Compositional analysis of human acquired enamel pellicle by mass spectrometry

Relatively little is known about the formation of the acquired enamel pelli cle other than that it involves the selective adsorption of specific protei ns from oral fluids. Previous studies on the identification of pellicle com ponents have relied largely on immunological or enzymatic detection and hav e been hampered by the fact that only minute quantities of pellicle call be removed from tooth surfaces. The present work describes an improved method of harvesting pellicle that combines mechanical and chemical removal; this approach was used to investigate systematically the dt sorption of in vitr o pellicle components with different solutions. Eleven major in vitro pelli cle proteins were identified by using a combination of electrophoretic sepa ration and matrix-assisted laser desorption/ionization-reflectron time-of-f light mass spectrometry. A similar analysis of in vivo-formed pellicle reve aled the presence of intact statherin, lysozyme, albumin and amylase. Furth er analysis of in vivo pellicle by liquid chromatography-electrospray ioniz ation mass spectrometry suggested the presence of numerous low molecular-we ight fragments of precursor proteins. The protein composition of in vitro w hole-salivary pellicle adsorbed to hydroxyapatite and that of in vivo ename l pellicle differed for proline, the result of a reduction in the content o f acidic proline-rich proteins in the in vivo samples. Unique features of t he oral environment such as enzymatic activities or mineral surface propert ies may account for these differences between in vivo and in vitro pellicle formation. (C) 2001 Elsevier Science Ltd. All rights reserved.