Under oxygenated conditions bovine hemoglobin reacts with mono(3,5-dibromosalicyl)-fumarate which specifically acylates the EF5 lysines in the p-cleft of the protein. The chemical modification introduces in the molecule a pseudo-crosslink which hinders the dissociation of the hemoglobin molecule into dimers. Retention time in circulation of the chemically modified bovine hemoglobin, measured in the rat, is increased fivefold with respect to untreated bovine hemoglobin. The oxygen affinity at 37°C and at pH 7.4, has a P50 = 5.4 kPa and a value of n = 1.9. Under the same experimental conditions the oxygen affinity is not sensitive to anions and polyanions whereas it is sensitive to COz. The Bohr effect is shifted toward the alkaline pH range by 0.5 -1 : the maximum number of protons released is 1 S/tetramer, similar to normal bovine hemoglobin (1.8 protons/tetramer). Analysis of the binding isotherms, using the two-state Monod-Wyman-Changeux model and fixing the value of the allosteric constant L = lo5, shows that the oxygen affinity of the T structure is not modified, and that the low oxygen affinity of the system is due to a decrease of the oxygen affinity of the R structure. Analysis using the sequential Adair model shows a modification of the overall binding constants and suggests a redistribution of the intermediate species of oxygenation.At variance with human hemoglobin (HbA) where the oxygen affinity in vivo is modulated by the interaction with 2,3-bis-phosphoglycerate [Gri(2,3)Pz], the oxygen affinity of bovine Hb(HbBv) is modulated by the interaction with chloride ions [l, 21. As a result, a different mechanism of allosteric modulation of oxygen affinity is introduced in HbBv. The sites of C1-binding are not known; however, they are most likely located in the j chains [3].In the HbA molecule the regulatory site of oxygen affinity is the j-cleft, where Gri(2,3)Pz binds. The question addressed in this paper is whether this is true also in HbBv in spite of the fact that the oxygen affinity of the molecule is not modulated by the interaction with Gri(2,3)P2.Comparison of the amino acid composition of HbBv and HbA shows that, out of the 28 substitutionslap dimer, only two are in the p-cleft, one at the amino terminus where a single methionine replaces NAl-Valp and NA2-Hisp of HbA, and one in position H C l j where an arginine replaces lysine of HbA. It has been proposed that the substitution present at the amino terminus of the p chains is relevant to the mechanism by which the oxygen affinity of HbBv is decreased with respect to HbA [2-41.In order to define the role of the P-cleft in the regulation of the functional properties of the bovine system, we have altered the distribution of charges within this region of the molecule, by reacting HbBv with mono(3,5-dibromosalicyl)-fumarate (FMDA). In HbA this reagent specifically acylates acid residues are invariant in human and bovine Hbs. Tryptic fingerprinting, followed by peptide separation and amino acid analysis, indicated that in HbBv also the lysines EF5P ...

This article presents the analysis of fi n drag force in a Biomimetic Underwater Vehicle (BUV). To carry out numerical simulations Incompressible Computational Fluid Dynamics (ICFD) solver was used. The simulation model was verifi ed in the designed laboratory test stand. The laboratory test stand was equipped with specialized sensors for force measurements and control of fl uid velocity. An average value of fl uid velocity in the water tunnel was measured by specialized high accuracy ultrasonic fl owmeter. A vision system was used for analysis of laminar and turbulent fl ows in the fl uid structure interaction area. The research of fl uid-structure interaction phenomena was depicted using dimensional analysis. Sažetak U radu se daje analiza sile otpora biomimetičkog podvodnog vozila (BUV). Za provođenje numeričkih simulacija koristio se program Računalna dinamika fl uida (ICFD). Simulacijski model provjeren je u posebno izrađenom laboratoriju. Laboratorij je opremljen specijaliziranim senzorima za mjerenje sile i kontrole brzine fl uida. Prosječna vrijednost brzine fl uida u vodenom tunelu izmjerena je specijaliziranim i vrlo preciznim ultrasoničnim uređajem za mjerenje brzine strujanja. Sustav promatranja koristio se za analizu laminarnih i turbulencijskih strujanja u području interakcije u strukturi fl uida. Istraživanje fenomena interakcije u strukturi fl uida provedeno je uporabom dimenzionalne analize. KEY WORDS artifi cial fi sh fl uid structure interaction (FSI) computational fl uid dynamics (CFD) biomimetic underwater vehicle KLJUČNE RIJEČI umjetna riba interakcija u strukturi fl uida (FSI) računalna dinamika fl uida (CFD) biomimetičko podvodno vozilo

No abstract

No abstract

The article presents the analysis of the automatic alternate current motor control system, carried out by the author. The automatic control system has been implemented on the existing laboratory stand, containing: the squirrel-cage asynchronous motor and the frequency inverter. The existing stand imposed one of the available speed control methods for the motor and the necessity of the appropriate elements selection for the automatic control system [1]. The automatic control system has been designed and created as the constant value follow-up digital controller. To designate the parameters of the control object the unit step method of was used. After registering the output changes caused by the unit step, the characteristic curve was received that allowed to determine the alternative transmittance of the control object which, in turn, has made possible to find the appropriate controller settings.