Alexa Fluor Dye-labeled Peptide Synthesis Service

Thermo Scientific Custom Peptide synthesis service offers dye-labeled peptide synthesis for a broad range of dyes, featuring our highly cited, high performance Alexa Fluor dyes to meet a variety of research needs. Peptides between 6 and 70 amino acids in length are synthesized and labeled using the latest FMOC solid-phase technology and purified using HPLC. A range of peptide synthesis scales (1 mg–10 mg) and purity (crude to 98%) are available.

Custom Alexa Fluor Dye-Labeled Peptide synthesis service specifications

Peptide length 6-70* amino acids
Manufacturing scale 1-10mg**
Purity options From crude to >98% pure
Quality control MALDI MS and analytical HPLC
Production time 2-3 weeks
Modifications Extensive list of modifications and labels
Conjugation site considerations
  • -C-terminal conjugation to carboxyl groups (-COOH). The side chains of Asp and Glu will (partly) react
  • N-terminal conjugation to amino groups (-NH2). The side chains of Lys will react
  • Conjugation to the thiol group (-SH) of Cys. In this case all Cys in the sequence will react

* Please inquire about shorter or longer peptide lengths
** Greater amounts available upon request.

Synthesis service features

  • High performing dyes–Alexa Fluor dye conjugates exhibit more intense fluorescence compared to other spectrally similar conjugates
  • Versatility–broad selection of dyes and other modifications for detection available
  • Validation–all peptides are analyzed by MALDI MS alone or combined with analytical HPLC
  • Economical–conjugation services with Alexa Fluor dyes are cost effective compared to other suppliers

Alexa Fluor dyes available

Alexa Fluor dye Absorption
max. (nm)
Emission
max (nm)
Emission color* Extinction
coefficient**
Alexa Fluor 350 346 442 Blue 19,000
Alexa Fluor 405 401 421 Blue 34,000
Alexa Fluor 430 433 541 Green/Yellow 16,000
Alexa Fluor 488 496 519 Green 71,000
Alexa Fluor 532 532 553 Yellow 81,000
Alexa Fluor 546 556 573 Orange 104,000
Alexa Fluor 555 555 565 Orange 150,000
Alexa Fluor 568 578 603 Orange/Red 91,000
Alexa Fluor 594 590 617 Red 73,000
Alexa Fluor 610 612 628 Red 138,000
Alexa Fluor 633 632 647 Far Red 239,000
Alexa Fluor 635 633 647 Far Red 140,000
Alexa Fluor 647 650 665 Near-IR*** 239,000
Alexa Fluor 660 663 690 Near-IR*** 132,000
Alexa Fluor 680 679 702 Near-IR*** 184,000
Alexa Fluor 700 702 723 Near-IR*** 192,000
Alexa Fluor 750 749 775 Near-IR*** 240,000
Alexa Fluor 790 784 814 Near-IR*** 270,000
* Typical emission color seen through the eyepiece of a conventional fluorescence microscope with appropriate filters.
** Extinction coefficient at lmax in cm–1M–1
*** Human vision is insensitive to light beyond ~650 nm; it is not possible to view near-IR fluorescent dyes.

Frequently asked questions

What is the delivery format?

Our standard peptides are delivered lyophilized with trifluoroacetate (TFA) as a counterion and packaged in glass vials, stored under argon to protect from oxygen. For additional formats, such as delivery in low-binding plastics or 2-D barcoded plates, or in-solution with different solvents, please inquire.

What is your quality control (QC)?

The detailed spectra are included on the Certificate of Analysis for your records. Additional quality controls such as amino acid analysis (AAA) and further nonstandard analysis are available on request.

Q. How should peptides be stored?

A. We recommend preparing single-use aliquots and storing the products immediately at –20°C, upon receipt. In this manner, the lyophilized peptides are stable for several years. Solubilized peptides should be used immediately because they are unstable (the lower the concentration, the more unstable the peptides are). Any remaining peptides in solution should be re-lyophilized for longer storage.

Q. How should peptides be handled?

A. Always wear gloves when working with peptides to avoid contamination (e.g., enzymatic, bacterial, etc.). As many peptides are light-sensitive, they should also be protected from direct light. Avoid repeated freeze-thaw cycles.

Q. How are peptides solubilized?

A. Peptides are complex biomolecules, and each peptide has unique chemical and physical properties because of the unique amino acid composition. Although some peptides are easy to dissolve in aqueous solutions, peptides are often insoluble, especially when they contain long stretches of hydrophobic amino acids.

General guidelines for solubilizing peptides:

Because of the unique solubility of each peptide, we recommend first testing the solubilization of each peptide with a small amount of product.

  1. Always use sterile water or buffer [phosphate buffered saline (PBS), Tris or phosphate, pH 7] to solubilize peptides.
  2. Oxygen-free solvents should be used to solubilize peptides containing cysteine, methionine or tryptophan, which are susceptible to rapid oxidation.
  3. Allow the peptide to warm to room temperature (preferably in a desiccator) prior to adding the solvent of choice.
  4. Solubilization can be improved by warming (<40°C) or sonicating the solution.
  5. If the pH of the solution needs to be increased, use only very weak bases to prevent immediate inactivation or racemization.

Guidelines for solubilizing hydrophobic peptides:

  1. If the product proves to be insoluble in aqueous buffers due to high hydrophobicity, dissolve a small amount of product in the smallest possible volume of a 50% (v/v) DMSO/water mixture. Then add the desired aqueous solution until the target concentration is achieved.
  2. If the product precipitates during this process and cannot be redissolved by adding dimethylsulfoxide (DMSO), then lyophilize the peptide and try again, adding a little more 50% DMSO than in the previous attempt.
  3. If DMSO interferes with your experimental system, dimethylformamide (DMF) or acetonitrile can serve as alternate solvents.

