The technique makes use of an Escherichia coli strain expressing the redΑßΓ operon under the control of an inducible promoter. This enables the strain to carry out homologous recombination with only 50-60 bp of homologous sequence. The procedure does not require any DNA ligation and is very rapid. It allows a single gene or region on a cosmid to be replaced by a bi-functional selectable marker (having both an E. coli and an A. fumigatus marker). - [Read A Rapid Method for Generating Gene Deletions in Aspergillus fumigatus Protocol]
Adaptors are short double-stranded synthetic oligonucleotides that carry an internal restriction endonuclease recognition site and single-stranded tails at one or both ends. Adaptors are used to exchange restriction sites at the termini of linear DNA molecules. They may be purchased in phosphorylated and unphosphorylated forms. - [Read Attaching Adaptors to Protruding Termini Protocol]
Pairs of oligonucleotide primers used in PCR are often designed with restriction sites in their 5' regions. In many cases, the sites are different in the two primers. In this case, amplification generates a target fragment whose termini now carry new restriction sites that can be used for directional cloning into plasmid vectors. The purified fragment and the vector are digested with the appropriate restriction enzymes, ligated together, and transformed into E. coli. - [Read Cloning PCR Products by Addition of Restriction Sites to the Termini of Amplified DNA Protocol]
Protocol describes the use of PCR to screen for bacteria that carry recombinant plasmids. The PCR can be carried out using the same primers as for amplification of the cloned insert. To determine the orientation of the insert, a third, insert-specific primer that is asymmetrically distanced from the clonal insertion site can be used. - [Read Colony PCR Protocol II]
Protocol describes how subcellular-sized particles are accelerated to high velocity to carry double-stranded RNA (dsRNA) into Drosophila embryos. The major advantage of this procedure over microinjection (Microinjection of dsRNA into Drosophila Embryos) is that particle bombardment is easier and faster to perform. In addition, the mechanical trauma received is far less than by microinjection, allowing better survival of embryos and fewer phenotypic artifacts. - [Read Delivery of dsRNA into Drosophila Embryos by Gene Gun Protocol]
The simplest way to determine whether two monoclonal antibodies bind to distinct sites on a protein antigen is to carry out a competition assay. The assay can be used with antibodies that bind both conformational and linear epitopes, and it is most useful in the analysis of monoclonal antibody specificity because polyclonal sera typically recognize multiple different epitopes. - [Read Epitope Mapping by Competition Assay Protocol]
LCM technology can harvest the cells of interest directly or can isolate specific cells by cutting away unwanted cells to give histologically pure enriched cell populations. A variety of downstream applications exist: DNA genotyping and loss-of-heterozygosity (LOH) analysis, etc. Protocol provides a thorough description of LCM techniques, with an emphasis on tips and troubleshooting advice derived from LCM users. The total time required to carry out this protocol is typically 1–1.5 h. - [Read Laser-capture Microdissection Protocol]
Protocol for northern hybridization. Protocol describes how to carry out northern hybridization at high stringency in phosphate-SDS-buffers. Although a wide variety of formats are available, hybridization is usually performed in heat-sealable bags, roller bottles, or plastic boxes, as described here. - [Read Northern Hybridization Protocol]
Protocol describes methods to superinfect bacteria carrying a recombinant phagemid with a high-titer stock of an appropriate helper virus and to assay the yield of filamentous virus particles that carry single-stranded copies of the phagemid DNA. The key to success in using phagemids is to prepare a stock of helper virus whose titer is accurately known. - [Read Producing Single-stranded DNA with Phagemid Vectors Protocol]
Protocol exploits the discovery that Rnase A can efficiently cleave at single rC or rU bases embedded in double-stranded DNA. Entire plasmid vectors are amplified using long, high-fidelity PCR with riboprimers, which carry a single rC residue at their 3' end. Target DNA is amplified using similar primers, which also end in a rC residue. - [Read Ribocloning: DNA Cloning and Gene Construction Using PCR Primers Terminated with a Ribonucleotide]
Protocol for southern hybridization of radiolabeled probes to nucleic acids immobilized on membranes. Protocol describes how to carry out Southern hybridizations at high stringency in phosphate-SDS buffers. Although a wide variety of formats are available, most Southern hybridizations are carried out in heat-sealable bags, roller bottles, or plastic boxes. - [Read Southern Hybridization of Radiolabeled Probes to Nucleic Acids Immobilized on Membranes Protocol]