Mussel mooring made mighty by metals Mussels produce an exceptional proteinaceous adhesive so they can withstand waves and currents. Metal ions bound to modified tyrosine residues play an important role in reinforcing the adhesive. Priemel et al . brought together a variety of spectroscopy and microscopy techniques to study the cellular mechanisms involved in adhesive fabrication in mussels (see the Perspective by Wilker). They found that metal ion–rich vesicles are secreted alongside vesicles containing the adhesive protein and mix in a microfluidic-like process within interconnected microchannels found in the lateral duct of the mussel foot to create porous, adhesive plaque filaments. —MAF

Confocal micro-X-ray fluorescence spectroscopy can be performed with laboratory spectrometers for elemental imaging with 3D resolution. Due to self-absorption inside a specimen and energy effects induced by the used polycapillary...

Grazing incidence and grazing emission X-ray fluorescence spectroscopy (GI/GE-XRF) are techniques that enable nondestructive, quantitative analysis of elemental depth profiles with a resolution in the nanometer regime. A laboratory setup for soft X-ray GEXRF measurements is presented. Reasonable measurement times could be achieved by combining a highly brilliant laser produced plasma (LPP) source with a scanning-free GEXRF setup, providing a large solid angle of detection. The detector, a pnCCD, was operated in a single photon counting mode in order to utilize its energy dispersive properties. GEXRF profiles of the Ni-L line of a nickel-carbon multilayer sample, which displays a lateral (bi)layer thickness gradient, were recorded at several positions. Simulations of theoretical profiles predicted a prominent intensity minimum at grazing emission angles between 5° and 12°, depending strongly on the bilayer thickness of the sample. This information was used to retrieve the bilayer thickness gradient. The results are in good agreement with values obtained by X-ray reflectometry, conventional X-ray fluorescence and transmission electron microscopy measurements and serve as proof-of-principle for the realized GEXRF setup. The presented work demonstrates the potential of nanometer resolved elemental depth profiling in the soft X-ray range with a laboratory source, opening, for example, the possibility of in-line or even in situ process control in semiconductor industry.

<p>To anchor in seashore habitats, mussels fabricate adhesive byssus fibers mechanically reinforced by protein-metal coordination mediated via 3,4-dihydroxyphenylalanine (DOPA) – providing a well-established role model for bio-inspired design of smart metallopolymers and underwater glues. However, currently, the mechanism by which metal ions are integrated as cross-links during byssus formation is completely unknown. Here, we investigated the byssus formation process, combining traditional and advanced methods to identify how and when metals are incorporated into the material. We discovered that mussels concentrate and store iron and vanadium ions in intracellular metal storage particles (MSPs) complexed with previously unknown catechol-based storage molecules. During thread formation, stockpiled secretory vesicles containing concentrated fluid proteins are mixed with MSPs within a complex microfluidic-like network of interconnected channels where they coalesce forming protein-metal bonds within the nascent byssus. These insights are important for bio-inspired materials design, but also from a biological and chemical perspective – the active accumulation and utilization of vanadium is extremely rare in nature.</p>

The uptake of inorganic nutrients by rootless parasitic plants, which depend on host connections for all nutrient supplies, is largely uncharted. Using X‐ray fluorescence spectroscopy (XRF), we analyzed the element composition of macro‐ and micronutrients at infection sites of the parasitic angiosperm Cuscuta reflexa growing on hosts of the genus Pelargonium. Imaging methods combining XRF with 2‐D or 3‐D (confocal) microscopy show that most of the measured elements are present at similar concentrations in the parasite compared to the host. However, calcium and strontium levels drop pronouncedly at the host/parasite interface, and manganese appears to accumulate in the host tissue surrounding the interface. Chlorine is present in the haustorium at similar levels as in the host tissue but is decreased in the stem of the parasite. Thus, our observations indicate a restricted uptake of calcium, strontium, manganese and chlorine by the parasite. Xylem‐mobile dyes, which can probe for xylem connectivity between host and parasite, provided evidence for an interspecies xylem flow, which in theory would be expected to carry all of the elements indiscriminately. We thus conclude that inorganic nutrient uptake by the parasite Cuscuta is regulated by specific selective barriers whose existence has evaded detection until now.