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Which Formulation Should I Choose?


Information on this page will help you select the best radiochemical formulation for your needs. For additional help, please contact us at global.techsupport@perkinelmer.com.

Radionucleotides


The radionucleotides in the tables below are labeled on either the alpha phosphate group, or the gamma phosphate group. This designation does not refer to the type of energy that is emitted. 32P, 33P, and 35S are all beta-emitters (they give off beta energy in the form of beta particles). The "alpha" and "gamma" designation refers to the phosphate group of the nucleoside triphosphate that is labeled with the radioisotope. If you are performing an enzymatic assay (phosphorylation with a kinase, end labeling an oligonucleotide with terminal transferase, etc.), it is important to consider how your enzyme is using the nucleotide as a substrate. Your goal is probably to have the enzyme transfer a radiolabeled group from the radionucleotide to a DNA chain, an RNA chain, or a protein. You will need to understand how your enzyme works. Is it incorporating the nucleoside monophosphate (base, sugar, and alpha phosphate group) as part of a DNA or RNA chain? Is it transferring the terminal (gamma) phosphate group from the nucleotide to another substrate? Do you need to use a nucleotide that is deoxy at the 2' position of the sugar (a deoxyribonucleotide, dNTP)? Do you need a "chain terminator" that is deoxy at the 3' position?

nucleotide_structure_ASK.jpg
Structure of ATP. The entire molecule comprises a nucleotide (also called a nucleoside triphosphate). The alpha, beta, and gamma phosphate groups are indicated. This is not a deoxyribonucleotide, because there is a hydroxyl group at the 2' position of the ribose sugar. This would also not be a chain terminator, as there is a potentially reactive hydroxyl group at the 3' position.

Most NEN® radionucleotides are available as "EasyTides®", ready-to-use nucleotides in a buffer that allows for ambient shipment and storage at 2 -8°C. This formulation also includes an inert dye for ease of use. NEN radionucleotides are also available in a "Frozen" version, to be shipped frozen and then stored at -20°C. Note that the higher salt concentration of the EasyTides formulation may interfere with some thermophilic DNA polymerases. See the tables below for detailed ordering information.

Deoxyribonucleotides (DNA nucleotides) for labeling

Use this table to help you select the optimal 32P, 33P or 35S deoxyribonucleotide for your labeling application. View more information on DNA and RNA labeling assays. 

View this table and information as pdf

ApplicationCompoundSpecific Activity (Ci/mmol)Rad. conc. (mCi/mL)Molar conc. (μM)EasyTides Version Containing Dye in Buffer (Shipped ambient, store at 2-8°C)Frozen Version (Shipped on dry ice, store at -20°C)
DNA labeling (Random primer or nick translation) or DNA sequencing 

(Klenow, T7 DNA polymerase, terminal transferase...)            
dATP,[alpha-32P]  8001012.5BLU512A/NEG512A 
3000103.3BLU512H/NEG512HBLU012H/NEG012H
6000203.3BLU512Z/NEG512ZBLU012Z/NEG012Z
dCTP,[alpha-32P]  8001012.5BLU513A/NEG513ABLU013A
3000103.3BLU513H/NEG513HBLU013H/NEG013H
6000203.3BLU513Z/NEG513ZBLU013Z/NEG013Z
dGTP,[alpha-32P] 3000103.3BLU514H/NEG514H 
6000203.3BLU514Z/NEG514ZBLU014Z/NEG014Z
dTTP,[alpha-32P] 8001012.5BLU505A/NEG505ABLU005A/NEG005A
3000103.3BLU505H/NEG505HBLU005H/NEG005H
dATP,[alpha-33P]3000103.3NEG612HNEG312H
dCTP,[alpha-33P]3000103.3NEG613HNEG313H
dTTP,[alpha-33P]3000103.3NEG605H 
3' end labeling of DNA using terminal transferase3'dATP,[alpha-32P]5000102 BLU026/NEG026

Guidelines for choosing a deoxyribonucleotide from the above table:

