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  • M13KO7 Helper Phage


    M13KO7 is an M13 derivative which carries the mutation Met40Ile in gII, with the origin of replication from P15A and the kanamycin resistance gene from Tn903 both inserted within the M13 origin of replication (1). M13KO7 is able to replicate in the absence of phagemid DNA. In the presence of a phagemid bearing a wild-type M13 or f1 origin, single-stranded phagemid is packaged preferentially and secreted into the culture medium.This allows easy production of single-stranded phagemid DNA for mutagenesis or sequencing.

    Properties and Usage

    Affinity Tag


    Storage Temperature


    Supplied As


    Long Term Storage

    • Shelf life 24 months

    Quality Control

    Quality Control Assays

    The following Quality Control Tests are performed on each new lot and meet the specifications designated for the product. Individual lot data can be found on the Product Summary Sheet/Datacard or Manual which can be found in the Supporting Documents section of this page.
    • Absolute Phage Titer:
      Infection of a mid-log culture of E. coli with phage followed by plating, yields ≥ the specified pfu/ml.
    • Functional Test (Helper Ratio) :
      M13KO7 helper phage is tested for its ability to preferentially package single-stranded phagemid and secrete the packaged phagemid into the supernatant. The supernatant is plated both for plaques and colonies on ampicillin plates to determine the ratio of packaged helper phage vs. packaged phagemid.
    • Viable Cell Titer:
      The phage suspension is tested for viable bacterial cells by plating on LB Agar.


    1. Vieira, J. and Messing, J. (1987). R. Wu and L. Grossman(Ed.), Methods Enzymol.. 153, 3-11. San Diego: Academic Press.
    2. Sambrook, J. and Russell, D.W. (2001). Sambrook, J. and Russell, D.W.. 3.17-3.32.

    Supporting Documents

    Material Safety Datasheets

    The following is a list of Material Safety Data Sheets (MSDS) that apply to this product to help you use it safely. The following file naming structure is used to name these document files: [Product Name] MSDS. For international versions please contact us at info@neb.com.


    The Product Summary Sheet, or Data Card, includes details for how to use the product, as well as details of its formulation and quality controls. The following file naming structure is used to name the majority of these document files: [Catalog Number]Datasheet-Lot[Lot Number]. For those product lots not listed below, please contact NEB at info@neb.com or fill out the Technical Support Form for appropriate document.
    1. Use of M13KO7 Helper Phage for isolation of single-stranded phagemid DNA

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