PE Biosystems Group's $330 million stock acquisition of Third Wave Technologies Inc. raises the possibility that some of the best private companies - and hence the best of the IPO candidates - might be picked off before they have a chance to go public.

While Third Wave (Madison, Wis.) had not yet filed for an IPO, it was no secret that the developer of single nucleotide polymorphism (SNP) detection systems was an IPO candidate for the first half of this year.