Stanislav Pospíšil

Oxidation of Lincomycin by Hydrogen Peroxide Restricts Its Potential Biotransformation with Haloperoxidases

Lincomycin biotransformation was conducted by usingStreptomyces venezuelae andStreptomyces phaeochromogenes cell-free extracts. Reaction products were isolated and identified by MS and NMR spectroscopy as lincomycin sulfoxide and lincomycin sulfone. Both compounds arise also by chemical oxidation with hydrogen peroxide; this reaction represents a new efficient way for the preparation of lincomycin sulfoxide and lincomycin sulfone and simultaneously excludes the biotransformation of lincomycin using haloperoxidases.

Glucosylglycerate is an osmotic solute and an extracellular metabolite produced byStreptomyces caelestis

Streptomyces caelestis DSM 40084produces two osmolytes,viz. 2-O-(α-d-glucopyranosyl)-ζ-glyceric acid (GG) and trehalose. Both compounds were isolated and identified by nuclear magnetic resonance spectroscopy and mass spectrometry. A very sensitive regulation of the cell osmolytes was demonstrated in exponentially growing cultures. The intracellular levels of GG and trehalose increased 2× in response to a step change of medium osmolarity caused by 0.3 % NaCl.1H NMR analysis of the cell extracts did not confirm the presence of additional osmolytes. GG is aS. caelestis metabolite commonly released from the cells; its concentration reached 3 g/L during the cultivation in a yeast extract-(NH4)2SO4-glycerol medium. This is the first report on the occurrence of the ionic osmolyte GG in the genusStreptomyces and on its free excretion to the medium.

New carbasugars from Streptomyces lincolnensis.

Two new carbasugars (9 and 10) were isolated from Streptomyces lincolnensis DSM 40355 along with streptol (valienol, 8), gabosine I (valienone, 14), and glucosylglycerate. The reported 1H and 13C assignments are based on 1D (1H, 13C, 1D‐TOCSY, homodecoupling) and 2D (gCOSY, J‐resolved, TOCSY, ROESY, gHSQC, gHMBC) NMR techniques and electrospray ionization FT mass spectrometry (ESI FTMS). Copyright

Numerical and Experimental Investigations of Air Flow Turbulence Characteristics in the Wind Tunnel Contraction

Flow characteristics contraction of rectangular cross-section are investigated numerically and experimentally so as to gain an additional insight into the contraction design. They observed velocity field and turbulent intensity in the area of contraction and downstream of it. Individual numerical models sofware Ansys Fluent are evaluated and compared with measurements in a wind tunnel.

Heavy Laminated Timber Frames with Rigid Three-Dimensional Beam-to-Column Connections

AbstractThis article presents the seismic performance of a timber frame with three-dimensional (3D) rigid connections. The connections were made with self-tapping screws and hardwood blocks were used to support the beams. The frame was designed to resist high seismic excitations with the goal of controlling the drift. The moment-rotation characteristics of the connections were measured in the laboratory by applying static cyclic loads. The frame made of laminated wood beams and columns, and cross-laminated lumber deck, was subjected to seismic, white noise, snapback, and sinusoidal sweep excitations. The synthetic seismic excitation was designed to contain a considerable amount of energy close to the frame’s first natural frequency. The structure showed no significant damage up to a peak ground acceleration of 1.25g. Failure of the frame occurred due to shearing of the columns with a peak ground acceleration of 1.5g. The designed structure fulfilled with current serviceability limits up to 0.8g.