  • Application
    • dNTPs (deoxynucleoside triphosphates) that are labeled on the alpha phosphate group are typically used in reactions involving enzymes that will incorporate the deoxynucleoside monophosphate (base, sugar, and alpha phosphate) into a chain of DNA.
    • 3’ end labeling of DNA typically utilizes a chain terminator, such as a dATP that is deoxy at the 3’ position, to prevent further elongation once the radionucleotide has been incorporated. (This controls the degree of labeling). However, “tailing reactions” can also be performed to insert multiple nucleotides at the 3’ end of a DNA molecule using a radionucleotide that is not a chain terminator.
  • Compound
    • Radionucleotides are labeled with either a 32P, 33P, or 35S radioisotope. 32P is a high energy beta emitter, and will produce the highest signal. 33P and 35S are considered low energy beta emitters, and are sometimes used instead of32P to improve resolution, especially in sequencing reaction and in situ.
    • Radiolabled dATP, dCTP, dGTP, and dTTP are available. If your reaction is template-dependent, you may need to refer to the sequence of your template to choose the best radionucleotide for your assay. Some enzymatic assays are template-independent (such as end labeling with terminal transferase), and it will not matter whether the radionucleotide is a dATP, a dCTP, etc.
    • 3’ dATP is a chain terminator, because it is deoxy- (missing an oxygen) at the 3’ position. It is often used in lieu of ddATP.
  • Specific activity
    • Specific activity indicates how much radioactivity there is per molecule. The units for specific activity in the table above are Curies per millimole of nucleotide. The theoretical maximum specific activity for 32P is ~9120 Ci/mmol. The theoretical maximum specific activity for 33P is ~5000 Ci/mmol. The theoretical maximum specific activity for 35S is ~1488 Ci/mmol. Because the nucleotides in this table have only one possible labeling position, the closer the specific activity is to the theoretical maximum specific activity for the radioisotope, the greater the proportion of nucleotide molecules that are labeled with the radioisotope in the stock vial. Remember to factor in decay.
    • If you are trying to generate “hot” probes, you will want to choose a radionucleotide with a high specific activity.
    • Specific activity can always be decreased by adding more of the same “cold” (unlabeled) nucleotide. This will increase the molar concentration of the nucleotide.
  • Radioactive concentration
    • Radioactive concentration indicates the amount of radioactivity per volume. If your protocol tells you to add a certain amount of Curies to a reaction, you will need to use the radioactive concentration to determine how much to pipette. Remember to factor in decay.
  • Molar concentration refers to the molar concentration of both the labeled and unlabeled nucleotide (combined) in the stock vial.
  • Catalog numbers
    • You have up to four choices for each radionucleotide. These differ by:
      • Container: BLU products are packaged in a lead-free container (“pig”). NEG products are packaged in a lead-lined container (plastic pig containing a layer of lead). Lead provides more shielding from beta energy, but beta particles can interact with lead to generate Bremsstrahlung X-rays (Bremsstrahlung effect). You should talk to your radiation safety officer regarding container selection.
      • Formulation: EasyTides products are provided in a proprietary buffer that contains a dye to aid in pipetting, and can be stored at 4°C (avoiding freeze-thaw cycles). The EasyTides proprietary buffer does contain a somewhat higher concentration of salt, so you may want to choose a non-EasyTides (frozen) formulation if your enzyme is sensitive to salt (thermophilic polymerases for PCR such as Taq). Frozen products do not contain a dye in the buffer, and should be aliquotted (to avoid freeze-thaw cycles) and stored at -20°C.

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Ribonucleotides (RNA nucleotides) for labeling

Use this table to help you select the optimal 32P, 33P or 35S ribonucleotide for your labeling application. View more information on DNA and RNA labeling assays. 


View this table and information as pdf

ApplicationCompoundSpecific Activity (Ci/mmol)Rad. conc. (mCi/mL)Molar conc. (μM)EasyTides Version Containing Dye in Buffer (Shipped ambient, store at 2-8°C)Frozen Version (Shipped on dry ice, store at -20°C)
RNA labeling (SP6, T3, T7 RNA polymerase)ATP, [alpha-32P]8001012.5 BLU003X/NEG003X
3000103.3BLU503H/NEG503HBLU003H/NEG003H
CTP, [alpha-32P] 8001012.5BLU508X/NEG508XBLU008X/NEG008X
3000103.3BLU508H/NEG508HBLU008H/NEG008H
GTP, [alpha-32P] 8001012.5 BLU006X/NEG006X
3000103.3BLU506H/NEG506HBLU006H/NEG006H
UTP, [alpha-32P]    8001012.5BLU507X/NEG507XBLU007X/NEG007X
8002025BLU507T/NEG507T 
8004050BLU507C/NEG507CBLU007C/NEG007C
3000103.3BLU507H/NEG507HBLU007H/NEG007H
6000406.7BLU507Z/NEG507ZBLU007Z/NEG007Z
ATP, [alpha-33P]3000103.3NEG603H 
CTP, [alpha-33P]3000103.3NEG608H 
GTP, [alpha-33P]3000103.3NEG606H 
UTP, [alpha-33P]3000103.3NEG607HNEG307H
ATPalphaS, [35S]125012.510 NEG033H
CTPalphaS, [35S] 125012.510 NEG064H
12507056 NEG064C
UTPalphaS, [35S] 8004050 NEG039C
125012.510NEG739HNEG039H
3' end labeling of RNA 
using T4 RNA ligase
pCp, [5'-32P]3000103.3 BLU019A/NEG019A
5' end labeling of DNA 
or RNA (T4 PNK)      
ATP, [gamma-32P]    102200 BLU002/NEG002
300051.7BLU502H/NEG502HBLU002H/NEG002H
3000103.3BLU502A/NEG502ABLU002A/NEG002A
6000101.7BLU502Z/NEG502ZBLU002Z/NEG002Z
600015025 NEG035C
ATP, [gamma-33P]3000103.3NEG602HNEG302H
ATP, [gamma-33P] for 
HTS (stabilized)
3000103.3NEG602K 

Guidelines for choosing a ribonucleotide from the above table:

