Esther Appel

Bio: Esther Appel is an academic researcher from University of Kiel. The author has contributed to research in topics: Resilin & Wing. The author has an hindex of 15, co-authored 29 publications receiving 757 citations.

Air/water interfacial formation of freestanding, stimuli-responsive, self-healing catecholamine Janus-faced microfilms

Abstract: A catecholamine freestanding film is discovered to be spontaneously formed at the air-water interface, and the film has unique properties of robust surface adhesiveness, self-healing, and stimuli-responsive properties. The interfacial film-producing procedure is a simple single step containing polyamines and catechol(amine)s. It is found that oxygen-rich regions existing at an air-water interface greatly accelerate the catecholamine crosslinking reaction.

Ultrastructure of dragonfly wing veins: composite structure of fibrous material supplemented by resilin

Abstract: Dragonflies count among the most skilful of the flying insects. Their exceptional aerodynamic performance has been the subject of various studies. Morphological and kinematic investigations have showed that dragonfly wings, though being rather stiff, are able to undergo passive deformation during flight, thereby improving the aerodynamic performance. Resilin, a rubber-like protein, has been suggested to be a key component in insect wing flexibility and deformation in response to aerodynamic loads, and has been reported in various arthropod locomotor systems. It has already been found in wing vein joints, connecting longitudinal veins to cross veins, and was shown to endow the dragonfly wing with chordwise flexibility, thereby most likely influencing the dragonfly's flight performance. The present study revealed that resilin is not only present in wing vein joints, but also in the internal cuticle layers of veins in wings of Sympetrum vulgatum (SV) and Matrona basilaris basilaris (MBB). Combined with other structural features of wing veins, such as number and thickness of cuticle layers, material composition, and cross-sectional shape, resilin most probably has an effect on the veins material properties and the degree of elastic deformations. In order to elucidate the wing vein ultrastructure and the exact localisation of resilin in the internal layers of the vein cuticle, the approaches of bright-field light microscopy, wide-field fluorescence microscopy, confocal laser-scanning microscopy, scanning electron microscopy and transmission electron microscopy were combined. Wing veins were shown to consist of up to six different cuticle layers and a single row of underlying epidermal cells. In wing veins of MBB, the latter are densely packed with light-scattering spheres, previously shown to produce structural colours in the form of quasiordered arrays. Longitudinal and cross veins differ significantly in relative thickness of exo- and endocuticle, with cross veins showing a much thicker exocuticle. The presence of resilin in the unsclerotised endocuticle suggests its contribution to an increased energy storage and material flexibility, thus to the prevention of vein damage. This is especially important in the highly stressed longitudinal veins, which have much lower possibility to yield to applied loads with the aid of vein joints, as the cross veins do. These results may be relevant not only for biologists, but may also contribute to optimise the design of micro-air vehicles.

Functional diversity of resilin in Arthropoda

Abstract: Resilin is an elastomeric protein typically occurring in exoskeletons of arthropods. It is composed of randomly orientated coiled polypeptide chains that are covalently cross-linked together at regular intervals by the two unusual amino acids dityrosine and trityrosine forming a stable network with a high degree of flexibility and mobility. As a result of its molecular prerequisites, resilin features exceptional rubber-like properties including a relatively low stiffness, a rather pronounced long-range deformability and a nearly perfect elastic recovery. Within the exoskeleton structures, resilin commonly forms composites together with other proteins and/or chitin fibres. In the last decades, numerous exoskeleton structures with large proportions of resilin and various resilin functions have been described. Today, resilin is known to be responsible for the generation of deformability and flexibility in membrane and joint systems, the storage of elastic energy in jumping and catapulting systems, the enhancement of adaptability to uneven surfaces in attachment and prey catching systems, the reduction of fatigue and damage in reproductive, folding and feeding systems and the sealing of wounds in a traumatic reproductive system. In addition, resilin is present in many compound eye lenses and is suggested to be a very suitable material for optical elements because of its transparency and amorphousness. The evolution of this remarkable functional diversity can be assumed to have only been possible because resilin exhibits a unique combination of different outstanding properties.

