Self-assembly behavior

Based on the intrinsic mitochondriotropism of dequalinium and its unique self-assembly behavior, we have developed a strategy for direct mitochondrial transfection (47-49), which involves the transport of a DNA-mitochondrial leader sequence (MLS) peptide conjugate to mitochondria using DQAsomes, the liberation of this conjugate from the cationic vector upon contact with the mitochondrial outer membrane followed by DNA uptake via the mitochondrial protein import machinery. We have demonstrated that DQAsomes fulfill all essential prerequisites for a mitochondria-specific DNA delivery system they bind and condense pDNA (24), protect it from... 

Pollino JM, Week M. Supramolecular side-chain functionalized polymers synthesis and self-assembly behavior of polynorbornenes bearing Pd SCS pincer complexes. Synthesis 2002 9 1277-1285. 

The study of the self-assembly behavior of amphiphilic molecules, macromolecules and biohybrid systems, has led to the discovery of numerous spectacular and stunning nanometer and micrometer sized architectures. Only when the basic rules relating the resultant... 

Although a wide range of polymers have been investigated with various cyclodex-trins, these studies mainly focused on the IC preparation techniques and characterization of solid phases. The solution properties, such as the self - assembly behavior, dissociation, particle size an surface activity, were not commonly reported. These solution properties, especially the assembly and surface behavior, are vital for the potential applications of such systems in biomedical science, such as in controlled drug delivery. 

Molecular self-organization in solution depends critically on molecular structural features and on concentration. Molecular self-organization or aggregation in solution occurs at the critical saturation concentration when the solvency of the medium is reduced. This can be achieved by solvent evaporation, reduced temperature, addition of a nonsolvent, or a combination of all these factors. Solvato-chromism and thermochromism of conjugated polymers such as regioregular polythiophenes are two illustrative examples, respectively, of solubility and temperature effects [43-45]. It should therefore be possible to use these solution phenomena to pre-establish desirable molecular organization in the semiconductor materials before deposition. Our studies of the molecular self-assembly behavior of PQT-12, which leads to the preparation of structurally ordered semiconductor nanopartides [46], will be described. These PQT-12 nanopartides have consistently provided excellent FETcharacteristics for solution-processed OTFTs, irrespective of deposition methods. 

Kimura, Shirai and coworkers used two chiral dimeric porphyrins 95 and 96 to investigate their self-assembling behavior [162,163]. While incorporation into fibers made of the alkylamide derivatives of (fl,fl)-DACH, 95 formed stable well-resolved fibrous assemblies as visualized by transmission electron microscopy, the fluorescence of which was not quenched by external electron acceptors [162]. However, the induced CD was not detected indicating an inability of 95 to form chirally orientated aggregates under the applied conditions. In contrast, 96 was able to produce optically active inter molecular self-assemblies with an enhanced chiroptical response through the //-oxo bridging in an alkali solution, while intramolecular //-oxo dimer formation was excluded on the basis of steric reasons [163]. 

Scheme 3.3 Self-assembly behavior of self-complementary (8) and non-self-complementary (9) dipyridone modules.

In a recent report we described the preparation of cavitand 35, which bears only two tolylpyridyl moieties as bridging ligands in an AC distal position, and its self-assembly behavior with [Re(CO)5Br], which undergoes cis ligand exchange exclusively (Scheme 7.10) [45]. In this case, the self-assem bled/ac-[ Rc(CO)3352Br] cage 36 is neutral and kinetically stable at room temperature. 

Besides solution studies, a variety of thiophene derivatives have been studied in respect of their self-assembling behavior at the solid/liquid interface. Andostrene-based compounds arrange in lamellae <1999CEJ96>, urea-functionalized thiophenes assemble also in lamellae but the thiophene rings are tilted with respect to the surface due to some steric hindrance within the monolayer <2000L10385>. 

Developments in nanotechnology and control over the self-assembly behavior of components is expected to provide new insights into delivery of bioactives (Mezzenga et al. 2005 Chen et al., 2006 Sanguansri and Augustin 2006b). The development of nanoparticles with different size and structure is expected to provide a new generation of encapsulated bioactives, (Moraru et al. 2003). 

Various processes may be used to alter the size and structure of food materials at various length scales and this has the potential to modulate the self-assembly behavior of food components and alter functionality. 

Yang, S. and Zhang, S. (2006) Self-assembling behavior of designer lipid-like peptides. Supramolecular Chemistry, 18, 389-96. 

The opposite way to modulate the supramolecular structure can be provided by variation in the coil structure while maintaining the rod segment constant. The influence of cross-sectional area of coil segment upon the self-assembly behavior were explored by ABA type coil-rod-coil molecules 15 and 18 that have identical coil volume fraction (fcod = 0.78) relative to mesogenic rod segment, but different coil segments, i.e., PPO and PEO, re-... 

Polyferrocenylsilane block copolymers also phase separate in solid state to generate periodic, nanoscopic iron-rich domains that can be observed by TEM without resorting to staining techniques.24 This bulk self-assembly behavior has been studied with various block copolymers, such as PS-fe-PFS,24,52 PI-h-PFS,49 and PFS-b-PMMA.22 Additional self-assembly complications... 

The obtained PCL diol was modified with a-bromopropionyl to yield a tel-echelic ATRP macroinitiator. After ATRP of styrene, the obtained PS-b-PCL-b-PEG-fc-PCL-fc-PS revealed interesting self-assembly behavior in water forming spherical micelles, rod-like micelles, vesicles, lamellae and large compound micelles depending on the block copolymer composition and concentration (Figure 12.11). The same author also extended this concept to the synthesis of... 

Cai G, Jiang H et al (2009) Synthesis, characterization and self-assemble behavior of chltosan-0-poly([epsllon]-caprolactone). Eur Polym J 45 1674-1680... 

ITC and NMR studies on this self-assembly behavior [94] in aqueous solution revealed that the dimerization step is the key to the formation of a linear polymeric supramolecular architecture, which is driven by favorable entropic contributions. 

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