Phosphorus-32

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Phosphorus-32, 32P
General
Beta emission
1.70912
Isotopes of phosphorus
Complete table of nuclides

Phosphorus-32 (32P) is a radioactive isotope of phosphorus. The nucleus of phosphorus-32 contains 15 protons and 17 neutrons, one more neutron than the most common isotope of phosphorus, phosphorus-31. Phosphorus-32 only exists in small quantities on Earth as it has a short half-life of 14 days and so decays rapidly.

Phosphorus is found in many

metabolic pathways) and radioactively label DNA
.

Decay

Phosphorus-32 has a short half-life of 14.268 days and decays into sulfur-32 by beta decay[1] as shown in this nuclear equation:

32
15P
 → 32
16S1+
 +
e−
 +

ν
e

1.709 

acrylic glass
.

The sulfur-32 nucleus produced is in the ground state so there is no additional gamma ray emission.

Production

Phosphorus-32 has important uses in medicine, biochemistry and molecular biology. It only exists naturally on earth in very small amounts and its short half-life means useful quantities have to be produced synthetically. Phosphorus-32 can be generated synthetically by irradiation of sulfur-32 with moderately fast neutrons as shown in this nuclear equation:

32
16S
 +
n
 → 32
15P
 +
p

The sulfur-32 nucleus captures the neutron and emits a proton, reducing the atomic number by one while maintaining the mass number of 32.

This reaction has also been used to determine the yield of nuclear weapons.[3][4]

Uses

Phosphorus is abundant in biological systems and, as a radioactive isotope is almost chemically identical with stable isotopes of the same element, phosphorus-32 can be used to

label
biological molecules. The beta radiation emitted by the phosphorus-32 is sufficiently penetrating to be detected outside the organism or tissue which is being analysed

Nuclear medicine

Many radioisotopes are used as tracers in nuclear medicine, including iodine-131, phosphorus-32, and technetium-99m. Phosphorus-32 is of particular use in the identification of malignant tumours because cancerous cells have a tendency to accumulate more phosphate than normal cells.[5] The location of the phosphorus-32 can be traced from outside the body to identify the location of potentially malignant tumors.

The radiation emitted by phosphorus-32 can be used for therapeutic as well as diagnostic purposes. The use of 32P-chromic phosphate has been explored as a possible chemotherapy agent to treat disseminated ovarian cancer.[6] In this situation, it is the long-term toxic effects of beta radiation from phosphorus-32 accumulating in the cancerous cells which has the therapeutic effect. Phosphorus-32 is widely used for cancer detection and treatment, especially in eyes and skin cancer.

Biochemistry and molecular biology

The

pulse chase
experiments where a culture of cells is treated for a short time with a phosphorus-32-containing substrate. The sequence of chemical changes which happen to the substrate can then be traced by detecting which molecules contain the phosphorus-32 at multiple time points following the initial treatment.

phosphodiester linkages between bases in the oligonucleotide chain. DNA can therefore be tracked by replacing the phosphorus with phosphorus-32. This technique is extensively used in Southern blot
analysis of DNA samples. In this case, a phosphorus-32-containing DNA probe hybridises to its complementary sequence where it appears in a gel. Its location can then be detected by photographic film.

Plant sciences

Phosphorus-32 is used in

fertiliser uptake show how the plant takes up and uses the phosphorus from fertiliser.[7]

Safety

The high energy of emitted beta particles and the low half-life of phosphorus-32 make it potentially harmful; Its molar activity is 338.61 TBq/mmol (9151.6 Ci/mmol) and its

perspex radiation shield to protect the body. Dense shielding, such as lead, is less effective due to the high-energy bremsstrahlung produced by the interaction of the beta particle and the shielding. Because the beta radiation from phosphorus-32 is blocked by around 1 m of air it is also advisable to wear dosimeters on the parts of the body, for example the fingers
, which come into close contact with the phosphorus-32-containing sample.

References

  1. doi:10.1088/1674-1137/41/3/030001
    .
  2. ^ "Phosphorus 32". www.site.uottawa.ca:4321. Archived from the original on 2014-02-22.
  3. ^ Kerr, George D.; Young, Robert W.; Cullings, Harry M.; Christy, Robert F. (2005). "Bomb Parameters" (PDF). In Robert W. Young, George D. Kerr (ed.). Reassessment of the Atomic Bomb Radiation Dosimetry for Hiroshima and Nagasaki – Dosimetry System 2002. The Radiation Effects Research Foundation. pp. 42–43. Archived from the original (PDF) on 2015-08-10. Retrieved 2014-03-13.
  4. ^ Malik, John (September 1985). "The Yields of the Hiroshima and Nagasaki Explosions" (PDF). Los Alamos National Laboratory. Retrieved March 9, 2014.
  5. ^ "radioactivity". Encyclopædia Britannica. Retrieved 2016-02-13.
  6. PMID 7799078
    .
  7. ^ Singh, B., Singh, J., & Kaur, A. (2013). Applications of Radioisotopes in Agriculture. International Journal of Biotechnology and Bioengineering Research,4(3), 167-174.

External links

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