Pipette Filling

An alternative method (Tasaki et ai, 1954) involves immersing the pipettes into 40°C methanol and then placing the assembly in a vacuum chamber. The chamber is evacuated and the alcohol allowed to boil for approximately 8 min. In this time the micropipettes are filled. The assembly is then removed from the vacuum chamber and the methanol replaced by the filling electrolyte. In about two day s time, the methyl alcohol will be replaced with electrolyte by diffusion. The disadvantage of this process is the two-day delay. 

Ideally the filling electrolyte should be a saline solution which is isotonic to the physiological system in which the microelectrode is to be used. In practice, with such solutions, too high electrode resistance results (see Section 4.4). For this reason 3m KCl is frequently used. Other electrolytes include 1 % NaCl, 2m NaCl, 0.6m K2SO4, and others. In some instances, electrode application dictates what electrolyte should be used (Eccles et ai, 1957 Boistel and Fatt, 1958 Ito et al, 1962). 

To prevent electrode plugging, freshly prepared and filtered electrolytes should be used. They should be boiled to sterilize them to avoid bacterial growth in the micropipette lumen and contamination of the life system being studied. 

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The pipette has a stated volume of 25 ml. However, due to the manufacturing process the actual volume of liquid from a particular pipette filled to the calibration mark (ignoring any random errors) is found to be 25.02 ml. This is within the permitted tolerance for a 25 ml Class A pipette ( 0.03 ml according to BS 1583 1986 [6]). This is a systematic error, as the volume of liquid delivered from the pipette will always be 0.02 ml greater than the stated volume each time the... 

McCarron We clamped the ATP via the patch pipette filling solution. 

To a solution of 0.25 mmol (58 mg) of f-)-(S )-l-amino-2-(/e/- -butyIdimelhylsilyloxymcthyi)pyrrolidinc (SASP) and 0.2 g of MgS04 in 2.5 mL of cyclohexane, 0.20 mmol of the aldehyde is added and stirred at r.t. for 20 min. The solution is filtered from the MgS04, the solvent is evaporated under reduced pressure, and the crude product is filtered through a Pasteur pipette filled with silica gel using petroleum ether/elhyl acetate (98 2). The diastereomeric excess (de, which is the ee of the aldehyde) is then determined by analytical HPLC using hexane/elhyl acetate/ isopropyl alcohol (99 1 0.2). 

Nanomat in combination with Capillary Dispenser Camag offers the advantage of easy application of sample onto TLC and HPTLC plates or sheets in the form of a small spot. The capillary pipettes, filled with sample solution, are loaded into the dispenser in magazines having closely controlled tolerances and inertness, and the tip of the capillary cannot damage the surface of the layer because it is lowered precisely onto the layer at a selected position. The capillary touches the thin layer with a constant pressure, which is determined solely by the friction against a permanent magnet. 

Thaw animal plasma sample on ice, and spin down the blood at >2,400 for 10 min to remove insoluble materials. In a sterile tissue-culture hood, fill one column of a 384-well intermediate plate with 24 pi of the blood. Mix 0.5 ml animal plasma and 25 pi of200 mM vanadate solution by pipette. Fill another column of the 384-well intermediate plate with this vanadate-control group to monitor substrate degradation in... 

Fig. 2. Filamentous actin structures in cells stimulated by attractant. Cells of D. discoideum migrate toward a micro-pipette filled with cAWlP (first bright-fleld Imag and accumulate there within 8 min (last image). Actin structures are labeled with LimEA-GFP and viewed throughout the entire cell bodies by maximum projection 1, filopodia 2 and 3, macropinocytic cups showing membrane internalization at the front and other sites of the cell surface 4 and 5, actin waves propagating on the substrate-attached cell surface. Time is indicated in seconds, tip position of the pipette by circles. Bar, f 0 p,m. In cooperation with Ulrike Engel at the Nikon Imaging Center, University of Fleidelberg.

For the micropipette assay, a droplet of a cell suspension was placed on a glass slide yielding a cell density of 5 x 10 cells/cm the droplet has a diameter of about 10 mm and a height of 3 mm. After the cells were allowed to adhere, a pipette filled with 100 pM cAMP is placed just above the glass surface. cAMP was delivered from the femtotip at a pressure ranging from 0 to 100 hPa. 

