The design of multifunctional systems is in focus today as a key strategy for coping with complex challenges in various domains that include chemistry, medicine, environmental sciences, and technology. Herein, we introduce protein-containing polymer nanoreactors with dual functionality: peroxynitrite degradation and oxygen transport. Vesicles made of poly-(2-methyloxazoline)-poly(dimethylsiloxane)-poly(2-methyloxazoline) successfully encapsulated hemoglobin (Hb), which serves as a model protein because of its dual function in oxygen transport and peroxynitrite degradation. By inserting channel proteins, the polymer membranes of vesicles permitted passage of various compounds that served for the assessment of in situ Hb activity. The requisite conformational changes in the protein structure and the change in oxidation states that took place within the confined space of the vesicle cavity demonstrated that Hb preserved its dual functionality: peroxynitrite degradation and oxygen transport. The functionality of our nanoreactor, combined with its simple procedure of production and extensive stability over several months, supports it as a promising system for further medical applications.

Using centrifugation assay and light scattering measurements, we study the condensation of DNA by the salmon protamine, a highly basic protein carrying 21 positive charges out of 30 amino acids, in the presence of a high amount of monovalent salt. The DNA condensation is followed by a macroscopic phase separation. It occurs while a large amount of polycations remains freely diffusing in the bulk. A similar behavior was described before for small multivalent ions in diluted DNA solution in a lower salt range. Sensitivity to the salt is however amplified when increasing the charge of polycations. Indeed, a high power-law dependence is observed here with an exponent 11. This variation agrees with the power-law dependence that characterizes the binding of small polycations to DNA. In other words, we show that protamines behave like small polycations in the diluted DNA-high salt regime, while they behave like other large polycations in the diluted DNA-low salt regime as shown in a previous study. In addition, instead of the classical view where binding of polycations to DNA is supposed to trigger DNA condensation in low and moderate salt conditions, we propose that, under high salt conditions, the potential presence of a DNA dense phase triggers the binding of protamines to DNA.