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Silicateins - A Novel Paradigm in Bioinorganic Chemistry: Enzymatic Synthesis of Inorganic Polymeric Silica
2013
The inorganic matrix of the siliceous skeletal elements of sponges, that is, spicules, is formed of amorphous biosilica. Until a decade ago, it remained unclear how the hard biosilica monoliths of the spicules are formed in sponges that live in a silica-poor (<50 mu m) aquatic environment. The following two discoveries caused a paradigm shift and allowed an elucidation of the processes underlying spicule formation; first the discovery that in the spicules only one major protein, silicatein, exists and second, that this protein displays a bio-catalytical, enzymatic function. These findings caused a paradigm shift, since silicatein is the first enzyme that catalyzes the formation of an inorga…
Identification of a silicatein(-related) protease in the giant spicules of the deep-sea hexactinellid Monorhaphis chuni.
2008
SUMMARYSilicateins, members of the cathepsin L family, are enzymes that have been shown to be involved in the biosynthesis/condensation of biosilica in spicules from Demospongiae (phylum Porifera), e.g. Tethya aurantium and Suberites domuncula. The class Hexactinellida also forms spicules from this inorganic material. This class of sponges includes species that form the largest biogenic silica structures on earth. The giant basal spicules from the hexactinellids Monorhaphis chuni and Monorhaphis intermedia can reach lengths of up to 3 m and diameters of 10 mm. The giant spicules as well as the tauactines consist of a biosilica shell that surrounds the axial canal, which harbours the axial f…
The silicatein propeptide acts as inhibitor/modulator of self-organization during spicule axial filament formation.
2013
Silicateins are crucial enzymes that are involved in formation of the inorganic biosilica scaffold of the spicular skeleton of siliceous sponges. We show that silicatein acquires its structure-guiding and enzymatically active state by processing of silicatein from pro-silicatein to the mature enzyme. A recombinant propeptide (PROP) of silicatein from the siliceous demosponge Suberites domuncula was prepared, and antibodies were raised against the peptide. In sponge tissue, these antibodies reacted with both surface structures and the central region of the spicules. Using phage display expression, spicule-binding 12-mer peptides were identified that are rich in histidine residues. In the pre…
Involvement of aquaporin channels in water extrusion from biosilica during maturation of sponge siliceous spicules.
2015
Aquaporins are a family of small, pore-forming, integral cell membrane proteins. This ancient protein family functions as water channels and is found in all kingdoms (including archaea, eubacteria, fungi, plants, and animals). We discovered that in sponges aquaporin plays a novel role during the maturation of spicules, their skeletal elements. Spicules are synthesized enzymatically via silicatein following a polycondensation reaction. During this process, a 1:1 stoichiometric release of water per one Si-O-Si bond formed is produced. The product of silicatein, biosilica, is a fluffy, soft material that must be hardened in order to function as a solid rod. Using the model of the demosponge sp…
Biosilica formation in spicules of the sponge Suberites domuncula: synchronous expression of a gene cluster.
