XPS and ATR-FTIR study on chemical modifications of cold atmospheric plasma (CAP) operated in air on the amino acids L-proline and trans-4-Hydroxy-l-proline

Abstract

Amino acids L-proline and trans-4-Hydroxy-l-proline were exposed to cold atmospheric plasma (CAP) generated by dielectric barrier discharge and operated in ambient air at dry conditions. Surface analysis reveals an oxygenation of both amino acids the degree of which is dependent on treatment time. New (Formula presented.) or NO2 groups are attached to the surfaces. Proline and hydroxyproline respond differently to the cold atmospheric plasma, proline being more prone to ring opening, fragmentation of the molecule, and attachment of COH and CO groups. Aging experiments show that plasma mediated attachment of new functional groups is, to a great degree, reversible over time.