What is a small molecule and what is a large (biological) molecule

Biomolecular polymers including polypeptides, polynucleotides, polysaccharides, and their complexes that meet the following criteria are accepted:

For polypeptide structures
1. all gene products
2. all naturally-occurring peptides that are non-ribosomal in origin
3. all peptidic repeat units of larger polymers (such as fibrous and amyloid polymers)
4. Non-biological synthetic peptides with at least 24 residues within a polymer chain
Polynucleotide structures of four or more residues
Polysaccharide structures of four or more residues

Crystal structures of peptides with fewer than 24 residues within any polymer chain that do not meet criteria 1, 2, or 3 can be deposited at the Cambridge Crystallographic Data Centre (CCDC, http://www.ccdc.cam.ac.uk/products/csd/deposit/). NMR structures of such molecules can be submitted to Biological Magnetic Resonance Data Bank (BMRB) through the Small Molecule Structure Deposition (SMSdep, http://smsdep.bmrb.wisc.edu/bmrb-adit/) system. Smaller oligonucleotides (dinucleotides and trinucleotides) can be deposited at the Nucleic Acid Database (NDB, http://ndbserver.rutgers.edu).