Low DNA Performance in Downstream Applications Due to Contaminants (DNA Cleanup & Plasmid Purification)

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Purified DNA fails or performs poorly in downstream applications (transformation, restriction digestion, PCR, sequencing) despite acceptable concentration and A260/280 ratio. Common causes: 1) Ethanol carryover from wash step not completely removed before elution 2) Column tip contacted flow-through during transfer, contaminating sample 3) Excessive salt in sample from skipped or inadequate wash steps 4) Excessive carbohydrate carryover from strains with high endogenous carbohydrate (e.g., HB101, JM100 series) 5) Plasmid Wash Buffer 1 step skipped allowing carbohydrate contamination 6) Undissolved agarose leached salts into eluted DNA (gel extraction) Solutions: 1) Centrifuge final wash for full 1 minute to ensure complete ethanol removal 2) Ensure column tip does not contact flow-through or walls of collection tube during transfers 3) Use both Plasmid Wash Buffers; never skip wash steps to ensure salt removal 4) Avoid strains with high carbohydrate content (e.g., HB101, JM100 series); always include Plasmid Wash Buffer 1 step 5) For gel extraction, ensure gel slice is fully dissolved before loading to prevent salt leaching 6) When transferring column to elution tube, ensure column tip does not contact tube walls