Custom Alexa Fluor Dye-Labeled Peptide synthesis service specifications

Peptide length 6-70* amino acids
Manufacturing scale 1-10mg**
Purity options From crude to >98% pure
Quality control MALDI MS and analytical HPLC
Production time 2-3 weeks
Modifications Extensive list of modifications and labels
Conjugation site considerations
  • -C-terminal conjugation to carboxyl groups (-COOH). The side chains of Asp and Glu will (partly) react
  • N-terminal conjugation to amino groups (-NH2). The side chains of Lys will react
  • Conjugation to the thiol group (-SH) of Cys. In this case all Cys in the sequence will react

* Please inquire about shorter or longer peptide lengths
** Greater amounts available upon request.

Synthesis service features

  • High performing dyes–Alexa Fluor dye conjugates exhibit more intense fluorescence compared to other spectrally similar conjugates
  • Versatility–broad selection of dyes and other modifications for detection available
  • Validation–all peptides are analyzed by MALDI MS alone or combined with analytical HPLC
  • Economical–conjugation services with Alexa Fluor dyes are cost effective compared to other suppliers

Alexa Fluor dyes available

Alexa Fluor dye Absorption
max. (nm)
Emission
max (nm)
Emission color* Extinction
coefficient**
Alexa Fluor 350 346 442 Blue 19,000
Alexa Fluor 405 401 421 Blue 34,000
Alexa Fluor 430 433 541 Green/Yellow 16,000
Alexa Fluor 488 496 519 Green 71,000
Alexa Fluor 532 532 553 Yellow 81,000
Alexa Fluor 546 556 573 Orange 104,000
Alexa Fluor 555 555 565 Orange 150,000
Alexa Fluor 568 578 603 Orange/Red 91,000
Alexa Fluor 594 590 617 Red 73,000
Alexa Fluor 610 612 628 Red 138,000
Alexa Fluor 633 632 647 Far Red 239,000
Alexa Fluor 635 633 647 Far Red 140,000
Alexa Fluor 647 650 665 Near-IR*** 239,000
Alexa Fluor 660 663 690 Near-IR*** 132,000
Alexa Fluor 680 679 702 Near-IR*** 184,000
Alexa Fluor 700 702 723 Near-IR*** 192,000
Alexa Fluor 750 749 775 Near-IR*** 240,000
Alexa Fluor 790 784 814 Near-IR*** 270,000
* Typical emission color seen through the eyepiece of a conventional fluorescence microscope with appropriate filters.
** Extinction coefficient at lmax in cm–1M–1
*** Human vision is insensitive to light beyond ~650 nm; it is not possible to view near-IR fluorescent dyes.

Frequently asked questions

What is the delivery format?

Our standard peptides are delivered lyophilized with trifluoroacetate (TFA) as a counterion and packaged in glass vials, stored under argon to protect from oxygen. For additional formats, such as delivery in low-binding plastics or 2-D barcoded plates, or in-solution with different solvents, please inquire.

What is your quality control (QC)?

The detailed spectra are included on the Certificate of Analysis for your records. Additional quality controls such as amino acid analysis (AAA) and further nonstandard analysis are available on request.

Q. How should peptides be stored?

A. We recommend preparing single-use aliquots and storing the products immediately at –20°C, upon receipt. In this manner, the lyophilized peptides are stable for several years. Solubilized peptides should be used immediately because they are unstable (the lower the concentration, the more unstable the peptides are). Any remaining peptides in solution should be re-lyophilized for longer storage.

Q. How should peptides be handled?

A. Always wear gloves when working with peptides to avoid contamination (e.g., enzymatic, bacterial, etc.). As many peptides are light-sensitive, they should also be protected from direct light. Avoid repeated freeze-thaw cycles.

Q. How are peptides solubilized?

A. Peptides are complex biomolecules, and each peptide has unique chemical and physical properties because of the unique amino acid composition. Although some peptides are easy to dissolve in aqueous solutions, peptides are often insoluble, especially when they contain long stretches of hydrophobic amino acids.

General guidelines for solubilizing peptides:

Because of the unique solubility of each peptide, we recommend first testing the solubilization of each peptide with a small amount of product.

  1. Always use sterile water or buffer [phosphate buffered saline (PBS), Tris or phosphate, pH 7] to solubilize peptides.
  2. Oxygen-free solvents should be used to solubilize peptides containing cysteine, methionine or tryptophan, which are susceptible to rapid oxidation.
  3. Allow the peptide to warm to room temperature (preferably in a desiccator) prior to adding the solvent of choice.
  4. Solubilization can be improved by warming (<40°C) or sonicating the solution.
  5. If the pH of the solution needs to be increased, use only very weak bases to prevent immediate inactivation or racemization.

Guidelines for solubilizing hydrophobic peptides:

  1. If the product proves to be insoluble in aqueous buffers due to high hydrophobicity, dissolve a small amount of product in the smallest possible volume of a 50% (v/v) DMSO/water mixture. Then add the desired aqueous solution until the target concentration is achieved.
  2. If the product precipitates during this process and cannot be redissolved by adding dimethylsulfoxide (DMSO), then lyophilize the peptide and try again, adding a little more 50% DMSO than in the previous attempt.
  3. If DMSO interferes with your experimental system, dimethylformamide (DMF) or acetonitrile can serve as alternate solvents.