Figure 1. SDS-PAGE of parotid salivary proteins in 16% tricine electrophoresis gels (Invitrogen, Paisley, UK). Resolved proteins were stained (with 0.2% Coomassie Brilliant Blue R250 in 25% methanol, 10% acetic acid) in gels or transferred onto nitrocellulose for antibody binding (see online Appendix). (A) Interaction of parotid salivary proteins (S) with tea (T). Increasing amounts of tea (1, 10, and 50 µL) were added to saliva (50 µL), and interacting salivary proteins were depleted from the electrophoretic profile. Ten µL of sample (equivalent to approximately 25 µg of salivary protein) were added to sample wells. Arrows indicate some protein bands showing a noticeable depletion. Preliminary identities, assigned on the basis of electrophoretic mobility and staining characteristics, are proline-rich protein (A) and histatin (B). The mobilities of standard proteins (M), with relative molecular weights ranging from 210 down to 3 kDa, are shown. (B) The salivary proteins binding to hydroxyapatite (HA) from a sample of parotid saliva (S) under assay conditions (1 hr at 37°C). The presence of statherin binding to hydroxyapatite is shown by a Western blot (W) of the proteins eluted from hydroxyapatite, probed with an anti-statherin antibody. (C) Histatin (Hp) and proline-rich protein (Pp) enriched fractions from saliva and the profiles of enriched proteins binding to hydroxyapatite under assay conditions. For comparison with the enriched histatin fraction, a sample of synthetic histatin 5 (Hs Sigma Chem. Co. Ltd.) is shown.