Kristi Myers

  1. Stirring Magnetic Beads in 500ml Bottles with Demagnetized Stir Bars

    We make stir devices that create a powerful vortex and the centrifugal forces are strong enough to keep magnetic beads suspended.

    Our part: VP 776-8-50DM is a demagnetized, round, PTFE encapsulated Alnico stir bar  50mm  long & 8mm in diameter. When used in combination with the VP 710D2 Multi Stirrus™, your magnetic beads will remain in uniform suspension. They are only weakly attached to the stir bar, and the centrifugal forces easily dislodges them and keeps them from settling to the bottom of the bottle.

    The same approach can be used for mixing magnetic beads in automation-friendly reservoirs with the use of our parylene encapsulated stainless steel bubble paddles. 

    Watch this video for a demonstration.

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  2. Drop-seq: Single-Cell RNA-Seq Protocol

    The new Single-Cell RNA-Sequencing protocol called “Drop-Seq” uses V&P Scientific’s Magnetic Tumble Stirrer {VP 710D2}, Support Stand {VP 710D2-4}, and Magnetic Stir Discs for stirring in a syringe on a syringe pump.

     A very interesting paper was recently published in Cell titled, “Highly Parallel Genome-Wide Expression Profiling of Individual Cells Using Nanoliter Droplets,” by Evan Macosko et al in the Steve McCarroll lab at Harvard.

     As a former bench scientist who has done her share of gene expression analyses the really old fashioned way, from large numbers of cells of singular origin, like a culture flask of yeast, I can attest that this Drop-seq method is a powerful system these researchers have developed to study complex mixtures of cells at the single cell level.

    Read their article to see how the Drop-seq method can be used in your own research. 

    I will explain the use of V&P Magnetic Tumble Stirrer in the Drop-seq protocol to ensure proper setup & use for fellow researchers.

    I would follow what the researchers have outlined in their protocol for the mixing of the beads. However, I would like to add some details to their setup description. They have a nice diagram of the relative positions of the syringe pumps and the microscope, but it does not include the position of the VP 710D2 relative to the syringe pump it is stirring. They do describe putting the syringe pump in a vertical position such as this:

    But what they don’t mention is the VP 710D2-4 Support Stand, which was designed for use when mixing in syringes on syringe pumps. The Stand positions the VP 710D2 above the syringe  to allow for more effective stirring by keeping the Magnetic Stirrer away from the pump. The reason for this can be found here.

    The magnetic stir bars mentioned for use within the syringe are actually stir discs! The thin, Parylene-coated Neodymium discs work well at a distance and do not interfere with the dispensing of fluid from the syringe. They are autoclavable, and priced so that they can be disposable. See our webpage for more information on these and other magnetic stir discs from V&P Scientific.

    This combination of V&P's innovative magnetic Tumble Stirrer and unique magnetic Stir Discs assisted Evan Macosko and the McCarroll lab at Harvard develop a method that, to paraphrase the title of their paper, profiles the genome-wide expression of individual cells on a large scale. We would love to help you do something similar with your research!

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  3. Magnetically Mixing Magnetic Beads for Dispensing: Large Volumes in a Bottle

    V&P Scientific is known for solving challenging mixing applications... We've done it again!

    We have several methods for magnetically mixing magnetic beads while dispensing to tubes or microplates from a container of concentrated stock.

    Starting small, one such method would be manually dispensing magnetic beads using a single pipette tip from a 1.5 ml tube with a Sandwich Style Stir Paddle VP 772FN-6-34, in which the magnet is kept out of the solution by being at the top of the Stir Paddle.

    Moving from small to medium size volumes, magnetic bead dispensing can be accomplished from 15 ml and 50 ml tubes with automated microplate dispensing instruments such as a Formulatrix Mantis or a ThermoScientific MultiDrop.

    Also in the medium volume range from 25 to 350 ml, multichannel pipettes {manual or automated} can be used to dispense magnetic beads from V&P’s Bubble Paddle Reservoirs {see Blog from Oct 23rd, 2015}.

    But how to mix the larger volumes used in cases where large batches of magnetic beads are being prepared and then dispensed?

    V&P Scientific introduces Magnetic Mixing of Magnetic Beads in a 500ml bottle with our VP 710D2 MultiStirrus in “conventional stir plate mode” and one of our “standard” PTFE-Encapsulated Magnetic Stir Bars, VP 776-10-80!

    Magnetic Stirrer VP 710D2 with VP 710D2-3 Accessory Stand {left}, PTFE Alnico Magnetic Stir Bars, VP 776-10-80 {middle} and VP 776-10-80C {right}.

    Because of the thickness of the PTFE around the not-so-strong Alnico magnetic core, the magnetic beads that do collect on the ends of the bar are easily spun off, within seconds, once the VP 710D2 MultiStirrus Stir Plate is turned on.

                                            10 seconds                                                           20 seconds                                               30 seconds                                

    And after the Magnetic Stir Bar is removed from the mixed solution, the only beads on the bar are held there by surface tension of the buffer! See below how easily they wash off with a small amount of buffer!

    The advantage of using our VP 710D2 MultiStirrus Stir Plate? It offers better magnetic coupling to our Alnico stir bars so that even viscous and concentrated magnetic bead solutions can be mixed in larger volumes.

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