To determine whether the beneficial effects observed at the electrophysiological level have a cognitive counterpart, 19-month-old rats were intraventricularly perfused for 4 weeks with a solution of cholesterol-MβCD (300 μM) + cholesterol (5 μM) dissolved in aCSF.
A solution of deuterated cholesterol was prepared by dissolving 10 mg of [25,26,26,26,27,27,27-H7]cholesterol in 10 mL of propan-2-ol to make a solution of 1 μg/μL.
Liposomes were prepared by mixing appropriate volumes of the stock solutions of phospholipids, cholesterol, or Py-met-chol (mole fractions were calculated according to the total quantity of lipids in a given suspension).
The aggregation number of PPG-PEG-PPG solution obtained after extraction of cholesterol and Zn-cholesterol complex in ABS was found to be greater in comparison to the pristine copolymer solution.
Since cholesterol was removed from the lipid fraction during the extraction procedure, the missing quantity (as determined for separate samples (supplementary material Table S1)) was introduced as a given volume of cholesterol solution in chloroform (Avanti lipids) to get cholesterol molar ratio of 9.0% and 17.4% for F. candida and E. albidus extracts, respectively.
To carry out the electrochemical detection, different concentrations of cholesterol solutions were prepared by dissolving required amount of cholesterol directly into the solution of 0.001 M H2SO4, maintaining the pH ~ 5.3.
Cholesterol-modified structures have a strong tendency to form aggregates in aqueous solutions due to their hydrophobic interactions; in fact, the critical micelle concentration of cholesterol in solution is 25 to 40 nM, which is below the concentration of cholesterol-modified DNA (>100 nM) in our assembly.
When cholesterol was added to the detection solution, COx catalyzed the oxidation of cholesterol to generate H2O2, which could be further catalyzed by hemin to produce O2 as the coreactant in the peroxydisulfate system for signal amplification.
A similar activation pattern was found when using a dilution of cholesterol stock solution containing Triton X-100 and taurocholate in water or in water/Triton X-100 and nonionic surfactants and bile acid salts have been described to affect the kinetic behavior at particular enzyme to surfactant ratios [ 18].
Lipid pellets resuspended in 5 μl TN buffer and 5 μl of cholesterol standard solutions ranging from 0.3 to 7.8mM were supplemented with 500 μl of cholesterol liquid stable reagent provided by Thermo Electron Corporation.
