The iron(III) salen-type complexes [Fe(salen)(L)](n) (1-6) involving heterocyclic N-donor ligands HL {HL = 1H-imidazole (Himz), 1H-tetrazol-5-amine (Hatz), 5-methyl-1H-tetrazole (Hmtz), 1H-benzimidazole (Hbimz), 1H-1,2,4-triazole (Htriz) and 1H-benzotriazole (Hbtriz)} have been prepared and characterised by elemental analysis, FT IR, CI mass and (57)Fe Mössbauer spectroscopies, and variable temperature magnetic measurements. Single crystal X-ray analysis of [Fe(salen)(btriz)](n) (6) revealed a 1D chain-polymeric structure of the complex with the btriz anion as a bridging ligand. Magnetic data for all complexes were fitted using Fisher's model (for S = 5/2) and also using a heptanuclear closed ring model showing a weak antiferromagnetic interaction (J approximately -1 to -2 cm(-1)), and moreover, molecule-based magnet properties have been observed in the case of [Fe(salen)(atz)](n) (2). The exponential correlation between the magnetic properties (the isotropic exchange parameter J) and the basicity of the free ligands (K(b)) has been found. The antiferromagnetic ordering as well as a moderate structural dissimilarity in the vicinity of iron atoms has been proved by the (57)Fe Mössbauer low-temperature (2 K) in-field (7 T) experiments in the case of (2), in which two sextets with the line intensities (3/4/1/3/4/1) have been observed. The compounds have been tested for their SOD-like activity, DNA cleavage activity, and in vitro cytotoxicity against two human cancer cell lines: chronic myelogenous erythroleukemia (K562) and breast adenocarcinoma (MCF7). The best result regarding the cytotoxicity has been achieved for the complex of [Fe(salen)(atz)](n) (2), where IC(50) = 6.4 microM against K562.

• MeSH
• adenokarcinom metabolismus   MeSH
• chronická myeloidní leukemie metabolismus   MeSH
• krystalografie rentgenová MeSH
• lidé MeSH
• ligandy MeSH
• nádorové buněčné linie MeSH
• nádory prsu metabolismus   MeSH
• proliferace buněk účinky léků   MeSH
• protinádorové látky chemická syntéza   chemie   farmakologie   MeSH
• spektroskopie Mossbauerova MeSH
• štěpení DNA MeSH
• superoxiddismutasa farmakologie   MeSH
• železité sloučeniny chemická syntéza   chemie   farmakologie   MeSH
• železo chemie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ligandy MeSH
• protinádorové látky MeSH
• superoxiddismutasa MeSH
• železité sloučeniny MeSH
• železo MeSH

The paper deals with problems related to computational modelling of stress-strain states in vascular smooth muscle cells (SMCs). First, motivation for stress-strain analysis of SMCs is presented. Problems of their structure, geometry, constitutive models and initial (stress-free) state are analyzed on the basis of anatomical, histological and physiological knowledge. Various types of computational FE models of SMCs are presented; their constitutive models are identified on the basis of published mechanical tests carried out with SMCs cultured in vitro. Results of two models are presented; the former is a homogeneous model of the cell tension test with hyperelastic constitutive relations of the cell material. The latter model is more complex, it comprehends cortical and deep cytoskeleton, modelled as a tensegrity structure, and homogeneous linear elastic nucleus and remaining cytoplasm; it is used in computational modelling of indentation test. Perspectives, assumptions and limitations of computational modelling of SMCs under physiological load are discussed.

• MeSH
• analýza metodou konečných prvků * MeSH
• biologické modely MeSH
• biomechanika MeSH
• cytoskelet fyziologie   MeSH
• lidé MeSH
• mechanický stres MeSH
• myocyty hladké svaloviny fyziologie   MeSH
• nelineární dynamika MeSH
• počítačová simulace MeSH
• pružnost MeSH
• statistické modely MeSH
• svaly hladké cévní cytologie   fyziologie   MeSH
• techniky in vitro MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

The majority of established model organisms belong to the supergroup Opisthokonta, which includes yeasts and animals. While enlightening, this focus has neglected protists, organisms that represent the bulk of eukaryotic diversity and are often regarded as primitive eukaryotes. One of these is the "supergroup" Excavata, which comprises unicellular flagellates of diverse lifestyles and contains species of medical importance, such as Trichomonas, Giardia, Naegleria, Trypanosoma and Leishmania. Excavata exhibits a continuum in mitochondrial forms, ranging from classical aerobic, cristae-bearing mitochondria to mitochondria-related organelles, such as hydrogenosomes and mitosomes, to the extreme case of a complete absence of the organelle. All forms of mitochondria house a machinery for the assembly of Fe-S clusters, ancient cofactors required in various biochemical activities needed to sustain every extant cell. In this review, we survey what is known about the Fe-S cluster assembly in the supergroup Excavata. We aim to bring attention to the diversity found in this group, reflected in gene losses and gains that have shaped the Fe-S cluster biogenesis pathways.

