Carbon-14 Labeling & Synthesis Techniques Flashcards

What is the established half-life of Carbon-14?

Answer: 5,730 years

Carbon-14 has a half-life of approximately 5,730 years, which makes it valuable for radiocarbon dating and long-duration metabolic tracing studies.

What type of radiation does Carbon-14 emit during its decay?

Answer: Low-energy beta particles

C-14 is a pure beta emitter with a maximum energy of 156.5 keV, classifying it as a low-energy beta emitter that requires liquid scintillation counting for detection.

What does 'specific activity' mean for a C-14 labeled compound?

Answer: The amount of radioactivity per unit mass or mole (e.g., Ci/mmol or GBq/mmol)

Specific activity expresses how much radioactivity is present per unit quantity of compound, indicating what fraction of the molecules carry the C-14 label.

In C-14 synthesis, what does 'position-specific labeling' mean?

Answer: Placing C-14 at one defined, predetermined carbon position within the molecular structure

Position-specific labeling places C-14 at an exact, known carbon atom, enabling researchers to track the metabolic fate of that specific bond or functional group.

Which primary approach is used to introduce C-14 into organic molecules at specific positions during synthesis?

Answer: Building the molecule from C-14 labeled small-molecule precursors such as 14CO2, K14CN, or 14CH2O

C-14 labeled compounds are synthesized by incorporating C-14 labeled building blocks (such as 14CO2, K14CN, or 14CH2O) at a defined step in a classical organic synthesis sequence.

What is the maximum beta particle energy (Emax) emitted by Carbon-14?

Answer: 156.5 keV

C-14 emits beta particles with a maximum energy of 156.5 keV, making it a low-energy beta emitter compared to high-energy emitters like P-32 (1.71 MeV).

Why is C-14 often preferred over stable C-13 for metabolic tracing in pharmaceutical research?

Answer: C-14 can be detected at trace concentrations using radioactivity counting, without requiring mass spectrometry

Radioactivity-based detection (liquid scintillation counting, AMS) is extremely sensitive, enabling C-14 tracing at very low concentrations without the need for expensive, specialized mass spectrometry instrumentation.