2 - Using MS2extract Batch Pipeline
Cristian Quiroz-Moreno
2023-02-28
batch_extract.RmdIntroduction
In the previous tutorial Introduction to MS2extract package, we described in a detailed manner the core functions of the package. If you are starting to use the MS2extract package with this tutorial, we encourage you to take a look at the aforementioned tutorial.
Now that you are familiar with the core workflow and functions of
this package, we can dive into an automated pipeline with the proposed
batch_*() functions.
We can remember the workflow summary where we specify the alternative
of core functions for batch_*() alternatives (Figure 1).
Three main steps has its own batch alternatives functions, importing
mzXML files, extracting MS/MS spectra, and detecting masses. However,
exporting the database in a msp file is able to detect if the provided
spectra comes from a single mzXML file or it is a batch set of
spectra.

Figure 1. Overview of general data processing pipeline to extract MS/MS spectra using the MS2extract package
Batch functions
We are familiar with the arguments that the core functions accepts,
in this section we describe extra arguments that specific
batch_*() functions requeire in order to work.
batch_import_mzxml
knitr::opts_chunk$set(warning = FALSE)
library(MS2extract)Similarly to import_mzxml() function, we need a compound
metadata, with at lest the Compound name, Formula, Ionization mode, and
optionally but suggested, the region of interest (min_rt and
max_rt).
# Select the csv file name and path
batch_file <- system.file("extdata", "batch_read.csv",
package = "MS2extract")
# Read the data frame
batch_data <- read.csv(batch_file)
# File paths for Procyanidin A2 and Rutin
ProcA2_file <- system.file("extdata",
"ProcyanidinA2_neg_20eV.mzXML",
package = "MS2extract")
Rutin_file <- system.file("extdata",
"Rutin_neg_20eV.mzXML",
package = "MS2extract")
# Add file path - User should specified the file path -
batch_data$File <- c(ProcA2_file, Rutin_file)
# Checking batch_data data frame
dplyr::glimpse(batch_data)
#> Rows: 2
#> Columns: 6
#> $ Name <chr> "Procyanidin A2", "Rutin"
#> $ Formula <chr> "C30H24O12", "C27H30O16"
#> $ Ionization_mode <chr> "Negative", "Negative"
#> $ min_rt <int> 163, 162
#> $ max_rt <int> 180, 171
#> $ File <chr> "/home/runner/work/_temp/Library/MS2extract/extdata/Pr…The only difference with the core import_mzxml()
met_metadata is that you can provide more compounds by adding rows. You
can see we are working with two compounds, Procyanidin A2 and Rutin.
Tip: you can specify multiple compounds to the same mzXML if they have different precursor ion m/z.
batch_compounds <- batch_import_mzxml(batch_data)
#> Reading MS2 data from ProcyanidinA2_neg_20eV.mzXML
#> Processing...
#> Reading MS2 data from Rutin_neg_20eV.mzXML
#> Processing...The raw mzXML data contains:
- Procyanidin A2: 24249 ions
- Rutin: 22096 ions
# Checking dimension by compound
purrr::map(batch_compounds, dim)
#> $`Procyanidin A2`
#> [1] 24249 4
#>
#> $Rutin
#> [1] 22096 4batch_extract_MS2
Now that we have our data in memory, we can proceed to extract the
most intense MS/MS scan. In this case, the
batch_extract_MS2() functions do not have extra arguments,
although most of the arguments remains fairly similar.
# Use extract batch extract_MS2
batch_extracted <- batch_extract_MS2(batch_compounds,
verbose = TRUE,
out_list = FALSE)

By using verbose = TRUE, we can display the MS/MS TIC
plot as well the raw MS/MS spectra.
batch_detect_mass
Now that we have the raw MS/MS spectra, we are going to remove
background noise based on intensity. Again,
batch_detect_mass() has the same arguments than its core
analogue.
batch_mass_detected <- batch_detect_mass(batch_extracted, # Compound list
normalize = TRUE, # Normalize
min_int = 1) # Minimum intensity
purrr::map(batch_mass_detected, dim)
#> $`Procyanidin A2`
#> [1] 38 4
#>
#> $Rutin
#> [1] 4 4We see a decrease of number of ions, 38 and 4 ions for Procyanidin A2 and Rutin, respectively.
write_msp
In contrast with the previous batch functions,
write_msp() is able to detect if the user is providing a
single spectra, or multiple spectra. However, the user needs to provide
information about each compound.
# Reading batch metadata
metadata_msp_file <- system.file("extdata",
"batch_msp_metadata.csv",
package = "MS2extract")
metadata_msp <- read.csv(metadata_msp_file)
dplyr::glimpse(metadata_msp)
#> Rows: 2
#> Columns: 8
#> $ NAME <chr> "Procyanidin A2", "Rutin"
#> $ PRECURSORTYPE <chr> "[M-H]-", "[M-H]-"
#> $ FORMULA <chr> "C30H24O12", "C27H30O16"
#> $ INCHIKEY <chr> "NSEWTSAADLNHNH-LSBOWGMISA-N", "IKGXIBQEEMLURG-NVPNHPE…
#> $ SMILES <chr> "C1C(C(OC2=C1C(=CC3=C2C4C(C(O3)(OC5=CC(=CC(=C45)O)O)C6…
#> $ IONMODE <chr> "Negative", "Negative"
#> $ INSTRUMENTTYPE <chr> "Q-TOF 6545", "Q-TOF 6546"
#> $ COLLISIONENERGY <chr> "20 eV", "20 eV"After having the clean MS/MS spectra and the compound metadata, we can proceed to export them into a msp files.
write_msp(spec = batch_mass_detected,
spec_metadata = metadata_msp,
msp_name = "ProcA2_Rutin_batch.msp")Session info
sessionInfo()
#> R version 4.2.2 (2022-10-31)
#> Platform: x86_64-pc-linux-gnu (64-bit)
#> Running under: Ubuntu 22.04.2 LTS
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#> BLAS: /usr/lib/x86_64-linux-gnu/openblas-pthread/libblas.so.3
#> LAPACK: /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblasp-r0.3.20.so
#>
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#>
#> attached base packages:
#> [1] stats graphics grDevices utils datasets methods base
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#> other attached packages:
#> [1] MS2extract_0.1.0
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#> [1] ProtGenerics_1.30.0 fs_1.6.1 doParallel_1.0.17
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#> [10] R6_2.5.1 affyio_1.68.0 BiocGenerics_0.44.0
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#> [49] Rcpp_1.0.10 munsell_0.5.0 S4Vectors_0.36.2
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