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Protein Labeling Service

KMD Bioscience has been striking on recombinant protein expression and antibody development for many years, and we understand the need for impurities, to produce clean, reproducible results. With a powerful protein modification platform, our experts can provide with you lots of protein modification services, including enzyme conjugation, fluorescent labeling, isotope labeling, PEG labeling, biotinylation, magnetic beads conjugation, quantum dots labeling services.


Enzyme Conjugation services


Enzyme labels often refer to horseradish peroxidase (HRP) and alkaline phosphatase (AP), which are often used to label antibodies and then used as enzyme-linked immunosorbent assay (ELISA). HRP consists of multiple isozymes with a molecular weight of 400,000 and the protein isoelectric point of pH 3-9. the optimal pH for enzyme catalysis will slightly different due to the hydrogen donor, but mostly at pH 5. HPR is more suitable for rapid chromogenic reaction. Adding a substrate to the ELISA, the OD 450 comes to 1.8-2.5 in 5-10 minutes. AP is more suitable for slow chromogenic reaction, the color development reaction time can be about 4-8 hours, the catalyzed yellow compound is more stable and is ideal for quantitative detection of enzymatic kinetics. The HRP and AP used by KMD Bioscience are both from Sigma and we have rich experiences in protein quantification. In order to ensure the optimal protein labeling, we are able to design the most appropriate protocol to reach the protein and enzyme label ratio of 1:1.

Moreover, we also provide Biotin labeling services for researchers. Biotin can be used as a fusion tag with target protein for recombinant expression for subsequent purification and screening, for example, biotin labeling has very high screening efficiency when phage display library screening and it is also very suitable for IHC to monitored tissue specific expression, protein with the Biotin labeled can be directly applied to IP and beads sorting.


Isotope labeling services


Protein isotope labeling is a very classic technique for protein tracing and proteomics quantification. Compared to the in vitro labeling techniques, isotope labeling belongs to in vivo labeling which is replaced corresponding amino acids in cell culture medium by essential amino acids labeled with native isotopes(light)or stable isotopes(heavy); after cultured 5-6 doubling-time, the stable isotope-labeled amino acid can completely integrate into the newly synthesized protein of the cells to replace the original amino acid. The lysed proteins of differently labeled cells were mixed in the proportion of the number of cells or the same amount protein, after separation and purification, detected by mass spectrometry. Based on thThe relative quantitation was performed based on the comparison of the two isotopic peptides in the first class mass spectrum. KMD Bioscience has our protein expression platform combined with cell culture platform which can provide our clients with 13C,15N,15N-13C,35S and 3H protein isotope labeling services.

The protein isotope labeling services can also use 125I and 131I, tested by HPLC or open column chromatography(depending on the characteristic of the iodinated molecule) to labeled the Tyrosine which in the protein and remove free iodine. Radioactive iodine is efficiently labeled onto proteins and other molecules, and radioactive iodine is used as a tracer or probe. Generally, TLC detects the labeled product to make sure the percentage of free iodine <5%.


Fluorescent labeling services


Fluorescent dye-labeled protein/polypeptide is a standard protein labeling technology in vitro, besides fused expression GFP GYP and other fluorescent proteins, the target protein can be directly labeled by fluorescent dye for live tracing, cell sorting, etc. KMD Bioscience can provide Fluorescent dye-labeled including FITC, FAM, RBITC, Colloidal gold labeled Co-Au, Cy3, Cy5, Cy5.5, Cy7, APC, PE, Alexa Fluor 350, Alexa Fluor 488, Alexa Fluor 555, Alexa Fluor 594, Alexa Fluor 647. For each peptide or protein that needs to be labeled, our technicians will rigorously evaluate the physicochemical characteristics of the polypeptide or the protein, such as peptide labeling, linker length, and type cross-linking position, which will be the most important factors.


Quantum dots labeling services


We provide quantum dots labeling services with inorganic structure ZnCdSe/ZnS as the core:


Carboxy and amino water-soluble quantum dots (Figure A): They are obtained by surface modification of oil-soluble quantum dots with a polymer and can be uniformly dispersed in an aqueous solution (such as borate buffer, PBS buffer solution), the surface carboxyl group and the amino group are reactive, the particle diameter ranges from 12 to 18 nm.


Oil-soluble quantum dots (Figure B): By coating the surface of the inorganic structure ZnCdSe/ZnS with a hydrophobic ligand, the quantum dots can be uniformly dispersed in a non-polar organic solvent (such as hexane, toluene, chloroform), which is easy to perform. The particle size ranges from 5 to 10 nm. The oil-soluble quantum dots by encapsulated can be used as an LED backlight source to enhance the display color area. In addition, after the surface modification of the oil-soluble quantum dots to introduce active groups, they can be conjugated with biomolecules, which can be used in biomarkers/detection, high-throughput coding, in vivo imaging, and dynamic tracing.



Beads conjugation services


Magnetic nanospheres (MNS) are nanospheres series products with high molecule polymer, magnetic nanoparticles (coated on the surface) and functional groups (carboxyl, amino groups). The products have good dispersibility, fast magnetic response, abundant surface functional groups, quick and easy separation. It is widely used in nucleic acid purification, protein purification, affinity chromatography, cell sorting, immunoassay and clinical diagnosis and other biomedicine research field.


PEG labeling services


KMD Bioscience also offers PEG labeling services with different molecular-weight. Please find more for PEG modification services. 


How to Order?

If you have any questions regarding our services or products, please feel free to contact us by E-mail: or Tel: +86-400-621-6806; +86-131-1603-8708