• Klíčová slova
• Evolution, Excavata, Fe–S cluster, Mitochondria,
• MeSH
• Eukaryota cytologie   metabolismus   MeSH
• mitochondrie metabolismus   MeSH
• proteiny obsahující železo a síru metabolismus   MeSH
• železo metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• proteiny obsahující železo a síru MeSH
• železo MeSH

Finite element (FE) analysis has been widely used to study the behaviour of bone or implants in many clinical applications. One of the main factors in analyses is the realistic behaviour of the bone model, because the behaviour of the bone is strongly dependent on a realistic bone material property assignment. The objective of this study was to compare isotropic and orthotropic inhomogeneous material models used for FE analyses of the "global" proximal femur and "small" specimens of the bone (cancellous and cortical). Our hypothesis was that realistic material property assignment (orthotropy) is very important for the FE analyses of small bone specimens, whereas in global FE analyses of the proximal femur, this assignment can be omitted, if the inhomogeneous material model was used. The three-dimensional geometry of the "global" proximal femur was reconstructed using CT scans of a cadaveric femur. This model was implemented into an FE simulation tool and various bone material properties, dependant on bone density, were assigned to each element in the models. The "small" specimens of cortical and cancellous bone were created in the same way as the model of the proximal femur. The results obtained from FE analyses support our above described hypothesis.

• MeSH
• algoritmy MeSH
• analýza metodou konečných prvků MeSH
• biologické modely MeSH
• biomechanika metody   MeSH
• femur anatomie a histologie   patologie   MeSH
• kostní denzita fyziologie   MeSH
• lidé MeSH
• mechanický stres MeSH
• mrtvola MeSH
• počítačová rentgenová tomografie metody   MeSH
• počítačová simulace MeSH
• pružnost MeSH
• statistické modely MeSH
• zatížení muskuloskeletálního systému fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Trypanosoma brucei, the causative agent of the African sleeping sickness of humans, and other kinetoplastid flagellates belong to the eukarytotic supergroup Excavata. This early-branching model protist is known for a broad range of unique features. As it is amenable to most techniques of forward and reverse genetics, T. brucei was subject to several studies of its iron-sulfur (Fe/S) protein biogenesis and thus represents the best studied excavate eukaryote. Here we review what is known about the Fe/S protein biogenesis of T. brucei, and focus especially on the comparative and evolutionary interesting aspects. We also explore the connections between the well-known and quite conserved ISC and CIA machineries and the tRNA thiolation pathway. Moreover, the Fe/S cluster protein biogenesis is dissected in the procyclic stage of T. brucei which has an active mitochondrion, as well as in its pathogenic bloodstream stage with a metabolically repressed organelle. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.

• Klíčová slova
• Fe/S cluster, Kinetoplastida, Protist, Trypanosoma brucei,
• MeSH
• biosyntetické dráhy * MeSH
• lidé MeSH
• mitochondrie metabolismus   MeSH
• proteiny obsahující železo a síru biosyntéza   MeSH
• protozoální proteiny biosyntéza   MeSH
• RNA transferová metabolismus   MeSH
• síra metabolismus   MeSH
• Trypanosoma brucei brucei metabolismus   MeSH
• trypanozomóza africká parazitologie   MeSH
• železo metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• proteiny obsahující železo a síru MeSH
• protozoální proteiny MeSH
• RNA transferová MeSH
• síra MeSH
• železo MeSH

Preparation of affinity polyacrylamide gels containing immobilized Fe(III) ions for the separation of proteins exhibiting metal ion binding properties is described. The presented method enables uniform distribution of immobilized metal ions in the affinity part of the polyacrylamide separating gel. Affinity gels prepared by this way are suitable to follow the effect of different concentrations of metal ions immobilized in polyacrylamide gel on a protein electrophoretic behavior. Polyacrylamide gels containing immobilized Fe(III) ions were used to study the electrophoretic behavior of two model proteins differing in their phosphate group content: chicken ovalbumin and bovine α-casein. For the electrophoretic separation, both the native and the denaturating conditions were used.

• Klíčová slova
• Affinity electrophoresis, Immobilized Fe(III) ions, Native electrophoresis, SDS electrophoresis,
• MeSH
• elektroforéza v polyakrylamidovém gelu * MeSH
• fosfoproteiny chemie   izolace a purifikace   MeSH
• ionty chemie   MeSH
• železité sloučeniny chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fosfoproteiny MeSH
• ionty MeSH
• železité sloučeniny MeSH

We have studied the detailed reaction mechanism of iron and manganese superoxide dismutase with density functional calculations on realistic active-site models, with large basis sets and including solvation, zero-point, and thermal effects. The results indicate that the conversion of O2- to O2 follows an associative mechanism, with O2- directly binding to the metal, followed by the protonation of the metal-bound hydroxide ion, and the dissociation of 3O2. All these reaction steps are exergonic. Likewise, we suggest that the conversion of O2- to H2O2 follows an at least a partly second-sphere pathway. There are small differences in the preferred oxidation and spin states, as well as in the geometries, of Fe and Mn, but these differences have little influence on the energetics, and therefore on the reaction mechanism of the two types of superoxide dismutases. For example, the two metals have very similar reduction potentials in the active-site models, although they differ by 0.7 V in water solution. The reaction mechanisms and spin states seem to have been designed to avoid spin conversions or to facilitate them by employing nearly degenerate spin states.

