ABSTRACT
In the present work we studied the effect of 2D WS2 nanoparticles on the conformational changes in lysozyme protein at different pH values (2.0-11.5). The contributions of various structural conformations (α-helix, ß-sheets parallel and antiparallel, unordered structure and side groups) were determined by decomposition of Amid I absorbance bands. The 2D WS2 were shown to have different impact on secondary structure depending on pH of the solution and protein concentration. The amyloid fibril presence was confirmed with confocal microscopy enhanced by gold support, and fluorescent spectroscopy with amyloid-sensitive dye Thioflavin T. Our data show that WS2 can both inhibit and stimulate amyloid formation. Additionally, we have also reported an unusual spectroscopic behavior displayed by lysozyme, indicated by narrowing of Amide I and Amide II bands at pH 2.5 and 3.5 when incubated with 2D WS2 nanoparticles.
Subject(s)
Amyloid/chemistry , Metal Nanoparticles/chemistry , Muramidase/chemistry , Sulfides/chemistry , Tungsten Compounds/chemistry , Animals , Benzothiazoles/chemistry , Chickens , Egg White/chemistry , Fluorescent Dyes/chemistry , Hydrogen-Ion Concentration , Protein Conformation, alpha-Helical , Protein Conformation, beta-Strand , Spectrum Analysis/methodsABSTRACT
Here, both neuroprotectants, i.e. cholesterol depletion of the plasma membrane of rat brain nerve terminals (synaptosomes) using methyl-ß-cyclodextrin (MßCD) and deep/propound hypothermia, were analyzed during their combined administration and regarding additive neuroprotective effect. The extracellular synaptosomal level of L-[14C]glutamate significantly increased after treatment with MßCD in both deep and profound hypothermia. Cholesterol depletion gradually enhanced inhibiting effect of deep and profound hypothermia on glutamate uptake and "excitotoxic" transporter-mediated release of L-[14C]glutamate. A decrease in L-[14C]glutamate release via heteroexchange from nerve terminals in deep and profound hypothermia was enhanced by cholesterol deficiency that confirmed previous result. Fluorometric studies with probes NR12S and DCVJ revealed oppositely directed effects of cholesterol depletion and hypothermia on synaptosomal membrane lipid order and microviscosity showing that cholesterol depletion can normalise up to the control hypothermia-induced increase in microviscosity, but not the lipid order of the synaptosomal membrane. Dynamics of changes in exocytosis in nerve terminals, which involved membrane fusion stage, was different from transporter-dependent ones. Hypothermia did not augment effects of cholesterol depletion on exocytotic L-[14C]glutamate release and lowering cholesterol enhanced the impact of deep, but not profound hypothermia on this parameter. Therefore, dual benefit of combined neuroprotection was demonstrated. Cholesterol depletion enhanced neuroprotective effects of hypothermia intensifying inhibition of "excitotoxic" transporter-mediated glutamate release and can normalise a hypothermia-induced increase in microviscosity of the synaptosomal membrane. This feature is prospective in mitigation of side effects of therapeutic hypothermia, and also for brain conservation preserving normal physical and chemical properties of the cellular membranes.
