The Optima™ MAX benchtop ultracentrifuge is a high-speed, easy-to-operate ultracentrifuge for a variety of applications. Due to its direct drive induction motor with thermoelectronic air-cooling and moisture-purging vacuum system, the Optima™ MAX is a low-maintenance instrument. When placing the rotor in the chamber, it is automatically secured to the drive hub through the self-locking rotor attachment, which is audible by a click-sound. The running parameters are microprocessor controlled and can be set easily and quickly at the display by entering the temperature (0 to 40 degree Celsius in 1 degree increments), speed (≤ 1019000 x g in 50 rpm settings), time (minutes, hours, hold), one of the 10 acceleration and 11 deceleration profiles followed by pressing enter and then start. Up to 10 centrifugation programs can be stored by users. A diagnostic display alerts the user to condition issues and errors (explanations in manual). Due to the use of a standard electrical connection and its small size, the Optima™ MAX can be placed on a benchtop, a pedestal table or in a fume hood. Beckmann offers a wide selection of fixed-angle and swinging bucket Titanium rotors (ML and TL Series) for different thin- and thick-wall polyallomer or polycarbonate tubes for centrifugation of solutions, from a few microliters to 64 ml. Therefore, the centrifuge can be used for a variety of applications, e.g. pelleting proteins, membranes, viruses or DNA, as well as separation of proteins or DNA on density gradients. The shorter path length of the tubes and the high speed shorten the centrifugation time necessary with conventional ultracentrifuges. The Optima™ MAX drive is very imbalance tolerant, accommodating differences in tube fillings up to 10% for opposing tubes, even though the company recommends balancing the tubes.
For pelleting membranes isolated from primary rat brain oligodendrocytes and astrocytes, I used the fixed angle rotor TLA-55 at close to maximum speed (99500 x g, 30 min). About 30 min before I started the centrifugation, I set the temperature to 4°C to cool the rotor chamber under vacuum. Since we performed most centrifugations with proteins, we always kept the rotors in the cold room for immediate use. Using the fixed-angle TLA-55 rotor, I could pipette my sample (usually 500-800 µl) into a 1.5 ml conical polyallomer centrifuge tube, specifically developed for high-speed centrifugation. I liked to use the centrifuge not only because of the smaller and much lighter rotors, but also because it is possible to centrifuge small volumes at high speed without needing to completely fill the tubes (in order to avoid there collapse). For isolating lipid rafts from solubilized membranes on a discontinuous density gradient, I used the TLS-55 rotor with swinging buckets and thin-wall polyallomer tubes. Since the gradient/sample volume was only 2.2 ml, the separation of the lipid rafts into the expected density band needed only 2 hours instead of the 18 hours needed for a 12 ml gradient in a swinging bucket rotor in a floor-model ultracentrifuge. The Optima™ MAX centrifuge saves not only time by cutting down the centrifugation time necessary for the application, but also allows quick access when placed on a laboratory bench; in addition, placement in the laboratory avoids longer transportation through the hallway, which is especially useful for sensitive samples (e.g. a density gradient).
For centrifugation of smaller volumes and/or shorter times, I highly recommend using the Optima™ Max centrifuge. It is easy to operate and allows you to perform a variety of applications with the different available rotors; it is also easy to maintain. Beckman Coulter’s website provides a brochure, a list of accessories and tubes available for the Optima™ MAX table top centrifuges as well as many protocols. The website also has a calculation option, to convert the speed and centrifugation time between different Beckman Coulter rotors; this feature is especially helpful when establishing a method from a protocol where a different rotor type was used.