Elastin enables the reversible deformation of elastic tissues and can withstand decades of repetitive forces. Tropoelastin is the soluble precursor to elastin, the main elastic protein found in mammals. Little is known of the shape and mechanism of assembly of tropoelastin as its unique composition and propensity to self-associate has hampered structural studies. In this study, we solve the nanostructure of full-length and corresponding overlapping fragments of tropoelastin using small angle X-ray and neutron scattering, allowing us to identify discrete regions of the molecule. Tropoelastin is an asymmetric coil, with a protruding foot that encompasses the C-terminal cell interaction motif. We show that individual tropoelastin molecules are highly extensible yet elastic without hysteresis to perform as highly efficient molecular nanosprings. Our findings shed light on how biology uses this single protein to build durable elastic structures that allow for cell attachment to an appended foot. We present a unique model for head-to-tail assembly which allows for the propagation of the molecule's asymmetric coil through a stacked spring design.AFM | SAXS | atomic force microscopy A ll mammals rely on elastin to convey extensional elasticity to their tissues. Elastin dominates the mass of the aorta where it encounters the peaks and troughs of systole and diastole over the course of two billion heartbeats in a lifetime (1). The lung expands with each intake of breath and elastically contracts on exhalation. The function of these tissues benefits from minimal energy loss during elastic return in each cycle of expansion and contraction. Additionally, elastin is required to function in an environment that relies on cellular contact (2-4) without compromising persistent elasticity. This high level of physical performance demanded of elastin vastly exceeds and indeed outlasts all human-made elastomers (5).Elastin is constructed by the hierarchical assembly and crosslinking of many tropoelastin monomers that accumulate on a microfibrillar skeleton. Tropoelastin is encoded by a single gene in humans and predominantly laid down in utero and early childhood, providing a durable resource that is intended to elastically serve until old age. This exquisite assembly helps to generate elastic tissues as diverse as artery, lung, and skin (4). Consequences of elastolytic damage in aortic aneurysms, emphysema, and solar elastosis confirm the key roles of elastin in structure and cellular interactions (6-8). These tissues rely on this paradoxical combination of organized tissue structures built from an intrinsically unstructured protein. Tropoelastin serves as a component of rigidly organized assemblies, yet enables the formation of dynamically distensible, elastic tissues.Tropoelastin is frequently described in the literature as an unstructured protein, mainly because models of elasticity invoke an element of disorder within the structure (4, 9, 10). While this concept appears to be the case at the fine, more subtle intramolecular leve...

Everyone desires healthy and beautiful-looking skin. However, as we age, our skin becomes old due to physiological changes. Reactive oxygen species (ROS) is an important pathogenic factor involved in human aging. Human skin is exposed to ROS generated from both extrinsic sources such as as ultraviolet (UV) light from the sun, and intrinsic sources such as endogenous oxidative metabolism. ROS-mediated oxidative stress damages the collagen-rich extracellular matrix (ECM), the hallmark of skin connective tissue aging. Damage to dermal collagenous ECM weakens the skin's structural integrity and creates an aberrant tissue microenvironment that promotes age-related skin disorders, such as impaired wound healing and skin cancer development. Here, we review recent advances in our understanding of ROS/oxidative stress and skin connective tissue aging.

The development and arrangement of the murine ciliary zonule are similar to those of humans, and consequently the mouse eye may be a useful model in which to study ocular complications of MS.

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