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What is the size of an antibody

Discussion of all aspects of biological molecules, biochemical processes and laboratory procedures in the field.

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Postby blcr11 » Fri Apr 06, 2007 12:37 pm

The crystal structures of antibodies are known. I haven't looked it/them up, but they have to be in the range of 40-50 angstroms in the shortest dimension to something like 150-200 angstroms in the largest--so say a "box of 50 x 50 x 200 angstroms might be a reasonable guess for the "size" of an antibody.

That would be an IgG. IgMs would be larger. A single IgG molecule is much smaller than a bacterium, but the surface of the bacterium gets coated with many such molecules which acts either to agglutinate the bacterium directly, or attract things like macrophages or eosinophils or leukocytes.
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Re: What is the size of an antibody

Postby tmerdol » Fri Jul 22, 2016 3:36 pm

I also want to learn the size, because some materials are used as nanoparticles in foods for preservation, enrichment or else, I am worried if they are dangerous for body to circulate in the blood. Producers claim that nanoparticuls are as tiny as antibody which body is used to...
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Postby stefangruenert » Thu Apr 27, 2017 11:34 am

If I understand you well you are concerned with the properies of Ig to crosslink pathogens, which can be comparatively large structures like bacteria with sizes exceeding 1 micrometer.

THis consideration is actually quite important and there is an interesting paper which deals with the misleading impressions textbook cartoons leave with us, you might want to check: http://www.slas.ac.cn/upload/20130815-4.pdf

Antibodies come in different types for a start, there are the typical Imunoglobulins G, which are made up of 4 polypeptide chains (2 heavy of 450 AA and 2 light of 210 AA) and are about 150 kDa. An IgG is approximately 10 nm high. But there are also IgA (Dimers) and IgM (Pentamers) which are consderably larger.

Referring to your question it is important to note that IGg are mainly to mark pathogens to induce interactions with immunecells, probably throug engaging several receptors on the cell surface. This was pointed out before. However, it is the considerably larger and multivalent IgM which tend to cross link pathogens and inactivate them. These can obviously have a better reach and also more sites to stabilise the crosslink and are probably much more relevant for viruses, as these would be mopped up and could be taken up by immunecells in bulk.

Here is a visualisation of a typical IgG in isolation based on the RCSB-PDB: https://www.youtube.com/watch?v=H4wcy01tmt8
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Re: What is the size of an antibody

Postby claudepa » Thu Apr 27, 2017 1:17 pm

10 nm length for an antibody means that it is indeed the size of small nanoparticles. I am working in therapeutic research with non biodegradable 7 nm nanoparticles. We look for this size because it can allow elimination by kidney. However it is not easy because they have a tendency to agregate and therefore form bigger nanoparticles. For biodegradable nanoparticles it can be frequently from 50 nm to 300 nm.
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