  • Application
    • rNTPs (ribonucleoside triphosphates) that are labeled on the alpha phosphate group are typically used in reactions involving enzymes that will incorporate the ribonucleoside monophosphate (base, sugar, and alpha phosphate) into a chain of RNA.
    • 3’ end labeling of RNA or DNA typically utilizes a chain terminator. Examples include 5’- 32P-pCp for use with T4 RNA ligase, or dATP that is deoxy at the 3’ position for use with terminal transferase. The use of chain terminators prevents further elongation once the radionucleotide has been incorporated, which controls the degree of labeling. However, “tailing reactions” can also be performed to insert multiple nucleotides at the 3’ end of a piece of RNA (or DNA) using a radionucleotide that is not a chain terminator.
  • Compound
    • Radionucleotides are labeled with either 32P, 33P, or 35S radioisotope. 32P is a high energy beta emitter, and will produce the highest signal. 33P and 35S are considered low energy beta emitters, and are sometimes used instead of32P to improve resolution.
    • Radiolabled ATP, CTP, GTP, and UTP are available. If your reaction is template-dependent, you may need to refer to the sequence of your template to choose the best radionucleotide for your assay. Some enzymatic assays are template-independent, and it will not matter whether the radionucleotide is an ATP, a CTP, etc.
    • 5’-pCp is a chain terminator because there is a phosphate group at the 3’ position of the sugar, rather than a hydroxyl group. The 5’ phosphate group of pCp is labeled with 32P.
    • 33P-gamma-ATP for high-throughput screening (NEG602K) contains a stabilizer in the buffer that allows you to keep the radiochemical at room temperature for longer periods of time while you are setting up plates
  • Specific activity
    • Specific activity indicates how much radioactivity there is per molecule. The units for specific activity in the table above are Curies per millimole of nucleotide. The theoretical maximum specific activity for 32P is ~9120 Ci/mmol. The theoretical maximum specific activity for 33P is ~5000 Ci/mmol. The theoretical maximum specific activity for 35S is ~1488 Ci/mmol. Because the nucleotides in this table have only one possible labeling position, the closer the specific activity is to the theoretical maximum specific activity for the radioisotope, the greater the proportion of nucleotide molecules that are labeled with the radioisotope in the stock vial. Remember to factor in decay.
    • If you are trying to generate “hot” probes, you will want to choose a radionucleotide with a high specific activity.
    • Specific activity can always be decreased by adding more of the same “cold” (unlabeled) nucleotide. This will increase the molar concentration of the nucleotide.
  • Radioactive concentration
    • Radioactive concentration indicates the amount of radioactivity per volume. If your protocol tells you to add a certain amount of Curies to a reaction, you will need to use the radioactive concentration to determine how much to pipette. Remember to factor in decay.
  • Molar concentration refers to the molar concentration of both the labeled and unlabeled nucleotide (combined) in the stock vial.
  • Catalog numbers
    • You have up to four choices for each radionucleotide. These differ by:
      • Container: BLU products are packaged in a lead-free container (“pig”). NEG products are packaged in a lead-lined container (plastic pig containing a layer of lead). Lead provides more shielding from beta energy, but beta particles can interact with lead to generate Bremsstrahlung X-rays (Bremsstrahlung effect). You should talk to your radiation safety officer regarding container selection.
      • Formulation: EasyTides products are provided in a proprietary buffer that contains a dye to aid in pipetting, and can be stored at 4°C (avoiding freeze-thaw cycles). The EasyTides proprietary buffer does contain a somewhat higher concentration of salt, so you may want to choose a non-EasyTides (frozen) formulation if your enzyme is very sensitive to salt. Frozen products do not contain a dye in the buffer, and should be aliquotted (to avoid freeze-thaw cycles) and stored at -20°C.

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Nucleotides for kinase and other protein-based assays

Use this table to help you select the optimal 32P, 33P or 35S nucleotide for your kinase or protein-based assay. View more information on phosphorylation assays. View more information on GTP binding assays. 


View this table and information as pdf

ApplicationCompoundSpecific Activity (Ci/mmol)Rad. conc. (mCi/mL)Molar conc. (μM)EasyTides Version Containing Dye in Buffer (Shipped ambient, store at 2-8°C)Frozen Version (Shipped on dry ice, store at -20°C)
Protein phosphorylation, 5' end labeling of DNA or RNA (T4 PNK, protein kinase)ATP, [gamma-32P]    102200 BLU002/NEG002
300051.7BLU502H/NEG502HBLU002H/NEG002H
3000103.3BLU502A/NEG502ABLU002A/NEG002A
6000101.7BLU502Z/NEG502ZBLU002Z/NEG002Z
600015025 NEG035C
ATP, [gamma-33P]3000103.3NEG602HNEG302H
ATP, [gamma-33P] for HTS (stabilized)3000103.3NEG602K 
GTP, [gamma-P32]6000101.7BLU504Z/NEG504ZBLU004Z/NEG004Z
Protein thiophosphorylationATPgammaS, [35S] 25-10012.5125-500 NEG027
125012.510 NEG027H
Cycle sequencingGTP, [gamma-33P]3000103.3NEG604H 
Adenyl and guanyl cyclase assaysATP, [alpha-32P] 8001012.5 BLU003X
3000103.3BLU503HBLU003H
GTP, [alpha-32P]8001012.5 BLU006X
ADP ribosylation of proteinsNAD, [32P]80056.3 BLU023X/NEG023X
GTP binding/G Protein/P2Y receptor studies GTPgammaS, 
[35S] 
non-
hydrolyzable 
125012.510 NEG030H
125010.8 NEG030X

Guidelines for choosing a ribonucleotide from the above table:

