IonDb: compound database with additional ion information

IonDb objects extends CompDb by allowing to store also information about measured ions to a CompDb() database. This information includes the type (adduct) of the ion, it's measured (or expected) retention time for a certain LC-MS setup and its mass-to-charge ratio.

As suggested use case, users might create (or download) a CompDb (SQLite) database e.g. containing compound (and eventually MS/MS spectra) annotations from public databases such as the Human Metabolome Database (HMDB) or MassBank. To store now measured ions (e.g. of lab-internal standards) for a certain LC-MS setup, such a CompDb can then be converted to an IonDb using the IonDb constructor function. Ions can be subsequently added using the insertIon function. In general, it is suggested to create one IonDb database for one specific LC-MS setup. Such an IonDb database can then be used to match experimental m/z and retention times against ions defined in the database (using the functionality of the MetaboAnnotation package).

Usage

# S4 method for IonDb
ionVariables(object, includeId = FALSE, ...)

# S4 method for IonDb
ions(
  object,
  columns = ionVariables(object),
  filter,
  return.type = c("data.frame", "tibble"),
  ...
)

# S4 method for IonDb
insertIon(object, ions, addColumns = FALSE)

# S4 method for IonDb
deleteIon(object, ids = integer(0), ...)

# S4 method for missing,missing
IonDb(x, cdb, ...)

# S4 method for character,missing
IonDb(x, cdb, ...)

# S4 method for CompDb,missing
IonDb(x, cdb, ions = data.frame(), ...)

# S4 method for DBIConnection,missing
IonDb(x, cdb, ions = data.frame(), ...)

# S4 method for character,CompDb
IonDb(x, cdb, ions = data.frame(), ...)

# S4 method for DBIConnection,CompDb
IonDb(x, cdb, ions = data.frame(), ...)

Arguments

object

For all methods: a IonDb object.

includeId

For ionVariables: logical(1) whether the ion ID (column "ion_id") should be included in the result. The default is includeId = FALSE.

...

additional arguments. Currently not used.

columns

For ions: character with the names of the database columns that should be retrieved. Use ionVariables for a list of available column names.

filter

For ions: filter expression or AnnotationFilter() defining a filter to be used to retrieve specific elements from the database.

return.type

For ions: either "data.frame" or "tibble" to return the result as a data.frame() or tibble(), respectively.

ions

for insertIon and IonDb: data.frame with ion definitions to be added to the IonDb database. Columns "compound_id" (character()), "ion_adduct" (character()), "ion_mz" (numeric()) and "ion_rt" (numeric()) are mandatory (but, with the exception of "compound_id", can contain NA).

addColumns

For insertIons: logical(1) whether columns being present in the submitted data.frame but not in the database table should be added to the database's ion table.

ids

For deleteIon: character() or (alternatively integer()) specifying the IDs of the ions to delete. IDs in ids that are not associated to any ion in the IonDb object are ignored.

x

For IonDb: database connection or character(1) with the file name of the SQLite database where the IonDb data will be stored or a CompDb() object that should be converted into an IonDb object.

For all other methods: an `IonDb` object.

cdb

For IonDb: CompDb object from which data should be transferred to the IonDb database.

Value

See description of the respective function.

Creation of `IonDb` objects/databases

A new IonDb database can be created and initialized with data from an existing CompDb database by passing either the database connection (e.g. an SQLiteConnection) or the file path of a (to be created) SQLite database with parameter x to the IonDb function and the CompDb object with parameter cdb. Optional parameter ions allows insert in addition ion definitions (which can also be added later using insertIon function calls).
An existing CompDb can be converted to an IonDb by passing the CompDb() object with parameter x to the IonDb function. Optional parameter ions allows to provide a data.frame with ion definitions to be inserted in to the database (which can also be added later using insertIon function calls). Note that this fails if the database connection for the CompDb is read-only.
Previously created IonDb databases can be loaded by passing either the database connection (e.g. an SQLiteConnection) or the file path of the (SQLite) database with parameter x to the IonDb function.

Retrieve annotations and ion information from the database

Annotations/compound informations can be retrieved from a IonDb in the same way as thay are extracted from a CompDb. In addition, the function ions allows to retrieve the specific ion information from the database. It returns the actual data as a data.frame (if return.type = "data.frame") or a tibble::tibble() (if return.type = "tibble"). An ions call will always return all elements from the ms_ion table (unless a filter is used).

General functions (beside those inherited from `CompDb`)

IonDb: connect to or create a compound/ion database.
ionVariables: returns all available columns/database fields for ions.

Adding and removing data from a database

IonDb inherits the insertCompound, insertSpectra, deleteCompound and deleteSpectra from CompDb(). In addition, IonDb defines the functions:

insertIon: adds ions to the IonDb object. Note that insertIon always adds all the ions specified through the ions parameter and does not check if they are already in the database. To add columns present in the submitted data.frame to the database table set addColumns = TRUE (default is addColumns = FALSE).
deleteIon: deletes ions from the IonDb object by specifying their IDs.

Filtering the database

Like compounds and Spectra also ions allows to filter the results using specific filter classes and expressions. Filtering uses the concepts from Bioconductor's AnnotationFilter package. All information for a certain compound with the ID "1" can for example be retrieved by passing the filter expression filter = ~ ion_id == 1 to the ions function.

Use the supportedFilters() function on the IonDb object to get a list of all supported filters. See also examples below or the usage vignette for details.

