Practice Can You Use Your Existing Rotor Inventory? Most rotors are compatible only with centrifuges produced by the same manufacturer. Confirm rotor compatibility with the manufacturer of your centrifuge. What Are Your Options If You Don't Have Access to the same Rotor Cited in a procedure? Ideally you should use a rotor with the angle and radius iden tical to that cited in your protocol. If you must work with alter native equipment, consider the g force effect of the rotor format when adapting your centrifugation strategy. The g force is a uni- versal unit of measure, so selecting a rotor based on a similar g force, or RCF, will yield more reproducible results than selecting a rotor based on rpm characteristics. Conversion between RCF and rpm g force=11. 18xR(rpm/1000 Rotor format Protocols designed for a swinging-bucket rotor cannot be easily onverted for use in a fixed-angle rotor The converse is also true Rotor Angle The shallower the rotor angle( the closer to vertical), the shorter the distance traveled by the sample, and the faster centrifugation proceeds. This parameter also alters the shape of a gradient gen- erated during centrifugation, and the location of pelleted materi als. The closer the rotor is to horizontal, the closer the pellet will form to the bottom of the tube(Figure 4.2 ). Radius The radius exerts several influences on fixed-angle and hori- zontal rotors. The g force is calculated as follows, and holds true for standard and microcentrifuges: g force=112×103× rxrpm r=radius in cm Centrifugation force can be described as a maximum(g-max) a miminum(g-min), or an average g force(g-average) If no suffix is given, the convention is to assume that the procedure refers to g-max. These various g forces are defined for each rotor by the manufacturer Troutman et alPractice Can You Use Your Existing Rotor Inventory? Most rotors are compatible only with centrifuges produced by the same manufacturer. Confirm rotor compatibility with the manufacturer of your centrifuge. What Are Your Options If You Don’t Have Access to the Same Rotor Cited in a Procedure? Ideally you should use a rotor with the angle and radius iden￾tical to that cited in your protocol. If you must work with alter￾native equipment, consider the g force effect of the rotor format when adapting your centrifugation strategy. The g force is a uni￾versal unit of measure, so selecting a rotor based on a similar g force, or RCF, will yield more reproducible results than selecting a rotor based on rpm characteristics. Conversion between RCF and rpm Rotor Format Protocols designed for a swinging-bucket rotor cannot be easily converted for use in a fixed-angle rotor. The converse is also true. Rotor Angle The shallower the rotor angle (the closer to vertical), the shorter the distance traveled by the sample, and the faster centrifugation proceeds. This parameter also alters the shape of a gradient gen￾erated during centrifugation, and the location of pelleted materi￾als. The closer the rotor is to horizontal, the closer the pellet will form to the bottom of the tube (Figure 4.2). Radius The radius exerts several influences on fixed-angle and hori￾zontal rotors. The g force is calculated as follows, and holds true for standard and microcentrifuges: g force = 1.12 ¥ 10-5 ¥ r ¥ rpm r = radius in cm Centrifugation force can be described as a maximum (g-max), a miminum (g-min), or an average g force (g-average). If no suffix is given, the convention is to assume that the procedure refers to g-max. These various g forces are defined for each rotor by the manufacturer. g R force = ¥ 11 18 1000 ( ) 2 . rpm 58 Troutman et al