Studies on the non-newtonian viscosity of poly-L-proline in an aqueous salt solution and its reverse mutarotation

Abstract

The viscosity changes of poly-L-proline and its non-Newtonian viscosities (up to maximum external pressure 2.5 psi) were measured in the reverse mutarotation (Form II-Form I) under various solvent systems, i.e. acetic acid-propanol (2:8 v/v), water-propanol (1:9 v/v) etc. The viscosity of the system under no external pressure is most large in acetic acid-propanol (2:8 v/v) mixture over a whole range of reverse mutarotation compared to other solvent mixture systems. Our experimental results exhibit also that the degree of non-Newtonian effect in the viscosity of poly-L-proline in reverse mutarotation under external pressure is larger in acetic acid-propanol system than water-propanol system. It may be caused by the fact that poly-L-proline attain more flexible rod in water-propanol system than acetic acid-propanol systems. The non-Newtonian viscosity of the poly-L-proline was also measured in aqueous salt solutions, it was found that the degree of the non-Newtonian behavior decreases as salt concentration increases, i.e. the order is pure water solution> 1M solution > 2M solution> … etc.