Amphiphilic moment

The molecular descriptors refer to the molecular size and shape, to the size and shape of hydrophilic and hydrophobic regions, and to the balance between them. Hydrogen bonding, amphiphilic moments, critical packing parameters are other useful descriptors. The VolSurf descriptors have been presented and explained in detail elsewhere [8]. The VolSurf descriptors encode physico-chemical properties and, therefore, allow both for a design in the physico-chemical property space in order to rationally modulate pharmacokinetic properties, and for establishing quantitative structure-property relationships (QSPR). 

Amphiphilic moment as vector from hydrophobic to hydrophilic domain center... 

Amphiphilic moment is defined as a vector pointing from the center of the hydrophobic... 

Amphiphilic moment A) is the vector pointing from the center of the hydro-phobic domain to the center of the hydrophilic domain. This parameter measures the distribution of the polar and nonpolar groups in the molecule. 

Amphiphilic moments are defined as vectors pointing from the center of the hydrophobic domain to the center of the hydrophilic domain of a molecule. It is defined as [Fischer, Gottschlich et al, 1998 Fischer, Kansy et al, 2001] ... 

The vector length is proportional to the strength of the amphiphilic moment and it may determine the ability of a compound to permeate a membrane [Cruciani, Crivori et al, 2000]. 

The first process is due to Schottky barriers [30], which are electrical dipole moments that form at the metal I molecule interfaces, as discussed above [34,40]. The second process arises if the electrically-active portion of the molecule is placed asymmetrically within the metal I molecule I metal sandwich. This geometry is common, because a long alkyl tail is often needed to make the molecule amphiphilic so that it will form well-ordered Langmuir-Blodgett monolayers [76-78]. 

Averaged helical hydrophobic moment ratios are evaluated in order to assess the potential of amphiphilic regions contributing to the helix-helix interaction responsible for stabilization of tropomyosin dimers. These ratios yield profiles that are higher in the amino-terminal half than in the carboxyl-terminal half of a and p tropomyosin chains. The higher profiles found in the amino-terminal half of a tropomyosin may contribute to the greater stability of the dimer in this region. 

Fig. 5 Linear Rf-Rh diblocks are amphisteric (different cross sections of the F- and //-blocks), amphiphilic (distinct cohesive energy density), and amphidynamic (distinct flexibility, conformations). The dashed arrow indicates the direction of the dipole moment arising at the CH2-CF2 connection. Reproduced with permission [66], copyright 2009, American Chemical Society (ACS)...

In addition to describing the conformation of the hydrocarbon chains for amphiphilic molecules at the A/W interface, external reflectance infrared spectroscopy is also capable of describing the orientation of the acyl chains in these monolayers as a function of the monolayer surface pressure. The analysis of the orientation distribution for an infrared dipole moment at the A/W interface proceeds based on classical electromagnetic theory of stratified layers (2). In particular, when parallel polarized radiation interacts with the A/W interface, the resultant standing electric field has contributions from both the z component of the p-polarized radiation normal to the interface, as well as the x component of the p-polarized radiation in the plane of the interface. The E field distribution for these two... 

There are many further issues that can be addressed by the model of the kind described here. Clearly, the HA model is amenable to a number of generalizations that allow one to study more sophisticated features of amphiphilic copolymers, including, for instance, backbone stiffness, orientational degrees of freedom, or additional structural constraints such as the saturation of monomer-monomer interactions [98], which are crucial, e.g., for the folding of RNA. Also, it is easy to introduce dipole moments for side H - P bonds and specific directional interactions (like hydrogen bonds) for some of the chain units. These additional factors can result in the formation of intramolecular secondary structures and lead to an increase in the stability of globules formed by such polymers. 

Hence, protonation of the poly(propylene imine)s leads to a more extended conformation of the dendritic core, resulting in a more loosely packed shell. At that moment the dendritic interior moves to the outside, while the hydrophobic chains tumble and form a bilayer. If we assume that this architecture is correct we can calculate the molecular volumes of the amphiphiles by multiplying the length of the amphiphiles by the molecular area (Table 4). 

Kucharski et al.161 have calculated the static / -hyperpolarizability of new sulphonamide amphiphiles using finite field SCF and INDO/S methods. In the latter case a solvent correction (SCRF option) was also included. The ab initio and INDO/S results for the isolated molecule were similar while the inclusion of the solvent correction increased the values by about 55-65%. Kassimi and Lin 168 have calculated the dipole moment and static polarizability of aza-substituted thiophene derivatives within the Hartree-Fock approximation. For a representative sub-set, correlation up to the MP4(SDQ4) level has been included. The results are expected to be accurate to within a few percent. 

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