Identification of new peptide ligands for epidermal growth factor receptor using phage display and computationally modeling their mode of binding.

Peptide phage display, a powerful method for ligand identification, was used to identify new peptide ligands for epidermal growth factor receptor. A-431 cells expressing epidermal growth factor receptor were used as the matrix in a cell-based subtractive biopanning approach using a 7-mer peptide displaying phage library. Two novel peptide ligands were identified and tested for their affinities and functional effects on epidermal growth factor receptor. The identified peptides were able to inhibit the epidermal growth factor-induced phosphorylation of epidermal growth factor receptor in a concentration-dependent manner. The results of affinity binding experiments showed that the natural ligand, that is epidermal growth factor, was able to inhibit competitively the binding of peptide-bearing phage to epidermal growth factor receptor expressing A-431 cells. Molecular modeling studies were used to calculate the free energies for the binding of peptides to the receptor-binding site as well as proposing the interaction modes for this binding. The calculated values for the binding energies were found to be similar to our experimental data and those of previously reported studies.

Detection of Helicobacter pylori using PCR in dental plaque of patients with and without gastritis.

OBJECTIVES: Helicobacter pylori (H.pylori) accounts for gastritis, peptic ulcer and is a probable cause of gastric cancer. Since its detection in the oral cavity, concerns have been raised about dental plaque as a reservoir for reinfection. The aim of this study was to detect the organism in the dental plaque and to determine the association, if any, between H. pylori gastritis and dental plaque contamination causing H.pylori. STUDY DESIGN: A polymerase chain reaction-based method was used for detection of H. pylori in clinical specimens. Supra and subgingival samples were collected from 67 patients with chronic periodontitis, 23 of whom were also suffering from gastritis. The data were analyzed with Chi square and Fisher exact test and the statistical significance was set to 0.05. RESULTS: H.pylori was scarce in patients with periodontitis(5.9%). There was a significant association between the presence of H.pylori in the dental plaque and gastritis (p=0.012). CONCLUSIONS: Although rarely seen, H.pylori infected dental plaque may be a source for reinfection. It is therefore suggested that professional plaque removal and oral hygiene procedures be performed, along with the antibiotic treatment of H.pylori.