Viscous sample — stringy lysate, hard to pipette (Protein Extraction)

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Accepted Answer

Lysate is stringy/sticky, pipettes slowly, sticks to the tip, and gives unreliable BCA quantification and bad SDS-PAGE loading. Common causes: 1) Genomic DNA contamination from broken cells/tissue 2) High mucopolysaccharide or lipid content 3) Incomplete lysis left cell aggregates 4) Ionic strength of lysis buffer was too high Solutions: 1) Add DNase I (5 – 10 μg/mL) and incubate at 37 °C for 15 – 30 min to degrade DNA 2) Raise NaCl concentration (300 – 500 mM) or switch to a high-salt lysis buffer 3) Vortex thoroughly and pass through a 40 – 70 μm filter 4) If needed, sonicate briefly or pipette repeatedly to shear DNA