European Biophysics Journal最新文献

N-acylmelatonins (NAMs), a class of fatty acid amides featuring melatonin as the polar head group, demonstrate significant biomedical potential. In this study, a homologous series of saturated NAMs (n = 9–18) were synthesized and fully characterized via FTIR, NMR and HRMS. The biophysical self-assembly behaviour was assessed by powder X-ray diffraction and fluorescence spectroscopy. The d-spacing determined from PXRD increases linearly with an increment of ~ 0.90 Å per CH₂ group, suggesting that the NAMs adopt a tilted bilayer structure. Fluorescence spectroscopy was employed to measure the critical micellar concentrations (CMCs) of NAMs by monitoring the spectral changes of 8-anilinonaphthalene-1-sulfonate (ANS). Fluorescence emission and lifetime measurements of NAMs show a red-shift (~ 10 nm) in emission maxima and a 2.4-fold emission intensity enhancement due to the hydrophobic acyl chain. Antioxidant properties, determined by DPPH radical scavenging assays, increased with concentration, showcasing potent activity. Notably, NAMs exhibited enhanced antimicrobial efficacy against clinically relevant bacterial and fungal strains, with minimum inhibitory concentrations comparable to standard drugs. In vitro anticancer screening revealed significant cytotoxicity against multiple human cancer cell lines, particularly with medium-chain NAMs. These findings highlight the broad-spectrum therapeutic potential of NAMs, driven by variable acyl chain length, self-assembly characteristics and strong biological applications.

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Geobacter bacteria produce multiheme c-type cytochrome nanowires that are involved in long-range extracellular electron transfer. The ability of these protein nanowires to conduct electrical current makes them promising candidates for electronic devices, offering several functional and sustainable advantages over traditional materials. Therefore, this study focused on synthesizing hybrid protein fibers that mimic the natural Geobacter extracellular nanowires. To achieve this, a mutated PpcA triheme protein variant was used as the building block, with thiol-ene coupling employed to bind the protein molecules. This engineered PpcA variant (PpcAK9CK22C) maintained a structure similar to that of the native protein. Thermal denaturation studies revealed a two-state process, with a melting temperature of 62 ± 1 °C and an enthalpy change of 61 ± 2 kcal/mol. The new protein nanowires showed a lower heme group content than the precursor protein and displayed distinct secondary structure features, with a slight reduction in helical content and an increase in β-sheet and unordered structures. Their thermal stability also differed, as it could not be described by the same model applied to the PpcA variant. Despite these differences, the nanowires retained their ability to undergo redox cycling. Morphologically, they consisted of linear single-protein filaments extending over 300 nm in length.

The green alga Chlamydomonas reinhardtii (CR) has been explored as the live component of biohybrid microrobots due to its intrinsic motility. However, cell performance depends on physiological state, which evolves with culture age. Using optical tweezers, we quantify the rotational dynamics of individual CR cells across lag, exponential, stationary, and death phases. We reveal a clear performance trajectory: rotation speed and corresponding hydrodynamic torque peak during the mid-exponential phase and decrease as cultures mature. Additionally, counterclockwise rotation consistently generates higher hydrodynamic torque than clockwise rotation. These findings provide quantitative benchmarks linking CR’s motility characteristics to growth phase, offering guidelines for designing living micromachines and establishing rotational dynamics as a sensitive proxy for cellular metabolic health.

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Viruses are complex supramolecular assemblies that propagate their genetic material from cell to cell, thereby relying on host cell mechanisms. Employing a combination of passive and active strategies, they efficiently package, transport and release nucleic acids. While structural and biochemical techniques offer insights into certain, static aspects of the viral life cycle, recent advancements in biophysical approaches now allow for direct measurement of their inherent dynamic activities in the research field commonly referred to as physical virology. One of these methods is optical tweezers, enabling the precise measurement of force and position at the single-molecule level over time. Over the past decades, the ability to optically trap beads and to manipulate biomolecules has revolutionised medical and biophysical research. In this paper, we provide a comprehensive analysis of optical tweezers, exploring its integration with imaging modalities and review its diverse applications in the study of viruses and viral components. In particular we focus on studies that use optical tweezers to study virus-cell interactions, genome packaging using molecular motors and co-assembly of viral assembly proteins with their nucleic acid.