  • Application
    • Protein thiophosphorylation is a protein phosphorylation technique (for protein kinases) that uses a 35S-labeled ATP. The reaction is the same as for protein phosphorylation assays using ATPγ 32P or 33P.
    • Cycle sequencing reactions measure the dissociation of the gamma phosphate group of GTP during hydrolysis of GTP to GDP.
    • Adenyl and guanyl cyclase assays measure the conversion of radioactive ATP or GTP to radioactive cAMP or cGMP, respectively.
    • ADP ribosylation measures ADP-ribosylated proteins by incorporation of radiolabeled NAD
    • GTP binding assays are functional assays for GPCRs, and measure exchange of GDP for radiolabeled, non-hydrolyzable GTP analog upon activation.
  • Compound
    • Radionucleotides are labeled with either 32P, 33P, or 35S radioisotope. 32P is a high energy beta emitter, and will produce high signal. 33P and 35S are considered low energy beta emitters, and are sometimes used instead of 32P to improve resolution in autoradiography.
    • 33P-gamma-ATP for high-throughput screening (NEG602K) contains a stabilizer in the buffer that allows you to keep the radiochemical at room temperature for longer periods of time while you are setting up plates
  • Specific activity
    • Specific activity indicates how much radioactivity there is per molecule. The units for specific activity in the table above are Curies per millimole of nucleotide. The theoretical maximum specific activity for 32P is ~9120 Ci/mmol. The theoretical maximum specific activity for 33P is ~5000 Ci/mmol. The theoretical maximum specific activity for 35S is ~1488 Ci/mmol. Because the nucleotides in this table have only one possible labeling position, the closer the specific activity is to the theoretical maximum specific activity for the radioisotope, the greater the proportion of nucleotide molecules that are labeled with the radioisotope in the stock vial. Remember to factor in decay.
  • Radiochemical concentration
    • Radiochemical concentration indicates the amount of radioactivity per volume. If your protocol tells you to add a certain amount of Curies to a reaction, you will need to use the radioactive concentration to determine how much to pipette. Remember to factor in decay.
  • Molar concentration refers to the molar concentration of both the labeled and unlabeled nucleotide (combined) in the stock vial.
  • Catalog numbers
    • You have up to four choices for each radionucleotide. These differ by:
      • Container: BLU products are packaged in a lead-free container (“pig”). NEG products are packaged in a lead-lined container (plastic pig containing a layer of lead). Lead provides more shielding from beta energy, but beta particles can interact with lead to generate Bremsstrahlung X-rays (Bremsstrahlung effect). You should talk to your radiation safety officer regarding container selection.
      • Formulation: EasyTides products are provided in a proprietary buffer that contains a dye to aid in pipetting, and can be stored at 4°C (avoiding freeze-thaw cycles). The EasyTides proprietary buffer does contain a somewhat higher concentration of salt, so you may want to choose a non-EasyTides (frozen) formulation if your enzyme is very sensitive to salt. Frozen products do not contain a dye in the buffer, and should be aliquotted (to avoid freeze-thaw cycles) and stored at -20°C.

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Methionine


Refer to information directly below the table for more guidance. View more information on cell labeling with 35S methionine.
View table and information as pdf

ProductWhen to Use This FormulationRad. conc./Specific ActivityBufferStorage and StabilityCatalog Number
EXPRESS [35S]-protein labeling mix 
  • Cell labeling only
  • Contains both 35S-L-methionine and 35S-L-cysteine (73:22) from E. coli hydrolysate.
11 mCi/mL 
1175 Ci/mmol
  • 50 mM Tricine pH 7.4
  • 10 mM β-mercaptoethanol
Shipped on dry ice. Store at -80°C. Use within 1 month.NEG072
  • Cell labeling only
  • EasyTag formulation (can be stored at 4 °C)
  • Contains both 35S-L-methionine and 35S-L-cysteine (73:22) from E. coli hydrolysate.
11 mCi/mL 
1175 Ci/mmol
  • 25 mM Tricine (pH 7.8)
  • With stabilizer, EasyTag but with no blue dye
  • No β-mercaptoethanol
Shipped ambient. Store at 4°C. Use within 1 month of receiptNEG772
Methionine, L-[35S]     
  • Cell labeling or IVT*
  • High radioactive concentration
43.3 mCi/mL 
1175 Ci/mmol
  • 50 mM Tricine (pH 7.8)
  • 10 mM β-mercaptoethanol
Shipped in dry ice, Store at -20°C or lower. Use within 1 month of receiptNEG009C
  • Cell labeling or IVT
  • Tricine-stabilized
10.2 mCi/mL 
1175 Ci/mmol
  • 50 mM Tricine (pH 7.8)
  • 10 mM β-mercaptoethanol
Shipped in dry ice, Store at -20°C or lower. Use within 1 month of receiptNEG009A
  • Cell labeling or IVT
  • EasyTag formulation (contains a blue dye in buffer and can be stored at 4°C).
10.2 mCi/mL 
1175 Ci/mmol
  • 25 mM Tricine (pH 7.8)
  • Stabilizer containing blue dye
  • 10 mM β-mercaptoethanol
Shipped ambient, Store at 4°C or lower. Use within 1 month of receiptNEG709A
  • Cell labeling or IVT
31.5 mCi/mL 
1175 Ci/mmol
  • 10 mM β-mercaptoethanol
Shipped in dry ice, Store at -20°C or lower. Use within 1 month of receiptNEG009L
  • Cell labeling or IVT
11 mCi/mL 
1175 Ci/mmol
  • 10 mM β-mercaptoethanol
Shipped in dry ice, Store at -20°C or lower. Use within 1 month of receiptNEG009H
  • Cell labeling or IVT (developed for IVT)
11 mCi/mL 
1175 Ci/mmol
  • 10 mM β-mercaptoethanol
Shipped in dry ice, Store at -20°C or lower. Use within 1 month of receiptNEG009T

