BY : - U PV ITA PAND EY

INTERNAL GUIDE : EXTERNAL GU IDE :PRO F. A .N .GARG PRO F. S US ANTA L AH I R I( S E N I O R P R O F. , A I N S T ) ( S O - ‘ G ’ , C S D , S I N P )

PEPTIDE LABELING & GAMMA RAY SPECTROSCOPY

AMITY SCHOOL OF NUCLEAR SCIENCE & TECHNOLOGY

SUMMER INTERNSHIP

• DISCOVERY OF RADIOACTIVITY• TYPES OF DECAY• WHAT IS RADIOLABELING ?• WHAT IS PEPTIDE ?• RADIOLABELED PEPTIDE• PEPTIDE RECEPTOR RADIONUCLIDE THERAPY• GAMMA RAY INTERACTION •SOME EXPERIMENTS

OUTLINE

RADIOACTIVITYThe emission of ionizing radiation or particles caused by the spontaneous disintegration of atomic nuclei.

In 1897, Becquerel accidentally discovered radioactivity in pitchblende while studying sunlight induced fluoroscence of various minerals. This mineral was found to produce a photographic image, even through black paper.

Further experiments demonstrated that a mixture of charged particles and electromagnetic radiations were being emitted and were responsible for the effect on photographic plate.

TYPES OF RADIOACTIVE DECAY

ALPHA PARTICLE DECAY : In this, a nucleus emits a particle consisting of two protons and two neutron i.e. 4He atom.

BETA DECAY : This is a type of decay in which a proton is transformed into a neutron, or vice versa, inside an atomic nucleus.

There are three common processes that will be discussed under beta decay :

1. NEGATRON DECAY : Negative electrons are emitted from the nucleus. In this Z increases by 1 unit.

2. POSITRON DECAY: Positive electrons are emitted from the nucleus. In this the value of Z is decreased by 1 unit.

3. ELECTRON CAPTURE: In this an orbital atomic electron is captured by the

excited nucleus. GAMMA DECAY: a nucleus changes from a higher energy state to a

lower energy state through the emission of electromagnetic radiation (photons).

WHAT IS RADIOLABELING ?

Radiolabeling is a technique where one of the atoms in a molecule is target with a radioactive atom, e.g 24NaCl, 14CH3COOH.

It is used for tracking the passage of a sample of a substance through a system.

The substance is labelled using radionuclides in its chemical composition.

As the radio nuclides decay, their presence can be tracked by detecting the minute amounts of radioactivity emitted.

PET scans use this technology.

Why Labeled Peptide ?The labeled peptides are small (molecular weight is in the range of l-3 K Dalton). This small size allows them to be cleared quickly from the body after intravenous administration and to rapidly penetrate into target tissues, including tumors. Rapid clearance from the blood combined with high specific binding to target tissues provides the high target/non-target ratios normally seen with Octreoscan.

WHAT IS PEPTIDE ??? Peptide is defined as a compound of two

or more amino acids in which a carboxyl group of one is united with an amino group of another.

RADIOLABELED PEPTIDE

Radiolabeled peptides have been used for diagnostic purpose in nuclear medicine.

The peptides are used as transport vehicles to guide the radionuclides to the tissues expressing a particular receptor.

The presence of multiple peptide receptors in selected cancers can be the basis for multireceptor targeting using two or more radiopeptides in parallel.

The radionuclides used are Yttrium 90 (64 hours), Lutetium 177 (6.6 days), 99m Technetium ( 24 hours), 111 Indium ( 2.80 days)

Factors That Must Be Considered When Selecting a Radionuclide To Be Incorporated Into a Therapeutic Radiopharmaceuticals are :

-Physical half life of the radionuclide - Type of radiation(s) emitted by the radionuclide -Energy of radiation(s) emitted by the radionuclide -Chemistry and chemical reactivity of the element/isotope/radiochemical containing the radionuclide. -Cost of the radionuclide -Availability of the radionuclide

PEPTIDE RECEPTOR RADIONUCLIDE THERAPY (PRRT)

What is peptide receptor radionuclide therapy (PRRT) and how does it work?

