Editorial Expression of Concern and Correction

APPLIED BIOLOGICAL SCIENCES PNAS is publishing an Editorial Expression of Concern regarding the following article: “Use of combinatorial genetic libraries to humanize N-linked glycosylation in the yeast Pichiapastoris,” by Byung-Kwon Choi, Piotr Bobrowicz, Robert C. Davidson, Stephen R. Hamilton, David H. Kung, Huijuan Li, Robert G. Miele, Juergen H. Nett, Stefan Wildt, and Tillman U. Gerngross, which appeared in issue 9, April 29, 2003, of Proc Natl Acad Sci USA (100:5022–5027; first published April 17, 2003; 10.1073/ pnas.0931263100). It has recently come to the attention of the editors that, since the time of submission to PNAS, patent protection and intellectual property issues have prevented the distribution of the yeast strains described in the above-noted article to qualified investigators. This is a violation of PNAS editorial policy and we are publishing this statement to alert readers. PNAS authors must ensure that all unique reagents described in their published paper are available to qualified researchers, and any restrictions on the sharing of materials must be disclosed to the editorial office at the time of submission (www.pnas.org/site/misc/iforc.shtml#viii).