Grafting Strategies of Oxidation-Prone Coiled-Coil Peptides for Protein Capture in Bioassays: Impact of Orientation and the Oxidation State

Lycorine esters exert anti-HCoV-OC43 effect through reversibly acylating cysteine residue in the nsp 12 NiRAN domain

By introducing ester warheads into the hydroxyl groups in lycorine (1), three types of lycorine mono-ester or di-ester analogues were synthesized and evaluated for their antiviral activities against HCoV-OC43. Most of them showed higher selective indexes (SI) than 1, up to nearly 14 times. Using compound 6b as a probe, we firstly demonstrated that lycorine esters directly targeted nidovirus RdRp-associated nucleotidyltransferase (NiRAN) domain in the non-structural protein 12 (nsp 12) by reversibly acylating Cys12 to induce the shrink of NiRAN pocket and block the viral replication, different from the known RdRp inhibitors. Meanwhile, the reversible acylation mode of lycorine esters guaranteed the higher SI values and long-acting effects of its kind. Thus, in addition to acting as prodrugs, ester compounds with a highly acylating warhead can be used as covalent probes to explore the detailed mode of action and improve the safety window. Compound 6b has been identified as a new reversible covalent RdRp allosteric inhibitor for further investigation.

Impact of Lectin biotinylation for surface plasmon resonance and enzyme-linked Lectin assays for protein glycosylation

Lectins are widely employed for the assessment of protein glycosylation as their carbohydrate binding specificities have been well characterized. In glycosylation assays, lectins are often conjugated with biotin tags, which interact with streptavidin to functionalize biosensing surfaces or recruit signal generating molecules, depending on the assay configuration. We here demonstrate that a high degree of biotin conjugation can limit total capture to streptavidin functionalized SPR surfaces due to multipoint binding, and can additionally bias the reported kinetic evaluations when measuring the interaction between lectins and glycoproteins by SPR. For microplate assays using different configurations, high biotinylation ratios can effectively amplify the signal obtained when using Streptavidin conjugates for detection, in some cases significantly lowering the limit of detection. The cumulative results express the importance of customizing the ligand biotinylation ratios for different assay configurations, as commercially obtained pre-biotinylated lectins are not necessarily optimized for different assay configurations.

A low-temperature SPR-based assay for monoclonal antibody galactosylation and fucosylation assessment using FcγRIIA/B

Monoclonal antibodies (MAbs) are powerful therapeutic tools in modern medicine and represent a rapidly expanding multibillion USD market. While bioprocesses are generally well understood and optimized for MAbs, online quality control remains challenging. Notably, N-glycosylation is a critical quality attribute of MAbs as it affects binding to Fcγ receptors (FcγRs), impacting the efficacy and safety of MAbs. Traditional N-glycosylation characterization methods are ill-suited for online monitoring of a bioreactor; in contrast, surface plasmon resonance (SPR) represents a promising avenue, as SPR biosensors can record MAb-FcγR interactions in real-time and without labeling. In this study, we produced five lots of differentially glycosylated Trastuzumab (TZM) and finely characterized their glycosylation profile by HILIC-UPLC chromatography. We then compared the interaction kinetics of these MAb lots with four FcγRs including FcγRIIA and FcγRIIB at 5°C and 25°C. When interacting with FcγRIIA/B at low temperature, the differentially glycosylated MAb lots exhibited distinct kinetic behaviors, contrary to room-temperature experiments. Galactosylated TZM (1) and core fucosylated TZM (2) could be discriminated and even quantified using an analytical technique based on the area under the curve of the signal recorded during the dissociation phase of a SPR sensorgram describing the interaction with FcγRIIA (1) or FcγRII2B (2). Because of the rapidity of the proposed method (<5 min per measurement) and the small sample concentration it requires (as low as 30 nM, exact concentration not required), it could be a valuable process analytical technology for MAb glycosylation monitoring.