Gold, colloidal preparation

Remove excess antibody by centrifuging the colloidal gold preparation twice on a glycerol step gradient (see Note 5). 

This relationship permits of experimental verification by direct observation of the diffusion coefficient and the measurement of the radius of the particle. Svedberg Zeit. Phys. Chem. LXVII. 105, 1907 Archiv f Kemi, etc., K. Svmska Vetensk. Akad. Stockholm, B, IV. 12,1911) employed colloidal gold prepared by reduction with phosphorus according to the directions of Faraday and Zsigmondy. 

Suspensions of colloidal gold prepared by Michael Faraday (1791-1867) are still on exhibit at the British Museum. 

Vorobyova, S.A., Sobal, N.S., and Lesnikovich, A.L, Colloidal gold, prepared by interphase reduction, Colloids Surf., 176, 273-277, 2001. 

This ion is very easily reduced to gold, and hence alkaline solutions of chloraurates(III) (often wrongly called gold chloride ) are used with a reducing agent to prepare colloidal gold. 

Ultramicroscope, Shaker Verlag, Aachen (b) Turkevich, J. (1985) Colloidal gold. Part I. Flistorical and preparative aspects, morphology and structure. 

Mahdihassan, S. Colloidal gold as an alchemical preparation. Janus 58 (Jan 1971) 112-118. 

Non-Aqueous Colloidal Metal Solutions. It has been difficult to prepare colloidal gold in non-aqueous media due to limitations in preparative methods (low salt solubilities, solvent reactivity, etc.), and the fact that the low dielectric constant of organic solvents has hindered stabilization of the particles. In aqueous solution the gold particles are stabilized by adsorption of innocent ions, such as chloride, and thus stabilized toward flocculation by the formation of a charged double layer, which is dependent on a solvent of high dielectric constant. Thus, it seemed that such electronic stabilization would be poor in organic media. 

Most preparations of colloidal gold consist of particles varying in diameter from about 5 nm to around 150 nm. The methods of forming small particle gold suspensions of known diameter are discussed in Section 2. 

The following sections discuss the preparation of colloidal gold suspensions of various particle sizes and their use in labeling proteins for detection purposes. Gold-labeled molecules and proteins are available from a number of manufacturers (Janssen, E-Y Labs, and Nanoprobes). 

Mix a stabilizing amount of antibody plus an additional 10 percent with the appropriate volume of colloidal gold. For example, Geoghegan (1988) found that an addition of 10-14 pg of antibody per ml of gold colloid resulted in stable preparations. Mix well after addition of antibody to the gold suspension. 

Considerable research effort was focused on systems of colloidal gold of which a broad variety of synthetic procedures were reported [140 b, fj. While native colloidal gold solutions are only stable for a restricted time, Brust et al. [141] were able to overcome this problem by developing a simple method for the in situ preparation of alkyl thiol-stabihzed gold nanoparticles. This synthetic route yields air-stable and easy to handle passivated nanoparticles of moderate polydispersity, and is now commonly employed for the preparation of inorganic-organic core-shell composites. Such composites are used as catalytic systems with principally two different functions of the protective 3D-SAM layer. Either the metal nanoparticle core can be used as the catalytically active center and the thiol layer is only used to stabihze the system [142], or the 3D-SAM is used as a Hnker system to chemically attach further catalytic functions [143]. 

Muhlpfordt, J. A. (1982) The preparation of colloidal gold particles using tannic acid as an additional reducing agent. Experientia 38, 1127-1128. 

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