Umjetna pužnica je neurosenzorička proteza, koja je suvremeni tehnički i tehnološki medicinski terapijski izbor liječenja osoba s teškom nagluhošću ili s gluhoćom. Postupak otokirurške ugradnje ...umjetne pužnice zove se kohlearna implantacija. Telemetrija je sastavni dio tog postupka. Predstavlja metodu mjerenja neuralnog odgovora slušnog živca na električnu stimulaciju. Telemetrijom se određuju pragovi čujnosti, pragovi neugode podražaja i dinamički raspon. Objektivnim parametrima telemetrije procjenjujemo i psihoakustičke parametre, koji su temelj simulacijskih mapa za buduću rehabilitaciju oštećenog sluha.
Artificial cochlea or cochlear implant is the name for neurosensory prosthesis, which is a current surgical treatment for severe hearing loss or deafness.The surgical procedure is cochlear ...implantation During the cochlear implantation one of the methods of neural response measuring of the auditory nerve to electrical stimulation is telemetry. It is an integral part of the cochlear implantation procedure. Telemetry determines audibility thresholds, stimulus discomfort thresholds, and dynamic range. With objective parameters, in telemetry we also estimate psychoacoustic parameters, which are the basis of simulation maps for the future hearing rehabilitation.
Reactions of copper(II) sulfate with 1,10-phenanthroline, l-serine, and a base were investigated under different solution-based and mechanochemical synthetic procedures. Six complexes with serine ...were obtained: Cu(l-ser)(H2O)(phen)2SO4·xH2O (x = 4, 6, or 10; 1·4H 2 O, 1·6H 2 O, and 1·10H 2 O), Cu(l-ser)(H2O)(phen)Cu(l-ser)(CH3OH)(phen)SO4·3H2O·CH3OH (1·2·3H 2 O·CH 3 OH), Cu(l-ser)(CH3OH)(phen)2SO4·xCH3OH (x = 2 or 2.5; 2·2CH 3 OH and 2·2.5CH 3 OH), and two without serine: Cu(SO4)(phen)2·xH2O (x = 4.5 or 6.75; 3·4.5H 2 O and 3·6.75H 2 O) (phen = 1,10-phenanthroline, l-ser = l-serinato). The X-ray crystal structure analysis of serine-containing complexes revealed extensive hydrogen bonding and π-interactions that link complex cations, sulfate anions, and solvent molecules into three-dimensional architectures. Most of the water/methanol solvent molecules in these porous compounds are found in channels, some in pockets connected to channels, and can be exchanged in vapors of the other solvent. Along with the solvent exchange, the solvent molecule apically coordinated to copper(II) is also exchanged in some transformations. By neat grinding, all serine-containing complexes transform into 1·6H 2 O. Quantum chemical calculations were done for compounds 1·4H 2 O and 1·6H 2 O in the gas phase and an aqueous (or methanol) surrounding. 1·6H 2 O and 3·4.5H 2 O showed pronounced antiproliferative activity toward human breast and lung tumor cell lines.
The key step in the enzymatic reaction catalyzed by tyrosine phenol-lyase (TPL) is reversible cleavage of the Cβ–Cγ bond of l-tyrosine. Here, we present X-ray structures for two enzymatic states that ...form just before and after the cleavage of the carbon–carbon bond. As for most other pyridoxal 5′-phosphate-dependent enzymes, the first state, a quinonoid intermediate, is central for the catalysis. We captured this relatively unstable intermediate in the crystalline state by introducing substitutions Y71F or F448H in Citrobacter freundii TPL and briefly soaking crystals of the mutant enzymes with a substrate 3-fluoro-l-tyrosine followed by flash-cooling. The X-ray structures, determined at ∼2.0 Å resolution, reveal two quinonoid geometries: “relaxed” in the open and “tense” in the closed state of the active site. The “tense” state is characterized by changes in enzyme contacts made with the substrate’s phenolic moiety, which result in significantly strained conformation at Cβ and Cγ positions. We also captured, at 2.25 Å resolution, the X-ray structure for the state just after the substrate’s Cβ–Cγ bond cleavage by preparing the ternary complex between TPL, alanine quinonoid and pyridine N-oxide, which mimics the α-aminoacrylate intermediate with bound phenol. In this state, the enzyme–ligand contacts remain almost exactly the same as in the “tense” quinonoid, indicating that the strain induced by the closure of the active site facilitates elimination of phenol. Taken together, structural observations demonstrate that the enzyme serves not only to stabilize the transition state but also to destabilize the ground state.
Amino acid transformations catalyzed by a number of pyridoxal 5′-phosphate (PLP)-dependent enzymes involve abstraction of the Cα proton from an external aldimine formed between a substrate and the ...cofactor leading to the formation of a quinonoid intermediate. Despite the key role played by the quinonoid intermediates in the catalysis by PLP-dependent enzymes, limited accurate information is available about their structures. We trapped the quinonoid intermediates of Citrobacter freundii tyrosine phenol-lyase with l-alanine and l-methionine in the crystalline state and determined their structures at 1.9- and 1.95-Å resolution, respectively, by cryo-crystallography. The data reveal a network of protein-PLP-substrate interactions that stabilize the planar geometry of the quinonoid intermediate. In both structures the protein subunits are found in two conformations, open and closed, uncovering the mechanism by which binding of the substrate and restructuring of the active site during its closure protect the quinonoid intermediate from the solvent and bring catalytically important residues into positions suitable for the abstraction of phenol during the β-elimination of l-tyrosine. In addition, the structural data indicate a mechanism for alanine racemization involving two bases, Lys-257 and a water molecule. These two bases are connected by a hydrogen bonding system allowing internal transfer of the Cα proton.