It is a molecular therapy  used to treat a specific type of cancer called neuroendocrine carcinoma. PRRT is also currently being investigated as a treatment for prostate and pancreatic tumors.A cell-targeting protein (or peptide) called octreotide is combined with a small amount of radioactive material, or radionuclide, creating a special type of radiopharmaceutical called a radiopeptide. When injected into the patient’s bloodstream, this radiopeptide travels to and binds to neuroendocrine tumor cells, delivering a high dose of radiation to the cancer.

What conditions are treated with PRRT?

NETs (neuroendocrine tumors) , Pheochromocytoma, Gastro-enteropancreatic Small cell carcinoma of the lung,Rare thyroid cancers

How is PRRT performed?

Up to 10 PRRT sessions spaced two to three months apart may be done as an outpatient procedure or may require a hospital stay of a few days

Begins with an amino acid solution delivered intravenously to protect the patient’s kidneys from the effects of the radiation. The radiopeptide is then injected into the patient, followed by additional amino acid solution. In total, the treatment session lasts approximately four hours. 

Advantages of PRRT?

It is highly effective in controlling advanced, progressive neuroendocrine tumors.It help to relieve symptoms and slow the progression of the disease. It typically has milder side effects compared with chemotherapy. It is a targeted therapy therefore limiting the radiation exposure to healthy tissue.

Ongoing research also includes studying the use of:

two radiopeptides together radiopeptides in conjunction with other chemotherapies repeated administrations of the radiotherapies increasing the number of indications for this therapy, inc1uding other disease targets other radionuclide-peptide combinations.

FUTURE DEVELOPMENT

GAMMA RAY INTERACTION

GAMMA rays are electromagnetic radiation, they have no charge and no rest mass. The interactions of GAMMA rays are, therefore, quite different from

those experienced by charged particles. Gamma rays are not subject to Coulomb interactions, and so they do not lose energy continuously as do the

charged particles.

Three major modes of interaction of gamma rays with matter will be discussed :

Photoelectric Effect

Compton Effect

Pair Production

PHOTOELECTRIC EFFECT

In a photoelectric effect, a gamma ray interacts with an atom in a process that results in the ejection of an electron from the atom in a process that results in the ejection of an electron from the atom and the complete disappearance of the gamma ray. The electron receieves all the energy of the gamma ray, minus its atomic binding energy:

Ee,PE = EƳ – BEe

The ejected electron can then induce secondary ionization events that may be detected.

The probability of occurrence of the PE is directly related to the Z of the absorber and inversely related to the energy of the Ƴ ray:

Probability (PE) = k(Zabs) /Eγ

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7/2

COMPTON SCATTERING

The Compton Scattering interaction is the scattering of a gamma ray off of a free or unbounded electron, thus creating a scattered gamma ray photon and a recoil electron. The energy of the incoming photon is divided between the scattered photon and the recoil nucleus by a relationship that is dependent on the scattering angle.

PAIR PRODUCTION

Pair production is a gamma-ray that turns into an electron-positron pair. This occurs when the gamma-ray is in the intense electric field near the nuclei of the absorbing material. There is a minimum amount of gamma-ray energy that is required for this process to take place. This minimum energy is the mass of the electron-positron pair, 2m0c2. Therefore, the conservation of kinetic energies gives

Ee− + Ee+ = h − 2m0c2

EXPERIMENT 1

INSTRUMENT USEDThe HPGe detector used in this experiment is kept inside a

747S extra deep lead shield to minimize suppression of events due to coincidences with background radiation.

AIM: To identify the unkown gamma energies from standard sources.

SOURCE: I- 137Cs ( Strength -- 613+/- 0.87% dps) II- 133Ba (Strength --525+/- 1.2% dps) III- 60Co (Strength --256+/- 1.13% dps)

STANDARD CHANNEL NO. HALF LIFE ENERGY(keV) INTENSITY

137Cs 30 years 31.817 2.05

32.194 3.77

36.357 1.04

1840 661.660 85.1

60Co 3260 5.27 years 1173.237 99.90

3700 1332.501 99.9824

133Ba 226 10.54 years 80.989 34.2

988 355.999 62.2

RESULT:

EXPERIMENT 2

INSTRUMENT USEDThe HPGe detector used in this experiment is kept inside a

747S extra deep lead shield to minimize suppression of events due to coincidences with background radiation.

