Possible mechanisms of conductivity in the combined AFM / STM and growing quantum dots of colloidal gold

Thrombocytes (TC), the avian equivalent of blood platelets, support hemostasis by aggregating at sites of injury. Studies in our lab suggested that fibrinogen (fib) is a requisite cofactor for TC aggregation but operates by an undefined mechanism. To study the interaction of fib with TC and to identify fib receptors on cells, fib was purified from pigeon plasma, conjugated to colloidal gold and used both to facilitate aggregation and as a receptor probe. Described is the application of computer assisted reconstruction and stereo whole mount microscopy to visualize the 3-D organization of fib receptors at sites of cell contact in TC aggregates and on adherent cells.Pigeon TC were obtained from citrated whole blood by differential centrifugation, washed with Ca++ free Hank's balanced salts containing 0.3% EDTA (pH 6.5) and resuspended in Ca++ free Hank's. Pigeon fib was isolated by precipitation with PEG-1000 and the purity assessed by SDS-PAGE. Fib was conjugated to 25nm colloidal gold by vortexing and the conjugates used as the ligand to identify fib receptors.

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The Application of Protein A-Gold Immunocytochemistry to Studies of Protein Secretion

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100118989 ◽

1985 ◽

Vol 43 ◽

pp. 426-429

Author(s):

George H. Herbener ◽

Antonio Nanci ◽

Moise Bendayan

Keyword(s):

Tissue Section ◽

Colloidal Gold ◽

Unit Area ◽

Protein A ◽

Extracellular Proteins ◽

Gold Complex ◽

Second Step ◽

Igg Antibodies ◽

Tissue Sections ◽

Antigenic Sites

Protein A-gold immunocytochemistry is a two-step, post-embedding labeling procedure which may be applied to tissue sections to localize intra- and extracellular proteins. The key requisite for immunocytochemistry is the availability of the appropriate antibody to react in an immune response with the antigenic sites on the protein of interest. During the second step, protein A-gold complex is reacted with the antibody. This is a non- specific reaction in that protein A will combine with most IgG antibodies. The ‘label’ visualized in the electron microscope is colloidal gold. Since labeling is restricted to the surface of the tissue section and since colloidal gold is particulate, labeling density, i.e., the number of gold particles per unit area of tissue section, may be quantitated with ease and accuracy.

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Comparative strengths and weaknesses of peroxidase and colloidal gold in pre- and post-embedding immunolabeling techniques

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100129279 ◽

1987 ◽

Vol 45 ◽

pp. 1002-1005

Author(s):

D. R. Abrahamson ◽

P. L. St.John ◽

E. W. Perry

Keyword(s):

Electron Microscopy ◽

Horseradish Peroxidase ◽

Light Microscopy ◽

Colloidal Gold ◽

Light Microscope ◽

Ultrastructural Localization ◽

The Other ◽

Quantitative Studies ◽

Dense Suspension ◽

Antigen Localization

Antibodies coupled to tracers for electron microscopy have been instrumental in the ultrastructural localization of antigens within cells and tissues. Among the most popular tracers are horseradish peroxidase (HRP), an enzyme that yields an osmiophilic reaction product, and colloidal gold, an electron dense suspension of particles. Some advantages of IgG-HRP conjugates are that they are readily synthesized, relatively small, and the immunolabeling obtained in a given experiment can be evaluated in the light microscope. In contrast, colloidal gold conjugates are available in different size ranges and multiple labeling as well as quantitative studies can therefore be undertaken through particle counting. On the other hand, gold conjugates are generally larger than those of HRP but usually can not be visualized with light microscopy. Concern has been raised, however, that HRP reaction product, which is exquisitely sensitive when generated properly, may in some cases distribute to sites distant from the original binding of the conjugate and therefore result in spurious antigen localization.

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