The best replacement for glycine is glycerol.

The best alternatives to glycine are rated as following:
★★★★★  glycerol
★★★★  l-glycine
★★  alanine
★  trimethylglycine
★  sarcosine
★  sinn
★  gaba
★  taurine
  glycerine
  fortis
  tmg
  proline

Your alternative for glycine is not listed? Suggest!
Speaking about glycine, one probably shouldn't forget about nitrous acid.

Other search terms related to glycine and their ratings are:
★★★★★ nitrous acid
★★★ biuret test
★★ ninhydrin
★★ ninhydrin test
★★ ethanoyl chloride
You have in mind a companion for glycine and it is not yet here? Propose!



Google Trends

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glycine
glycerol
l-glycine