Direct Color Observation of Light-Driven Molecular Conformation-Induced Stress.

Although usually complex to handle, nanomechanical sensors are exceptional, label-free tools for monitoring molecular conformational changes, which makes them of paramount importance in understanding biomolecular interactions. Herein, a simple and inexpensive mechanical imaging approach based on low-stiffness cantilevers with structural coloration (mechanochromic cantilevers (MMC)) is demonstrated, able to monitor and quantify molecular conformational changes with similar sensitivity to the classical optical beam detection method of cantilever-based sensors (≈4.6 × 10-3  N m-1 ). This high sensitivity is achieved by using a white light and an RGB camera working in the reflection configuration. The sensor performance is demonstrated by monitoring the UV-light induced reversible conformational changes of azobenzene molecules coating. The trans-cis isomerization of the azobenzene molecules induces a deflection of the cantilevers modifying their diffracted color, which returns to the initial state by cis-trans relaxation. Interestingly, the mechanical imaging enables a simultaneous 2D mapping of the response thus enhancing the spatial resolution of the measurements. A tight correlation is found between the color output and the cantilever's deflection and curvature angle (sensitivities of 5 × 10-3  Hue µm-1 and 1.5 × 10-1  Hue (°)-1 ). These findings highlight the suitability of low-stiffness MMC as an enabling technology for monitoring molecular changes with unprecedented simplicity, high-throughput capability, and functionalities.

Mechanochromic Detection for Soft Opto-Magnetic Actuators.

New multi-stimuli responsive materials are required in smart systems applications to overcome current limitations in remote actuation and to achieve versatile operation in inaccessible environments. The incorporation of detection mechanisms to quantify in real time the response to external stimuli is crucial for the development of automated systems. Here, we present the first wireless opto-magnetic actuator with mechanochromic response. The device, based on a nanostructured-iron (Fe) layer transferred onto suspended elastomer structures with a periodically corrugated backside, can be actuated both optically (in a broadband spectral range) and magnetically. The combined opto-magnetic stimulus can accurately modulate the mechanical response (strength and direction) of the device. The structural coloration generated at the corrugated back surface enables to easily map and quantify, in 2D, the mechanical deflections by analyzing in real time the hue changes of images taken using a conventional RGB smartphone camera, with a precision of 0.05°. We demonstrate the independent and synergetic optical and magnetic actuation and detection with a detection limit of 1.8 mW·cm-2 and 0.34 mT, respectively. The simple operation, versatility, and cost-effectiveness of the wireless multiactuated device with highly sensitive mechanochromic mapping paves the way to a new generation of wirelessly controlled smart systems.

Improving data quality and expanding BioSAXS experiments to low-molecular-weight and low-concentration protein samples.

The addition of compounds to scavenge the radical species produced during biological small-angle X-ray scattering (BioSAXS) experiments is a common strategy to reduce the effects of radiation damage and produce better quality data. As almost half of the experiments leading to structures deposited in the SASBDB database used scavengers, finding potent scavengers would be advantageous for many experiments. Here, four compounds, three nucleosides and one nitrogenous base, are presented which can act as very effective radical-scavenging additives and increase the critical dose by up to 20 times without altering the stability or reducing the contrast of the tested protein solutions. The efficacy of these scavengers is higher than those commonly used in the field to date, as verified for lysozyme solutions at various concentrations from 7.0 to 0.5 mg ml-1. The compounds are also very efficient at mitigating radiation damage to four proteins with molecular weights ranging from 7 to 240 kDa and pH values from 3 to 8, with the extreme case being catalase at 6.7 mg ml-1, with a scavenging factor exceeding 100. These scavengers can therefore be instrumental in expanding BioSAXS to low-molecular-weight and low-concentration protein samples that were previously inaccessible owing to poor data quality. It is also demonstrated that an increase in the critical dose in standard BioSAXS experiments leads to an increment in the retrieved information, in particular at higher angles, and thus to higher resolution of the model.

Positron annihilation lifetime spectroscopy (PALS) as a characterization technique for nanostructured self-assembled amphiphile systems.

Positron annihilation lifetime spectroscopy (PALS) has potential as a novel rapid characterization method for self-assembly amphiphile systems; however, a lack of systematic correlation of PALS parameters with structural attributes has limited its more widespread application. In this study, using the well-characterized phytantriol/water and the phytantriol/vitamin E acetate/water self-assembly amphiphile systems, the impact of systematic structural changes controlled by changes in composition and temperature on PALS parameters has been studied. The PALS parameters (orthopositronium (oPs) lifetime and intensity signatures) were shown to be sensitive to the molecular packing and mobility of the self-assembled lipid molecules in various lyotropic liquid crystalline phases, enabling differentiation between liquid crystalline structures. The oPs lifetime, related to the molecular packing and mobility, is correlated with rheological properties of the individual mesophases. The oPs lifetime links the lipid chain packing and mobility in the various mesophases to resultant macroscopic properties, such as permeability, which is critical for the use of these mesophase structures as diffusion-controlled release matrices for active liposoluble compounds.