Band centrifugation

This method, which is less used today, is nevertheless a great example of the use of band sedimentation technique for the simple reason that it takes advantage of the shape of the macromolecules in order to separate them. As such it is hugely instructive of the range of the technique and the manipulation that a researcher can resort to in order to exploit the technique fully. Also notable is the fact that both boundary and band centrifugation are resorted to. 

Illustration showing separation by equilibrium-density-gradient centrifugation. The homogeneous mixture in (a) separates into three bands (b) after applying centrifugal force. 

The approximate symmetry of the band is due to the fact that Bi — Bq, that is, the vibration-rotation interaction constant (Equation 5.25) is small. If we assume that B = Bq = B and neglect centrifugal distortion the wavenumbers of the i -branch transitions, v[i (J)], are given by... 

Fig. 5. Separation in Latham bowl (a) whole blood is pumped down the feed tube and enters bowl at bottom (b) centrifugal force spins denser cellular components outside, leaving plasma or platelet-rich plasma (PRP) in inner band (c) when bowl is full, plasma flows out effluent tube, followed by platelets and then leukocytes, until bowl is almost completely full of ted cells (d) after draw is completed, bowl stops spinning and uncoUected components are...

A 7.7 mg portion of band 5 was taken up in a minimum of acetone and refrigerated until crystals separated. This cold acetone mixture was centrifuged and the supernatant liquid removed by pipette. To the remaining crystals, a few drops of ice-cold ether-acetone, three to one mixture, were added, shaken, recentrifuged and the supernatant wash liquid removed by pipette. The ether-acetone wash was repeated. The resulting crystals were dried under vacuum yielding 3.3 mg of pure compound F, 17-hvdroxycorticosterone. 

Sample solution A 3 g sample of woodruff was added to 30 ml warm methanol and placed in the ultrasonic bath for 10 min. After filtration the solution was concentrated to ca. 20% of the initial volume under reduced pressure. A portion of the solution was centrifuged at 1200 rpm for 2 min and the clear supernatant was applied to the layer as a band. 

The specifications and standardization include raw materials, preparation method of the standard solution, concentration of proteins, and the main band on SDS-PAGE. The outline of the procedure for preparation of the calibrators is shovm in Eig. 4.2. Table 4.5 shows the raw materials and the preparation method of the initial extract. To prepare the calibrators, the raw materials are extracted by the standard solution containing SDS and mercaptoethanol. The initial extract is prepared by centrifugation and filtration of the extract. The diluted extract is then prepared by 10-fold dilution of the initial extract with phosphate-buffered saline (PBS pH 7.4). The protein concentration of the diluted extract is assayed using the 2-D Quant kit (Amersham Bio Sciences). The standard solution is then... 

The structure and roles of membrane microdomains (rafts) in cell membranes are under intensive study but many aspects are still unresolved. Unlike in synthetic bilayers (Fig. 2-2), no way has been found to directly visualize rafts in biomembranes [22]. Many investigators operationally define raft components as those membrane lipids and proteins (a) that remain insoluble after extraction with cold 1% Triton X-100 detergent, (b) that are recovered as a low density band that can be isolated by flotation centrifugation and (c) whose presence in this fraction should be reduced by cholesterol depletion. 

While fractions or samples can be removed from the centrifuge tubes using a pipette it is possible with appropriate equipment to pierce the base of a plastic tube to allow the contents to drip slowly out. Alternatively the contents of the tube may be displaced by slowly injecting a dense solution to the bottom of the tube (Figure 3.44) or by puncturing the tube in the appropriate position and withdrawing the desired band with a syringe. 

Fig. 12a-c. Schematic representation of the effective potential Vejf and of different possibilities of localized and itinerant states for electrons of high 1 quantum number, a) The solid line d represents the periodic potential set-up by the cores R and R +i, which is a superimposition of central potential a dashed line). The dashed line b represents the centrifugal potential of kinetic origin 1(1 + l)/2 R in an atom, and c dashed line) the effective potential V f for an atom (compare Fig. 6) and full line) for a solid, b) Relative to two shapes of the effective potential Ve, two examples of localized state are given 1. resonant state 2. fully localized state. Notice that 1. is very near to Ep. h and t represent hopping and tunneling processes, c) A narrow band is formed (resonance band), pinning Ep 3. narrow band... 

Binding proteins were eluted by 30 pL of SDS sample buffer solution, shaken at 25°C for 10 min, and centrifuged for 1 min. The resulting bands were stained with CBB, the silver method, or Western blotting, and then comparatively analyzed to identify COX2 (Fig. 2b). 

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