In kinetic assays, 105 CFU/mL of yeast were incubated with 5 μM of peptides in 20% YPD at 30°C for different times
from 15 min to 24 h, and the CFU recovery was also quantified by spreading onto peptide-free plates. For experiments with the different S. cerevisiae strains and deletion mutants, cultures were adjusted to 107 cells/ml in 20% YPD and serial 5-fold dilutions of cells were prepared and subjected separately to peptide treatment. The treatments contained 45 μl of each yeast dilution and 5 μl of a 10X stock solutions of each synthetic peptide, and were incubated in sterile 96-well microtiter plates (Nunc) at 30°C for ACY-738 either 2 or 24 h. Aliquots (5 μl) of each sample were dotted onto peptide-free YPD agar plates to determine buy MK-8931 viability after 2 h or 24 h of incubation. In all experiments, YPD medium contained 40 μg/ml chloramphenicol (to avoid bacterial contamination) and the agar plates were incubated at 30°C for 2 days to allow colony visualization and/or counting. In specific assays 4SC-202 clinical trial the temperature of incubation was 24°C. Calcofluor white (CFW) (Sigma-Aldrich F3543) or sodium dodecyl sulphate (SDS) (Sigma-Aldrich L4509) plates were prepared to desired final concentrations in YPD agar medium. On these plates, aliquots (5 μl) of serial 5-fold yeast dilutions (or ten-fold dilution in the case of CFW plates) were spotted
and growth was visualized after two days of incubation at 30°C. Fluorescence microscopy S. cerevisiae cells were grown to exponential phase (OD600 0.4-0.5) at 30°C with shaking and the number of cells/ml was determined independently for each strain. Yeast at 108 cells/ml (final concentration) were incubated in sterile water with 30 μM FITC-labeled PAF26 for 0.5-2 hours at 30°C in the dark. After this incubation, cells were further incubated with 2 μM propidium iodide (PI) and 25 μM calcofluor white (CFW) BCKDHA for 5 min in order to check for viability/membrane integrity and cell wall structure, respectively. Yeast cells were
washed and fluorescence was examined with an epifluorescence microscope (E90i, Nikon), with excitation/emission wavelengths of 488/510-560 nm for FITC detection, 544/612 nm for PI detection and 395/440 nm for CFW detection. Differential interference contrast (DIC) and fluorescence images were captured with ×40 and ×100 objectives using the software NIS-Elements BR v2.3 (Nikon). In order to confirm peptide internalization, S. cerevisiae at 5 × 105 cells/ml were incubated in sterile water with 30 μM FITC-PAF26 in the dark, and visualized with a TCS SL confocal laser scanning microscope (Leica), with excitation at 488 nm and emission wavelengths at 510-560 nm. Flow cytometry S. cerevisiae cells were prepared as detailed above and 2.