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What is the size of an antibody

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What is the size of an antibody

Postby Paragonidae » Thu Mar 15, 2007 8:26 pm

What is the size of an antibody, I am trying to figure this out.
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Postby Dr.Stein » Fri Mar 16, 2007 2:20 am

The size? :?
I don't get you point, I need the full context of it, thus maybe I could help you ;)
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Postby Paragonidae » Fri Mar 16, 2007 6:44 am

an antibody is a molecule, it has a size, I want to know what it is...
my really problem is understanding how a bacteria (for example) of size up to 300 µm (if I have my facts correct) can be connected to one another by a molecule which is relatively tiny - the anti body. that is why I want to know the size of antibodies.
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Postby Dr.Stein » Fri Mar 16, 2007 11:39 am

Well, the size could be molecule weight or else.
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Postby Caspase » Fri Mar 16, 2007 3:03 pm

Weird question. Is this in relation to a western blot or something??

I guess the size of an antibody depends on the amount of amino acids and sugar chains on them. I have never seen an exact amount because this is somewhat dynamic.

I would guess around 1,000-1,500 amino acids + sugar.

To ask the question in um I don't really know...
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Postby Paragonidae » Fri Mar 16, 2007 3:06 pm

I'll be satisfied with molecular weight but I would rather know the size in micro/nano meters
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Postby LilKim » Fri Mar 16, 2007 4:39 pm

Paragonidae wrote:an antibody is a molecule, it has a size, I want to know what it is...
my really problem is understanding how a bacteria (for example) of size up to 300 µm (if I have my facts correct) can be connected to one another by a molecule which is relatively tiny - the anti body. that is why I want to know the size of antibodies.


Yes, you are correct, AB's are much smaller than their targets however AB function in 3 ways.

1. Numberous AB will bind a pathogen all over (opsonization) which triggers a immune response .. in which phagocytic cells well be "target" to this pathogen covered in AB.

2. AB can bind and block at a specific antigen site, thereby blockin/inhibiting function of the target. (then size doesn't matter)

3. Numberous AB's can bind forming almost like a web-like strucutre that can essentially "trap" several antigens at once.

.. i'm sure there are other ways that AB's perform their tasks... but this is all I can think of at the moment.

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Postby Paragonidae » Fri Mar 16, 2007 6:33 pm

regarding 1st answer: well that is also unclear since for opsonization to occur the pathogen covered with AB must adhere to the phagocyte via fc receptors on the phgo' (is this correct?) then again the question of size comes up.
though I thank you for your answer I still am in great "need" to know their size... :o)
regarding 3rd: this is new info for me since I know that IgA can for dimers and IgM can for pentamers but I didn't know that more than that...
P.S
I read somewhere (can not remember where) that they can actually cause damage to the pathogens
don't forget the complement activation via classical pathway.
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Postby LilKim » Fri Mar 16, 2007 6:52 pm

As far as the 1st point: Once AB are attached to an antigen... it is essentially "marked" for phagocytosis by a phagocytic cell. Macrophages can therefore associate with the AB constant reagion by the FC receptor... which potently induces phagocytosis.


3rd point: Remember each antibody has (at least) 2 antigen binding sites, so, theoretically it can interact with 2 different antigens at the same time ... if you keep this notion in mind and add a few more antibodies and a few more pathogens you can imagine a 'clump' of cells with fewer Ab's in comparision to antigens.

but despite it all... I don't know the sizes, and I'm not sure why size is exactly relevant..... could you please let me kow why you're so curious about size? (i'm curious)
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Postby Caspase » Fri Mar 16, 2007 8:15 pm

The root of your question would help us answer it.

Antibodies have variable regions so size is not constant.

The wiki states that when antibodies are digested by papain 2 50 kDa Fab fragments and 1 50 kDa Fc fragment are obtained.
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Postby angelsmile » Fri Apr 06, 2007 2:45 am

Antibody is generally a kind of protein,and is it measured by Da or kDa?
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Postby Dr.Stein » Fri Apr 06, 2007 12:26 pm

Yes. Why?
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