It is likely that you have some Z-form DNA in your mixture, but you cannot claim that you have a DNA mixture that is purely Z-form.
See the following article for the predicted CD spectra of Z-form, B-form, and A-form: http://www.sciencedirect.com/science/article/pii/S104403050700181X
Additionally, see the following article for an example of CD spectra as the B-to-Z transition is induced by increasing salt concentration: http://pubs.rsc.org/en/content/articlelanding/2014/sc/c4sc00888j#!divAbstract
In the second article, you see that for the intermediate salt concentrations (when some but not all of the DNA is in Z-form) the CD shows a negative ellipticity around 295nm without a positive band around 265 (although this band is more positive compared to lower salt concentrations.) The conductance measurements show two distinct conductance values which suggest that this is due to a difference in population of B-form and Z-form DNA and not due to individual duplexes having an intermediate structure.
Dear Theodore J Zwang
Thank you very much for your reply. it is really helpful. Thanks again.
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