why did we not see his slides?

You forgot to mention the LC component of the LC/MS. Is the MS example you displayed from one component or from the complete mixture of compounds?
Also MS gives very limited structural information. There are methods available which would allow you to crystallize these proteins and carry out x-ray diffraction. Have you done this? X-ray could also be employed to examine these proteins bound to the receptor, are you trying this? I have references to this methodology if you are interested.
NMR could also be used for structure determination.