When a pipette filled with cAMP is positioned just above the fioor of a chamber, cAMP will diffuse effectively in a half-sphere. The point of the pipette is in the center of the sphere the opening of the pipette with opening is regarded as a small sphere from which cAMP diffuses. The diffusion equation is then given in sphere coordinates by ... 

Glass capillaries with an internal filament improve the pipette filling, but also may increase the noise produced by the pipette. This is because the capillarity determined by the internal filament causes the salt solutions to creep up by the internal surface of the pipettes. Furthermore, the internal filament can produce a tip deformation during the fire polishing, because the heat is not homogeneously distributed. 

SECM associated with scanning ion conductance microscopy (SICM) requires a double tip, on one side of which is a conventional microdisc electrode and on the other side is a narrow pipette filled with electrolyte and an electrode that measures ionic conductance through the mouth of the pipette with respect to another electrode in the bulk solution. When the pipette mouth is within one pipette tip radius away from the sample surface, the conductance varies sufficiently to be used as a control signal to maintain the z-position of the tip during the scans, thereby affording constant-distance SECM operations [133,134]. This methodology is fast and apparently less-challenging to implement than shear force SECM, but it requires the fabrication of double-barrel tips in which one channel is left empty and the other is filled with a conventional microdisc. 

The earliest type of ionophore-based potentiometric microelectrodes were prepared in the mid 1970s from micrometer-sized glass pipettes, filled at the end with the ionophore-doped hydrophobic phase (Figure 16). " For speciality applications, in particular, in biochemical and medical research, these microelectrodes continue to have a variety of applications. Particularly noteworthy are then-use to study intracellular ion concentrations, the release and uptake of ions into ceUs, and their recent use as... 

A second cleanup method, useful when only a few dosage units are available, employs a pipette filled with fluorosil, an acidic absorbent. An extract of the exhibit is placed on the top of the column, which is then inserted into a light box tmder UV light. The analyst can monitor the movement of the LSD via movement of the fluorescent band and place the mortar under the pipette at the appropriate time to catch the LSD. The process is shown in Figure 8.21. 

FIG U RE 1.29 (a) Video micrographs of a 15.5-pm-radius micropipette filled with an aqueous KCl solution and immersed in a DCE solution of DB18C6. No external pressure was applied to the pipette, and the micro-ITIES is flat. The insets show corresponding steady-state voltammograms of facilitated transfer of potassium (From Shao, Y. H. and M. V. Mirkin, 1998, Anal. Chem., Vol. 70, p. 3155. Used with permission), (b) Photomicrograph of a theta-pipette filled with an aqueous solution. A thin ([Pg.65]

By means of a constant-delivery dropping-pipette fill a constant amount (between 0 05 and 0 1 ml) of each dilution of the standard and test samples into each of 8 cups cut in a large plate, using a predetermined Latin square design, or into one cup in each of 16 petri-dishes, and allow to stand at laboratory temperature for about one hour. Incubate for sixteen to twenty hours at a specified temperature (usually 32° to 37 ) and then read the zones of inhibition as accurately as possible by means of a projection magnification optical device or with vernier calipers. 

Pipettes filled with water coloured with methylene blue. 

Two different arrangements were used to probe the transfer of tetraethylammonium cation (TEA+) between water and DCE [69]. Cell 1 includes a pipette filled with an aqneons solution containing supporting electrolyte (LiCl) and immersed in a DCE solution containing TEA+ ... 

Place the mesh (embryos facing out) on the inner edge of a 5-ml glass vial. Use a pas-teur pipette filled with approximately 1 ml of heptane to wash the embryos off the mesh into the vial (contaminating bits of agar will preferentially stick to the mesh). 

For lentivirus injection into the cerebellum, mice are anesthetized and fixed to the stereotaxic instrument as described above. A small cranial window is formed on the occipital bone with an electrical drill (for adult mice) or a 27-G needle (for pups), and the surface of cerebellar lobules VI-VII is exposed. A glass pipette filled with lentivirus solution is then inserted into the cerebellum. Two weeks later, mice are transcardially perfused with 4 % PFA. 

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