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Technique: Probe Phage Genomes for Host Binding Proteins

Posted by Guest Blogger on Sep 29, 2016 10:30:00 AM

This post was contributed by guest blogger, Jessica Sacher, a microbiology PhD student at the University of Alberta studying with the Szymanski lab.

Reasons to study how a phage recognizes its host

Bacteriophages (viruses that prey on bacteria) may be the most numerous and most diverse biological entities on our planet, but we still know collectively little about how they infect and influence the evolution of their bacterial prey. Currently, receptor binding proteins (RBPs, the host recognition factors of phages) constitute one of the most popular classes of phage proteins to study. These are highly useful for the biotech industry, which is in the process of capitalizing on phage RBPs as diagnostic tools and therapeutics. In addition, the strategic use of whole phages as therapeutics, which is also gaining a lot of new traction lately (1, 2), depends on knowledge of the structure(s) a given phage will recognize on a host cell.

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Topics: Microbiology, Plasmid Protocols and Tips, Plasmids

Site Directed Mutagenesis by PCR

Posted by Guest Blogger on Aug 2, 2016 10:30:00 AM

This post was contributed by guest blogger, Kristian Laursen from Cornell University.

Site directed mutagenesis is a highly versatile technique that can be used to introduce specific nucleotide substitutions (or deletions) in a tailored manner. The approach can be used in conventional cloning (to introduce or remove restriction sites), in mapping of regulatory elements (to mutate promoters/enhancers in reporter constructs), in functional analysis of proteins (to perform alanine scanning mutagenesis or targeted substitution of key residues), and in SNP analysis (to introduce naturally occuring SNPs in a plasmid context). The technique is also highly relevant in this age of CRISPR; site-directed mutagenesis generally applies to plasmids, but may also facilitate genome editing. Tailored mutations are commonly introduced to endogeneous DNA through homology-directed repair (HDR) of a CRISPR/Cas9 induced double-stranded break. This site-directed genome editing requires a template of high homology to the endogenous target, yet to facilitate the repair, the template should be resistant to Cas9 cleavage. If a plasmid contains the template, site-directed mutagenesis can be used to mutate the PAM sequence (an NGG sequence critical for Cas9 cleavage), thereby rendering the resulting construct resistant to Cas9 induced cleavage.

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Topics: Plasmid Protocols and Tips, PCR, Plasmids

Evolution of Lab Techniques

Posted by Guest Blogger on Jun 21, 2016 10:30:00 AM

This post was contributed by guest blogger, Krissy Lyon, a PhD candidate in Neuroscience at Harvard University.

Just as computers, cell phones, and cars become more technologically advanced leaving earlier versions obsolete, the techniques we use in lab are replaced by improved versions that save both time and money. Yet, knowledge of historical techniques comes in handy whether you are perusing classic papers or are brainstorming new technological innovations. Let’s take a look at three historical techniques: southern blotting, restriction mapping, and sequencing gels, as well as their modern equivalents and see what we can learn from their evolution.

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Topics: Plasmid Protocols and Tips, Plasmids

Plasmids 101: Optimizing Plasmid Yields

Posted by Amanda Hazen on May 26, 2016 10:30:00 AM

This post was updated on March 21, 2018.

Most of the time, plasmid prepping is a breeze. You get your stab from Addgene, streak for single colonies, sub-culture, and prep with a DNA prep kit or your lab's favorite in-house protocol. DNA yields for this procedure are typically in excess of 100 ng/ul, more than enough DNA to verify your plasmid via sequencing or restriction digest.

Chances are, you’ll even have DNA left over for other applications, like PCR, cloning, transfection, or long-term storage. But what about those pesky situations where your plasmid yield is sub-optimal? If you are consistently getting sub-optimal plasmid yields from your prep, try our tips below!

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Topics: Plasmids 101, Plasmid Protocols and Tips, Plasmids

Plasmids 101: Colony PCR

Posted by Beth Kenkel on May 12, 2016 10:30:00 AM

This post was contributed by guest blogger Beth Kenkel, a Research Assistant in the Department of Pediatrics at the University of Iowa. If you're interested in guest blogging, let us know!

Molecular cloning requires some method of screening colonies for the presence of an insert. Traditionally this has been done with restriction enzyme digest; however colony PCR can accomplish the same thing in less time and for less money. The key steps to colony PCR are: 1) design primers to detect the presence of your insert; 2) set up a standard PCR reaction (primers, dNTPs, polymerase) using the supernatant of lysed bacteria as template; and 3) run your PCR product on a gel to analyze product size. This blog post discusses some of the key things to consider when performing colony PCR.

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Topics: Plasmids 101, Plasmid Protocols and Tips, PCR, Plasmids

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