Colloidal gold advantages

Electron microscopy permits the detailed study of cell relationships within tissues and organelles within cells. Two ultrastructural techniques in which gold probes have proven invaluable are mununocytochemistry and in situ hybridization, and these will be described here. Until 1980, peroxidase was the marker of choice, but now colloidal gold is almost universally used. The advantages of colloidal gold are that ... 

Biotin is a small vitamin molecule (Mr 244) that binds with highaffinity (kD 10 I5M I) to avidin. Avidin is a larger glycoprotein molecule (Mr 70,000), mostly distributed in egg whites. This protein has the advantage of conjugating with different markers, including peroxidase, fluorescent dyes, colloidal gold, and ferritin. Because of this property it is... 

Besides hydrolysis, one can also utilize other exchange reactions in the preparation of disperse systems. It is, however, important to remember that a substantial amount of electrolyte, which is often present in the solution, may result in a loss of colloidal stability. One can sometimes remove excess electrolyte by washing and subsequent peptization of the precipitate. It is advantageous to prepare disperse systems at high supersaturations, which can be reached upon mixing concentrated solutions of reactants. The sols of Prussian Blue, various sulfides, stannic acid and its compound with colloidal gold (Cassian Purple) are all made by this method. 

Early studies relied on colloidal platinum or RO2 although other metals, e.g. Rh and Pd, have been employed. Ru, Au, Ir and Ag ° are reported to be ineffective, although some authors have claimed H2 production using a colloidal gold redox catalyst. RUO2 is active for hydrogen production from and has the added advantage that it does not catalyze the... 

Finally, colloidal gold offers some unique advantages over other labelling agents, e.g. QDs or organic dyes. For instance, it does not undergo any photodecomposition. 

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