MOBs are composed of two major components: a metal ion or cluster of metal ions and a biological molecule.  Examples include CuHARS which contain copper as the metal ion and cystine as the biological molecule.  Another example includes the use of silver as the metal ion in combination with cystine. Cystine is the dimer form of the amino acid cysteine.  Cobalt has also been used in combination with cystine to form CoMOBs.  
When combined with copper to form CuHARS, the cystine may provide a linker function leading to a linear, high-aspect ratio structure that gives CuHARS its name:  copper high-aspect ratio structures.  In contrast to CuHARS, MOBs formed with silver and cystine, result in silver nanoparticles with spherical, rounded structure.  These have been named AgCysNPs.  Figure 1 shows comparative electron microscopy of CuHARS and AgCysNPs.