Packing Angle

For standard designs, the pack angle <01. plale length L [Pg.186]

As the o-helix has 3.6 residues per turn, hydrophobic side chains spaced at combinations of three and four residues apart are required to make an amphipathic structure. For helices in globular proteins, a variety of combinations of three-plus-four spacings of hydrophobic residues are observed (Chothia et al., 1981). This leads to a range of helix-helix packing angles and arrangements. However, to form more persistent fibrous coiled-coil... 

Fig. 2. Helix packing angle ( 2) distributions. Gray bars The distribution of angles seen in 3498 helix packing interactions from soluble proteins. Black bars The distribution seen in 88 helix interactions from the membrane proteins, bacteriorhodopsin, bovine cytochrome c oxidase, and photosynthetic reaction center (Bowie, 1997a).

Fig. 15.8. Schematic representation of the orientation of a helices at the common packing angles. The dihedral angle is positive if the second helix (behind) is obtained by clockwise rotation of the first (in front)...

Packing Angle (degrees) Equivalent Diameter (mm) Constant Cj... 

Packing Angle (d iees) Equivalent IXameter (mm) Constant Q... 

Apart from these simple silanes, derivatives witli aromatic groups at different places in tire chain have also been investigated [136, 137], It was found tliat tire average tilt angle of tliese molecules depends on tire specific functional entities contained in tire chains. It is likely tliat apart from packing considerations—important for bulky groups, for example—otlier factors also influence tire resulting tilt. 

The systematic study of alkanetliiols (CH2(CH2) -SH) witli different chain lengtlis revealed tliat for = 11 or greater closely packed layers are obtained witli a tilt angle of tire alkyl chains between 30 and 35° from tire surface... 

Compressibility. The bulk density of a soHd is an essential value used in the analysis of its flow properties, such as when calculating mass flow hopper angles, opening sizes, bin loads, etc. Loose and/or packed density values ate not sufficient. Bulk soHds exhibit a range of densities that vary as a function of consoHdating pressure. This range of densities, called the compressibiHty of the soHd, can often be expressed on a log—log plot as a line or relationship. 

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