Better NGS Size Selection

One of the most critical parts of a Next Generation Sequencing (NGS) workflow is library preparation and nearly all NGS library preparation methods use some type of size-selective purification. This process involves removing unwanted fragment sizes that will interfere with downstream library preparation steps, sequencing or analysis.

Different applications may involve removing undesired enzymes and buffers or removal of nucleotides, primers and adapters for NGS library or PCR sample cleanup. In dual size selection methods, large and small DNA fragments are removed to ensure optimal library sizing prior to final sequencing. In all cases, accurate size selection is key to obtaining optimal downstream performance and NGS sequencing results.

Current methods and chemistries for the purposes listed above have been in use for several years; however, they are utilized at the cost of performance and ease-of-use. Many library preparation methods involve serial purifications which can result in a loss of DNA. Current methods can result in as much as 20-30% loss with each purification step. Ultimately this may necessitate greater starting material, which may not be possible with limited, precious samples, or the incorporation of more PCR cycles which can result in sequencing bias. Sample-to-sample reproducibility is a daily challenge that is also regularly cited as an area for improvement in size-selection.

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Of Elephant Research and Wildlife Crime – Molecular Tools that Matter

Here at Promega we receive some interesting requests…

Take the case of Virginia Riddle Pearson, elephant scientist. Three years ago we received an email from Pearson requesting a donation of GoTaq G2 Taq polymerase to take with her to Africa for her field work on elephant herpesvirus. Working out of her portable field lab (a tent) in South Africa and Botswana, she needed a polymerase she could count on to perform reliably after being transported for several days (on her lap) at room temperature. Through the joint effort of her regional sales representative in New Jersey/Pennsylvania (Pearson’s lab was based out of Princeton University at the time) and our Genomics product marketing team, she received the G2 Taq she needed to take to Africa. There she was able to conduct her experiments, leading to productive results and the opportunity to continue pursuing her work. Continue reading

Easy Automated Genomic DNA Isolation for GMO Testing: From Vision to Reality

29980616-July25-PureFood---Kelly-600x300The European Union (EU) has a zero tolerance policy for products containing any material from non-authorized genetically modified (GM) crops. Seed entering EU markets may not contain even trace amounts of non-authorized genetically modified material. In 2012, as the global use of GM crops increased, seed testing loads in the EU continued to build. Isolating genomic DNA (gDNA) using traditional manual methods was becoming impractical in the face of increasing amounts of material that required testing. There was a growing need for an automated method to isolate gDNA from seed samples. Working to address this need, a group of scientists from the Bavarian Health and Food Safety Authority collaborated with scientists from Promega Corporation to evaluate the Maxwell® 16 Instrument and the associated chemistry as possible a solution for the testing labs. Continue reading

The Making of a Promega Product: Teamwork = Success for the Maxwell RSC® ccfDNA Plasma Kit

Ever think about the kinds of challenges R&D scientists run up against in the course of developing a new product? The development of the Maxwell® RSC ccfDNA (circulating cell-free DNA) Plasma Kit is a particularly interesting example. Its path to commercialization was characterized by a number of unexpected technical hurdles, yet each was overcome through creative troubleshooting and aided by valuable collaborations across departments. All had a hand in finally launching the kit last August.

26062525-ccfDNA_Mar25-blog-DNAThe product’s launch was an exciting milestone for Promega as research interest in the role of ccfDNA as biomarkers in human disease continues to grow. Elevated levels of ccfDNA have now been reported in patients with cancer, inflammatory disease, infections and cardiovascular disease. In pregnant women, up to 10% of ccfDNA can be attributed to the fetus, so critical fetal DNA analysis can now be conducted through maternal blood samples. There are many advantages in the ability to isolate and analyze ccfDNA, so the development of a kit with high throughput capability was a priority for the Nucleic Acid Purification R&D team. Continue reading

DNA Purification from Plants: Not All Methods are Equal

pestle and mortar with leavesIsolating DNA from plant tissues is difficult for many reasons.  Unlike animal cells, plant cells have rigid cell walls, often made of tough fibrous material, and contain proteins and enzymes and other compounds such as polysaccharides and polyphenols that play a role in different cellular processes. These compounds can interfere with DNA isolation as well as downstream applications such as PCR.  For these reasons, DNA isolation methods that are used successfully for other sample types may not work well to isolate DNA from plant material. Continue reading

Tips and Tricks for Successful Nucleic Acid Preparation from FFPE Samples: Webinar Preview

FFPE_molecular_analysis_workflowFormalin-fixed, paraffin-embedded (FFPE) tissue samples are extremely common sample types. In this form, tissue is easy to store for extremely long periods of time and useful for immunohistochemical studies. Additionally FFPE samples are fairly inexpensive to produce. However the formalin fixation procedure, which was developed long before the advent of molecular biology, results in chemical crosslinking of nucleic acid and protein molecules inside the cells. This crosslinking presents a challenge for isolating intact, high-quality nucleic acid DNA; so getting at the wealth of molecular information within an FFPE sample can be difficult.

