Regions disordered

We now consider the interface between a vacuum and a system that undergoes a first-order (i.e., discontinuous) order-disorder transition in the bulk at a temperature Tc. Due to missing neighbors at a surface, we expect that the order parameter at temperatures T < Tc is slightly reduced in comparison with its bulk value (fig. 67). If this situation persists up to T > T, such that both the bulk order parameter < >(z oo) and the surface order parameter 4> = z = 0) vanish discontinuous the surface stays ordered up to Tc, a situation that is not of very general interest. However, it may happen (Lipowsky, 1982, 1983, 1984, 1987 Lipowsky and Speth, 1983) that the surface region disorders somewhat already at T < Tc, and this disordered layer grows as T T and leads to a continuous... 

A total of 182 patients (73 male, 109 female) with various facial region disorders were retrospectively studied using botulinum toxin injection for the treatment of facial region disorders [19 j. Improvement in symptoms was marked and good in subjects treated for blepharospasm, hemifacial spasm, facial s5mkinesis and Meige syndrome, and moderate for oromandibular dystonia and hypersalivation. Ptosis was the most common side effect. 

Joban A, Matur Z, Hanagasi HA, ParmanY. Efficacy of botulinum toxin injections in the treatment of various types of facial region disorders. Turk Noroloji Derg 2012 18 133-61. 

The time-temperature superposition principle has been applied to the loss and storage moduli. For the homogeneous blend (one phase at temperature equal to 115 C), the superposition method works very well. Typical low frequency behaviours of G and G are shown by the lines in Figure 10. For temperatures close to (125, 135 and 140 C), a shoulder develops in the low frequency region for the storage modulus and becomes more important as the temperature is closer to T. This behaviour is similar to that observed by Bates et al. [19] for block copolymers near in the homogeneous region (disordered zone). In fact, these temperatures are well below as determined... 

The question of non-classical manifestations is particularly important in view of the chaos that we have seen is present in the classical dynamics of a multimode system, such as a polyatomic molecule, with more than one resonance coupling. Chaotic classical dynamics is expected to introduce its own peculiarities into quantum spectra [29, 77]. In Fl20, we noted that chaotic regions of phase space are readily seen in the classical dynamics corresponding to the spectroscopic Flamiltonian. Flow important are the effects of chaos in the observed spectrum, and in the wavefiinctions of tire molecule In FI2O, there were some states whose wavefiinctions appeared very disordered, in the region of the... 

A large number of ordered surface structures can be produced experimentally on single-crystal surfaces, especially with adsorbates [H]. There are also many disordered surfaces. Ordering is driven by the interactions between atoms, ions or molecules in the surface region. These forces can be of various types covalent, ionic, van der Waals, etc and there can be a mix of such types of interaction, not only within a given bond, but also from bond to bond in the same surface. A surface could, for instance, consist of a bulk material with one type of internal bonding (say, ionic). It may be covered with an overlayer of molecules with a different type of intramolecular bonding (typically covalent) and the molecules may be held to the substrate by yet another fomi of bond (e.g., van der Waals). 

The reaction corresponds to a proton transfer and not to a net formation of ions, and thus the AS is of minor importance in the whole series, especially for the two t-Bu derivatives. This last effect is believed to be due to a structure-promoting effect of the bulky alkyl groups in the disordered region outside the primary hydration sphere of the thiazolium ion (322). 

Radiation Damage. It has been known for many years that bombardment of a crystal with energetic (keV to MeV) heavy ions produces regions of lattice disorder. An implanted ion entering a soHd with an initial kinetic energy of 100 keV comes to rest in the time scale of about 10 due to both electronic and nuclear coUisions. As an ion slows down and comes to rest in a crystal, it makes a number of coUisions with the lattice atoms. In these coUisions, sufficient energy may be transferred from the ion to displace an atom from its lattice site. Lattice atoms which are displaced by an incident ion are caUed primary knock-on atoms (PKA). A PKA can in turn displace other atoms, secondary knock-ons, etc. This process creates a cascade of atomic coUisions and is coUectively referred to as the coUision, or displacement, cascade. The disorder can be directiy observed by techniques sensitive to lattice stmcture, such as electron-transmission microscopy, MeV-particle channeling, and electron diffraction. 