In vitro metabolism of monensin A: microbial and human liver microsomes models

Abstract 1.u2002Monensin A, an important antibiotic ionophore that is primarily employed to treat coccidiosis, selectively complexes and transports sodium cations across lipid membranes and displays a variety of biological properties. 2.u2002In this study, we evaluated the fungi Cunninghamella echinulata var. elegans ATCC 8688A, Cunninghamella elegans NRRL 1393 ATCC 10028B and human hepatic microsomes as CYP-P450 models to investigate the in vitro metabolism of monensin A and compare the products with the metabolites produced in vivo. 3.u2002Mass spectrometry analysis of the products from these model systems revealed the formation of three metabolites: 3-O-demethyl monensin A, 12-hydroxy monensin A and 12-hydroxy-3-O-demethyl monensin A. We identified these products by tandem mass spectrometry and through comparison with the in vivo metabolites. 4.u2002This analysis demonstrated that the model systems produce the same metabolites found in in vivo studies, thus they could be used to predict the metabolism of monensin A. Furthermore, we verified that liquid chromatography coupled to mass spectrometry is a powerful tool to study the in vitro metabolism of drugs, because it allows the successful identifications of several derivatives from different metabolic models.

Experimental Set-Up for Advanced Aeroelastic Tests on Sectional Models

This article describes an original and multipurpose experimental set-up for the analysis of complex linear and non-linear aspects of aero-elastic behaviour of beam cross-sections. The apparatus meets rigorous theoretical assumptions and allows very precise and quick adjustment of stiffness and mass of a cross-section, which is not always possible with the traditional “parallel spring-supported bridge” approach used by many researchers. The principal advantages are described together with key construction details. Examples of the large amplitude non-linear response are presented, to illustrate the capacity and usefulness of the stand.

Jacobsen Catalyst as a Cytochrome P450 Biomimetic Model for the Metabolism of Monensin A

Monensin A is a commercially important natural product isolated from Streptomyces cinnamonensins that is primarily employed to treat coccidiosis. Monensin A selectively complexes and transports sodium cations across lipid membranes and displays a variety of biological properties. In this study, we evaluated the Jacobsen catalyst as a cytochrome P450 biomimetic model to investigate the oxidation of monensin A. Mass spectrometry analysis of the products from these model systems revealed the formation of two products: 3-O-demethyl monensin A and 12-hydroxy monensin A, which are the same ones found in in vivo models. Monensin A and products obtained in biomimetic model were tested in a mitochondrial toxicity model assessment and an antimicrobial bioassay against Staphylococcus aureus, S. aureus methicillin-resistant, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli. Our results demonstrated the toxicological effects of monensin A in isolated rat liver mitochondria but not its products, showing that the metabolism of monensin A is a detoxification metabolism. In addition, the antimicrobial bioassay showed that monensin A and its products possessed activity against Gram-positive microorganisms but not for Gram-negative microorganisms. The results revealed the potential of application of this biomimetic chemical model in the synthesis of drug metabolites, providing metabolites for biological tests and other purposes.

MODELS OF LOAD ON BULDINGS FROM THE EFFECTS OF THE FLOW FIELD

Abstracts Article describes two different approaches of the solution of benchmark solution of bluff aerodynamic, which is the solution of wind pressures upon the cube exposed to the effects of air flow field. Physical modeling is carried out at the wind tunnel of the Institute of Theoretical and Applied Mechanics in Telč whereas numerical modeling is performed at the Faculty of Civil Engineering, VSB Technical University of Ostrava of software using Ansys Fluent.

Oxidation and amidation of salicylate by Streptomyces species

Seven streptomycete strains were tested for biotransformation of salicylate. The products were identified by nuclear magnetic resonance spectroscopy and three types of conversion were found. Streptomyces cinnamonensis and Streptomyces spectabilis formed gentisate and salicylamide concurrently. Streptomyces rimosus transformed salicylate to salicylamide. Streptomyces lividans, Streptomyces coelicolor, Streptomyces griseus and Streptomyces avermitilis produced only gentisate. Time course studies of salicylate conversion by thin-layer chromatography and high pressure liquid chromatography showed that salicylamide was accumulated in the culture broth, whereas gentisate was further metabolized.Key words: salicylate, gentisate, salicylamide, biotransformation, Streptomyces spp.