ABSTRACT
Water is an important component of collagen in tendons, but its role for the function of this load-carrying protein structure is poorly understood. Here we use a combination of multi-scale experimentation and computation to show that water is an integral part of the collagen molecule, which changes conformation upon water removal. The consequence is a shortening of the molecule that translates into tensile stresses in the range of several to almost 100 MPa, largely surpassing those of about 0.3 MPa generated by contractile muscles. Although a complete drying of collagen would be relevant for technical applications, such as the fabrication of leather or parchment, stresses comparable to muscle contraction already occur at small osmotic pressures common in biological environments. We suggest, therefore, that water-generated tensile stresses may play a role in living collagen-based materials such as tendon or bone.
Subject(s)
Collagen/chemistry , Osmotic Pressure , Tendons/pathology , Animals , Bone and Bones/pathology , Female , Molecular Dynamics Simulation , Muscle Contraction , Osmosis , Pressure , Rats , Rats, Sprague-Dawley , Scattering, Radiation , Spectrum Analysis, Raman , Stress, Mechanical , Temperature , Tensile Strength , Water/chemistry , X-Ray Diffraction , X-RaysABSTRACT
Instabilities caused during the erosion of a surface by an ion beam can lead to the formation of self-organized patterns of nanostructures. Understanding the self-organization process requires not only the in-situ characterization of ensemble averaged properties but also probing the dynamics. This can be done with the use of coherent X-rays and analyzing the temporal correlations of the scattered intensity. Here, we show that the dynamics of a semiconductor surface nanopatterned by normal incidence ion beam sputtering are age-dependent and slow down with sputtering time. This work provides a novel insight into the erosion dynamics and opens new perspectives for the understanding of self-organization mechanisms.
Subject(s)
Models, Theoretical , Nanostructures/chemistry , Semiconductors , Materials Testing , Photoelectron Spectroscopy , Surface Properties , X-RaysABSTRACT
Incorporating sacrificial cross-links into polymers represents an exciting new avenue for the development of self-healing materials, but it is unclear to what extent their spatial arrangement is important for this functionality. In this respect, self-healing biological materials, such as mussel byssal threads, can provide important chemical and structural insights. In this study, we employ in situ small-angle X-ray scattering (SAXS) measurements during mechanical deformation to show that byssal threads consist of a partially crystalline protein framework capable of large reversible deformations via unfolding of tightly folded protein domains. The long-range structural order is destroyed by stretching the fiber but reappears rapidly after removal of load. Full mechanical recovery, however, proceeds more slowly, suggesting the presence of strong and slowly reversible sacrificial cross-links. One likely role of the highly ordered elastic framework is to bring sacrificial binding sites back into register upon stress release, facilitating bond reformation and self-repair.
Subject(s)
Mytilus/chemistry , Proteins/chemistry , Animals , Cryoelectron Microscopy , Elasticity , Mytilus/ultrastructure , Proteins/ultrastructure , Regeneration , Scattering, Small Angle , Stress, Mechanical , Tensile Strength , X-Ray DiffractionABSTRACT
Ion beam sputtering is a widely used technique to obtain patterned surfaces. Despite the wide use of this approach on different materials to create surface nanostructures, the theoretical model to explain the time evolution of the erosion process is still debated. We show, with the help of simulations, that two-time correlation functions can serve to assess the validity of different models. These functions can be measured experimentally with the x-ray photon correlation spectroscopy technique.
Subject(s)
Models, Theoretical , Photoelectron Spectroscopy , Surface Properties , Time FactorsABSTRACT
Using scanning X-ray diffraction microscopy with a spot size of 220 x 600 nm, it was possible to inspect individual GaAs nanorods grown seed-free through circular openings in a SiN(x) mask in a periodic array with 3 microm spacing on GaAs[111]B. The focused X-ray beam allows the determination of the strain state of individual rods and, in combination with coherent diffraction imaging, it was also possible to characterize morphological details. Rods grown either in the centre or at the edge of the array show significant differences in shape, size and strain state.
ABSTRACT
A compact portable vacuum-compatible chamber designed for surface X-ray scattering measurements on beamline ID01 of the European Synchrotron Radiation Facility, Grenoble, is described. The chamber is versatile and can be used for in situ investigation of various systems, such as surfaces, nanostructures, thin films etc., using a variety of X-ray-based techniques such as reflectivity, grazing-incidence small-angle scattering and diffraction. It has been conceived for the study of morphology and structure of semiconductor surfaces during ion beam erosion, but it is also used for the study of surface oxidation or thin film growth under ultra-high-vacuum conditions. Coherent X-ray beam experiments are also possible. The chamber is described in detail, and examples of its use are given.
