Structure file reader (PDB / mmCIF)

Read a PDB or mmCIF structure file — an RCSB PDB entry, or a model from AlphaFold DB, AlphaFold Server or ColabFold — and report what is in it: every polymer chain with its molecule type, name and one-letter sequence (all chains also as FASTA), how many residues have coordinates and which stretches of the sequence do not, bound ligands and waters, and the experimental method and resolution. When the file itself marks its B-factor column as a confidence score (a pLDDT metric, an AlphaFold title, or one value per residue with no experimental method), each chain's mean pLDDT and its stretches below 50 are reported too; otherwise B-factors are left alone. Only the first model of a multi-model file is read. Reads the text; nothing is fetched.