, Edison, NJ). Different capillaries having internal diameters of 0.9, 1.8, 3.0, and 4.0mm were used to determine viscosity of chitosan solutions. The measurements were performed selleck chemicals Ganetespib at inclination angle of 15�� at 25��C. For solution viscosities higher than 800cP, measurements were made with a rheometer using parallel plate geometry (RHOIS 902-30004, Rheometric Scientific Inc., Piscataway, NY, USA). The viscosities data was used to study kinetics of chitosan fragmentation.2.3.2. Intrinsic Viscosity Measurement The intrinsic viscosities of the original chitosan and its fragments were measured in two solvents: (1) 0.1M HAc/0.02M NaCl (solvent A) and (2) 0.25M HAc/0.25M NaAc (solvent B) at 25��C using a capillary viscometer with an internal capillary diameter of 0.9mm at inclination angle of 15��.

These conditions along with the use of solution concentration lower than 1.0% (w/v) were selected, so corrections for kinetic energy and shear rate were negligible. Efflux times were measured for chitosan solutions (ts) and the solvent (t0). Measurement of efflux times was repeated four times and average efflux time was then converted to the ratio of ts/t0, which is proportional to relative viscosity of chitosan solution. The intrinsic viscosity was determined by both Huggins and Kraemer plots [29, 30]. The average value of two intercepts obtained from the two linear plots was considered as intrinsic viscosity of the polymer sample, [��]. The intrinsic viscosity data was used to calculate viscosity-average molecular weight of the polymer samples, Mv. 2.3.3.

Calculation of Viscosity-Average Molecular Weight and Number of Chain Scissions The value of Mv was calculated in solvent A according to [31][��]=3.04��10?5Mv1.26(1)and in solvent B was calculated using [32][��]=1.49��10?4Mv0.79.(2)The average number of chain scissions, ��, was calculated using the following equation [33]:��=(Mv,oMv,f)?1,(3)where Mv,o and Mv,f are viscosity-average molecular weights of the original and the fragments, respectively.2.3.4. Size Exclusion Chromatography Size exclusion chromatography (SEC) was used to compare molecular weight and molecular weight distribution of the original chitosan and its fragments. A HPLC/SEC instrument (Hewlett-Packard, Series 1050) was used with a refractive index detector, whose response is directly proportional to the polymer concentration in the eluting solution.

Separation Drug_discovery was achieved at 35��C using a TosoHaas-TSK gel column (GMPWXL, 30cm �� 7.8mm) with 0.25M HAc/0.25M NaAc (solvent B for intrinsic viscosity measurement) as an eluent at a flow rate of 0.4mL?min?1. 2.3.5. Structural Analysis The chemical structure and the DA of the purified original chitosan and two fragments were determined by 1H NMR spectroscopy and elemental analysis. The procedures for structural analysis by the two techniques were the same as the procedures described by Hirai et al. [34] and Kasaai et al. [35].3. Results and Discussion3.1.