Centrifuge pipette

The disc centrifuge, developed by Slater and Cohen and modified by Allen and Svarovsky [Allen and Svarowsky, Dechema Monogram, Nuremberg, Nos. 1589-1625, pp. 279-292 (1975)], is essentially a centrifugal pipette device. Size distributions are measured from the solids concentration of a series of samples withdrawn through a central drainage pillar at various time intervals. 

Disadvantages It takes 25 or 26 h until you can read your result. In addition, you have to manipulate the sample repeatedly hydrolyze, speed-vac, pipette, centrifuge, pipette, heat up. This is not only a test of your patience exactness also suffers. Hence, I fear that the Starcher assay will not be able to reach a similar number of citations as the Lowry. However, it makes the impression of being reliable, and if you need a protein determination with low protein-to-protein variation I would recommend it. 

A cyUndrical or, preferably, a pear-shaped separatory funnel (Fig. II, 1, 5, e and d) of 10-15 ml. capacity is usually employed for the separation of immiscible liquids. For separations on a smaller scale, a dropper pipette may be used the upper layer is best removed with a bent pipette as in Fig. XII, 1,3. For liquids which tend to emulsify, centrifugation (a hand centrifuge is satisfactory) will usually produce a clean line of demarcation between two immiscible liquids. 

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. 

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. 

Laboratory wares, blood and centrifuge tubes, test tubes, beakers and pipette tips. .. 

Robot operation is controlled by user-created methods stored by the microcomputer. A method contains parameters that determine how samples are processed. Such parameters as centrifugation, grinding and wash times, reagent addition, pipette aspiration and dehvery volumes, and save sample options can be specified in different methods depending on the appHcation. TTie use of methods speeds up routine analyses by minimizing user inputs and interaction. For operation, the only inputs required are... 

Equipment PCR machine, scintillation counter, tabletop centrifuge, temperature-controlled water baths, equipment for horizontal and vertical electrophoresis, UV-illuminator, phosphor imager, automatic DNA sequencer, vacuum dot-blot manifold (Schleicher and Schuell). PCR 0.5 ml hot-start mbes, aerosol resistant pipette rips, autoclaved Eppendorf tubes (all from Fischer Scientific, Brightwaters, NY) and glassware, diethyl pyrocarbonate (DEPC, Sigma)-treated solutions. 

Evaporate the organic layers of the free and total samples to dryness at 40°C under a gentle stream of nitrogen. Add 10 pi triethylamine and 100 pi of 7% penta-fluorobenzylbromide in acetonitrile and derivatize at room temperature for 15 min. Add 150 pi of 0.5 M HC1 and extract with 1 ml hexane for at least 1 min. Centrifuge the samples for 2 min at 835 xg. Pipette the hexane into a sample vial and evaporate to dryness at 40°C. Add 50 pi hexane and redissolve the residue. Samples are ready for quantification with GC-mass spectrometry (GC-MS). 

Pipette plasma, urine (both 50 pi), or CSF (200 pi) into an Eppendorf tube. Add 50 pi internal standard. Add twice 250 pi acetonitrile while vortexing. Spin down the protein at 12,000 rpm (12,000 xg) in the refrigerated microcentrifuge for 10 min. Transfer the supernatant to an evaporation vial and blow nitrogen at 37°C until dry. The residue is taken up in 200 pi buffer and vortexed. Check the pH (11). Transfer to another Eppendorf vial, add 20 pi methyl chloroformate, react at ambient temperature for 5 min (check pH > 6). Stop the reaction with 20 pi 6 M HC1 (check pH=l). Centrifuge again at 12,000 rpm (12,000xg) and 4°C for 10 min (two layers will form). The upper layer is transferred to an autosampler vial. 

After 1 h add 1.0 ml 0.73% NaCl to the chloroform/methanol extracts. Vortex and centrifuge for 5 min at 1000 xg to separate the phases. Pipette the lower chloroform phase into a Pyrex tube. Extract the upper phase twice with 1 ml chloroform and add these chloroform lower phases to the first chloroform phase take the combined chloroform phases to dryness with nitrogen. 

Add to centrifuge tube 1.6 ml Tris-HCl buffer and 0.4 ml RBC sample. Boil for 3 min while stirring with glass rod, cool on ice, then centrifuge for 10 min at 2000 xg. Decant the supernatant in a new tube and centrifuge again for 5 min at 2000 xg. Pipette... 

Pipette 5 ml of fresh random urine into a centrifugation vial and adjust the pH to... 

Pipette 0.2 ml of CSF or amniotic fluid into an Ultrafree 10000 Filter Unit (Millipore), add 40 pi of water, 30 pi of 30% (w/v) TCA, and 1 mg of Mn02 (see above) shake for 5 min at room temperature. Centrifuge for 30 min at 2000 xg. Immediately transfer the clear supernatant into a vial. For sepiapterin determination, samples should be analyzed without oxidation. 

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