Spontaneous Liquid Droplet-to-Gel Transition of Citrulline Polypeptide Complexed with Nucleic Acids.

Inside cells, proteins complex with nucleic acids to form liquid droplets resulting from liquid-liquid phase separation. The presence of mutated proteins can change the state of these liquid droplets to solids or gels, triggering neurodegenerative diseases. The mechanism of the liquid to solid or gel transition is still unclear. Solutions of poly(l-ornithine-co-l-citrulline) (PLOC) copolymers, which exhibit upper critical solution temperature-type behavior, change state upon cooling. In this study, we evaluated the effect of nucleic acids complexed with PLOC on phase changes. In the presence of nucleic acids, such as polyC and polyU, PLOC formed liquid droplets at low temperatures. The droplets dissolved at temperatures above the phase separation temperature. The phase separation temperature depended on the chemical structure of the nucleobase, implying that electrostatic and hydrogen bonding interactions between the nucleic acid and PLOC influenced phase separation. Furthermore, the liquid droplets spontaneously changed to gel-like precipitates due to spontaneous release of nucleic acids from the complex. The rate of the liquid droplet-to-gel transition depended on the magnitude of electrostatic and hydrogen bonding interactions between PLOC and nucleic acid. PLOC complexed with mRNA also underwent a liquid droplet-to-gel transition upon the release of mRNA. This work provides insights into the mechanism of pathogenic transitions of the cellular droplets.

Smart Protein Refolding System Based on UCST-Type Ureido Polymers.

We have reported that ureido polymers exhibit upper critical solution temperature (UCST)-type phase behavior in solution, which is the opposite of lower critical solution temperature (LCST)-type behavior. Furthermore, UCST-type ureido polymers undergo liquid-liquid phase separation (LLPS) upon cooling rather than the liquid-solid phase transition of the typical LCST-type polymers. In this study, ureido polymers with hydrophobic groups were prepared to evaluate the effects of cooling-induced LLPS of UCST-type polymers on refolding of proteins. When protein was heated with a ureido polymer functionalized with undecyl groups, aggregation of the protein was prevented. Subsequent cooling incubation resulted in the spontaneous release of the protein from the polymer. The released protein had enzymatic activity, suggesting that the protein refolded properly. Interestingly, efficient refolding was observed when the solution of the UCST-type ureido polymer and protein was incubated at around the phase separation temperature of the polymer, implying that cooling-induced LLPS of the polymer enhanced the release of the protein. Additionally, by centrifugation at 4 °C, the refolded protein was readily separated from the ureido polymers, which precipitated upon cooling.

Acetaminophen and Febrile Seizure Recurrences During the Same Fever Episode.

OBJECTIVES: To confirm the safety of using acetaminophen for febrile seizures (FSs) and to assess its efficacy in preventing FS recurrence during the same fever episode. METHODS: In this single-center, prospective, open, randomized controlled study, we included children and infants (age range: 6-60 months) with FSs who visited our hospital between May 1, 2015, and April 30, 2017. The effectiveness of acetaminophen was examined by comparing the recurrence rates of patients in whom rectal acetaminophen (10 mg/kg) was administered every 6 hours until 24 hours after the first convulsion (if the fever remained >38.0°C) to the rates of patients in whom no antipyretics were administered. No placebo was administered to controls. The primary outcome measure was FS recurrence during the same fever episode. RESULTS: We evaluated 423 patients; of these, 219 were in the rectal acetaminophen group, and 204 were in the no antipyretics group. In the univariate analysis, the FS recurrence rate was significantly lower in the rectal acetaminophen group (9.1%) than in the no antipyretics group (23.5%; P < .001). Among the variables in the final multiple logistic regression analysis, rectal acetaminophen use was the largest contributor to the prevention of FS recurrence during the same fever episode (odds ratio: 5.6; 95% confidence interval: 2.3-13.3). CONCLUSIONS: Acetaminophen is a safe antipyretic against FSs and has the potential to prevent FS recurrence during the same fever episode.