Author

Andrea Vicini, Johannes Rainer

Examples


# We load a small compound test database based on MassBank which is
# distributed with this package.
cdb <- CompDb(system.file("sql/CompDb.MassBank.sql", package = "CompoundDb"))
cdb
#> class: CompDb 
#>  data source: MassBank 
#>  version: 2020.09 
#>  organism: NA 
#>  compound count: 70 
#>  MS/MS spectra count: 70 

# We next want to convert this CompDb into an IonDb, but the original CompDb
# database is read only, thus we have to provide the name (or connection) of
# an other database to transfer all the data from the CompDb to that.
idb <- IonDb(paste0(tempdir(), "/idb_ex.db"), cdb)
idb
#> class: IonDb 
#>  data source: MassBank 
#>  version: 2020.09 
#>  organism: NA 
#>  compound count: 70 
#>  MS/MS spectra count: 70 
#>  ion count: 0 

# It is also possible to load a previously created IonDb passing only the
# connection to the database.
idb2 <- IonDb(paste0(tempdir(), "/idb_ex.db"))

# Ion definitions can be added to the database with the `insertIon` function
# providing a `data.frame` with ion definition. This `data.frame` is expected
# to provide the IDs of the compounds, an adduct name/definition and the
# (experimentally determined) m/z and retention time of the ion. To list
# compound IDs from the CompDb database:
head(compounds(cdb, c("compound_id", "name")))
#>   compound_id         name
#> 1           1      Mellein
#> 2           2      Mellein
#> 3           3      Mellein
#> 4           4      Mellein
#> 5           5      Mellein
#> 6           6 AAL toxin TB

ions = data.frame(compound_id = c("1", "1", "2", "3", "6", "35"),
                  ion_adduct = c("[M+H]+", "[M+Na]+", "[M+Na]+",
                                 "[M+Na]+", "[M+2H]2+", "[M+H-NH3]+"),
                  ion_mz = c(179.0703, 201.0522, 201.0522,
                             201.0522, 253.66982, 312.0390),
                  ion_rt = 1:6)

# Inserting ion definitions.
idb <- insertIon(idb, ions)
idb
#> class: IonDb 
#>  data source: MassBank 
#>  version: 2020.09 
#>  organism: NA 
#>  compound count: 70 
#>  MS/MS spectra count: 70 
#>  ion count: 6 

ions(idb, columns = c("name", "formula", "ion_adduct", "ion_mz", "ion_rt"))
#>   ion_adduct   ion_mz ion_rt         name   formula
#> 1     [M+H]+ 179.0703      1      Mellein  C10H10O3
#> 2    [M+Na]+ 201.0522      2      Mellein  C10H10O3
#> 3    [M+Na]+ 201.0522      3      Mellein  C10H10O3
#> 4    [M+Na]+ 201.0522      4      Mellein  C10H10O3
#> 5   [M+2H]2+ 253.6698      5 AAL toxin TB C25H47NO9
#> 6 [M+H-NH3]+ 312.0390      6 Aflatoxin G1  C17H12O7

## List all available ion variables
ionVariables(idb)
#> [1] "compound_id" "ion_adduct"  "ion_mz"      "ion_rt"     

## Extract a data.frame with ion variables for all ions
ions(idb)
#>   compound_id ion_adduct   ion_mz ion_rt
#> 1           1     [M+H]+ 179.0703      1
#> 2           1    [M+Na]+ 201.0522      2
#> 3           2    [M+Na]+ 201.0522      3
#> 4           3    [M+Na]+ 201.0522      4
#> 5          35 [M+H-NH3]+ 312.0390      6
#> 6           6   [M+2H]2+ 253.6698      5

## List all database tables and their columns
tables(idb)
#> $ms_compound
#> [1] "compound_id" "formula"     "exactmass"   "smiles"      "inchi"      
#> [6] "inchikey"    "cas"         "pubchem"     "name"       
#> 
#> $ms_ion
#> [1] "ion_id"      "compound_id" "ion_adduct"  "ion_mz"      "ion_rt"     
#> 
#> $msms_spectrum
#>  [1] "accession"             "spectrum_name"         "date"                 
#>  [4] "authors"               "license"               "copyright"            
#>  [7] "publication"           "ms_level"              "polarity"             
#> [10] "splash"                "compound_id"           "precursor_intensity"  
#> [13] "precursor_mz"          "adduct"                "ionization"           
#> [16] "ionization_voltage"    "fragmentation_mode"    "collision_energy_text"
#> [19] "instrument"            "instrument_type"       "precursor_mz_text"    
#> [22] "spectrum_id"           "collision_energy"      "predicted"            
#> [25] "msms_mz_range_min"     "msms_mz_range_max"    
#> 
#> $msms_spectrum_peak
#> [1] "spectrum_id" "mz"          "intensity"   "peak_id"    
#> 
#> $synonym
#> [1] "compound_id" "synonym"    
#> 

## Filtering the database
##
## Get all ions with an m/z between 200 and 300
res <- ions(idb, filter = ~ ion_mz > 200 & ion_mz < 300)
res
#>   compound_id ion_adduct   ion_mz ion_rt
#> 1           1    [M+Na]+ 201.0522      2
#> 2           2    [M+Na]+ 201.0522      3
#> 3           3    [M+Na]+ 201.0522      4
#> 4           6   [M+2H]2+ 253.6698      5

## Get all ions that have a H in their adduct definition.
res <- ions(idb, filter = IonAdductFilter("H", "contains"))
res
#>   compound_id ion_adduct   ion_mz ion_rt
#> 1           1     [M+H]+ 179.0703      1
#> 2          35 [M+H-NH3]+ 312.0390      6
#> 3           6   [M+2H]2+ 253.6698      5