ABSTRACT
The hydroxyprolines are the most characteristic amino acids found in collagens. There are two position isomers, 4-hydroxyproline which is the most abundant, and 3-hydroxyproline which occurs only in minor amounts and only in some forms of collagens. 1 4-Hydroxyproline is a marker for all types of collagens, while 3-hydroxyproline is a marker for basement membrane collagen. Additionally, some noncollagen proteins such as elastin, acetylcholine esterase, and the lung protein alveolyn contain small amounts of 4-hydroxyproline. The development of sensitive methods of determination of proline and hydroxyprolines is thus of considerable importance. High performance liquid chromatography (HPLC) or ion exchange chromatography (IEC) followed by fluorometric detection has proved a sensitive way of determining amino acids in biological materials. The method, however, has the drawback that secondary amino acids such as proline and hydroxyproline do not react with a typical fluorogenic reagent, o-phthalaldehyde. Alternative procedures for the determination of these imino acids have therefore been devised. This section describes one of these techniques, derivatization with 4-chloro- or 4-fluoro-7-nitrobenzofurazan (NBD-Cl or NBD-F.) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003210337/16265204-ec09-48d7-8a17-b482394969bf/content/pg309_1.tif"/>