Interleukin-6 (IL-6) is an aggregation-prone cytokine whose recombinant production from Escherichia coli inclusion bodies remains challenging because of inefficient refolding. Here, we present a limited batch-mode process-analytical study comparing two practical buffer-exchange operations, “fast” and “slow”, during batch dilution refolding of IL-6. Using SDS-PAGE, size-exclusion chromatography (SEC), dynamic light scattering (DLS), and far-UV circular dichroism (CD) spectroscopy, we examined dimerization and aggregation under acidic and guanidine denaturation workflows. The data suggest that IL-6 forms predominantly non-covalent dimers and that batch buffer-exchange operation and timescale are associated with aggregation outcome. Because the acidic and guanidine workflows differed in starting solvent composition, residual denaturant, and final protein concentration, the results should be interpreted as comparisons of complete workflow conditions rather than isolated denaturant effects. Overall, the combined use of SEC, DLS, and far-UV CD provides a practical framework for monitoring IL-6 refolding outcomes, while mechanistic assignments remain beyond the scope of this study.

A novel constitutive material model for the collagenous tissue of bridging veins is presented in this article. The walls of blood vessels are structurally reinforced by the collagen fibers, which are interconnected with an elastin matrix. Collagen fibers are oriented according to a specific probability distribution, with a greater abundance of fibers along the longitudinal axis. It is possible to analyze the collective mechanical behavior of collagen fibers using statistical mechanics techniques. The article describes how to derive the macroscopic behavior of collagenous tissue using the formalism of the canonical ensemble of statistical mechanics. One of the innovations of this formulation is the incorporation of a damage variable that increases significantly under excessive stretching. This formalism enables the derivation of a constitutive material model that is thermodynamically consistent, in which entropy increases irreversibly with the level of damage. In the model, an increase in damage results in a permanent increase in entropy. Furthermore, for a given level of damage, an increase in strain induces organization in the fibers, which is consistent with the behavior of an entropically elastic material. In addition, the thermodynamic properties of the model account for specific empirical observations, such as the slight contraction that occurs in a blood vessel when it is heated. The model’s mechanical suitability was assessed by subjecting it to uniaxial tensile tests on bridging veins. The findings provide strong evidence that the proposed constitutive model accurately reproduces the stress–strain curves ((R^2_{adj}> 0.99)).

Host–guest interactions between cyclodextrins and small molecules are fundamental in drug delivery, supramolecular chemistry, and molecular sensing. In this study, we applied Flow-Induced Dispersion Analysis (FIDA) to investigate the binding of a tryptophan derivative with α-, β-, and γ-cyclodextrins. For this purpose, L-tryptophan (trp) was fluorescently labelled with fluorescein (Fl-trp) to serve as a detectable indicator, enabling both direct binding and competitive displacement assays. Direct FIDA measurements revealed preferential binding of Fl-trp to β-cyclodextrin, with an apparent association constant K ~ 470 M^− 1, while α- and γ-cyclodextrins showed weaker interactions, in agreement with literature. In competitive displacement experiments, the addition of unlabelled trp that binds to cyclodextrins effectively shifts the equilibria to the displacement of Fl-trp from the cyclodextrin cavities. The titration with [trp]_tot allows to indirectly monitor the complex dissociation via changes in Rₕ. These results demonstrate that FIDA can be successfully applied to quantify small-molecule host–guest interactions, including weak or transient complexes, by tracking relative Rₕ changes. This approach provides a versatile, quantitative complement to conventional techniques such as NMR, ITC, or fluorescence titrations, and can be extended to other small-molecule binding systems in complex matrices.

Spheroids are of great interest in the study of cancer as they can partially mimic the tumour microenvironment, thus allowing to investigate several aspects of cell – microenvironment interactions in healthy and diseased conditions, including those pertaining to mechanobiology. Atomic Force Microscopy (AFM) is a versatile tool for studying biological samples and their mechanobiological properties. In AFM, the tip shape and dimensions determine the contact geometry between the tip and the sample and the length scales at which the mechanical properties are probed. Given the complex multiscale structure of spheroids, the choice of tip geometry and size would allow, in principle, to dissect the mechanical response of the overall system into the contributions of the constituents, from the single cell level to the cellular aggregate. In this work, we studied the mechanical properties of spheroids derived from four cell lines (A549, NHLF, HT-29, and CCD-18Co cells). Our studies revealed that using different contact geometries in the fitting procedure results in significantly different Young’s modulus values, highlighting the multiscale response of these complex cellular systems and the importance of a precise experimental design and choice of the AFM probe for the nanomechanical measurements. We observed that the location of F-actin filaments is correlated with the rigidity of the spheroids.