Background: Extracting Protein-Protein Interactions (PPI) from research papers is a way of translating information from English to the language used by the databases that store this information. With recent advances in automatic PPI detection, it is now possible to speed up this process considerably. Syntactic features from different parsers for biomedical English text are readily available, and can be used to improve the performance of such PPI extraction systems. Results: A complete PPI system was built. It uses a deep syntactic parser to capture the semantic meaning of the sentences, and a shallow dependency parser to improve the performance further. Machine learning is used to automatically make rules to extract pairs of interacting proteins from the semantics of the sentences. The results have been evaluated using the AImed corpus, and they are better than earlier published results. The F-score of ent system is 69.5% for cross-validation between pairs that may come from the same...