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#organic extraction layers

2 public questions tagged with this topic.

DNA & RNA isolation

The interphase in organic extraction contains:

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.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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DNA & RNA isolation

What determines the location of DNA in organic extraction layers?

Organic extraction partitioning of DNA depends on physicochemical properties like solubility and polarity rather than size alone. Nucleic acids are highly hydrophilic polyanions due to sugar-phosphate backbone, favoring aqueous phase. Proteins, especially after phenol denaturation, expose hydrophobic residues and partition into organic phase or interphase. Phenol-chloroform mixture creates immiscible layers where hydrophilic molecules dissolve in water and hydrophobic in organic. Temperature, pH of phenol influences RNA vs DNA partitioning, and size influences precipitation, but phase preference is fundamentally determined by relative solubility differences.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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