Phosphorus-32
Encyclopedia
Phosphorus-32 is a radioactive isotope
of phosphorus
. The nucleus of phosphorus-32 contains 15 proton
s and 17 neutron
s, 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 and so decays rapidly.
Phosphorus is found in many organic molecules and so phosphorus-32 has many applications in medicine
, biochemistry
and molecular biology
where it can be used to trace phosphorylated molecules, e.g. in elucidating metabolic pathways, and radioactively label DNA
.
as shown in this nuclear equation:
1.709 MeV
of energy is released during the decay. The kinetic energy of the electron
varies with an average of approximately 0.5 MeV and the remainder of the energy is carried by the nearly undetectable electron antineutrino. In comparison to other beta radiation-emitting nuclides the electron is moderately energetic. It is blocked by around 1 m of air or 5 mm of perspex.
The sulphur-32 nucleus produced is in the ground state
so there is no additional gamma ray
emission.
, biochemistry
and molecular biology
. Its short half-life means useful quantities have to be produced synthetically. Phosphorus-32 can be generated synthetically by irradiation
of sulphur-32 with moderately fast neutrons as shown in this nuclear equation:
The sulphur-32 nucleus captures the neutron and emits a proton, reducing the atomic number
by one while maintaining the mass number
of 32.
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. 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.
s of organisms extensively use phosphorus in the generation of different biomolecules within the cell. Phosphorus-32 finds use for analysing metabolic pathways in 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.
DNA
contains a large quantity of phosphorus in the 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.
s to the leaves
. The phosphorus-32-labelled fertiliser is given to the plant hydroponically or via water in the soil and the usage of the phosphorus can be mapped from the emitted beta radiation. The information gathered by mapping the fertiliser uptake show how the plant takes up and uses the phosphorus from fertiliser.
to monitor exposure and an acrylic
or perspex radiation shield to protect the body. 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 finger
s, which come into close contact with the phosphorus-32-containing sample.
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
of phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
. The nucleus of phosphorus-32 contains 15 proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
s and 17 neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s, one more neutron than the most common isotope of phosphorus, phosphorus-31. Phosphorus-32 only exists in small quantities on Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
as it has a short half-life and so decays rapidly.
Phosphorus is found in many organic molecules and so phosphorus-32 has many applications in medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
and molecular biology
Molecular biology
Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...
where it can be used to trace phosphorylated molecules, e.g. in elucidating metabolic pathways, and radioactively label DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
.
Decay
Phosphorus has a short half-life of 14.29 days and decays into Sulphur-32 by beta decayBeta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
as shown in this nuclear equation:
| → |
1.709 MeV
MEV
MeV and meV are multiples and submultiples of the electron volt unit referring to 1,000,000 eV and 0.001 eV, respectively.Mev or MEV may refer to:In entertainment:* Musica Elettronica Viva, an Italian musical group...
of energy is released during the decay. The kinetic energy of the electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
varies with an average of approximately 0.5 MeV and the remainder of the energy is carried by the nearly undetectable electron antineutrino. In comparison to other beta radiation-emitting nuclides the electron is moderately energetic. It is blocked by around 1 m of air or 5 mm of perspex.
The sulphur-32 nucleus produced is in the ground state
Ground state
The ground state of a quantum mechanical system is its lowest-energy state; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state...
so there is no additional gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
emission.
Production
Phosphorus-32 has important uses in medicineMedicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
and molecular biology
Molecular biology
Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...
. Its short half-life means useful quantities have to be produced synthetically. Phosphorus-32 can be generated synthetically by irradiation
Neutron source
A Neutron source is a device that emits neutrons. There is a wide variety of different sources, ranging from hand-held radioactive sources to neutron research facilities operating research reactors and spallation sources...
of sulphur-32 with moderately fast neutrons as shown in this nuclear equation:
| → | + |
The sulphur-32 nucleus captures the neutron and emits a proton, reducing the atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
by one while maintaining the mass number
Mass number
The mass number , also called atomic mass number or nucleon number, is the total number of protons and neutrons in an atomic nucleus. Because protons and neutrons both are baryons, the mass number A is identical with the baryon number B as of the nucleus as of the whole atom or ion...
of 32.
Uses
Phosphorus is an 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. The location of the phosphorus-32 can be traced from outside the body to identify the location of potential 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
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
agent to treat disseminated ovarian cancer. 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.
Biochemistry and molecular biology
The metabolic pathwayMetabolic pathway
In biochemistry, metabolic pathways are series of chemical reactions occurring within a cell. In each pathway, a principal chemical is modified by a series of chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function...
s of organisms extensively use phosphorus in the generation of different biomolecules within the cell. Phosphorus-32 finds use for analysing metabolic pathways in 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.
DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
contains a large quantity of phosphorus in the phosphodiester linkages between bases
Bases
Bases may refer to:*Bases , a military style of dress adopted by the chivalry of the sixteenth century.*Business Association of Stanford Entrepreneurial Students...
in the oligonucleotide
Oligonucleotide
An oligonucleotide is a short nucleic acid polymer, typically with fifty or fewer bases. Although they can be formed by bond cleavage of longer segments, they are now more commonly synthesized, in a sequence-specific manner, from individual nucleoside phosphoramidites...
chain. DNA can therefore be tracked by replacing the phosphorus with phosphorus-32. This technique is extensively used in Southern blot
Southern blot
A Southern blot is a method routinely used in molecular biology for detection of a specific DNA sequence in DNA samples. Southern blotting combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization. The method is named...
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 plant sciences for tracking a plant's uptake of fertiliser from the rootRoot
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...
s to the leaves
Leaves
-History:Vocalist Arnar Gudjonsson was formerly the guitarist with Mower, and he was joined by Hallur Hallsson , Arnar Ólafsson , Bjarni Grímsson , and Andri Ásgrímsson . Late in 2001 they played with Emiliana Torrini and drew early praise from the New York Times...
. The phosphorus-32-labelled fertiliser is given to the plant hydroponically or via water in the soil and the usage of the phosphorus can be mapped from the emitted beta radiation. The information gathered by mapping the fertiliser uptake show how the plant takes up and uses the phosphorus from fertiliser.
Safety
The high energy of emitted beta particles and the low half-life of phosphorus-32 make it potentially harmful, its maximum specific activity is 9131 Ci/mmole. Typical safety precautions when working with phosphorus-32 include wearing a personal dosimeterDosimeter
Dosimeters measure an individual's or an object'sexposure to something in the environment — particularly to a hazard inflicting cumulative impact over long periods of time, or over a lifetime...
to monitor exposure and an acrylic
Acrylic glass
Poly is a transparent thermoplastic, often used as a light or shatter-resistant alternative to glass. It is sometimes called acrylic glass. Chemically, it is the synthetic polymer of methyl methacrylate...
or perspex radiation shield to protect the body. 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 finger
Finger
A finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates....
s, which come into close contact with the phosphorus-32-containing sample.