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Comprehensive drug‐screening performed by liquid chromatography−high resolution mass spectrometry (LC−HRMS) enables identification of hundreds to thousands of drug compounds in a single analysis. Forensic drug screening is generally performed with positive electrospray ionization (ESI+), targeting basic drugs; however, a few toxicologically important drugs such as barbiturates, may require analysis by negative ESI. In this work, screening targets for barbiturates were determined using our LC−HRMS screening with ESI+. For several years, our forensic whole blood samples have been analyzed using the LC−HRMS−ESI+ screening in parallel with a multi‐target LC–MS/MS−ESI− method. From 2014 to 2018, 23 samples were positive for phenobarbital (0.5−81 mg/kg). Retrospective data analysis of 4816 blood samples (15 positive) revealed several potential screening targets for phenobarbital. The targets were tentatively identified by exact mass and isotopic pattern as uncommon adducts of phenobarbital and as a decomposition product of phenobarbital N‐glucoside (C17H24N2O7). Analysis of a test set containing eight positive (0.5–65 mg/kg phenobarbital) and 31 negative samples supported the use of the observed target m/z 323.0614 at 5.14 minutes, corresponding to the [M + HCOONa+Na]+ adduct of phenobarbital. The [M + HCOONa+Na]+ adduct was confirmed as a screening target for common barbiturates, by analysis of barbiturate reference standards in ESI+/ESI−. The [M + HCOONa+Na]+ adduct allowed retrospective analysis with 91% sensitivity (n = 23) and 100% specificity (n = 4855) for phenobarbital in our existing LC−HRMS−ESI+ screening. The two negative results were the two whole‐blood samples with the lowest phenobarbital concentration (<1.8 mg/kg). Thus, a specialized screening is not necessary and use of this adduct likely enables screening for other barbiturates.

Inhibition of PSD‐95 has emerged as a promising strategy for the treatment of ischemic stroke, as shown with peptide‐based compounds that target the PDZ domains of PSD‐95. In contrast, developing potent and drug‐like small molecules against the PSD‐95 PDZ domains has so far been unsuccessful. Here, we explore the druggability of the PSD‐95 PDZ1‐2 domain and use fragment screening to investigate if this protein is prone to binding small molecules. We screened 2500 fragments by fluorescence polarization (FP) and validated the hits by surface plasmon resonance (SPR), including an inhibition counter‐test, and found four promising fragments. Three ligand efficient fragments were shown by 1H,15N HSQC NMR to bind in the small hydrophobic P0 pockets of PDZ1‐2, and one of them underwent structure‐activity relationship (SAR) studies. Overall, we demonstrate that fragment screening can successfully be applied to PDZ1‐2 of PSD‐95 and disclose novel fragments that can serve as starting points for optimization towards small‐molecule PDZ domain inhibitors.

Analysis and identification of seized doping-related products are important tasks for customs or forensic laboratories in order to prevent potentially dangerous and illegal compounds to go into circulation. At the Section of Forensic Chemistry in Copenhagen, we have a workflow consisting of four complimentary validated methods to identify common doping-related substances: liquid chromatographyultraviolet (LC-UV), LC coupled with time of flight mass spectrometry (LC-TOF-MS), the colorimetric Bradford assay, and an immunoassay. The Bradford assay screens for peptide or proteins in the sample, and the immunoassay confirmed human chorionic gonadotropin (hCG). LC-UV was carried out with a C4 protein column for identification of peptides and proteins from a standard reference library, based on retention times and ratios between peak areas at 220, 254, and 280 nm. LC-TOF-MS was performed using a C18 column, and identification was based on comparison of