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ninhydrin reaction

n.
  1. A test for proteins, peptones, peptides, and amino acids possessing free carboxyl and alpha-amino groups in which ninhydrin reacts with such compounds to produce a blue color.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.