Practice question

During phenol-chloroform extraction, lysate separates into three distinct zones after centrifugation. Upper aqueous phase contains hydrophilic nucleic acids, lower organic phase contains lipids and hydrophobic molecules dissolved in phenol-chloroform. Denatured proteins, containing both hydrophobic and hydrophilic residues, are insoluble in either phase and accumulate as white flocculent precipitate at interphase between aqueous and organic layers. Centrifugation traps them there firmly. DNA and RNA remain aqueous, buffers remain aqueous, but interphase is diagnostic of successful protein denaturation and effective purification during extraction.