Tyrosine phenol-lyase, a tetrameric pyridoxal 5‘-phosphate dependent enzyme, catalyzes the reversible hydrolytic cleavage of l-tyrosine to phenol and ammonium pyruvate. Here we describe the crystal ...structure of the Citrobacter freundii holoenzyme at 1.9 Å resolution. The structure reveals a network of protein interactions with the cofactor, pyridoxal 5‘-phosphate, and details of coordination of the catalytically important K+ ion. We also present the structure of the apoenzyme at 1.85 Å resolution. Both structures were determined using crystals grown at pH 8.0, which is close to the pH of the maximal enzymatic activity (8.2). Comparison of the apoenzyme structure with the one previously determined at pH 6.0 reveals significant differences. The data suggest that the decrease of the enzymatic activity at pH 6.0 may be caused by conformational changes in the active site residues Tyr71, Tyr291, and Arg381 and in the monovalent cation binding residue Glu69. Moreover, at pH 8.0 we observe two different active site conformations: open, which was characterized before, and closed, which is observed for the first time in β-eliminating lyases. In the closed conformation a significant part of the small domain undergoes an extraordinary motion of up to 12 Å toward the large domain, closing the active site cleft and bringing the catalytically important Arg381 and Phe448 into the active site. The closed conformation allows rationalization of the results of previous mutational studies and suggests that the observed active site closure is critical for the course of the enzymatic reaction and for the enzyme's specificity toward its physiological substrate. Finally, the closed conformation allows us to model keto(imino)quinonoid, the key transition intermediate.
Rubber mats have not yet been widely established in pig production. However, studies mostly focusing on lesions, lameness and behaviours of lactating and group-housed pregnant sows have reported ...favourable results. To the best of our knowledge, lesions and lameness in sows or gilts housed individually in rubber floor gestation stalls have not been previously investigated. This study was carried out on a commercial pigbreeding farm service unit during a 28-day production cycle in all seasons. Twentyeight gilts were divided into two equal groups, control and experimental groups, and observed for each cycle. The control group was housed in standard gestation stalls with concrete slatted floor, which in the experimental group was covered with an adjusted rubber mat. During each cycle, lesions were scored on days 1, 8, 15 and 28, and lameness on day 1 and upon gilt transfer from the service unit on day 29. Gilts in rubber floor stalls showed significant reduction (P<0.05) in lesions during the cooler period. Conversely, mats had no impact on lameness score in any season. No significant correlations were found between lesions and the percentage of gilts with a particular lameness score. Accordingly, rubber flooring may improve the welfare of gilts in gestation stalls through lower lesion incidence; however, ambient temperature should be taken into consideration when available.
Gumene podne obloge u svinjogojskoj proizvodnji nemaju još primjenu u praksi. Međutim, istraživanja koja su se uglavnom odnosila na ozljede, hromost i ponašanje dojnih i skupno držanih gravidnih krmača polučila su pozitivne rezultate. Prema našim saznanjima, nisu provedena istraživanja pojavnosti ozljeda i hromosti u krmača ili nazimica koje su tijekom gravidnosti držane pojedinačno, u odjeljcima s gumenom podnom oblogom. Ovo istraživanje provedeno je u pripustilištu komercijalne svinjogojske farme tijekom 28-dnevnog proizvodnog ciklusa u svim godišnjim dobima. Svaki ciklus obuhvatio je 28 nazimica podijeljenih u dvije jednake skupine, kontrolnu i pokusnu. Nazimice kontrolne skupine bile su u standardnim odjeljcima za pojedinačno držanje tijekom gravidnosti, s betonskim rešetkastim podom, koji je u pokusnoj skupini nazimica bio prekriven prilagođenom gumenom podnom oblogom. Ozljede su se procjenjivale 1., 8., 15. i 28. dana svakog ciklusa, a hromost 1. dana pojedinog ciklusa i prilikom premještanja nazimica iz pripustilišta (29. dan). U nazimica pokusne skupine utvrđeno je značajno manje (P<0,05) ozljeda u hladnijem razdoblju, dok obloge nisu imale utjecaja na hromost nazimica ni u jednom godišnjem dobu. Nisu ustvrđene značajne povezanosti između ozljeda i udjela nazimica s određenim stupnjem hromosti. Može se zaključiti da gumene podne obloge poboljšavaju dobrobit nazimica držanih u pojedinačnim odjeljcima tijekom gravidnosti, kroz manju učestalost ozljeda; međutim, pri njihovoj primjeni trebaju se uzeti u obzir ambijentalne temperature.
Profilin from wheat (Triticum aestivum) has been identified as an allergen (Tri a 12). The recombinant 14 kDa protein was produced in Escherichia coli, purified and crystallized using the hangingdrop ...vapour-diffusion method. A diffraction-data set was collected in-house from a single crystal to a resolution of 3.3 Å. The crystals belonged to space group P3221, with unit-cell parameters a = b = 58.9 Å, c = 82.5 Å, α = β = 90° and γ = 120°. PUBLICATION ABSTRACT
New dinuclear pentacoordinate molybdenum(V) complexes, Mo2VO3L2 L = thiosemicarbazonato ligand: C6H4(O)CH:NN:C(S)NHR′ and C10H6(O)CH:NN:C(S)NHR′; R′ = H, CH3, C6H5) were obtained either by oxygen ...atom ion from MoVIO2L with triphenylphosphine or by using Mo2O3(acac)4 in the reaction with the corresponding ligands H2L. Crystal and molecular structure of Mo2O3{C6H4(O)CH:NN:C(S)NHC6H5}2·CH3CN has been determined by the single‐crystal X‐ray diffraction method.
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