Protein contamination - How to remove all protein from my DNA? - (Sep/22/2011 )

Hi,
My DNA extraction are using NaOH and a kitt of DNAzol. However when I measure the concentration of the DNA using spec at 260/280 i've got 3.57 for NaOH and 2.89 for DNAzol. My friend said it may be due to protein contamination.
So my question is: how to remove all the protein and obtain pure DNA concentration?

Perhaps a proteinase K treatment before DNA extraction could be helpful.

A phenol choroform extraction removes all proteins. Make sure to do a chloroform only extract to remove traces of phenol from the final product.

Thanks for the suggestions. However, actually i don't want to use phenol-chloroform since i'm doing a research of comparing 3 different methods of DNA extraction. Besides NaOH and DNAzol, i'm also using method extraction of phenol-chloroform & isoamylic acohol. So i don't want to mix these method cause i'm afraid it will affect my results of comparison.
So is there any other suggestion of how to remove the contaminant which i assume proteins?