Analysis of seized peptide and protein-based doping agents using four complimentary methods: Liquid chromatography coupled with time of flight mass spectrometry, liquid chromatography-ultraviolet, Bradford, and immunoassays.

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 chromatography-ultraviolet (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 the retention time and the accurate mass with those of reference standards. In 2019, we received 36 samples for peptide/protein analysis, all of which were tested using the LC-UV, LC-TOF-MS, and colorimetric method, and samples suspected of containing hCG were confirmed with an immunoassay. We found a total of 15 samples containing an illegal doping substance, 12 samples containing substances not prohibited by the Danish Doping List, and nine samples containing no peptides or proteins. In conclusion, the four complimentary methods constitute a suitable approach for identifying common peptide/protein doping substances in the day-to-day routine of a forensic laboratory, with limited sample preparation and interpretation of data.

Developing Inhibitors of the p47phox-p22phox Protein-Protein Interaction by Fragment-Based Drug Discovery.

Nicotinamide adenine dinucleotide phosphate oxidase isoform 2 is an enzyme complex, which generates reactive oxygen species and contributes to oxidative stress. The p47phox-p22phox interaction is critical for the activation of the catalytical NOX2 domain, and p47phox is a potential target for therapeutic intervention. By screening 2500 fragments using fluorescence polarization and a thermal shift assay and validation by surface plasmon resonance, we found eight hits toward the tandem SH3 domain of p47phox (p47phoxSH3A-B) with KD values of 400-600 µM. Structural studies revealed that fragments 1 and 2 bound two separate binding sites in the elongated conformation of p47phoxSH3A-B and these competed with p22phox for binding to p47phoxSH3A-B. Chemical optimization led to a dimeric compound with the ability to potently inhibit the p47phoxSH3A-B-p22phox interaction (Ki of 20 µM). Thereby, we reveal a new way of targeting p47phox and present the first report of drug-like molecules with the ability to bind p47phox and inhibit its interaction with p22phox.

Identification of phenobarbital and other barbiturates in forensic drug screening using positive electrospray ionization liquid chromatography-high resolution mass spectrometry.

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 (C17 H24 N2 O7 ). 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.