Antigen can be detected or measured by a sandwich ELISA .In this technique, the antibody (rather than the antigen) is immobilized on a microtiter well. 
A sample containing antigen is added and allowed to react with the immobilized antibody. After the well is washed, a second enzyme- linked antibody specific for a different epitope on the antigen is added and allowed to react with the bound antigen
After any free second antibody is removed by washing, substrate is added, and the colored reaction product is measured.

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#Unit 1. Molecules and their Interaction Relevant to Biology

The greater the effective nuclear charge the more tightly an electron is held in by the nucleus because there is less electron shield between the valence electrons and the nucleus, and so, the smaller the radius.

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#Unit 1. Molecules and their Interaction Relevant to Biology

Ranks the following in increasing atomic radius

S, Mg, Al

S: 16-10 +6

Mg: 12-10 = +2

Al: 13-10 +3

So: S < AlMg

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#Unit 1. Molecules and their Interaction Relevant to Biology

Electron affinity: The enthalpy change that results from adding an electron to a gaseous atom.

Electron affinity is becoming less negative (less exothermic) and less likely to gain an electron. 

#Id: 7753

#Unit 1. Molecules and their Interaction Relevant to Biology

Electron affinity: The enthalpy change that results from adding an electron to a gaseous atom.

Electron affinity is becoming less negative (less exothermic) and less likely to gain an electron. 

#Id: 7754

#Unit 1. Molecules and their Interaction Relevant to Biology

#Id: 7755

#Unit 1. Molecules and their Interaction Relevant to Biology

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. The Pauling scale is the most commonly used.