Retrieving a pdb format from protein data bank: https://www.rcsb.org/pdb/software/wsreport.do

Exploring Protein data bank:

https://www.ebi.ac.uk/training/online/course/pdbe-exploring-protein-data-bank-pdb-entry

Hope this helps.

Collagen is a large, fibrous molecule and there are many types of collagen expressed in a specific tissue. These can frequently not be crystallized as whole molecules, but there are various structures of fragments available.

You best do a blast search on www.rcsb.org (advanced search: sequence features: Sequence(blast/PSI-blast) with the sequence of the collagen form or its subsequence you are most interested in. While the hits you get may not specifically be porcine skin gelatin, key structures are conserved between species.

What is sold as porcine skin gelatin anyhow is a wild mixture of collagen isoforms, e.g. Sigma-Aldrich "Gelatin is a heterogeneous mixture of water-soluble proteins of high average molecular masses, present in collagen. Proteins are extracted by boiling the relevant skin, tendons, ligaments, bones, etc. in water. Type A gelatin is derived from acid-cured tissue. Type B is derived from lime-cured tissue."

Depending on what your interested in, you might want to look at structures of the typical collagen triple helix that makes up the fibrous part of the molecule, or those of various non-collagen (globular) domains that govern the interactions with other components of the extracellular matrix.

Dear Dr. Honegger,

Thank you for your complete reply. Do you mean collagen is representative of gelatin? Evan though in the fragments of collagen some amino acids of gelatin are not exist?

Gelatin is an extract of skin and and cartilage containing a mixture of multiple components, the most abundant of which are collagens. Collagens are a family of extracellular matrix proteins (https://en.wikipedia.org/wiki/Collagen) that share a structural feature, the trimerization through the formation of the collagen triple helix. This feature is stabilized by specific posttranslational modifications, the hydroxylation of Proline and Lysine residues, a process that requires Vitamin C - thence the effect of Scurvy on connective tissue integrity. See this article for a comprehensive review: Article Collagen Structure and Stability

I would assume that the powder diffraction pattern (XRD data) of gelatin is dominated by the periodicity of these collagen fibers, although gelatin powder is not really crystalline. Therefore XRD data is not sufficient to determine the full structure of the different collagen forms in gelatin.