Non-aggregators

Fig. 6 Radius of gyration as a function of particle weight for AX-I in several solvents. The single, non-aggregated chains has = 62000g/mol, determined with the percarbani-lated sample in dioxane [102]...

In addition to its role as the P-subunit of PHY, PDI acts independently by catalysing thiol/protein disulphide interchange. The role of PDI as the P-subunit in prolyl 4-hydroxylase is not related to its disulphide isomerase activity and experiments where the vertebrate PDI was mutated in both thioredoxin-like active domains had no effect on tetramer assembly (Vuori et al., 1992). PDI appears to function as a molecular chaperone, retaining the a-subunits in the correct catalytically active, non-aggregated form in the ER-lumen (John et al, 1993). Dissociation of the P-subunits results in insoluble aggregates of the a-subunits, analogous to a-subunits expressed in the absence of PDI. An additional function of PDI in the complex is to maintain the ER luminal location of the a-subunits, since deletion of the ER retention signal from PDI results in the secretion of the complex (Vuori et al., 1992). 

Bis(ethylacetoacetonate)-lanthanide(III) alkoxides, represented by structure (314), also initiate the well-controlled ROP of CL.895 Mn increases linearly with conversion (with Mw/Mn<1.10 throughout), and increasing [M]0/[I]o- Kinetic analysis implies a first order dependence on the lanthanide initiator, consistent with a non-aggregated active site. Block copolymers with moderately narrow polydispersities (1.25-1.45) have also been prepared using these initiators. NMR spectroscopy confirms well-controlled block sequences suggesting that these initiators are less susceptible to transesteriflcation than other lanthanide alkoxides. Initiation occurs exclusively at the alkoxide bond, and the tris(ethylacetoacetonate) analogs are inactive under the same conditions. 

Corresponding approaches were developed in all the research methods theoretical, computer simulation, and, moreover, experimental. Thus, copolymers were synthesized in vitro, which form non-aggregating structures of the type hydrophobic core-hydrophilic shell. The structure of such copolymers is similar in this respect to that of protein macromolecules [125-127]. 

S. Setayesh, A.C. Grimsdale, T. Weil, V. Enkelmann, K. Mullen, F. Meghdadi, E.J.W. List, and G. Leising, Polyfluorenes with polyphenylene dendron side chains toward non-aggregating, light-emitting polymers, J. Am. Chem. Soc., 123 946-953, 2001. 

The parameter Wi which takes the concentration of the non-aggregated surfactant in the oil into account - the cpc - is directly proportional to the radius of the reverse micelles rrev. mic. because of the volume to surface ratio of spherical droplets [64-66] ... 

Carbanionic active centers are non aggregated and sp-5 hybrid-izated. Isoregulation is ascribed to a most probable position for the complexation of active centers by the monomer molecules ... 

At low concentrations range the species tend to dissociate, increasing the concentration of non aggregated PILi, but the complexation by means of the amine drops the reactivity. At high concentrations range, the enhanced reactivity is explained by a high concentration of complexed specie (PILi/amine) despite its low reactivity compared to the non complexed specie. 

Vinogradova et al.182) found that the rate of polymerization of butadiene in petroleum ether at 20 °C reaches a maximum value when the ratio of [TMEDA] [Li] is about 4. Measurement of the flow times of a dilute solution of high molecular weight poly(butadienyl)lithium containing an equal amount of TMEDA before and after termination, suggested that the chains are largely in the non-aggregated form. Analysis of the IR spectrum showed that the stoichiometry of the complexed chain end is RLi TMEDA. 

However, the absence of a simple correlation need not be totally surprising if propagation is only through the intermediacy of a minute proportion of chains present in a non-aggregated form with the NMR spectrum reflecting the structure in the predominant aggregates. 

Worsfold and Bywater 212) have proposed that propagation through non-aggregated chains is kinetically (and not thermodynamically) controlled and yields only the carbanion having the cis conformation this can isomerize to the trans form unless the geometry is locked in by a further act of propagation ... 

Ce(IV) ions efficiently catalyse the hydrolysis of phospho monoesters in nucleotides under physiological conditions. The proposed mechanism for the hydrolysis is illustrated in (217).189 Uranyl cations (U021) catalyse the hydrolysis of aggregated and non-aggregated p-nitrophenyl phosphodiesters such as (218)/(219) and (220), respectively.190 Bis(/>-nitrophenyl) phosphate (218) hydrolysis is accelerated ca 2.8 x 109-fold by Th(IV) cations in aqueous Brij micelles.191 The reactivity of Th(IV) towards (219) and (221 R = Et, C16H33) also exceeds that of uranyl ion190 and is comparable to that of Ce(IV) and exceeds that of other metal cations. 

A comparison of the results with other data on the deposition of submicrometre aerosols, all related to a tidal volume of 11, is shown in Fig. 1.14. Although the density of the lead particles was greater than that of the other particles, the fractional deposition was similar, except possibly for the 0.5 pm size, because deposition was by Brownian motion. The percentage deposition increases for particles of diameter less than 0.1 /urn, and this means increased uptake of lead, relative to a given PbA, for persons exposed to non-aggregated aerosol, as found alongside major roads. 

Metal-free catalysts for the hydrolysis of RNA derived from 2-aminobenzimidazoles were reported. The most active catalysts, tris derivatives (99 R = H, CC Me) built upon a framework of tris(2-aminoethyl)amine, were shown by fluorescence correlation spectroscopy to aggregate with oligonucleotides. However, at very low concentrations the compounds were still active in the non-aggregated state. Conjugates of the ester (99 CC Me) with antisense oligonucleotides or RNA binding peptides will, it was claimed, be promising candidates as site specific artificial ribonucleases.98... 

Figure 2. Magnetization curves of the tCo = 0.2 ran sample fit by averaging a Langevin curve over a Gaussian distribution of sizes with a =0.26. Inset, dotted line, fit to the paramagnetic contribution of non-aggregated Co above 2500 Oe/K, thick line, contribution due to the Co clusters.

Table 1. Parameters of the Gaussian distribution of particle sizes obtained by TEM (Briatico et al., 1999) (a) and from the fit of the magnetization and susceptibility data (b). The width a is given in units of jl j. xpiriis the fraction of non-aggregated Co.

Whereas the surface area of a crystalline silica is in fact the external surface area, the surface area and the pore size distribution of an amorphous silica are actually determined by the dimensions of the silica spheres (primary particles) that build up the network. For non-aggregated spherical particles, this relationship is very straightforward. In this silica type, the primary particles are not clustered and Sheinfain s3 globular theory can be applied. The globular theory predicts an inverse relationship between surface area and the primary particle size by the following equation ... 

For enantiopure [4]helicene 19 and [5]helicene 20, which were apparently non-aggregated, small values of gabs = IgcppiJ = 0.0008-0.001 were reported [73]. 

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