Although it doesn't alter the analogy much, there is also the even higher level of 'quinary structure' - although it is disputed: https://www.ncbi.nlm.nih.gov/

Although it doesn't alter the analogy much, there is also the even higher level of 'quinary structure' - although it is disputed: https://www.ncbi.nlm.nih.gov/pubmed/23943406 https://www.ncbi.nlm.nih.gov/pubmed/23943406