Radioisotopes

Elements with same atomic number (SAN) but different atomic weights (DAW).

There are two types of isotopes:

1. Stable Isotopes

• Naturally occurring
• Do not emit radiations
• Identified and quantitated by mass spectrometry or nuclear magnetic resonance.
• Sometimes used in biochemical investigations.

2. Unstable or Radioactive Isotopes (IMP SAQ)

Nucleus unstable → Decay → αβ and gamma rays emission

Curie : Defined as the amount of radioactivity equivalent to 1 gm of radium (2.22 x 10 raised to 12) disintegration per minute.

Millicurie = 2.2 x 10 raise to 9

Microcurie = 2.2 x 10 raise to 6

• Geiger counters
• Liquid scintillation counter
• Autoradiography

• Determine metabolic origin of complex molecules like heme , cholesterol , purines and phospholipids.

• Determining the precursor-product relationship in metabolic pathways ex. Krebs cycle, urea cycle etc..

• Study of metabolic pools and metabolic turnovers.
• Endocrine and immunological studies

• To elucidate drug metabolism.

• Scanning of organs – thyroid ¹³¹I , bone ⁹⁰Sr , kidney ¹³¹ I hippuran.

• Treatment of cancer