Co-assembly

Keywords Co-assembly Functionalization Molecular dynamics Self-assembly Solid phase synthesis... 

Woolfson and Mahmoud have classified the routes to preparation of decorated self-assembling peptide materials [53] as (1) co-assembly, where the functional part is already attached to a self-assembling component prior to assembly, and (2) postassembly, where a non-functionahsed self-assembled structure is modified by covalent or non-covalent means. This discussion adheres to this classification. A third route, beyond the scope of this review, is the use of structured peptides as templates for inorganic materials. Section 4.1 discusses functionalised self-assemblies formed from co-assembly-type approaches, while post-assembly modifications of self-assembled structures are considered in Sect. 4.2. 

The NMDA receptors come in four main flavours depending on which NR2 subunit (or subunits) is involved in forming the receptor (Table 3.2). Functional NMDA receptors result from the co-assembly of one or more members of three different subfamilies of subunits NRl, NR2 and NR3. 

The diversity of the GABAa subunits (Figure 3.2d) is reflected in a very complex pharmacology. Expression of the subunits in heterologous systems shows that the combinations a, (3, and y can yield functional receptors, indicating that the limitation in subunit combination is defined by expression levels and most likely cell-dependent assembly mechanisms also. The pj to p3 subunits mainly co-assemble with each other to form the GABAC receptors. 

Fig. 8.18 Schematic diagram showing the potential scope of organically functionalized magnesium phyllosilicate (shown in top centre of figure) for the preparation of functional bioinorganic nanomaterials. (A) biomolecule-induced co-assembly of exfoliated aminopro-pyl-functionalized organoclay sheets to produce layered nanocomposites containing functional protein molecules (top left) or DNA (bottom left). (B) molecular wrapping...

Nanohybrids can be prepared in the form of intercalated layered nanocomposites produced by co-assembly of guest biomolecules in the presence of exfoliated organoclay sheets (Section 8.4), or by wrapping single biomolecules in ultrathin layers of condensed organoclay oligomers (Section 8.5). Such approaches should provide new general routes towards the development of functional biomaterials with numerous applications. 

Knockout mice have also revealed further subunit requirements for the assembly of particular GABAa receptor subtypes. Thus, the absence of the a6 subunit in cerebellar granule cells results in a complete loss of 5 subunit protein, although mRNA expression levels were unaffected (59,62). These results indicate that the 8 subunit cannot be incorporated in a receptor lacking a() in cerebellar granule cells. Likewise, in 50/0 mice, the levels of a4 subunit protein are reduced in all forebrain regions in which the 8 subunit is normally abundant, pointing to a preferential co-assembly of these subunits in several neuronal populations (63). 

Keyser KT, Britto ERG, Schoepfer R, Whiting P Cooper J, Conroy W, Brozozowska-Prechtl A, Karten HJ, Lindstrom J (1993) Three subtypes of a-bungarotoxin-sensitive nicotinic acetylcholine receptors are expressed in chick brain. J Neurosci 13 442-452 Khiroug S, Harkness PC, Lamb PW, Sudweeks S, Khiroug L, Millar NS, Yakel JL (2002) Rat nicotinic ACh receptor al and fil subunits co-assemble to form functional heteromeric nicotinic receptor channels. J Physiol 540 425 34... 

NANOPOROUS AND NANOSTRUCTURED CATALYSTS Self-Assembly AND Co-Assembly of Multiple Site-Isolated Catalytic Sites on Mesoporous Materials... 

Receptors containing the as subunit are of minor abimdance in the brain (Table 1) but are expressed to a significant extent in the hippocampus, where they comprise 15%-20% of the diazepam-sensitive GABAa receptor population, predominately co-assembled with the Ps and y2 subunits. Pharmacologically, the as receptors are differentiated from aiP2y2> a2Psy2 and asP3y2 receptors by a lower affinity to CL 218,872 and near-insensitivity to zolpidem (Table 1). 

Through a co-assembling route, mesostructured lamellar molybdenum sulfides are formed hydrothermally at about 85 °C using cationic surfactant molecules as the templates. The reaction temperature and the pH value of the reaction system are important factors that affect the formation of the mesostructured compounds. The amount of the template and that of the S source are less critical in the synthesis of the compounds. For the three as-synthesized mesostructured materials, the interlayer distance increases linearly with the chain length of the surfactant. Infrared and X-ray photoelectron spectroscopy reveals that the individual inorganic layers for the three compounds are essentially the same both in composition and in structure. The formal oxidation state of the molybdenum in the materials is +4 whereas there exist S2 anions and a small amount of (S-S)2 ligands in the mesostructures. The successful synthesis of MoS-L materials indicates that mesostructured compounds can be extended to transition metal sulfides which may exhibit physico-chemical properties more diverse than non-transition metal sulfides because of the ease of the valence variation for a transition metal. 

Steinert, P. M., Chou, Y.-H., Prahlad, V., Parry, D. A. D., Marekov, L. N., Wu, K. C., Jang, S.-I., and Goldman, R. D. (1999b). A high molecular weight intermediate filament-associated protein in BHK-21 cells is nestin, a Type VI intermediate filament protein Limited co-assembly in vitro to form heteropolymers with Type III vimen-tin and Type IV a-Internexin./ Biol. Chem. 274, 9881-9890. 

Kalinin, A. E., Idler, W. W., Marekov, L. N., McPhie, P., Bowers, B., Steinert, P. M., and Steven, A. C. (2004). Co-assembly of envoplakin and periplakin into oligomers and Ca(2+)-dependent vesicle binding Implications for cornified cell envelope formation in stratified squamous epithelia./. Biol. Chem. 279, 22773-22780. 

The transfer of chirality of the amide component to the photochromic components of achiral LMWGS co-assembled within the same gel fibers, the effect of solvent on the transfer, and the interaction between chiral and achiral molecular units of the gel fibers are examined. 

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