Receiver plates

FT-ICR detection is accomplished by monitoring the image current induced by the orbiting ion packet as it cycles between the two receiver plates of the ceU. After formation by an ionization event, all trapped ions of a given mIz have the same cyclotron frequency but have random positions in the FT-ICR cell. The net motion of the ions under these conditions does not generate a signal on the receiver plates of the FT-ICR cell because of the random locations of ions. To detect cyclotron motion, an excitation pulse must be applied to the FT-ICR cell so that the ions bunch... 

As a result of this excitation step, the net coherent ion motion produces a time-dependent signal on the receiver plates, termed the image current , which represents aU ions in the FT-ICR cell. The image current is converted to a voltage, ampMed, digitized, and Fourier transformed to yield a frequency spectrum that contains complete information about frequencies and abundances of all ions trapped in the cell. A mass spectrum can then be determined by converting frequency into mass because frequency can be measured precisely, the mass of an ion can be determined to one part in 10 or better. 

A schematic of the INSIGHT screening tool is shown in Figure 4A. The INSIGHT screen consists of two polycarbonate or Teflon plates, each 12.7 mm thick (84). The top plate consists of a square matrix of 100 wells (each 3 mm in diameter). The bottom plate contains a symmetric matrix of 100 wells. The wells in the top plate act as the donors, and the wells in the bottom plate act as the receiver chambers in a FDC. Screening of formulations is performed using pigskin as a model. The skin is sandwiched between the donor and receiver plates. The SC is exposed to the test formulations in the donor. The receiver wells are filled with phosphate buffered... 

For vapor phase measurement of dry oil oxidation, the plate assembly shown in Figure 5 is used. The lower glass or terephtha-late plastic plate holds a disk of polyamide (1.2 x 0.1 cm) on which 1 pi of a suitable oil (linoleic acid, methyl linoleate, cottonseed oil) is deposited from a micropipette. A Buna "0" ring of 1.5-mm thickness is placed surrounding the spot and a similar plate with a polyamide disk is inverted over the ring forming a tight seal when clamped with "C" clamps. The plate assembly is placed in a 65°C draft oven with the receiver plate bottommost. 

It is disassembled, the receiver plate removed, and the fluorescence measured. 

Fit a 96-well microtiter plate (200 pL) or 2-mL collection microtubes into the vacuum manifold, carefully aligning the drop-formers to the receiver plate wells. Add 100 pL elution buffer and incubate for 2 min. Then apply a vacuum of 200-400 mbar and release vacuum after material has flowed through. Store the plate of eluted proteins at 4°C for short term or until evaluated, and then at -80°C for longterm storage. 

Figure 1. Schematic representation of a cubic trapped ion cell commonly used in FTMS. Coherent motion of ions in the cell induces an image current in the receiver plates. The time domain signal is subjected to a Fourier transform algorithm to yield a mass spectrum.

Transfer 300 pL/wcll of each plasma/drug mixture to one column of each of two Multi- Screen plates with Ultracel-PPB fitted with receiver plates. Cover the assemblies with sealed plate covers or the supplied extended centrifugal covers... 

If molecules are allowed to escape from an enclosure into an evacuated space through a small hole under the conditions described for the effusion method in Section 3.3, they may be collimated into a molecular beam by the use of slits. If a pulse of this molecular beam is allowed to fall on a moving receiving plate, the condensed... 

The cyclotron orbits of thermal energy ions when they first enter the ICR cell are both too small and incoherent to be detected. However, if an excitation pulse is applied at the cyclotron frequency, the resonant ions will absorb energy and be brought into phase with the excitation pulse. They will have a larger orbital radius and the ion packets will orbit coherently. The ions may then be detected as an image current induced in the receiver plates. Additionally, this excitation pulse increases the kinetic energy of the trapped ions to the extent that fragmentation can be collisionally induced by ion—molecule reactions. Alternatively, the excitation pulse may be used to increase the cyclotron radius so that ions are ejected from the ICR cell. 

A sandwich is formed from two plates, a donor plate and a receiver plate. The donor plate is usually of a specially designed geometry, available from pION Inc. for use with its Evolution system and GUT box or from Millipore Inc. These plates are machined to minimize vortexing during shaking so that the buffer solution remains in contact with the lower surface of the receiver plate at all times without the formation of a meniscus. The receiver is a 96-well microfilter plate. The filters are generally 125 pm thick with 0.45 pm pores and 0.3 cm2 cross-sectional area with 70%... 

The samples as DM SO stock solutions are added to the donor wells and are diluted with buffer. The receiver plate is placed on top of the donor wells, the lipid solution is added carefully to ensure that there is complete coverage of the filter support, and then the buffer solution for the receiver system is added. The resulting sandwich is covered to avoid evaporation and is shaken. Figure 6.7 shows a schematic representation of the construction and incubation of the PAMPA sandwich system. 

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