2005
The formation of spicules is a complicated morphogenetic process in sponges (phylum Porifera). The primmorph system was used to demonstrate that in the demosponge Suberites domuncula the synthesis of the siliceous spicules starts intracellularly and is dependent on the concentration of silicic acid. To understand spicule formation, a cluster of genes was isolated. In the center of this cluster is the silicatein gene, which codes for the enzyme that synthesizes spicules. This gene is flanked by an ankyrin repeat gene at one side and by a tumor necrosis factor receptor-associated factor and a protein kinase gene at the other side. All genes are strongly expressed in primmorphs and intact anim…
Axial growth of hexactinellid spicules: Formation of cone-like structural units in the giant basal spicules of the hexactinellid Monorhaphis
2008
The glass sponge Monorhaphis chuni (Porifera: Hexactinellida) forms the largest bio-silica structures on Earth; their giant basal spicules reach sizes of up to 3 m and diameters of 8.5 mm. Previously, it had been shown that the thickness growth proceeds by appositional layering of individual lamellae; however, the mechanism for the longitudinal growth remained unstudied. Now we show, that the surface of the spicules have towards the tip serrated relief structures that are consistent in size and form with the protrusions on the surface of the spicules. These protrusions fit into the collagen net that surrounds the spicules. The widths of the individual lamellae do not show a pronounced size …
Garnet and spinel lherzolite assemblages in MgO-Al2O3-SiO2 and CaO-MgO-Al2O3-SiO2: thermodynamic models and an experimental conflict
2012
The recent publication of an updated thermodynamic dataset for petrological calculations provides an opportunity to illustrate the relationship between experimental data and the dataset, in the context of a new set of activity–composition models for several key minerals. These models represent orthopyroxene, clinopyroxene and garnet in the system CaO–MgO–Al2O3–SiO2 (CMAS), and are valid up to 50 kbar and at least 1800 °C; they are the first high-temperature models for these phases to be developed for the Holland & Powell dataset. The models are calibrated with reference to phase-relation data in the subsystems CaO–MgO–SiO2 (CMS) and MgO–Al2O3–SiO2 (MAS), and will themselves form the basis o…
Immediate effects of the respiratory stimulation on ventilation parameters in ischemic stroke survivors: A randomized interventional study (CONSORT).
2019
Background: Post-stroke brain damage, which affects the central control of respiration, leads to various respiratory disorders. They can be caused by the weakening of the respiratory muscles and chest movements, which can indirectly contribute to an impairment of the ventilation function. The aim of the study is an objective assessment of the effect of a single-session intervention of respiratory stimulation through Proprioceptive Neuromuscular Facilitation (PNF) on chosen respiratory parameters and the following comparison of these changes with a group in which positioning was used (intra- and intergroup comparison). Methods: This was a randomized interventional study evaluating the respir…
Kompensējamo diurētisko vielu aprite "Benu aptiekā -53" no 2014. līdz 2015.gadam
2016
Diurētiskās vielas ir vienas no visbiežāk izmantotajiem līdzekļiem terapijā sirds mazspējas un hipertensijas ārstēšanai. Valsts kompensē četru dažādu aktīvo diurētisko vielu medikamentus: Indamax 1,5mg, Indapamide Actavis 1,5mg, Indapen SR 1,5mg, Indatens 2,5mg, Proindap 2,5mg, Rawel SR 1,5mg, Tertensif SR 1,5mg, savukārt furosemīdu saturošs diurētiskais medikaments, kurus kompensē valsts ir Furosemīds Olainfarm 40mg, bet hidrohlortiazīdu- Hypothiazid 25mg. Spironolaktonu saturoši diurētiskie medikamenti, kurus šobrīd kompensē valsts ir Spirix 25mg N20, Spirix 25mg N60, Spirix 50mg N20, Spirix 50mg N60, Spirix 100mg, Spirogamma 100mg, Verospiron 25mg N20, Verospiron 25mg N60, Verospiron 50m…
Fiziskās aktivitātes un sports Jelgavā un Jelgavas apriņķī 1920.-1940.
2019
Maģistra darbā “Fiziskās aktivitātes un sports Jelgavā un Jelgavas apriņķī 1920. – 1940.” analizēta Jelgavas un Jelgavas apriņķa sporta dzīve. Jelgavā jau līdz Pirmajam pasaules karam sports bija nozīmīga sabiedriskās dzīves daļa. Fizisko aktivitāšu un sporta attīstību ietekmēja pilsētas un apriņķa ekonomiskā situācija, sabiedrības attieksme pret sportu, sporta biedrību skaits un aktivitātes, pilsētas sporta politika. Jelgavas un Jelgavas apriņķa sporta dzīve pētīta kontekstā ar tā stāvokli Latvijā. Balstoties uz informāciju Arhīva un prese materiālos, secināts, ka Jelgavas un Jelgavas apriņķa sporta dzīve daļēji balstījās uz līdz Pirmajam pasaules karam izveidotajām sporta biedrībām. Neatk…