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Hi,Dev.



I am now asking you some question.

We know, Antibody can be detected by Indirect ELISA & Antigen can be detected by Direct ELISA.

Now, Is there any difference between Indirect ELISA & Direct ELISA  except that point that i mentioned earlier.

My next question :

One of the most important function of agar is solidifying. Except this any others function it has.If it has please tell me.

Thanks.

Answer
Is there any difference between Indirect ELISA & Direct ELISA;;;;indirect ELISA measures amount of anitbody present; sandwich ELISA measures amount of antigen present...
the difference is in the structure of the protocol.  direct elisa, the antibody bound to the enzyme will be bound directly to the antigen of interest. (noted, that will be bound to an antibody bound to the plate. but don't worry about that at the moment)

in indirect elisa, the antibody that is bound to the enzyme, will bind to a DIFFERENT antibody. and the DIFFERENT antibody will be bound to the antigen.

it's really wierd. and you have some german dude from the 1940s to thank for that. but i hope that helps.

www.elisa-antibody.com/.../ELISA-types/direct-elisa

One of the most important function of agar is solidifying [An Introduction to Agar

With its distinctive smell, one can easily distinguish agar from the other materials commonly found in a laboratory. Chemically, agar is a polymer made up of subunits of the sugar galactose, and is a component of the cell walls of several species of red algae that are usually harvested in eastern Asia and California. Dissolved in boiling water and cooled, laboratory agar looks gelatinous. Although agar's chief use is as a culture medium for various microorganisms, particularly for bacteria, its other less well-known uses include serving as a thickening for soups and sauces, in jellies and ice cream, in cosmetics, for clarifying beverages, and for sizing fabrics.(1)

One might ask why agar, as opposed to regular gelatin (like that found in Jello), is used for culturing bacteria. The answer is agar, unlike gelatin, won't be degraded (eaten) by bacteria. Also, agar is firmer and stronger than gelatin. It's still possible, however, to use gelatin as a culture medium for bacteria if agar is unavailable.(2)

The Difco & BBL Manual gives more details about agar and its usage:(3)

   Agar is a phycocolloid extracted from a group of red-purple marine algae (Class Rhodophyceae) including Gelidium, Pterocladia and Gracilaria. Gelidium is the preferred source for agars. Impurities, debris, minerals and pigment are reduced to specified levels during manufacture.

   Agar is a gel at room temperature, remaining firm at temperature as high as 65C. Agar melts at approximately 85C, a different temperature from that at which it solidifies, 32-40C. This property is known as hysteresis. Agar is generally resistant to shear forces; however, different agars may have different gel strengths or degrees of stiffness.

http://www.microrao.com/micronotes/culture_media.pdf

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