*IVT stands for In Vitro Translation


Guide for using above table:

  • Product
    • EXPRE35S35S labeling mix contains both 35S-methionine and 35S-cysteine. The material is prepared from a crude extract of E. coli
    • In EXPRE35S35S labeling mix, the relative concentration of methionine and cysteine is 73% to 22%.
  • When to use...
    • Cell labeling experiments refer to cell-based assays.
    • IVT refers to cell-free in vitro translation assays (for example, using a reticulocyte lysate).
  • Radioactive concentration/specific activity
    • Radioactive concentration is sometimes used to determine what volume of radiochemical to use to make your working solutions, or what volume of radiochemical to add to your assay. If your protocol dictates that you add a certain amount of Curies to each reaction, you will use the radioactive concentration to determine how much to pipette.
    • All products are currently offered at the same specific activity. Specific activity indicates the amount of radioactivity per millimole of methionine. The maximum theoretical specific activity for 35S is ~1488 Curies per millimole of sulfur. Because there is only one possible labeling position on these radiochemicals, a specific activity of 1175 Ci/mmol indicates that a large proportion of the molecules in the vial are labeled on the calibration date.
    • Molar concentration (of both hot and cold methionine in the stock vial) can be determined by taking the radioactive concentration and dividing by the specific activity. Make sure your units cancel out correctly. If your protocol is telling you to add a higher molar concentration than what the product is supplied as, you may need to increase the molar concentration by adding cold methionine. This will decrease the specific activity of radiolabeled methionine in the assay.
  • Buffer
    • Tricine is a stabilizing buffer. Products packed in tricine should have greater stability through multiple manipulations, though we still recommend using 35S-methionine products within one month of receipt.
    • EasyTag products are in a proprietary buffer formulation that allows the product to be stored at 4°C
    • β-mercaptoethanol is a reducing agent, and helps to slow the build-up of volatile 35S by-products in the stock vial over time. However, β-mercaptoethanol can be somewhat toxic to cells. Regardless of which formulation you chose, always take appropriate safety precautions when working with radioactivity – talk to your radiation safety officer for more guidance.
  • Storage and stability
    • Most products need to be stored at -20°C or lower. EasyTag products can be stored at 4°C.
    • We recommend you use 35S-methionine within one month of receipt.

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Thymidine


Refer to the information below the table for more guidance. View more information on thymidine uptake assays

View this table and information as pdf

Primary ApplicationCompoundSpecific ActivityRad. conc. (mCi/mL)Packaging BufferStorage Temp.NotesCatalog Number
DNA proliferation         Thymidine, [methyl-14C] 40-60 mCi/mmol0.1Steri-packaged, aqueous solution5°C NEC568
50-62 mCi/mmol0.05Steri-packaged, aqueous solution5°C NEC568D
Thymidine, [methyl-3H]       2 Ci/mmol1Steri-packaged, aqueous solution5°CRecommend use within one month of receiptNET027A
6.7 Ci/mmol1Steri-packaged, aqueous solution5°CRecommend use within one month of receiptNET027
20 Ci/mmol1Steri-packaged, aqueous solution5°CRecommend use within one month of receiptNET027X
20 Ci/mmol170% ethanol-20°C NET027E
23-27 Ci/mmol110% ethanol5°C NET027L
40-60 Ci/mmol12% ethanol5°C NET027W
70-90 Ci/mmol1Steri-packaged, aqueous solution5°CRecommend use within one month of receiptNET027Z
100-130 Ci/mmol12% ethanol5°CRecommend use within one month of receiptNET512V
Total nucleic acid proliferation  Thymidine, [2-14C]>50 mCi/mmol0.1Steri-packaged, aqueous solution5°C NEC156
Thymidine, [6-3H] >10 Ci/mmol1Steri-packaged, aqueous solution5°C NET355
5-6 Ci/mmol1Steri-packaged, aqueous solution5°C NET355L
DNA probe labeling    Deoxythymidine triphosphate, [methyl-3H]    10-25 Ci/mmol150% ethanol-20°C NET221H
70-90 Ci/mmol150% ethanol-20°C NET221X
70-90 Ci/mmol2.510 mM Tricine buffer pH 7.6-80°C NET221A
90-120 Ci/mmol2.510 mM Tricine buffer pH 7.6-80°C NET520A
90-130 Ci/mmol150% ethanol-20°C NET520V

Guidelines for choosing a thymidine radiochemical from the table above:

