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Received Sep 29, 2017; Accepted Dec 31, 2017
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1. Introduction
Many natural proteins act as a functional basis of biologic drugs [1]. One of the first steps, required to outline the design of the therapeutic properties of protein drugs, is their thermodynamic characterization [2]. The attainment of desired thermodynamic features of proteins is a relatively new area in biotechnology. Thus, protein stabilization becomes a main goal in medicine and scientific research. The mechanism of folding and unfolding gives knowledge on the function and the possibilities of protein stabilization. Differential scanning calorimetry (DSC) is the most useful technique for analyzing the protein thermal stability. This method measures the heat capacity change, associated with protein thermal denaturation, as a function of temperature. The integral of the excess heat capacity function is the enthalpy in this process. Thermodynamic parameters, such as temperature of unfolding (Tm) and change in enthalpy, give huge information about the structure and functional parameters of the proteins, as well as about the nature of their interactions with other ligands or drug [3–5].
Hemocyanins (Hcs) are oligomeric copper-containing glycoproteins that function as oxygen carriers in the hemolymph of several molluscs and arthropods [6, 7]. Besides their important biological function, a variety of medical applications of molluscan Hcs emerged. Recently, we have established that the Hcs of marine mollusk Rapana thomasiana (RtH) and β-Hc isoform of H. pomatia (β-HpH) are suitable as potential bioadjuvants for subunit vaccines and that these Hcs could be used as natural adjuvants or protein carriers [8, 9]. The anticancer properties of both molluscan Hcs have been demonstrated on a murine model of colorectal cancer in vivo [10]. A number of DSC studies have shown that Hcs possess considerable thermal stability. Melting temperature (Tm) in the range 83–90°C was observed for the RtH [11], β-HpH [12], and the Hc of marine gastropod Concholepas concholepas (CCH) [13]. Calorimetric studies demonstrate also the high thermostability of Hcs from arthropods, for example, Hcs of tarantula Eurypelma californicum (Tm 90°C) [14] and of...