Dr. Jesús Angulo - University of Seville

**Abstract** The study of weak protein-ligand complexes is challenging due to the limitations of biophysical techniques as the low affinity of the interaction leads to highly dynamic complexes where the biomolecules exchange between bound and free states too rapidly.[1] This makes extremely difficult to accurately 'capture' the features of the bound state to characterise the structure of the ligand in the complex, due to its very short residence time in the protein binding pocket. Yet, weak biomolecular complexes are essential for understanding cellular responses that are crucial for life. Protein-carbohydrate interactions are examples of weak interactions with high specificity and playing an important role in various biological processes.[2] In addition, in drug discovery, initial screening often identifies weak binders, making it difficult to determine their 3D structures, preventing the elucidation of structural features of the bound state and thus hindering the development of more effective drugs.[3] Saturation transfer difference (STD) NMR spectroscopy is a powerful ligand-based NMR technique for weak ligand screening of protein targets and for obtaining quantitative structural information from biologically relevant protein-ligand complexes.[4] STD NMR is suitable for small/medium molecules of medium/weak affinity, there is no upper limit on protein size and no labelling is required. In this presentation, the molecular recognition of ligands by biologically relevant protein receptors using STD NMR will be presented, with a focus on the application to specific cases of ligand recognition by carbohydrate-binding proteins. We will highlight novel developments in STD NMR that have been made in our laboratory to access to 3D structural information, such as the novel multifrequency STD NMR approaches,[5] a novel reduced matrix computational approaches to validate proposed 3D structures of protein-ligand complexes from molecular docking or molecular dynamics simulations, by means of the experimental STD NMR data,[6] and a novel “Epitope Perturbation by Mutation” approach (EPM-STD NMR), which has been successfully applied to unravel the mechanism of inhibition of a promising ligand of a bacterial virulence factor, NleB1, opening the door to the development of non-antibiotic antimicrobial drugs.[7] **References** [1] J. Qin, A.M. Gronenborn, The FEBS Journal 281 (2014) 1948–1949. [2] J.I. Quintana, et al, Chem. Soc. Rev. 52 (2023) 1591–1613. [3] Q. Li, Frontiers in Molecular Biosciences Volume 7-2020 (2020). [4] M. Mayer, B. Meyer, J. Am. Chem. Soc. 123 (2001) 6108–6117. [5] S. Monaco, et al., Angew. Chem. Int. Ed., 56 (2017) 15289–15293. [6] R. Nepravishta, et al., J. Med. Chem., 67 (2024) 10025–10034. [7] J. Ramírez-Cárdenas, et al., JACS Au 5 (2025) 1279–1288 **Biography** Jesús Angulo is a Research Scientist and Group Leader at the Institute for Chemical Research (IIQ), Spanish National Research Council (CSIC)–University of Seville, where he leads the Biomolecular Interactions and Structural Glycobiology group. His research focuses on the development and application of advanced NMR spectroscopy and computational methods to understand biomolecular recognition, with particular emphasis on protein–ligand and protein–glycan interactions and on weak-affinity molecular complexes. He obtained his PhD in Chemical Sciences from the University of Seville in 2002, working on the three- dimensional structure and dynamics of glycosaminoglycan oligosaccharides using NMR spectroscopy and molecular dynamics. He subsequently joined the group of Prof. Thomas Peters at the University of Lübeck, Germany, where he developed his expertise in ligand-observed NMR approaches for studying protein–ligand interactions. After returning to CSIC as a Juan de la Cierva and later Ramón y Cajal researcher, he established his first independent research group at the University of East Anglia (UK) in 2013, where he progressed to Associate Professor in NMR Spectroscopy before returning to Seville. His laboratory has made methodological contributions to STD NMR, including approaches for quantitative affinity determination, the characterization of multimodal binding, spin-STD NMR, DEEP-STD NMR, and NMR- guided methods for determining ligand orientation and validating three-dimensional models of biomolecular complexes. His group has also developed the RedMat and RedDat computational tools for the analysis and validation of protein–ligand complexes using STD NMR data. Angulo has published more than 100 scientific articles and has led numerous national and international research projects. He is President of the NMR Specialized Group of the Spanish Royal Society of Chemistry (GERMN-RSEQ) and Scientific Director of the CSIC Biomolecular Interactions Platform in Seville. His international career has included extended research appointments in Germany and the United Kingdom, and he currently maintains broad collaborations at the interface of NMR spectroscopy, structural glycobiology, computational chemistry and molecular recognition.