This requires further enrichment of the molecular formula database entries.
Thus, the molecular formula database should not include useless entries.
Thus, derivatization of the molecular formula database was attempted by creating KNApSAcK plus.
The branching-ratio parameters were obtained for each molecular formula database for various experimental errors of mass analysis and searching thresholds (Δthres) listed in Table S1.
The latter strategy (higher completeness, α) requires further enrichment of the molecular formula database, which is inevitably accompanied by an increase in the density of the database (γ3).
Therefore, molecular formula databases should not include useless entries, and a small, customized compound database suitable for the specific research purpose is preferable to a large, all-in-one database.
The two concepts of database, completeness and density, have been introduced in this study to describe the properties of molecular formula databases, corresponding to the parameters α and γ1 3 in the classification scheme shown in Fig. 3, respectively.
In order to obtain the ground truth of performance of in silico fragmentation software it is important to exclude all pre-knowledge or any bias such as molecular formula lookup, database ranking or any other means that would influence the score.
First, chemical names may appear in various forms, ranging from the popular and human-readable trivial and brand names to the more obscure abbreviations, molecular formulas and database identifiers, to long nomenclature-conforming expressions, e.g., International Union of Pure and Applied Chemistry IUPACC) names and Simplified Molecular-Input Line-Entry System (SMILES) strings [6 8].
Metabolite information such as the name, molecular formula and metabolic database identifiers of compounds were included in the network, and refined from available metabolomics data for 157 metabolites [ 35].
One metabolite, m/z 144.048, was identified as 4-methyl-5-thiazoleethanol, a degradation product of thiamine (vitamin B1), with molecular formula C6H9NOS by database searches and confirmed by MS/MS using commercially available authentic chemical standard.