  • Primary application
    • Most cell proliferation assays measure DNA proliferation (incorporation of radiolabeled thymidine into DNA, specifically)
    • Total nucleic acid proliferation can also be studied using a thymidine that is radiolabeled, but not on the methyl group.
    • DNA probes are created by incorporation of deoxythymidine triphosphate (dTTP)
  • Compound
    • Either 14C-labeled thymidine or 3H-thymidine can be used in proliferation assays. 14C has higher energy compared to3H. 14C also has higher efficiency compared to 3H in liquid scintillation counting. Your radioactive license may restrict you to one radioisotope or the other. You will want to consult your radiation safety officer when selecting a radioisotope for your assay.
  • Specific activity
    • Specific activity indicates how much radioactivity there is per molecule. The units for specific activity in the table above are Curies per millimole of thymidine, or milliCuries per millimole of thymidine. The theoretical maximum specific activity for 3H is ~29 Ci/mmol. Because there are multiple possible H labeling positions in these products, the specific activity of some 3H thymidine products will be greater than the theoretical maximum specific activity for 3H. This indicates that on average, each thymidine molecule has more than one tritium. The theoretical maximum specific activity for 14C is ~62 mCi per millimole of 14C. Because there is only one possible carbon labeling position on these products, products with a specific activity that approaches the theoretical maximum specific activity for 14C indicate that nearly every thymidine molecule is labeled with 14C.
    • If you need your assay to be very sensitive, choose a product with high specific activity (for the given radioisotope).
    • Specific activity can always be decreased by adding more of the same “cold” (unlabeled) thymidine. This will increase the molar concentration of thymidine.
  • Radioactive concentration
    • Radiochemical concentration indicates the amount of radioactivity per volume. If your protocol tells you to add a certain amount of Curies to a reaction, you will need to use the radioactive concentration to determine how much to pipette.
  • Packaging buffer
    • Thymidines that are packaged in ethanol tend to have a longer shelf-life, however, ethanol can be toxic to cells. You may need to evaporate off any ethanol prior to using in an assay.
    • Products that are “steri-packaged” are prepared with additional precautions to substantially reduce product bioburden and enhance product stability. PerkinElmer makes no warranties, whether expressed or implied, with respect to the sterility or non-pyrogenicity of these or any products.
  • Notes
    • Some products have explicit recommended time frames during which they can be used. This is because degradation studies have shown the chemical structure of the product degrades over time to the extent that it is no longer recommended for its intended application. The packaging buffer influences the shelf-life of the product. Thymidine packaged in ethanol will have a longer shelf-life than aqueous thymidine.

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Iodine for protein labeling


Iodine-125 and Iodine-131 are typically used for labeling peptides and proteins. See 125I Labeling of proteins for applications information. For help in choosing between 125I and 131I, see Choosing an iodination technique

View this table and information as pdf

ProductWhen to Use This FormulationRad. conc./Specific ActivityBufferStorage and Stability
NEZ033 Iodine-125 (carrier-free)High pH formulation minimizes volatility. Adjust pH as needed with HCl or acetic acid. Packaged in 0.1 mL volume regardless of amount of radioactivity ordered. (Radioactive concentration varies depending on amount ordered.)Radioactive concentration depends on size ordered, ~17 Ci/mg0.1M NaOH, pH 12-14Shipped ambient. Store at room temperature.
NEZ033A Iodine-125 (carrier-free)Lower pH is more convenient, requiring less adjustment.100 mCi/mL, ~17 Ci/mg1X10-5M NaOH, pH 8-11Shipped ambient. Store at room temperature.
NEZ033H Iodine-125 (carrier-free)High pH formulation minimizes volatility. Adjust pH as needed with HCl or acetic acid. Recommended for Iodogen labeling.350 mCi/mL, ~17 Ci/mg0.1M NaOH, pH 12-14Shipped ambient. Store at room temperature.
NEZ033L Iodine-125 (carrier-free)Lower pH is more convenient, requiring less adjustment.350 mCi/mL, ~17 Ci/mg1X10-5M NaOH, pH 8-11Shipped ambient. Store at room temperature.
NEZ035A Iodine-131High pH formulation minimizes volatility. Adjust pH as needed with HCl or acetic acid. Flat-bottom vial that can hold up to 5 mL reaction volume if reaction performed in vial.>5 Ci/mg0.1 N NaOH, pH 12-14Shipped ambient. Store at room temperature.
NEZ035H Iodine-131High pH formulation minimizes volatility. Adjust pH as needed with HCl or acetic acid. Round-bottom vial that can hold up to 0.8 mL reaction volume if reaction performed in vial.>500 mCi/mL, >5 Ci/mg0.1 N NaOH, pH 12-14Shipped ambient. Store at room temperature.
NEX120 Bolton-Hunter Reagent125I mono-iodinatedThe mono-iodinated form is generally recommended for most Bolton-Hunter iodinations.2200 Ci/mmolPackaged in anhydrous benzene. A charcoal trap is included with each vial.Shipped ambient. Store at room temperature
NEX120H Bolton-Hunter Reagent125I di-iodinatedDouble the specific activity (or 4400 Ci/mmol) for each molecule of reagent. Use when the extra sensitivity is important relative to decrease in stability.4400 Ci/mmolPackaged in anhydrous benzene. A charcoal trap is included with each vial.Shipped ambient. Store at room temperature

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Glucose for glucose uptake assays


Refer to the information below this table for guidance in choosing your glucose or glucose analog for a glucose uptake assay. View more information on glucose uptake assays

