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How to measure the cellular uptake of peptides? | LifeTein Peptide Blog

TMR/Cy3/Cy5 was introduced for the fluorescent label with peptides to evaluate each peptide’s cell-penetrating ability and intracellular distribution. Cells (HeLa or Huh-7) were seeded on 24-well culture plates (40,000 cells/well) and incubated in 400 μL of DM

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TMR/Cy3/Cy5 was introduced for the fluorescent label with peptides to evaluate each peptide’s cell-penetrating ability and intracellular distribution.

Cells (HeLa or Huh-7) were seeded on 24-well culture plates (40,000 cells/well) and incubated in 400 μL of DMEM containing 10% fetal bovine serum (FBS).

The medium was then replaced with fresh medium containing 10% FBS and Tetramethylrhodamine carboxylic acid (TMR)-labeled peptides.

The solution was added to each well at an appropriate concentration (e.g., 0.5 uM, 1 uM, 1.5 uM, 2 uM).

After 1, 2, 3, or 4 hours of incubation, the medium was removed, and cells were washed with ice-cold PBS and trypsin.

After adding medium containing 10% FBS, cells were centrifuged at 1600 rpm for 3 min at 4 °C. The cell pellets obtained were suspended in ice-cold PBS, centrifuged at 1600 rpm for 3 min at 4 °C, and then treated with Cell lysis buffer.

The fluorescence intensity of each lysate was measured using a spectrofluorometer. The amount of protein in each well was concomitantly determined using the BCA protein assay.

The results are presented as the mean and standard deviation from 3 samples.

Reference: https://www.nature.com/articles/srep19913#s1

Cy5 labeled peptide in cells

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Research context

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Can I purchase custom FAM-labeled peptides for my research?

Yes. Specialized providers such as LifeTein offer custom synthesis of FAM-labeled peptides with high purity (>98%) and rigorous analytical validation. Their services include choices between 5-FAM and 6-FAM, optional spacers (Ahx, β-Ala), and a variety of conjugation positions (N-terminus, lysine side chain, cysteine-specific labeling).

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Intracellular Localization Studies

Texas Red-labeled antibodies and peptides have been instrumental in studying the localization of specific molecules within cells. By targeting specific antigens or proteins, researchers can visualize their distribution in various cellular compartments:

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Practical and safety references

These excerpts are educational, not personalised medical instructions.

How-to reference

How to solubilize my synthetic peptides? #

Please refer to this FAQ for details: Handling and Storage of Synthetic Peptides. If the peptides are still cloudy, or turbid, you may have reached the limit of solubility. When the peptides are insoluble in the buffer, please try to sonicate, centrifuge, and lyophilize the peptide. Make sure to break the lyophilized lumps into a fine powder. Then try a small volume of a good agent 8M Urea, NMP, DMF, or DMSO to dissolve the peptide. Then dilute with water or your desired buffer. For peptides with Arg or LYs, you should try to lower the pH to 6 because the protonated amino acids will help solubility. Sonication and the following solvents may help with difficult peptides: 1) Begin with 100 % acetonitrile then dilute with water until 50% 2) Begin with 100% DMSO then dilute with water until 30 % 3) Dissolve it with 8M Urea 4) Dissolve it with 6 or 8 M Guanidine hydrochloride 5) 6M GuHCL, 0.05% TFA, pH2, 6) 100% TFA 7) 40% AcOH, 30%ACN, 30% water

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Storage reference

Chemical Stability

Cy3 is chemically stable and can be conjugated to various biomolecules without significant loss of fluorescence. This stability is essential for long-term imaging and tracking experiments.

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