[CrimpJiggler]

So from what I've gathered, a tag is attached to each bead so the compound attached to each bead can later be identified. The tags are usually chains of amino acids or nucleotides. I'm confused about how the tags can tell you what reactant was added at what step though. Lets say I synthesise this library of tetramers:

I read about a bar code method where say alanine on its own represents the white monomer, lysine on its own represents the blue monomer, valine represents the yellow monomer and alanine + valine represents the red monomer etc. I can see how this tag tells you that a specific monomer was used in one of the steps but how does it tell you what monomers where used in multiple steps?

[Honclbrif]

I suppose if there's a 1:1 correlation between amino acid and monomer it would be easy to tell what order things were done in. Otherwise you would probably have to build it up into a codon system.

"alanine on its own represents the white monomer, lysine on its own represents the blue monomer, valine represents the yellow monomer and alanine + valine represents the red monomer"

This latter part is where things begin to break down. How do I know, when I sequence the bar code, that the bead was functionalized with just a red monomer, and not white and yellow monomer or vice versa. I.e, how do I know that 'AVLL' is White-Yellow-Blue-Blue and not Red-Blue-Blue? Unless there was other information provided in the code, it would be impossible to tell these apart using this system.

[CrimpJiggler]

Yeah thats what I was thinking. I know how I'd do it myself. I'd use one amino acid as a stop signal. For example, cysteine is the stop signal so I would find out what reaction I could use to cleave all bonds to cysteine. Then I could just do an edman degradation. I don't understand what they mean by this barcoding system. What I proposed there wouldn't require a barcode system.