View this table and information as pdf

ChemicalRadioisotopeLabelingSolventSpecific ActivityRad. conc.StorageCatalog Number
2-deoxy-D-glucose      3H   N (1,2 position)90% ethanol5-10 Ci/mmol1 mCi/mL-20°CNET328
N (1,2 position)steri-packaged aqueous solution5-10 Ci/mmol1 mCi/mL4°CNET328A
N (1,2 position)90% ethanol25-50 Ci/mmol1 mCi/mL-20°CNET549
N (1,2 position)steri-packaged aqueous solution25-50 Ci/mmol1 mCi/mL4°CNET549A
14C  (position 1)90% ethanol45-60 mCi/mmol0.1 mCi/mL-20°CNEC495
(position 1)steri-packaged aqueous solution45-60 mCi/mmol0.1 mCi/mL4°CNEC495A
Usteri-packaged aqueous solution250-350 mCi/mmol0.1 mCi/mL4°CNEC720A
3-O-methyl-D-glucose14C(methyl group)90% ethanol30-60 mCi/mmol0.1 mCi/mL-20°CNEC377
D-Glucose          3H    N (2 position)90% ethanol20-30 Ci/mmol1 mCi/mL-20°CNET238C
(3 position)90% ethanol10 -20 Ci/mmol1 mCi/mL-20°CNET331C
(3 position)steri-packaged aqueous solution10-20 Ci/mmol1 mCi/mL4°CNET331A
N (5 position)90% ethanol10-20 Ci/mmol1 mCi/mL-20°CNET531
N (6 position)90% ethanol25-50 Ci/mmol1 mCi/mL-20°CNET100C
14C     (position 1)90% ethanol45-60 mCi/mmol0.1 mCi/mL4°CNEC043X
(position 6)3% ethanol50-62 mCi/mmol0.2 mCi/mL-20°CNEC045X
U90% ethanol1-5 mCi/mmol0.1 mCi/mL4°CNEC042A
U90% ethanol250-360 mCi/mmol1 mCi/mL4°CNEC042B
U90% ethanol250-360 mCi/mmol0.1 mCi/mL4°CNEC042X
U3% ethanol250-360 mCi/mmol0.2 mCi/mL-20°CNEC042V

How to select a radiochemical from the above table:

  • Chemical
    • Deoxy-D-glucose (DOG) is a glucose analog that is readily transported into most cells, is phosphorylated and trapped by the cells (unidirectional transport), and cannot be further metabolized. It is the most-common chemical used in glucose uptake assays.
    • 3-O-methyl-D-glucose (OMG) is another glucose analog that is readily transported into most cells, but does not become phosphorylated and therefore will equilibrate across the cell membrane. Equilibrium is usually reached rapidly, so the assay may only be linear for a short period of time; you may need to take your measurements fairly quickly. This analog also cannot be further metabolized by cells.
    • D-Glucose (non-analog) can be incorporated into lipids, which provides a measurement of glucose transport. It is a metabolized tracer.
  • Radioisotope: Either 14C-labeled glucose and glucose analogs, or 3H-labeled glucose and glucose analogs, can be used in glucose uptake assays. 14C has higher energy compared to 3H. 14C also has higher efficiency compared to 3H in liquid scintillation counting. Your radioactive license may restrict you to one radioisotope or the other. You will want to consult your radiation safety officer when selecting a radioisotope for your assay.
  • Packaging
    • Glucose that is packaged in ethanol will be more-resistant to contamination by bacteria or other microbes. Preventing contamination is one way to ensure the longest shelf-life for a chemical (particularly in the case of glucose, because it is an excellent food-source for microbes).
    • For cell labeling or in vivo experiments, you may need to evaporate off any ethanol in the stock material prior to use, as ethanol can be toxic to cells.
    • Products that are “steri-packaged” are prepared with additional precautions to substantially reduce product bioburden and enhance product stability. PerkinElmer makes no warranties, whether expressed or implied, with respect to the sterility or non-pyrogenicity of these or any products.
  • Labeling positions: for uptake assays, the actual positioning of label is of less importance than it would be if you were performing an enzymatic assay, as uptake of the intact glucose or glucose analog is being traced
    • U (uniformly-labeled): designation for compounds labeled in all positions in a uniform or nearly uniform pattern
    • N (nominally-labeled): designation when the method of preparation requires some (usually a significant amount) of the label to be at a specific site or sites, but no further information is available on the extent (if any at other positions)
    • G (generally-labeled): designation for compounds in which there is a random distribution of radioactivity at various positions
    • Specifically labeled: designation used when all labeled positions are identified and the radioactivity at these positions is greater than 95% of the total incorporated into the compound
  • Specific activity: the higher the specific activity, the greater the amount of radioactivity there is per glucose molecule. Specific activity is given in units of Curies per millimole of glucose or glucose analog, or milliCuries per millimole of glucose or glucose analog. The theoretical maximum specific activity of tritium is ~29 Ci/mmol (Curies per millimole of tritium). 3H products with a specific activity over this value indicate that on average, each glucose or glucose analog molecule contains more than one tritium. The theoretical maximum specific activity of 14C is ~62 mCi/mmol (milliCuries per millimole of carbon). 14C products with a specific activity over this value indicate that on average, each glucose or glucose analog molecule contains more than one labeled carbon. Specific activity can be decreased by adding cold glucose or glucose analog.

