Browsing by Subject "myosin S1 units"

The literature review deals with water distribution in meat, the structure of the myofibrillar matrix, and the aspects related to the water-protein interaction. Special focus was given to the large water accessible area of myosin S1 units, surface hydrophobicity of proteins and factors affecting the hydrophobicity. Also the possible mechanisms of water-holding in meat were briefly introduced. The aim of the thesis was to study the effect of different ions and pH values on the surface hydrophobicity of the myosin S1 units, adding knowledge to the understanding of the interaction between myosin S1 units and water. Myosin S1 units were prepared from porcine longissimus dorsi muscle 48 h postmortem. Obtained myosin S1 units were subjected to 0.2 M, 0.4 M and 0.6 M ionic strength of NaCl and KCl and to pH 5.0, 5.5, 6.0, 6.5 and 7.0. The surface hydrophobicity of myosin S1 units was measured by fluorescent molecular probe (cis-Parinaric acid) method. The method of purifying myosin S1 units from porcine longissimus dorsi muscle 48 h postmortem was established under the conditions of our laboratory. Surface hydrophobicity was found to increase with increasing ionic strength of both KCl and NaCl. Concerning the different ions studied, only at 0.6 M, significantly higher surface hydrophobicity of myosin S1 units was measured in KCl compared to NaCl. This phenomenon is in accordance with chaotropic effect of K+ and Cl- and kosmotropic effect of Na+. Regarding the effect of pH, within KCl samples, more hydrophobicity myosin S1 unit was detected towards to the more acidic direction pH values than pH 6.0. For NaCl samples, at pH 5.5 and 6.0, surface hydrophobicity was significantly higher than at pH 5.0, 6.5 and 7.0. Differences may have been induced by the changes in the net charges of protein, and further in protein conformation. Considering the property of the protein surface, more hydrophobic protein results in less water-protein interaction. However, to look at the whole scenario of the interaction between myosin S1 units and water, changes of net charges of myosin S1 units and water structure at vicinity of them should be further studied.