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a) Alkaline phosphatase
b) Restriction endonuclease
c) Reverse transcriptase
d) DNA ligase.
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Types of luminescence
Light is produced by exposing the substance to UV radiation.
Photoluminescence involves Fluorescence and Phosphorescence phenomenon
Emission of light by a living organism and biological process.
Emission of light by chemical reaction. called Chemiluminescence.
Emission of light by interaction of radioactive particles with the compounds called Radioluminescence.
Mechanism of fluorescence and phosphorescence
Fluorescence involves singlet-singlet transition while phosphorescence involves triplet-singlet transition.
Out of two electron in “ground singlet state” –> one of electron is excited to higher energy level. –> if excitation not associated with change in spin of electron still spins are in opposite direction electron present in “excited singlet state” and if excitation associated with change in spin and both the electron spin in same direction –> electron present in “excited triplet state”.
Fluorescence and Phosphorescence are the deactivation processes
excited singlet state –> ground singlet state –> no change in spin à emits absorb energy –> fluorescence
excited triplet state –> ground singlet state –> change in spin –> emits absorb energy –> phosphorescence
|No change in spin||Change in spin|
|excited singlet state à ground singlet state||excited triplet state à ground singlet state|
|singlet-singlet transition||triplet-singlet transition|
|Life time of excited state is small (10-6 to 10-9 sec)||Life time of excited state is long (10-4 to second or minutes)|
|It stops immediately as soon as the source of excitation is removed||It seen for longer period even after removing source of excitation|