what - I still don't see any exaHertz radiation in play. FRET would have very similar issue. One can tell the distance between labels with at least 1nm precision, ~500 times shorter than the wavelength. Thanks, Ed. -- Edwin Pozharski, PhD, Assistant Professor University of Maryland, Baltimore ---------------------------------------------- When the Way is forgotten duty and justice appear; Then knowledge and wisdom are born along with hypocrisy. When harmonious relationships dissolve then respect and devotion arise; When a nation falls to chaos then loyalty and patriotism are born. ------------------------------ / Lao Tse /
