Text: I told the landlord with the common sense of a medical major that it was a lie. 1. Peptides that can cross biological barriers are not small molecules, but are called cell-crossing peptides. If macromolecules bind to them, they can carry macromolecules across the biological barrier. The so-called small molecular peptides do not have the structure of cross peptides and cannot be absorbed across the biological barrier. 2. All drugs based on trans peptides can only be injected into organisms, because peptides are formed by amino acid contraction, which is essentially protein, but the amount of amino acids is very small. Taking these orally is equivalent to ingesting protein, and protein will be hydrolyzed into peptides in the stomach and further hydrolyzed into amino acids by trypsin in the small intestine (of course, there are other substances, only the main hydrolysis products are mentioned here, regardless of the PETX carrier family. The liar said that the small molecular peptide was too big to use PETX vector. In fact, even through peptides, the oral absorption rate is