Amyloids are insoluble protein aggregates that arise through protein misfolding and are associated with numerous neurodegenerative disorders, systemic amyloidosis, and other human diseases. Nuclear magnetic resonance (NMR) spectroscopy, encompassing both solution-state and solid-state approaches, offers unique capabilities to investigate each stage of the complex amyloid formation pathway, from soluble monomeric precursors through transient intermediate states and oligomeric assemblies to highly ordered mature fibrils. This residue-specific and atomic-level characterization of the aggregation process is difficult to achieve using other biophysical techniques.NMR is particularly well suited for elucidating the mechanisms of amyloid formation because it provides detailed structural and dynamic information across multiple aggregation states at molecular resolution. This review highlights the application of solution-state and solid-state NMR methods in characterizing the conversion of natively folded amyloidogenic proteins into amyloid fibrils, with particular emphasis on the identification and characterization of transient intermediates, including both observable and “invisible” species, high-molecular-weight oligomers, and insoluble fibrillar aggregates. Representative examples of natively folded amyloidogenic precursor proteins are discussed, together with an overview of the NMR method used to elucidate their misfolding and aggregation mechanisms. Collectively, these studies demonstrate the power of NMR spectroscopy in providing mechanistic and structural insights into amyloid formation at residue-level resolution.
The deposition of β-amyloid peptide (Aβ) aggregates in the brain is widely accepted as one of the major factors driving the development of Alzheimer's disease (AD). Tacrine (9-amino-1,2,3,4-tetrahydroacridine) is one of the most potent acetylcholinesterase inhibitors approved for the symptomatic treatment of AD, but its clinical use was discontinued due to hepatotoxicity. Recent studies have reported that tacrine can interact with Aβ and inhibit its aggregation, although the underlying mechanism is not yet fully elucidated, highlighting the need for detailed spectroscopic characterization under physiologically relevant conditions. Here, we report, to the best of our knowledge, the first complete and unambiguous assignment of the 1H and 13C NMR resonances of tacrine in aqueous solution at near-physiological pH using a combination of ROESY, HSQC, and HMBC experiments. pH-dependent 1HNMR studies revealed that aromatic proton resonances are highly sensitive to protonation state, displaying pronounced but fully reversible chemical-shift variations. The resulting spectral map provides a reliable basis for ligand-observed NMR investigations of tacrine and related compounds in aqueous media. Moreover, saturation transfer difference (STD)-NMR experiments were optimized to investigate the interaction of tacrine with soluble Aβ1–40 aggregates. Under the optimized conditions, clear STD effects were observed exclusively in the presence of Aβ1–40, confirming direct ligand–aggregate interaction. Differential saturation transfer among aromatic protons, particularly for H-7, suggests distinct proximity relationships within the tacrine– Aβ1–40 complex. Together, these results establish a robust spectroscopic and methodological framework for future NMR studies of tacrine-based ligands and their interactions with amyloid assemblies.
Type-2 diabetes mellitus remains a major global health challenge, requiring therapeutic strategies that ensure long-term safety while addressing its multifactorial pathology. Although existing pharmacotherapies effectively control glycemia, their largely single target mechanisms and variable tolerability underscore the need for complementary approaches. In this study, we present a comprehensive evaluation of NAMIG-5, an polyherbal formulation, for Type-2 diabetes mellitus management. Pharmacognostic and phytochemical analyses using spectroscopic and chromatographic techniques, confirmed the authenticity of the formulation along with the chemical consistency. In a nicotinamide–streptozotocin-induced diabetic model, NAMIG-5 exhibited significant antihyperglycemic activity without acute or sub-chronic toxicity. A randomized, active-controlled clinical trial involving 90 participants demonstrated significant reductions in fasting and postprandial glucose levels, improved lipid profiles, and excellent tolerability, with efficacy exceeding metformin, a widely prescribed anti-diabetic medication (p < 0.05). Mechanistically, the components of NAMIG-5 synergistically inhibited human islet amyloid polypeptide aggregation. Bioactivity-guided fractionation identified the key active constituents, establishing NAMIG-5 as a safe therapeutic candidate for Type-2 diabetes mellitus.
This paper describes a detailed characterization of simple magnetoliposomes (MLPs), in relation to the design, production and economic accessibility of magnetic-triggered antitumoral systems. It focuses on the effect of maghemite nanoparticles (Fe2O3 NPs) on the lipidic parameters of MLPs. Magnetometry studies have shown that the saturation magnetization of MLPs was around 16% lower than the one related to Fe2O3 NPs. Dynamic light scattering (DLS) analyses demonstrated that the size variation of MLPs, stored between 20 and 50 days, corresponded to half of the one related to liposomes. ζ-potential values higher than -30 mV were obtained in this period. Small angle X-ray spectroscopy (SAXS) indicated that the presence of Fe2O3 NPs preserved the number, spacing and thickness of the lipid bilayers. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) data indicated that Fe2O3 NPs restrict the lipid motions of MLPs. Correlations between the structural events, lipid motion, and stability of MLPs were found and performed.
