cells are complex systems whose physiology is governed by an intricate network of molecular interactions ( mis ) of which a relevant subset are protein  protein interactions ( ppis ) .
signal transduction pathways and transcriptional regulation are typical examples of such biological processes mediated by ppi .
the mi database ( mint , ) was designed to collect experimentally verified ppis in a binary or complex representation . over the past four years , mint has undergone a profound reorganization of both the data model and the database structure , and has dramatically increased the number of stored interactions .
intact is an open source database designed for the storage , presentation and analysis of mis ( 1 ) ( schema available at ) .
the main advantages of adopting the intact model lie in its ability to represent protein complexes and other types of molecules as interaction participants , and in the ease with which new features and toolkits for data storage , representation and analysis can be added .
in addition mint , from now on , will be compatible with all the upgrades and tools developed by the intact consortium .
mint is based on the open source postgresql database management system ( ) . all the data can be accessed as java objects through the intact api by using ojb ( ) as the object - relational mapping tool . the web application is based on the struts framework ( ) running on the tomcat servlet container ( ) and the apache server ( ) .
since mint was first reported ( 2 ) the number of curated entries has grown significantly . given the new database structure , binary and n - ary interactions can now be represented .
the number of binary interactions has increased > 20-fold ( figure 1 ) . as of september 2006 , more then 95  000 physical interactions involving 27  461 proteins from 325 organisms are stored in mint ( figure 2 ) . although , 90% of the interactions stored in the database are the result of large scale , genome wide experiments , the value of mint resides in the high number of curated articles , each of which reports a small number of interactions .
this is reflected in the steady increase of curated articles that is mainly due to the curation of publications describing low - throughput experiments ( figure 1 ) .
the mint curation team consists of two full - time and one part - time curators .
this is not sufficient to capture all the interaction information steadily reported in research articles .
thus , we have chosen to focus our efforts on consistently curating all the issues of febs letters ( since january 2005 ) and embo journal and embo reports ( since january 2006 ) .
this choice was made in agreement with the other members of the international molecular - interaction exchange consortium ( imex ) , including dip ( 3 ) , intact ( 1 ) , mpact ( 4 ) and bind ( 5 ) .
imex aims at avoiding work overlaps , at sharing the curation workload and at exchanging completed records on mi data .
the graph on the left represents the growth in the number of interactions stored in mint .
the pie charts represent the number of interactions stored in mint for the different species .
since january 2006 , the syntax and the semantics for data representation have been provided by the proteomics standards initiative - molecular interaction ( psi - mi 2.5 ) standards .
the psi workgroup develops and maintains a common data standard allowing users to retrieve all relevant data from different data providers and to perform comparative analysis ( 6 ) .
each stored interaction represents , according to the psi - mi standards , a physical interaction , a direct interaction or a co - localization .
all the database records created before january 2005 underwent a drastic quality control performed by the new mint curation staff composed of phd level curators .
all the previous entries were re - curated according to the new psi - mi standard .
entries that could not be updated according to psi - mi standards were deleted from the database in order to maintain a high quality dataset .
the mint curation reference manual is being developed in collaboration with the other imex partners and is available at .
the new data submission html forms benefit from an improved automatic check based on curation rules .
this ensures that mandatory fields are filled and that annotated ranges or residues are consistent with the protein length reported by uniprot .
in addition , for the purpose of ensuring high fidelity annotation , every new entry derived from low - throughput experiments undergoes a further validation step performed by a different curator before release to the public .
the new web - based interface includes a number of improvements and enhancements allowing a more efficient database exploration .
most notably , the query can be based on protein or gene names , uniprot keywords or identifiers of external databases : uniprotkb , pdb , ensembl , flybase , sgd , wormbase , omim , huge , pubmed and reactome .
it is also possible to query species specific datasets ( mammalian , saccharomyces cerevisiae , caemorhabaditis elegans , drosophila melanogaster , viruses ) .
finally , a sequence similarity search ( blast ) can also be performed to search for proteins which are homologous to the query protein .
the query results are displayed in a table showing in the left frame a summary of the protein features reported in uniprot and , in the right frame , the list of the interaction partners curated in mint .
the interactions can be displayed graphically by an enhanced version of the  mint viewer , a java applet derived from the applet graph ( ) . the viewer represents the interactions by lines ( edges ) and nodes ( proteins ) , and assigns the nodes a size proportional to the protein 's molecular weight and a color which depends on the species .
the graph displayed by the viewer can be expanded and edited interactively by moving or deleting nodes .
proteins linked to omim are now highlighted in red . in order to attribute a reliability index to the reported interactions
, we have also assigned each interaction a confidence level , based on the experimental detection method and experimental conditions .
the results of the analysis performed in the mint viewer can be captured in different formats ready for export : psi1.0-xml , psi2.5-xml , flat - file , osprey .
mint is now also complemented by homomint ( 7 ) , an inferred human protein interaction network where interactions discovered in model organisms ( and collected in mint ) are mapped onto the corresponding human orthologs . through the mint web pages
a web service allows direct computational access so as to freely retrieve interaction networks in different formats : flat - file , psi1.0-xml , psi2.5-xml .
it is also possible to download specific subsets of the database based on the taxonomy of the interactors .
 the molecular interaction database ( mint , ) aims at storing , in a structured format , information about molecular interactions ( mis ) by extracting experimental details from work published in peer - reviewed journals . at present 
 the mint team focuses the curation work on physical interactions between proteins . 
 genetic or computationally inferred interactions are not included in the database . over 
 the past four years mint has undergone extensive revision . 
 the new version of mint is based on a completely remodeled database structure , which offers more efficient data exploration and analysis , and is characterized by entries with a richer annotation . over the past few years the number of curated physical interactions has soared to over 95 000 . 
 the whole dataset can be freely accessed online in both interactive and batch modes through web - based interfaces and an ftp server . 
 mint now includes , as an integrated addition , homomint , a database of interactions between human proteins inferred from experiments with ortholog proteins in model organisms ( ) . 
INTRODUCTION
DATABASE STRUCTURE
DATA GROWTH
DATABASE CURATION
DATA ACCESS AND DISTRIBUTION