Targeted Microbiome Intervention by Microencapsulated Delayed-Release Niacin Beneficially Affects Insulin Sensitivity in Humans

Abstract: OBJECTIVE Gut microbiota represent a potential novel target for future prediabetes and type 2 diabetes therapies. In that respect, niacin has been shown to beneficially affect the host-microbiome interaction in rodent models. RESEARCH DESIGN AND METHODS We characterized more than 500 human subjects with different metabolic phenotypes regarding their niacin (nicotinic acid [NA] and nicotinamide [NAM]) status and their gut microbiome. In addition, NA and NAM delayed-release microcapsules were engineered and examined in vitro and in vivo in two human intervention studies (bioavailability study and proof-of-concept/safety study). RESULTS We found a reduced α-diversity and Bacteroidetes abundance in the microbiome of obese human subjects associated with a low dietary niacin intake. We therefore developed delayed-release microcapsules targeting the ileocolonic region to deliver increasing amounts of NA and NAM to the microbiome while preventing systemic resorption to avoid negative side effects (e.g., facial flushing). In vitro studies on these delayed-release microcapsules revealed stable conditions at pH 1.4, 4.5, and 6.8, followed by release of the compounds at pH 7.4, simulating the ileocolonic region. In humans in vivo, gut-targeted delayed-release NA but not NAM produced a significant increase in the abundance of Bacteroidetes. In the absence of systemic side effects, these favorable microbiome changes induced by microencapsulated delayed-release NA were associated with an improvement of biomarkers for systemic insulin sensitivity and metabolic inflammation. CONCLUSION Targeted microbiome intervention by delayed-release NA might represent a future therapeutic option for prediabetes and type 2 diabetes.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Polydopamine Surface Chemistry: A Decade of Discovery.

Abstract: Polydopamine is one of the simplest and most versatile approaches to functionalizing material surfaces, having been inspired by the adhesive nature of catechols and amines in mussel adhesive proteins. Since its first report in 2007, a decade of studies on polydopamine molecular structure, deposition conditions, and physicochemical properties have ensued. During this time, potential uses of polydopamine coatings have expanded in many unforeseen directions, seemingly only limited by the creativity of researchers seeking simple solutions to manipulating surface chemistry. In this review, we describe the current state of the art in polydopamine coating methods, describe efforts underway to uncover and tailor the complex structure and chemical properties of polydopamine, and identify emerging trends and needs in polydopamine research, including the use of dopamine analogs, nitrogen-free polyphenolic precursors, and improvement of coating mechanical properties.

Gut microbiota-derived metabolites as key actors in inflammatory bowel disease.

Abstract: A key role of the gut microbiota in the establishment and maintenance of health, as well as in the pathogenesis of disease, has been identified over the past two decades. One of the primary modes by which the gut microbiota interacts with the host is by means of metabolites, which are small molecules that are produced as intermediate or end products of microbial metabolism. These metabolites can derive from bacterial metabolism of dietary substrates, modification of host molecules, such as bile acids, or directly from bacteria. Signals from microbial metabolites influence immune maturation, immune homeostasis, host energy metabolism and maintenance of mucosal integrity. Alterations in the composition and function of the microbiota have been described in many studies on IBD. Alterations have also been described in the metabolite profiles of patients with IBD. Furthermore, specific classes of metabolites, notably bile acids, short-chain fatty acids and tryptophan metabolites, have been implicated in the pathogenesis of IBD. This Review aims to define the key classes of microbial-derived metabolites that are altered in IBD, describe the pathophysiological basis of these associations and identify future targets for precision therapeutic modulation. Alterations in the gut microbiota and metabolite profiles of patients with IBD have been described. In this Review, Lavelle and Sokol discuss these alterations and their pathophysiological basis, and identify future targets for precision therapeutic modulation.

Versatile Polydopamine Platforms: Synthesis and Promising Applications for Surface Modification and Advanced Nanomedicine

Abstract: As a mussel-inspired material, polydopamine (PDA), possesses many properties, such as a simple preparation process, good biocompatibility, strong adhesive property, easy functionalization, outstanding photothermal conversion efficiency, and strong quenching effect. PDA has attracted increasingly considerable attention because it provides a simple and versatile approach to functionalize material surfaces for obtaining a variety of multifunctional nanomaterials. In this review, recent significant research developments of PDA including its synthesis and polymerization mechanism, physicochemical properties, different nano/microstructures, and diverse applications are summarized and discussed. For the sections of its applications in surface modification and biomedicine, we mainly highlight the achievements in the past few years (2016-2019). The remaining challenges and future perspectives of PDA-based nanoplatforms are discussed rationally at the end. This timely and overall review should be desirable for a wide range of scientists and facilitate further development of surface coating methods and the production of PDA-based materials.