Stack columns

Some thiophenolate monolayers also have been investigated. Thiophenolate, C H S—, forms ordered monolayers on Ag(lll) with a (/7 X v, 88°)R40.9°, and benzene rings closely packed in face-to-face stacked columns (294). Benzylthiolate (295),/xpyridinethiolate (296), and (9-pyridinethiolate (296), also form ordered monolayers on Ag(lll), but with fewer close-packed aromatic rings. 

Four column systems are available from Amersham Pharmacia Biotech that can be used to pack SEC media for various applications at the laboratory scale. These include C, XK, SR, and HR column systems. All of the laboratory-scale columns are constructed with borosilicate glass tubes. Columns for larger scale process applications include INdEX, BPG, EineLINE, BPSS, and Stack columns. The larger scale columns are constructed to meet stringent validation requirements for the production of biopharmaceuticals. Each of the column types are described. 

Stack columns are a modular process system that allows several column units to be stacked in series. This column system is well suited for packing soft compressible gels in short segments that can then be hooked in series. The... 

In some cases the column construction used does not support a movable adapter, e.g., the popular stack column (see Section V) where a stable bed is achieved by shrinking the gel slightly in an ethanol-water mixture prior to packing. After the column is packed and the column has been closed the gel is allowed to expand by equilibrating the column in distilled water. 

Figure 3. Cofacial 7i-stacked columns of alternating [Fe(Cp )2] cations and 2a anions.

Figure 7. Edge-to-edge sheets (A) and 7r-stacked columns (B) of [MeFT][4a].

The TT-stacked eolumns are detailed in Figure 7B and are eomprised of alternating sets of one 4a anion to two methylpyridinimn eations, and thus all of the cations in the crystal reside within these 7i-stacked columns. In contrast to the anions comprising the edge-to-edge sheets, the anions here are completely planar (<1 deviation). The face-to-face distance between anions and cations is 3.6... 

Figure 13. Short contacts between anions in [Et4N][ll] (A) and 7i-stacked columns of 12 (B).

Irrespective of its biological function, the DNA double helix may be described as a prototype 7r-stacked column and therefore a novel medium through which to examine electron-transfer reactions. The double helix is a polymer containing a relatively rigid, electronically coupled column of stacked base pairs within a water-soluble polyanion, the sugar-phosphate backbone. The electronic coupling within the column is reflected in the extensive hypochromicity of the stacked double helix compared to the random coil, and it is this stacking interaction that accounts substantially for the stabilization of the helical form (23). 

Analogous studies have been carried out on dichalcogen-bridged acenaphthenes (3). The crystal structure was determined for the complex with TCNQ. Both acceptor and donor were found to take planar conformations. They form unusual modified, mixed stacking columns along the [1.1.1] direction. A pair of donors and a pair of acceptors make an alternately stacking column <88BCJ20I3>. 

Sephadex G-100 stack column Elute with 0.01 M phosphate buffer (140 L, pH 7.0)... 

Figure 15-11. Stacked column arrangement for cough syrup analysis.

Planar coordination compounds with aromatic ligands (Fig. 42), especially those having extended 77 systems, show 77-77 interaction in solid states. In alkene or alkyne 77-bonded Cud) complexes, in-plane coordination ofaC = CorC = C bond to trigonal planar Cu(I) centers often leads to planar molecular conformations (167-171). The infinite 77-77 stacking columns are confirmed in the 2,2 -bipyridine (L55) com-... 

L46 molecules and a water oxygen. The coordinated molecules form an alternating 77-77 stacking column, with the nearest intermolecular separation being 3.46 A. 

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