What's the chemistry behind flocculation when Qiagen P2 is mixed with N3 - (May/01/2013 )

P2 (or the lysis buffer) is 200mM NaOH and 1% SDS. N3 (or neutralization buffer) is 4.2M GuHCl and 0.9M potassium acetate. What is floccing out? Is it the SDS which is bound to proteins?

KDS is much less soluble than SDS, so it precipitates. The main role is to physically capture the genomic DNA to reduce gDNA contamination in the final eluted product.