In a antibody micro array (Ab+Ag <-> AbAg K=[AbAg]/[Ab][Ag]), we can use the relationship between the reaction constant K, concentration of antibody: [Ab], concentration of antigen:[Ag] to estimate the dynamic range of the sensing system.
If we assume {Ab}=109/ml, now we take a droplet (100 nl) spotting on surface with a spot diameter=200 mm. Assume K=[AbAg]/[Ab][Ag]=106 ml, and Ag
labeled with fluorescence..
a. Please calculate the numbers of Ab on the spot, and the distance among each Ab
if all the antibodies are uniformly distributed on the surface.
b. Please estimate the minimum and maximum measurable numbers of Ag and concentration of {Ag} before the sensing system become saturated (please draw the relationship between [AbAg] and {Ag}. Here we assume all the antibodies are immobilized on the surface, and background noise is zero). What is the dynamic range now (maximum detectable signal /minimum detectable signal)?
c. If the background noise is around 1% of the antibody on the spot, please estimate the minimum measurable concentration of {Ag} and dynamic range of the sensor.