Back-to-Back - Superloop Replacement
by Hüseyin Besir, Labtimes 02/2014
Replace your breakable and expensive superloops with two unbreakable and cheap plastic syringes to load protein samples onto your affinity columns.
Affinity chromatography often requires pumping solutions of 10 to 100 ml onto the affinity columns. To this end, chromatography systems may be equipped with costly sample pumps, which dissipate considerable amounts of sample volume when the columns are loaded with small volumes. Hence, many researchers rely on small glass tubes, such as the popular superloops with volumes of 10, 50 or 150 ml, instead of a sample pump to introduce solutions into the fluid system of the chromatography device.
Hüseyin Besir’s sample loading system. The disposable plastic syringe on the right is connected with the chromatography pump. The piston of the sample loading syringe on the left is pushed inwards by its counterpart on the right.
Superloops work fine, however, they are made of glass and have a tendency to exactly follow Murphy’s law and break at the worst time of the experiment. Aside from being very tedious, this will also set you back about 600 €.
In order to avoid these problems and to minimise costs, Hüseyin Besir and his group at the EMBL Protein Expression and Purification Core Facility in Heidelberg, Germany, have developed a simple loading system based on two disposable plastic syringes. The syringes are mounted “back-to-back” in opposite directions into a specially-designed syringe clamp made of plexiglass (see picture).
The principle of the loading system is pretty straightforward. The syringe on the right side of the clamp is connected via a standard Luer lock fitting with the pump of the chromatography system. Pumping liquid into this syringe will move the piston towards the loading syringe on the left side of the clamp and will drive its piston inwards. Hence, the probe or buffer solution, which has been injected into the loading syringe will be pushed – via a tube connected to the syringe with a Luer lock system – onto the chromatography column.
The Luer lock fitting enables a cheap, simple and safe integration of disposable syringes into the circuit of the chromatography system. Pressure tests showed that syringes and Luer lock fittings withstand a pressure of at least eight Bar, which is almost two times above the pressure limit of a typical Ni-affinity column.
The disposable plastic syringes may be easily integrated into the chromatography circuit via Luer lock fittings.
Loading the column with our syringe system has several advantages over superloop loading. Mounting the syringes into the clamp is much more comfortable than the handling of the superloop and the syringes are not breakable in contrast to the glass tube of the superloop. Loading larger volumes is also easier. You just have to exchange the empty syringe against a filled one.
It also comes in very handy that the horizontal orientation of the syringe pair reduces the risk of pumping air bubbles into the chromatography system, considerably. Last but not least, the disposable syringes will save you from cumbersome cleaning of the damageable glass tubes of the superloop.
The syringe loading system needs only minor adjustments during the loading procedure. Since the pump will stop when the syringe is empty, you have to switch the valve in front of the column from “inject” to “loading” at this point, in order to continue the liquid flow. You may wish to circumvent this by simply programming the loading volume into the chromatography system software. After pumping the programmed volume onto the column, the software will automatically shift the valve from injection to loading mode.
Manufacturing the syringe clamp using plexiglas blocks should be no big deal for a scientific workshop. Alternatively, a 3D-printer may be used to prepare the parts at even lower costs. Construction plans showing details of the loading system, as well as an adapter to mount the whole system onto a chromatography device are available from Hüseyin Besir (firstname.lastname@example.org).
Last Changed: 20.03.2014