Practice question

Polyethylene glycol polymer repeating ethylene oxide units average MW 1500 Da widely employed fusogen hybridoma generation due unique physicochemical properties affecting membrane biophysics. Mechanism involves strong hygroscopic nature binding water around phospholipid headgroups phosphatidylcholine sphingomyelin reducing hydration repulsion normally maintaining 2-3 nm separation bilayers enabling close apposition <1 nm allowing hemi-fusion stalk outer leaflets merge. High concentration 50 percent w/v creates osmotic stress withdrawing water cells shrinkage lipid disorder increasing lateral mobility promoting fusion pore channel connecting cytoplasms. Protocol exposes pellet containing ratio 5:1 10^8 splenocytes 10^7 myeloma to prewarmed PEG solution exactly 60 seconds 37 degrees gentle stirring pipette tip then slowly dilutes over 5 min 10 volumes serum-free DMEM minimizing toxicity maintaining heterokaryons newly fused. PEG MW influences efficiency PEG 1000 insufficient dehydration low fusion frequency <1 percent PEG 4000 excessive toxicity cytoskeleton disruption calcium influx triggering apoptosis. Alternative electrofusion applies alternating current 1 MHz aligning cells pearl chains dielectrophoresis followed direct current pulse 1 kV/cm breaking membranes achieving heterokaryon formation higher viability some cell types improving hybrid generation rate.