In the upcoming webinar “Successfully Overcoming the Challenges of Working with FFPE Samples”, Dr. Trista Schagat of Promega Corporation discusses some of the key considerations for anyone who is attempting to isolate nucleic acid from FFPE samples. Continue reading

Extraction of Plant DNA Made Easy

By Trillium1946 at en.wikipedia (Transferred from en.wikipedia) [Public domain], from Wikimedia Commons

My one attempt at working with plant DNA when I was at the lab bench was trying to create a shotgun library from a rice BAC. Never have I needed to isolate nucleic acid from the source material, but based on my conversations with plant scientists, it can be problematic endeavor between the tough tissue and the compounds that can copurify during extraction and inhibit downstream applications. And if you want to isolate DNA or DNA from plant samples in an automated format, that just adds to the difficulties. Here I review an Applications in Plant Sciences article that compares DNA isolation using the Maxwell® 16 System with two other methods on 25 different plant species samples. The authors note that Promega provided the Maxwell® 16 instrument, DNA isolation cartridges and advice on its use. Continue reading

Freedom to Focus: Maxwell® Rapid Sample Concentrator

Wish I had one of these when I was at the lab bench...

Wish I had one of these when I was at the lab bench…

Back in the dark ages, when I was a graduate student, my idea of “automated” plasmid DNA extraction involved performing home-brew, “toothpick preps” in “strip tubes” or , if I was really feeling ambitious, a 96-well plate. I would get just enough DNA to check for the presence of an insert, but the quality of the DNA was too low and the quantity too small to even consider using it for any other downstream experiments like amplification. And increased throughput for other nucleic acid extraction needs? Nope. If I wanted genomic DNA, RNA or high-quality plasmid DNA, I spent time with columns and tubes, giving each sample my undivided individual attention. Remember cesium chloride preps for RNA isolation? Even with the advent of column purification, which greatly simplified and standardized my protocols, nucleic acid purification was still a manual task that required a lot of time and effort to get the high-quality product I needed. Doing the experiments that would answer the questions that I really wanted to ask (those “downstream experiments”), meant spending time at the bench performing careful (if tedious) work to isolate and clean up the highest quality nucleic acid possible. Even then inconsistency in sample prep could wreak havoc on downstream work. Fortunately, for the modern scientist, personal, bench top automation, has progressed far beyond the toothpick and the strip tube to quality-tested, reliable nucleic acid extraction platforms like the Maxwell® Rapid Sample Concentrator (RSC). The Maxwell® RSC improves sample preparation consistency, eliminating variability associated with manual handling, and your downstream results will reflect this consistency.  With the RSC you can extract DNA or RNA from up to 16 samples in approximately 1 hour and viral total nucleic acids in less than an hour. The instrument is easy to use: simply load the sample, push a button and walk away. Cross contamination is minimized and the instrument is supported by the Promega technical support and service you have come to trust over the past 35 years. Do you want to know more about how the Maxwell® RSC can become your research partner, giving you the freedom to focus on the work that interests you the most? Register for the free webinar and see the data for yourself: high-quality nucleic acid that performs well in downstream analyses. You’ll even be able to view videos illustrating RSC  setup and use. Register today for the free webinar.

Methods for Quantitating Your Nucleic Acid Sample

Nucleic acid quanitation webinarFor most molecular biology applications, knowing the amount of nucleic acid present in your purified sample is important. However, one quantitation method might serve better than another, depending on your situation, or you may need to weigh the benefits of a second method to assess the information from the first. Our webinar “To NanoDrop® or Not to NanoDrop®: Choosing the Most Appropriate Method for Nucleic Acid Quantitation” given by Doug Wieczorek, one of our Applications Scientists, discussed three methods for quantitating nucleic acid and outlined their strengths and weaknesses. Continue reading

Don’t Let Ribonucleases Ruin Your Week(end): Establish a Ribonuclease-free Environment

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My very first job in science was in a lab that worked exclusively with RNA, and it was only after I moved on to a different job that I learned just how much different the world of DNA research is from that of RNA. When working with DNA, for example, you rarely if ever have the sample you have labored over reduced to a fuzzy blur at the bottom of a gel because it has been degraded beyond rescue. With RNA, unfortunately, this happens all too frequently. In fact, a labmate of mine once put up a poll on the door to our lab asking if it was better to discover that your RNA sample was degraded on a Monday or a Friday.

The culprits in this scenario are Ribonucleases (RNases). They are everywhere. They are incredibly stable and difficult to inactivate. And, if you work with RNA, they are your enemy. Take heart though, they can be defeated if you follow some pretty simple steps. Continue reading