Packing modes

As examples of such quasi-equivalent arrangement of subunits, we will examine the T = 3 and T = 4 packing modes, both of which are found in known virus particles. In the T = 3 structure, which has 180 subunits (3 x 60),... 

Figure 15 shows a stereoscopic view of the crystalline 1 1 complex where R7 = i-CsHn and R8 = (CH2)2Ph 9). The packing mode of the four molecules in the unit cell of this complex corresponds to the association scheme of tetramer 17 (Fig. 8). Of particular interest is that a pair of groups with similar geometrical shape, NMe2 and CHMe2 [part of C6H4NMe2 and (CH2)2CHMe2], are in close contact.

Simple geometric relations exist for the packing mode of the M 4 units within the different structure types MRgMT4B4 for details see also Table 3 and Fig. 3... 

Fora comprehensive review of the packing modes of aliphatic carboxylic acids, see Leiserowitz, L. Acta Crystallogr. B 32, 775 (1976)... 

L Leiserowitz, Molecular packing modes. Carboxylic acids , Acta CrystaUogr. Section B, 1976,32,775-802... 

In addition to the regular rotation, the drive can also be used in the (fast rotating) packing mode . In particular a P-CAC column may be packed with the resin automatically in the way that the resin slurry is pumped to the annular col-... 

It follows from what has been said above that free-volume is a value that is determined by both hole volume and empty volume, the latter being connected with the packing mode. In this case an empty volume ve = vr — vw, where vr is the real (observed) volume at temperature T and vw the volume of the substances as calculated from the Van der Waals dimensions obtained by an X-ray diffraction method or from the gas-kinetic collision cross-section3. Then the expansion volume vex = v - v0, where v0 is the volume occupied by the molecules at 0 K in a close-packed crystalline state. 

Comment. All the less- or more-disordered packing modes introduced above are frequently encountered for arrays of helical molecules. The problem of disorder results in an additional (compared with most single crystal analyses) deconvolution problem when X-ray diffraction patterns of such systems are being interpreted. Although complications from disorder effects are not unique to fibrous systems, they are more frequently encountered there. I suspect that this has... 

Figure 9. The n-h map for amylose showing observed n-h values as dots on the total allowed zones. Note that there are two cluster of dots that correspond to efficient packing modes. For further information, see Ref. 4. Increments for n and h were I and 0.2 A, respectively.

L. Leiserowitz, F. Nader, The molecular packing modes and the hydrogen-bonding properties of amide dicarboxylic acid complexes, Acta Cryst. B33 (1977) 2719-2733. 

---