Self-aggregation

Renilla luciferase. The luciferase of Renilla reniformis has been purified and characterized by Karkhanis and Cormier (1971) and Matthews et al. (1977a). The purified luciferase has a molecular weight of 35,000, and catalyzes the luminescence reaction of coelenterazine. The luciferase-catalyzed luminescence is optimum at pH 7.4, at a temperature of 32°C, and in the presence of 0.5 M salt (such as NaCl or KC1). The luciferase has a specific activity of 1.8 x 1015 photons s"1mg"1, and a turnover number of 111/min. The luminescence spectrum shows a maximum at 480 nm. The absorbance A28O of a 0.1% luciferase solution is 2.1. The luciferase has a tendency to self-aggregate, forming higher molecular weight species of lower luminescence activities. 

Morishima etal. [29 — 31] prepared amphiphilic copolymers of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) with various hydrophobic comonomers, and studied the tendency of their self-aggregation and the nature of the hydrophobic microdomains thus formed in aqueous solution. Chart 1 shows some of these amphiphilic copolymers. Here, the value of x indicates the mol% content of hydrophobic comonomer units. 

It represents the critical St content in the copolymer in the sense that it is the onset of progressive self-aggregation of the St groups. 

NMR line broadening occurred more pronouncedly for copolymers with aromatic hydrophobic units than for those with aliphatic ones [31]. This implies that polycyclic aromatic rings tend to be more tightly packed when self-aggregating than do aliphatic groups. 

The presence of a critical St content in ASt-x can also be seen in fluorescence spectra [29], This copolymer in aqueous solution shows an excimer emission peaking at 325 nra. As shown in Fig. 8, the intensity of the excimer emission increases, while the monomer emission decreases, with increasing St content. Eventually the excimer dominates the monomer emission at an St content of 72 mol%. The excimer emission becomes apparent at an St content of about 50 mol%, which agrees with the critical St content estimated by viscometry and NMR spectroscopy. The existence of the critical St content suggests the hydro-phobic self-aggregation to be a cooperative process. 

Lee et al. reported a novel and simple method for delivery of adriamycin using self-aggregates of deoxycholic acid modified chitosan. Deoxycholic acid was covalently conjugated to chitosan via a carbodiimide-mediated reaction generating self-aggregated chitosan nanoparticles. Adriamycin was... 

Huxley suggested that crossbridges can move out in this way and bind to actin because S-2 of HMM acted as a flexible link between LMM in the thick filament backbone and S-1. This was based on the observation that heavy meromyosin could be digested by chymotrypsin into two further subffagments (Lowey et al., 1966), S-1 and S-2, as described above, and that S-1 contained the ATPase and actin binding sites, whereas S-2 did not moreover, S-2 did not self-aggregate, as did the rod or LMM portion of myosin. 

Miyata, Y. Yahara, I. (1992). The 90-kDa heat shock protein, hsp90, binds and protects casein kinase 11 from self aggregation and enhances its kinase activity. J. Biol. Chem. 267, 7042-7047. 

Bovine growth hormone, a difficult protein for which to develop controlled release systems due to its propensity toward self-aggregation and inactivation, has successfully been incorporated into polyanhydride matrices (18). The growth hormone was colyophilized with sucrose, dry-mixed with finely powdered polyanhydride, and then compression molded into 1.4-cm-diaraeter wafers, 1 mm thick. As is shown in Fig. 15, release of bovine growth hormone was well controlled over a prolonged period of time. The assay for bovine... 

FIG. 42 Schematic of the self-aggregation process for semiconductor nanoparticles. 

We have found that dendrimers can be used to encapsulate active moieties, thereby preventing them from interacting. This passivation effect limits inter-molecular interactions such as self-aggregation and molecular clustering. We also found that dendrimers can be made dipolar. This asymmetry in molecular orientation enables dendrimers to be used in NLO. In this chapter we describe our application of dendrimers to lasers and NLO. 

Houbiers, C. et al.. Color stabilization of malvidin 3-glucoside self-aggregation on the of flavylium cation and copigmentation with the Z-chalcone form, J. Phys. Chem. B, 102, 3578, 1998. 

Aqueous micellar solutions, i.e. solutions containing a surfactant at a concentration above its critical micelle concentration, have been studied extensively during the last decade, in part from curiosity, and because of the possibility of providing unique chromatographic selectivity compared to conventional RPC [345-349]. Above the critical micelle concentration individual surfactant molecules self-aggregate to form structures known as micelles which are microscopically... 

Associates (donor-acceptor complexes or salts, self-aggregates and hydrogen-bonded conjugates)... 

Rossotti and co-workers45 introduced the term "oligomers for dimers and even multimers or ra-mers in non-aqueous solutions real examples of such self-aggregates (non-hydrogen bonded) have been reported46 for quaternary ammonium thiocyanates, iodides and perchlorates with ra-mers with n even up to 20. 

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