The optical and bactericidal properties of acetic and basic chitosan films were studied. By the ORD technique, we found that these films differed in the values of their specific optical rotation and of their rotary and dispersive constants. A sign inversion of was observed when the acetic chitosan films were heat-treated. The bactericidal activity of the initial and dehydrated acetic films was analyzed, and their moisture content and optical and biological activities were compared. 1. Introduction The aminopolysaccharide chitosan is an optically active (chiral) biopolymer. The presence of asymmetrically substituted carbon atoms (chiral centers) in chitosan molecules leads to the emergence of optical activity in its link and, hence, in the macromolecule as a whole. Optical rotatory dispersion (ORD) and circular dichroism (CD) spectroscopy techniques are commonly applied to studying optical activity. They are based on unequal changes in the phase and intensity (the polarization vector module) of the left and right circularly polarized waves (their factors of refraction and extinction) in optically active media. CD spectroscopy is used to estimate the deacetylation degree of chitosan and its derivatives [1, 2], to characterize their physical and chemical properties [3, 4], to study liquid crystals (LC) of chitosan dispersions with nucleic acids [5] and lyotropic LC solutions of chitosan derivatives [6], and to establish the nativity degree of biologically active substances encapsulated into a polysaccharide matrix [7]. ORD is useful in estimating conformational properties of chitooligomers [8, 9], peculiarities of the spatial structure of chitosan and its salts with chiral organic acids [10], and so forth. Comparison of the capabilities of the ORD and CD techniques shows that within the wavelength range outside of the absorption bands of the chromophores (which, for the given aminopolysaccharide, falls within the far UV range), optical rotatory spectroscopy in some cases yields more information on optical activity and its correlation with other physical and chemical parameters of chitosan. For example, fairly recently, the ORD technique was used to reveal a correlation between chitosan’s optical activity and its molecular weight and deacetylation degree [11, 12], as well as to clarify the character of its biological activity [13]. The influence of metal ions (Ca2+, K+, and Na+) on macromolecular conformation was also shown [14]. It should be noted that all the previously-cited works have dealt with chitosan solutions and that no data on the optical
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