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Phosphate for cell labeling


Refer to the information below this table for guidance in choosing a product for your cell labeling assay. View this table and information as pdf

ProductIsotopeDiluentSpecific ActivityRadioactive ConcentrationCatalog Number
Orthophosphoric acid (orthophosphate), carrier-free    32P   Water   8500-9120 Ci/mmol   Depends on size ordered - packaged in 1 mL water, no matter sizeNEX053
>500 mCi/mLNEX053C
10 mCi/mLNEX053H
150 mCi/mLNEX053S
33PWater40-158 Ci/mg5 mCi/mL 
NEZ080
Disodium phosphate32PWater900-1100 mCi/mmolVaries depending on amount of radioactivity ordered - packaged in 1 mL water, no matter sizeNEX011
Dipotassium phosphate32PWater900-1100 mCi/mmolVaries depending on amount of radioactivity ordered - packaged in 1 mL water, no matter sizeNEX055
Monopotassium phosphate32PWater900-1100 mCi/mmolVaries depending on amount of radioactivity ordered - packaged in 1 mL water, no matter sizeNEX060
Monosodium phosphate32PWater900-1100 mCi/mmolVaries depending on amount of radioactivity ordered - packaged in 1 mL water, no matter sizeNEX063

Guidance for using above table:

  • Most protocols use orthophosphate rather than a phosphate salt for labeling
  • If your protocol calls for carrier-free 32P or 33P phosphate, use NEX053/NEX053C/NEX053H/NEX053S for 32P or NEZ080 for 33P
  • Higher specific activity indicates that there is more radioactivity per millimole or milligram of phosphorus. Units are given either as Curies per millimole of phosphorus, or Curies per milligram of phosphorus. As you approach the theoretical maximum specific activity for a radionuclide (~9120 Ci/mmol for 32P; or ~5000 Ci/mmol for 33P), a greater proportion of phosphorus in the stock vial is labeled. Products at maximum theoretical specific activity for a given isotope are termed "carrier-free". Specific activity can be lowered by adding cold phosphate.
  • For the products above, use the molecular weight of phosphorus itself (rather than the phosphate salt) to convert from Ci/mmol to Ci/mg, and vice versa

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Radioligands for ligand binding assays


View more information on radioligand binding assays. You can also view our GPCR/radioligand selection guide. When selecting a radioligand, there are a few factors to keep in mind:

When selecting a radioligand, there are a few factors to keep in mind:

  • High specific activity: Radioligands with a high specific activity are well-suited for ligand binding assays. Specific activities indicates how much radioactivity there is per molecule of ligand, and is usually given in units of Curies per millimole of ligand. Several of our 125I-labeled ligands are offered at maximum specific activity (2200 Ci/mmol if one 125I labeling site is available, 4400 Ci/mmol if two 125I labeling sites are available, etc.). This indicates that virtually every molecule of ligand provided in the stock vial is radiolabeled. For tritiated ligands (3H ligands), you should ideally pick a ligand that has a specific activity above 20 Ci/mmol. The maximum theoretical specific activity per tritium is 29 Ci/mmol (Curies per millimole of tritium). Specific activities above this value indicate that on average, each molecule of ligand has at least one tritium.
  • Low non-specific binding: Hydrophobic ligands will generally show higher non-specific binding. This can sometimes be compensated by coating filters with BSA to reduce non-specific binding. Including BSA, salts or detergents in the wash or binding buffer can also help reduce non-specific binding. If the stock radiochemical is packaged in a silanized vial (refer to the tech data sheet), this may indicate the ligand is somewhat hydrophobic
  • High purity: Ideally, the ligand should have a radiochemical purity above 90%. Radiochemical purity decreases over time, and the actual rate of this degradation accelerates over time. Radiochemical purity and degradation rates for our various radiochemicals can be found on the lot-specific technical data sheets.
  • High selectivity: The more selective the ligand is for your receptor, the better your data will be. High selectivity indicates the ligand will mostly be recognized by only one receptor-of-interest, over other receptors that may be present in a cell membrane. Also, using membranes that over-express the receptor of interest may help reduce any potential contribution from receptors endogenously expressed in the membrane.
  • Stability: If you will need to use your radioligand over an extended period of time, stability may be a factor for you. 125I-labeled ligands should generally be used within one to two months of the manufacture date. Tritiated ligands should usually be used within 3-6 months of manufacture date; however, there are exceptions to this. Degradation rates and manufacturing dates can be found on our lot-specific technical data sheets. You can also contact technical support to discuss the recommended use time for each PerkinElmer radiochemical - our contact information is on the upper right-hand corner of this page.
  • Energy3H releases beta energy, which can be measured on a scintillation counter after the addition of scintillant (in the form of a scintillation cocktail, Meltilex® solid scintillant, an SPA bead, a FlashPlate®, etc.). The beta energy interacts with the scintillant to produce photons, which are measured by the detector. 125I releases both beta-like energy and gamma energy. If you only have access to a gamma counter, you should use a radioligand labeled with 125I. An additional factor is assay format. 125I gives off more beta-like energy than 3H. If you will be performing a FlashPlate assay, it will be easier to develop an assay using a radioligand labeled with 125I because the scintillant is embedded within the walls of the plate (greater distance between radioligand and scintillant). For SPA assays, either 3H or 125I-labeled ligands can be used effectively.

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