Oligo aggregation

Aggregation of proteins into oligo- and poly-globular complexes. In this case the opposite situation will occur, i.e., a shift of the density of bands towards the high-molecular weight zone (start). 

Figure 11.22 (a) Cholesteryl-oligo(L-lactic acid)-(lysine) G2 amphiphiles and (b) variations in aggregate morphology with dendron generation. 

Electrostatic self-assembly was combined with supramolecular chemistry to obtain inclusion complexes of a polymeric nonlinear optical (NLO) active dye and modified [3-cyclodextrin with induced chromophore orientation [37], The polyanion is a N,N-diallyl-aniline and sodium-2-acrylamido-2-methylpropanesulfonate copolymer functionalized with pendant azo group. The modified /i-cyclodextrin oligo-cation was obtained by treatment of hcptakis(6-dco y-6-iodo-/i-cyclodcxtrin) with excess pyridine. A linear polyamine, chitosan, was also combined with the polyanion, for comparison. Films were deposited on glass slides by dipping them alternatively in aqueous solutions of the cation and the polyanion. UV-visible spectra indicate dye aggregation and suggest the formation of an inclusion complex of the dye with the cyclodextrin, thus isolating the chromophores. 

Note that the excess free dye often aggregates and runs as multiple bands on the gel. To avoid misidentifica-tion of the bands, it is essential to perform the precipitation step (3.1-3.4), removing the excess dye, and to run a test gel (1.3) to establish the mobility of the labeled oligo. 

A short oligo(L-alanine) segment was envisioned to induce self-assembly into high-aspect-ratio ID aggregates in solution via the formation of (5-sheets. 

Similar helical aggregates have been constructed for oligo(pyridine—pyrimidine)s and a oligo(pyridine— pyridazine) in a solution of chloroform, dichloro-methane, or pyridine.276,277 The helical structure was elucidated by NMR spectroscopy, vapor pressure osmometry, and freeze-fracture electron micrography and was supported by molecular modeling. 

Polymerization of phthalocyanines in water occurs for derivatives substituted with oligo (ethylene oxide) side-chains (27c).167 168 In the lyotropic mesophases in water supramolecular polymers are present, and a comparative aggregation study between tetraphen-ylporphyrins and phthalocyanines proved the polymerization of the phthalocyanines to be stronger.168 The strong arene—arene interactions and the flatness of the aromatic core in the phthalocyanines causes them to aggregate more strongly, also mediated by the additional hydrophobic effect. 

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