CoUision cascades (see Fig. 1) lead to a distribution of vacancies, interstitial atoms, and other types of lattice disorder in the region around the ion... 

Figure 9.14 The two domains of the POU region bind in tandem on opposite sides of the DNA double helix. Both the POU-specific domain and the POU homeodomain have a helix-turn-helix motif (blue and red) which binds to DNA with their recognition helices (red) in the major groove. The linker region that joins these domains is partly disordered. (Adapted from J.D. Klemm et al.. Cell 77 21-32, 1994.)...

The phosducin polypeptide chmn, of some 240 amino acids, is folded into two domains (Figure 13.16). The N-terminal domain is mostly a-helical and appears to be quite flexible since only a weak electron density is obtained in the structure determination. The actual path of the polypeptide chain from the end of helix to the beginning of helix Ba is tentative due to slight disorder. This region is close to serine 73 at the beginning of Ba, which also becomes disordered on phosphorylation. 

Figure 13.30 Ribbon diagram of the structure of Src tyrosine kinase. The structure is divided in three units starting from the N-terminus an SH3 domain (green), an SH2 domain (blue), and a tyrosine kinase (orange) that is divided into two domains and has the same fold as the cyclin dependent kinase described in Chapter 6 (see Figure 6.16a). The linker region (red) between SH2 and the kinase is bound to SH3 in a polyproline helical conformation. A tyrosine residue in the carboxy tail of the kinase is phosphorylated and bound to SH2 in its phosphotyrosine-binding site. A disordered part of the activation segment in the kinase is dashed. (Adapted from W. Xu et al.. Nature 385 595-602, 1997.)...

Progress in deducing more structural details of these fibers has instead been achieved using NMR, electron microscopy and electron diffraction. These studies reveal that the fibers contain small microcrystals of ordered regions of the polypeptide chains interspersed in a matrix of less ordered or disordered regions of the chains (Eigure 14.9). The microcrystals comprise about 30% of the protein in the fibers, are arranged in p sheets, are 70 to 100 nanometers in size, and contain trace amounts of calcium ions. It is not yet established if the p sheets are planar or twisted as proposed for the amyloid fibril discussed in the previous section. 

The molecular basis for quasi-equivalent packing was revealed by the very first structure determination to high resolution of a spherical virus, tomato bushy stunt virus. The structure of this T = 3 virus was determined to 2.9 A resolution in 1978 by Stephen Harrison and co-workers at Harvard University. The virus shell contains 180 chemically identical polypeptide chains, each of 386 amino acid residues. Each polypeptide chain folds into distinct modules an internal domain R that is disordered in the structure, a region (a) that connects R with the S domain that forms the viral shell, and, finally, a domain P that projects out from the surface. The S and P domains are joined by a hinge region (Figure 16.8). 

The N-terminal part of the tomato bushy stunt virus polypeptide chain (the R-segment in Figure 16.8) is disordered in all the subunits. As in the core of many other single-strand RNA viruses this region of the polypeptide chain... 

In order to examine whether this sequence gave a fold similar to the template, the corresponding peptide was synthesized and its structure experimentally determined by NMR methods. The result is shown in Figure 17.15 and compared to the design target whose main chain conformation is identical to that of the Zif 268 template. The folds are remarkably similar even though there are some differences in the loop region between the two p strands. The core of the molecule, which comprises seven hydrophobic side chains, is well-ordered whereas the termini are disordered. The root mean square deviation of the main chain atoms are 2.0 A for residues 3 to 26 and 1.0 A for residues 8 to 26. 

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