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Diversity of Phage-Displayed Libraries of Peptides during Panning and Amplification
Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada
School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
Department of Bioengineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
* Author to whom correspondence should be addressed.
Received: 27 December 2010; in revised form: 10 February 2011 / Accepted: 17 February 2011 / Published: 21 February 2011
Abstract: The amplification of phage-displayed libraries is an essential step in the selection of ligands from these libraries. The amplification of libraries, however, decreases their diversity and limits the number of binding clones that a screen can identify. While this decrease might not be a problem for screens against targets with a single binding site (e.g., proteins), it can severely hinder the identification of useful ligands for targets with multiple binding sites (e.g., cells). This review aims to characterize the loss in the diversity of libraries during amplification. Analysis of the peptide sequences obtained in several hundred screens of peptide libraries shows explicitly that there is a significant decrease in library diversity that occurs during the amplification of phage in bacteria. This loss during amplification is not unique to specific libraries: it is observed in many of the phage display systems we have surveyed. The loss in library diversity originates from competition among phage clones in a common pool of bacteria. Based on growth data from the literature and models of phage growth, we show that this competition originates from growth rate differences of only a few percent for different phage clones. We summarize the findings using a simple two-dimensional “phage phase diagram”, which describes how the collapse of libraries, due to panning and amplification, leads to the identification of only a subset of the available ligands. This review also highlights techniques that allow elimination of amplification-induced losses of diversity, and how these techniques can be used to improve phage-display selection and enable the identification of novel ligands.
Keywords: phage display; diversity; competition; amplification; fast-growing clones
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Derda, R.; Tang, S.K.; Li, S.C.; Ng, S.; Matochko, W.; Jafari, M.R. Diversity of Phage-Displayed Libraries of Peptides during Panning and Amplification. Molecules 2011, 16, 1776-1803.
Derda R, Tang SK, Li SC, Ng S, Matochko W, Jafari MR. Diversity of Phage-Displayed Libraries of Peptides during Panning and Amplification. Molecules. 2011; 16(2):1776-1803.
Derda, Ratmir; Tang, Sindy K.; Li, S. Cory; Ng, Simon; Matochko, Wadim; Jafari, Mohammad R. 2011. "Diversity of Phage-Displayed Libraries of Peptides during Panning and Amplification." Molecules 16, no. 2: 1776-1803.