The spine is an ordered list of all of the contents of the book. It uses the item IDs you’ve created in the manifest. Each item gets an item ref, and you use the item id that you created in the manifest for the id ref.
the spine lists the book content in the form \<itemref idref=\"sameasinmanifest\"\/>
OPF file in an epub is 'open package format' and lists the content of an epub. some metadata (title, date, creator, identifier,language, publisher) the manifest point to needed resources (images, fonts, css, navigation file and all xhtml pages) spine gives the content of the book (reusing the ids in the manifest).
we establish Saturated Programmable Insertion Engineering (SPINE), an unbiased, comprehensive, and targeted domain insertion library generation technique using oligo library synthesis and multi-step Golden Gate cloning