• MeSH
• konformace proteinů MeSH
• molekulární modely MeSH
• počítačová simulace MeSH
• superoxiddismutasa chemie   metabolismus   MeSH
• vazebná místa MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• superoxiddismutasa MeSH

The aim of this study is to develop mathematical 3D finite element (FE) models for numerical simulations of vibroacoustic properties of the human vocal tract after a tonsillectomy. Similar experimental studies are not easily realizable on living subjects. The FE models of the acoustic spaces corresponding to the human vocal tract for the Czech vowels /a:/ and /i:/ and the acoustic space around the human head were used in numerical simulations of phonation. The acoustic resonant characteristics of the FE models were studied using modal and transient analyses (excitation by a short pulse). Calculated results show that a tonsillectomy causes a frequency shift of the 3rd (down by approximately 180 Hz) and 4th (down by approximately 120 Hz) formants down to the lower frequencies for the vowel /a:/ and similarly for the 2nd, 4th and 5th formants for the vowel /i:/ (all down by approximately 100 Hz). Similar effects and results can be found in experimental studies in literature. The formant changes are dependent on the size of additional acoustic spaces that occur after a tonsillectomy. The verification of the model was performed on the recordings of patients before and after the tonsillectomy operation. Multi-Dimensional Voice Program (MDVP Advanced, KAY Elemetrics Corp.) was used for the comparing of the formant centre frequencies. Very small differences in the results of subjective evaluation of the voice before and after tonsillectomy were found.

• MeSH
• analýza metodou konečných prvků MeSH
• biologické modely * MeSH
• dospělí MeSH
• hlas fyziologie   MeSH
• lidé MeSH
• matematické výpočty počítačové MeSH
• mladiství MeSH
• počítačová simulace * MeSH
• poruchy hlasu etiologie   patofyziologie   MeSH
• tonzilektomie * škodlivé účinky   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Detailed atomic-scale understanding is a crucial prerequisite for rational design of next-generation single-atom catalysts (SACs). However, the sub-ångström precision needed for systematic studies is challenging to achieve on common SACs. Here, we present a two-dimensional (2D) metal-organic system featuring Fe-N4 single-atom sites, where the metal-organic structure is modulated by 0.4 Å corrugation of an inert graphene/Ir(111) support. Using scanning tunneling microscopy and density functional theory, we show that the support corrugation significantly affects the reactivity of the system, as the sites above the support "valleys" bind TCNQ (tetracyanoquinodimethane) significantly stronger than the sites above the "hills". The experimental temperature stability of TCNQ varies by more than 60 °C, while computations indicate more than 0.3 eV variation of TCNQ adsorption energy across the Fe-N4 sites placed atop different regions of the corrugated graphene unit cell. The origin of this effect is steric hindrance, which plays a role whenever large molecules interact with neighboring single-atom catalyst sites or when multiple reactants coadsorb on such sites. Our work demonstrates that such effects can be quantitatively studied using model SAC systems supported on chemically inert and physically corrugated supports.

• Klíčová slova
• 2D metal−organic frameworks, Fe−N4 site, adsorption, density functional theory, scanning tunneling microscopy, single atom catalysis,
• Publikační typ
• časopisecké články MeSH

The article presents the results of research carried out using a water model of a refining ladle for the Fe-Si ferroalloys treatment. These studies were aimed at improving the efficiency of refining and homogenization of liquid Fe-Si ferroalloy in the refining ladle by using a new method of blowing gas through a system of nozzles installed at the bottom of the ladle. The obtained results allowed to determine the proper location of the plug at the bottom of the refining ladle and the possibility of using combined blowing. The tests were carried out for a refining ladle with a capacity of 3 m3 using a physical model on a linear scale of 1:3. The gas flow rate used in the model corresponded proportionally to the value previously used in industrial practice and amounted to 26.8 l/min. Experiments were performed for both combined blowing applications and through a purging plug at the bottom of the ladle. In the case of combined blowing, the volume of the gas stream was divided into two blowing sources (lance and purging plug). As a result of laboratory tests, one of the variants was selected and tested in industrial conditions. These studies confirmed the improvement in the efficiency of refining treatment of the FeSi alloy in terms of reducing the carbon and aluminum content in the alloy.x.

• Klíčová slova
• Ferroalloys, Ferrosilicon, Physical modelling, Refining gas, Steel, Water models,
• Publikační typ
• časopisecké články MeSH