AIM: Estimation of U-238 activity in soils and leaf samples and comparing their activity

SOURCE: U-238, 3 soil sample and 2 leaf samples weighing 30g.

DECAY CHAIN:

METHODS: The samples were pre dried, grinded, weight and hermetically sealed in petriplates and kept aside for a month to establish the secular equilibrium. After completion of the month the sample so prepared were analyzed for estimation of U-238 activity by using CANBERRA HPGe detector in Saha Institute of Nuclear Physics, Kolkata. The sample spectra was analyzed by using GENIE software an associated electronics procured from CANBERRA. The respective data were recorded and a graph was plotted that represented the U-238 activity of the corresponding samples.

OBSERVATIONS :

SAMPLE NAME

Ra-226 l86.2keV Intensity 0.0328 Activity (Bq) Bq/kg Error(%)

Sample. l l.l 36.66 7.43

Sample.2 0.ll 3.66 42.38

Sample.3 l.76 58.66 9.24

Sample.4 l.78 59.33 9.68

Sample.5 0.l5 5.00 30.34

SAMPLE NAME

Pb-2l4 295.6keV Intensity 0.l92 Activity (Bq) Bq/kg Error(%)

Sample.l 0.84 28.00 6.24

Sample.2 0.00 0.00 0.00

Sample.3 0.5l l7.00 5.85

Sample.4 0.76 25.33 4.85

Sample.5 0.00 0.00 0.00

SAMPLE NAME

Pb-2l4 35l.9keV Intensity 0.37l Activity (Bq) Bq/kg Error(%)

Sample.l l.l7 39.00 2.78

Sample.2 0.00 0.00 0.00

Sample.3 0.74 24.66 2.73

Sample.4 l.l0 36.66 2.l3

Sample.5 0.02 0.66 54.45

SAMPLE NAME

Bi-2l4 608.9keV Intensity 0.46l Activity (Bq) Bq/kg Error(%)

Sample.l l.l6 38.66 3.33

Sample.2 0.0035 0.l2 l48.2

Sample.3 0.82 27.33 3.32

Sample.4 l.0l 33.66 3.00

Sample.5 0.00 0.66 0.00

SAMPLE NAME

Bi-2l4 608.9keV Intensity 0.46l Activity (Bq) Bq/kg Error(%)

Sample.l l.l3 37.66 7.70

Sample.2 0.00 0.00 0.00

Sample.3 0.96 32.00 8.32

Sample.4 l.l0 36.66 8.53

Sample.5 0.09 30.00 38.05

Sample 1 Sample 2 Sample 3 Sample 4 Sample 50

5

10

15

20

25

30

35

40

45

36.11

1.24

36.38

41.83

6.78

U-238 Activity Bq/kg

SAMPLE NO.

ACTI

VITY

CO

NCEN

TRAT

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IN B

Q/K

G

RESULT: The global average for U-238 activity is 35 Bq/kg. It is observed that in leaf samples the U-238 activity less as compared to the soil samples. 

Sample No. U-238 Activity Bq/kgSample 1 36.11Sample 2 1.24Sample 3 36.38Sample 4 41.83Sample 5 6.78

INTERPRETATION:

Naturally occurring radioactive materials are present everywhere on our earth which releases gamma energy. In this experiment soil and leaf samples are taken to observe the amount of U-238 activity present in it. The activity of U-238 was negligible in the leaf samples whereas in case of the three soil samples the activity was estimated as 36.11, 36.38 and 41.83 Bq/kg respectively. So we found that the exposure of natural radiation is more from terrestrial sources like soil as in this experiment.

CONCLUSION

The amount of naturally occuring radioactive materials are transported from soil through roots to the plant .

The little amount of activity is transported which cause no harm to the environment.