1H high-resolution magic-angle spinning (HR-MAS) NMR analysis of ligand density on resins using a resin internal standard

Molecular Basis of the Antiangiogenic Action of Rosmarinic Acid, a Natural Compound Targeting Fibroblast Growth Factor-2/FGFR Interactions

Fibroblast growth factor (FGF2)/fibroblast growth factor receptor (FGFR) signalling plays a major role both in physiology and in several pathologies, including cancer development, metastasis formation and resistance to therapy. The development of small molecules, acting extracellularly to target FGF2/FGFR interactions, has the advantage of limiting the adverse effects associated with current intracellular FGFR inhibitors. Herein, we discuss the ability of the natural compound rosmarinic acid (RA) to induce FGF2/FGFR complex dissociation. The molecular-level description of the FGF2/FGFR/RA system, by NMR spectroscopy and docking, clearly demonstrates that RA binds to the FGFR-D2 domain and directly competes with FGF2 for the same binding site. Direct and allosteric perturbations combine to destabilise the complex. The proposed molecular mechanism is validated by cellular studies showing that RA inhibits FGF2-induced endothelial cell proliferation and FGFR activation. Our results can serve as the basis for the development of new extracellular inhibitors of the FGF/FGFR pathways.

High-resolution magic angle spinning (1) H NMR measurement of ligand concentration in solvent-saturated chromatographic beads

A method based on (1) H high-resolution magic angle spinning NMR has been developed for measuring concentration accurately in heterogeneous materials like that of ligands in chromatography media. Ligand concentration is obtained by relating the peak integrals for a butyl ligand in the spectrum of a water-saturated chromatography medium to the integral of the added internal reference. The method is fast, with capacity of 10 min total sample preparation and analysis time per sample; precise, with a reproducibility expressed as 1.7% relative standard deviation; and accurate, as indicated by the excellent agreement of derived concentration with that obtained previously by (13) C single-pulse excitation MAS NMR. The effects of radiofrequency field inhomogeneity, spin rate, temperature increase due to spinning, and distribution and re-distribution of medium and reference solvent both inside the rotor during spinning and between bulk solvent and pore space are discussed in detail. © 2016 The Authors Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.

¹³C SPE MAS measurement of ligand concentration in compressible chromatographic beads

A method for measuring the ligand concentration in heterogeneous materials like chromatography media is described. In this method, (13)C single pulse excitation magic angle spinning NMR experiment with broadband (1)H decoupling is used to determine the peak integrals for a butyl ligand in the spectrum of a dried chromatography medium. Within a carefully controlled protocol, those integrals compared with that of the internal reference compound dimethyl sulfone provide the required volume concentration with an accuracy of ca 2%. The effects of temperature, degree of hydration, and other experimental parameters are discussed.

Quantitative assessment of preloaded 4-alkoxybenzyl alcohol resins for solid-phase peptide syntheses by 1D and 2D HR-MAS NMR

The quality of preloaded Wang resins is very important for the success of solid-phase peptide syntheses (SPPS). A critical factor is the capping of remaining hydroxyl groups after loading with the first amino acid, since these free alcohols lead to truncated sequences during the following SPPS steps. Because the detection of hydroxyl groups by color tests is difficult and unreliable, the capping efficiency is often controlled by time-consuming peptide test syntheses. Here, we describe a two-dimensional, high resolution magic angle spinning NMR method for the quantitative determination of remaining 4-alkoxybenzyl alcohols in Fmoc-Xaa-Wang resins with a detection limit of 1 mol-%. The NMR method was validated with samples of known ratios between Fmoc-Ala-Wang and 4-alkoxybenzylalcohol resin. Application to a set of preloaded Fmoc-Ala- and Fmoc-Thr(tBu)-Wang test resins demonstrated that the full range of essential amino acids can be quantified without further spectrometer calibration. Compared to established test synthesis protocols, the NMR method represents not only advantages in terms of time and cost savings but also eliminates all inaccuracies due to further sample treatment like SPPS and cleavage from the resin.