Sugary interfaces mitigate contact damage where stiff meets soft

The byssal threads of the fan shell Atrina pectinata are non-living functional materials intimately associated with living tissue, which provide an intriguing paradigm of bionic interface for robust load-bearing device. An interfacial load-bearing protein (A. pectinata foot protein-1, apfp-1) with L-3,4-dihydroxyphenylalanine (DOPA)-containing and mannose-binding domains has been characterized from Atrina's foot. apfp-1 was localized at the interface between stiff byssus and the soft tissue by immunochemical staining and confocal Raman imaging, implying that apfp-1 is an interfacial linker between the byssus and soft tissue, that is, the DOPA-containing domain interacts with itself and other byssal proteins via Fe3(+)-DOPA complexes, and the mannose-binding domain interacts with the soft tissue and cell membranes. Both DOPA-and sugar-mediated bindings are reversible and robust under wet conditions. This work shows the combination of DOPA and sugar chemistry at asymmetric interfaces is unprecedented and highly relevant to bionic interface design for tissue engineering and bionic devices

Mechanical properties of the compass depressors of the sea-urchin Paracentrotus lividus (Echinodermata, Echinoidea) and the effects of enzymes, neurotransmitters and synthetic tensilin-like protein

The compass depressors (CDs) of the sea-urchin lantern are ligaments consisting mainly of discontinuous collagen fibrils associated with a small population of myocytes. They are mutable collagenous structures, which can change their mechanical properties rapidly and reversibly under nervous control. The aims of this investigation were to characterise the baseline (i.e. unmanipulated) static mechanical properties of the CDs of Paracentrotus lividus by means of creep tests and incremental force-extension tests, and to determine the effects on their mechanical behaviour of a range of agents. Under constant load the CDs exhibited a three-phase creep curve, the mean coefficient of viscosity being 561±365 MPa.s. The stress-strain curve showed toe, linear and yield regions; the mean strain at the toe-linear inflection was 0.86±0.61; the mean Young's modulus was 18.62±10.30 MPa; and the mean tensile strength was 8.14±5.73 MPa. Hyaluronidase from Streptomyces hyalurolyticus had no effect on creep behaviour, whilst chondroitinase ABC prolonged primary creep but had no effect on secondary creep or on any force-extension parameters; it thus appears that neither hyaluronic acid nor sulphated glycosaminoglycans have an interfibrillar load transfer function in the CD. Acetylcholine, the muscarinic agonists arecoline and methacholine, and the nicotinic agonists nicotine and 1-[1-(3,4-dimethyl-phenyl)-ethyl]-piperazine produced an abrupt increase in CD viscosity; the CDs were not differentially sensitive to muscarinic or nicotinic agonists. CDs showed either no, or no consistent, response to adrenaline, L-glutamic acid, 5-hydroxytryptamine and γ-aminobutyric acid. Synthetic echinoid tensilin-like protein had a weak and inconsistent stiffening effect, indicating that, in contrast to holothurian tensilins, the echinoid molecule may not be involved in the regulation of collagenous tissue tensility. We compare in detail the mechanical behaviour of the CD with that of mammalian tendon and highlight its potential as a model system for investigating poorly understood aspects of the ontogeny and phylogeny of vertebrate collagenous tissues.(undefined)info:eu-repo/semantics/publishedVersio

Viability and Stability of Yeast-cells and Filamentous Fungus Spores During Freeze-drying - Effects of Protectants and Cooling Rates

Two parameters of a one step freeze-drying process, cooling rate and protecting media, are studied in an effort to improve the viability and the stability of the preserved fungal strains. Cooling rates of 1.6 C, 3 C and 40 C/min are applied on cells of Saccharomyces cerevisiae and Brettanomyces bruxellensis and on spores of Trichoderma viride and Arthrobotrys arthrobotryoides preserved in 93 suspending media containing polymers, sugars, albumin, milk, honey, polyols, amino acids alone or in combination. The viability rate of Saccharomyces cerevisiae cells is increased from 30% to 96-98% by using an appropriate protecting medium containing 10% skim milk with 2 compounds among honey, sodium glutamate, trehalose or raffinose in the freeze-drying process carried out at a 3 C/min cooling rate. In the same conditions Arthrobotrys arthrobotryoides spores, the most sensitive strain among the four tested, provides 60-65% viability, while this strain does not survive a classical freeze-drying in 10% skim milk. Moreover, with the improved method the stability of properties of Penicillium expansum is demonstrated

Efficacité de différentes surfaces de séchage pour poissons Stolothrissa tanganicae et Limnothrissa miodon au Burundi

Efficiency of different drying areas for fishes Stolothrissa tanganicae and Limnothrissa miodon in Burundi. The length of conservation of the fish called Ndagala in Burundi is very short because of an inefficient drying. Several drying area have been tested. The best one is the road asphalt. After drying on this surface it is possible to keep the fish twice longer than with the systems that are already installed in Burundi

Protein and chitin nitrogen contents and protein content in Pleurotus ostreatus var columbinus

Proteins and chitin were extracted and purified from dried fruitbodies of P. ostreatus var. columbinus grown on wheat straw and grass hay. Water- and sodium chloride-extractable proteins were purified by dialysis and precipitated by 10% TCA. These proteins contained 15.2% nitrogen (Kjeldahl and amino acid methods). The protein/nitrogen ratio of 6.58 was found and recommended as the new conversion factor. Chitin was purified from acid- and alkali-insoluble residue by 2% KMnO4 and 15% NaHSO3. This chitin contained 5.9% nitrogen and its infrared spectrum was similar to that of commercial chitins. The chitinous nitrogen content was about 0.34% dry weight of fruitbodies. The protein content was calculated from the non-chitinous nitrogen content and the factor 6.58. It was 17.1 and 23.5% dry weight of fruitbodies on wheat straw and grass hay, respectively, rather than 18.4 and 24.4% (as total nitrogen x 6.25). Copyright (C) 1996 Elsevier Science Lt