This
study tests the effect of using the combination of graphene
oxide (GO) with different valence cations as a heterogeneous nucleant
on promoting catalase crystallization. By using GO and three types
of salts with different valences, NaCl, MgCl2, and YCl3, the addition of GO with all three salts resulted in an increase
in the percentage of crystal drops and a decrease in induction time.
The experimental results further verified that there is a synergistic
effect of GO and cations as the percentage of crystal drops was higher
when GO with cations was added compared to control experiments where
only GO or cations presented. It was also observed that the improvement
in crystallization became more significant when cations with higher
valence were utilized. It is believed that the enhancement in crystallization
was due to the synergistic effect arising from the cation-π
and electrostatic interactions between GO sheets and cations. These
interactions subsequently contributed to the positively charged salt,
which adsorbed and connected both negatively charged catalase molecules
and the GO surfaces, increasing the local protein concentration and
leading to crystallization. In addition, we compared LaCl3 and CeCl3 with YCl3 to verify the effect of
the same valence salt on catalase crystallization and found that the
higher the charge density, the more pronounced the promotion effect.
This study provides a new protein crystallization methodology by exploiting
GO with cations as heterogeneous nucleant to promote catalase crystallization
and brings about a new model for investigating protein crystallization
mechanisms.
The effects of auxiliary blowing agent were investigated. Based on the results, new combined blowing agents were studied. The difference between the kinetics and thermodynamics of decomposition of the typical blowing agents were compared. Compared with the typical single blowing agents, the new combined blowing agents had the below characteristics: (1) The endothermic enthalpy equals exothermic-enthalpy; (2) The rate of gas evolution of the combined blowing agents is relatively rapid but not abrupt to form more regular and small cell structure; (3) They comprised of blowing agent, nucleation agent and blowing auxiliary agent. The blowing fratures in actual processing by Brabender extruder were verified. The data and the results are valuable to flowing research and can provide the theoretical basis for producing cellular PVC material by extruding.
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