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Protein Bioconjugation

Custom Protein Conjugation and Modification

Bio-Synthesis has many years of experience in protein conjugation and modification through chemical conjugation of oligonucleotides, proteins, toxins, bifunctional ligands,haptens, fluorophores, and metal chelates for radio-isotope labeling. Our expertise,however, is not only limited to protein conjugation / modification, we also perform in-house recombinant protein expression. We offer the best quality protein bioconjugates in the industry by implementing a state-of-the art gene synthesis platform and expertise in providing high quality nucleic acid bioconjugate reagents. Gene-to-Protein Expression, Modification and Conjugates produced at Bio-Synthesis have substantial purity.  Each protein-biopolymer conjugate is meticulously monitored and controlled according to our stringent quality assurance and quality control standards. QA (quality assurance) procedures are also followed independently to double guarantee the high quality of every delivered peptide. The Bio-Synthesis Total Quality Management System (TQM) has been successfully upgraded to fully comply with ISO 9001:2008 regulations

Protein Biopolymer Conjugation Services

Bio-Synthesis, leader in providing custom protein expression services as well as protein conjugation and modification with target molecule of your choice. We are devoted to delivering affordable peptide-biopolymer hybrid complexes, and offer comprehensive modification and labeling options to be used for life science research, diagnostics, and drug discovery.

Over the decades, we have accumulated a continually growing portfolio of peptide modification and conjugation services. If you can't find what you want, contact our National Customer Service Center at 800.220.0627, or contact us online with your detailed project descriptions.

Service Portfolios

  • Conjugation of protein to enzyme for immuno-assay
  • Hapten conjugation to carrier protein for immunogen preparation
  • Conjugation of poly(ethylene glycol) to protein
  • Protein dextran modification
  • Protein-drug conjugates for therapeutic drug delivery
  • Protein-antibody conjugates for targeted delivery
  • Protein-macrocyclic metal chelator as targeted medical imaging agents
  • Protein-support immobilization for detection
  • Bioconjugation of Protein Capture Agents to Biosensor Surfaces
  • Protein glycopolymer conjugate
  • Biotinylation of proteins for use with streptavidin- or avidin-based reagents
  • Development of key properties of therapeutic proteins in the optimization of in-vitro and in-vivo performance

As each conjugation is unique, our support team will work closely with each client to identify their objective and determine proper coupling chemistry. As we are the experts in protein bioconjugation techniques, Bio-SynthesisI can provide a properly conjugated product quickly and efficiently.

Protein Conjugation Service Descriptions


Coupling of preactivated small molecule and biomolecule with chemical reactive groups such as amine, thiol, carboxylate, hydroxyl, aldehyde and ketone, active hydrogen, photo-chemical and cycloaddition reactions, zero-length cross-linking, homobifunctional, heterobiofunctional, or multifunctional cross-linking chemistries, denrimer and dendrons, and cleavable reagent systems.

Some commonly used cross-linking reagents include:

  • glutaraldehyde - links carrier molecules to N-terminus of peptide
  • carbodiimide (EDC), - attaches carrier to C-terminus of peptide
  • succinimide esters (e.g. MBS, SMCC) - binds free amino group and Cys residues
  • benzidine (BDB), - links to Tyr residues
  • periodate, - attaches to carbohydrate groups

Service Specification

After standard desalting, or purification, a small percent of heterogeneous products containing single or multi-site conjugate


  • Protein
    • Natural, recombinant protein, or synthetic peptides
  • Biopolymers
    • Protein: Enzyme, antibodies, antigens, cell adhesion molecules
    • Peptides: Synthetic polypeptides
    • Saccharides: Sugars, oligosaccharides and polysaccharides
    • Lipids: Fatty acids, phospholipids, glycolipids and any fat-like substances.
    • Ligands: Hormone receptors, cell surface receptors, avidin and biotin, small molecules
    • Labels: Fluorescent dyes, infrared-absorbing and UV-Vis absorption chromophores, nonradioactive labels
    • Nucleic acids and nucleotides: DNA, RNA, PNA, nucleic acid analogs and genomic DNA
    • Synthetic polymers: PEG, Nanoparticles, gold particles, dendrimers, dendron, PAMAM
    • Others: Conjugated or mixtures of any the above
    • Soid Supports:agarose, glass plates, membrane, beads


All custom synthesis of biomolecules, modification, or bioconjugation services are manufactured under strict quality control processes.Analytical HPLC and MS analyses are performed in every development cycle. Final target conjugates must first be isolated from excess or unreacted reagent. In many cases, simple dialysis removes unreacted reagent from the reaction solution. Additional purification such as stirred cell filtration, tangential flow filtration (TFF), or gel filtration chromatography may also be used to either remove excess reagent or to isolate and characterize the cross-linked product with an additional fee. For reagents that are similar in size or larger than the antibody (mostly protein and other biological molecules), other purification techniques such as affinity chromatography, ion-exchange chromatography, and hydrophobic interaction chromatography.

The cross-linked target molecule may then be further characterized by biochemical or biophysical techniques. Once the product has been purified, it may be subject to various characterization methods including spectrometric (MALDI-TOF, ESI, LC-MS),fluorescence, electrophoresis, and immunochemical, biochemical, and enzymatic analysis. QC (quality control) and QA (quality assurance) procedures are also followed independently to ensure the highest quality possible of every delivered conjugate. Moreover, our dedicated technical account managers will guide your project through every step of the process and keep you informed of the latest progress.

Delivery Specifications

The typical delivery consists of lyophilized sample in individual fully labeled vials. The shipment also contains COA, MS, HPLC and/or other analytical data. Additional analytical data is also available upon request.

Pricing varies based on the project specifications. Our service includes materials and labor for conjugation only! Price does not include the cost of biopolymer synthesis or purchase of biopolymer from a commercial vendor and, if deemed necessary, biopolymer modification to introduce additional functional groups, extra linkers, spacers. Please contact us for a quote.

Basic Biopolymer Modification BIOCON10000
Acylation BIOCON13000
Alkylation BIOCON13001
Amidation BIOCON13002
Arylation BIOCON13003
Block sulfhydryl BIOCON13004
Cyanogen Bromide BIOCON13005
Diazotization BIOCON13006
Dicarbonyls BIOCON13007
Disulfide Bond Reduction BIOCON13008
Esterification BIOCON13009
Hydrazide BIOCON13010
Introduction of Aldehyde Group BIOCON13011
Introduction of photoreactive crosslinkers BIOCON13012
Nitration BIOCON13013
Oxidation BIOCON13014
Protein Amino Acid Oxidation BIOCON13015
Protein Fragmentation BIOCON13016
Protein PEGylation BIOCON13017
Protein Dextran Modification BIOCON13018
Sulfenyl Halides BIOCON13019

Ordering and Submitting Requests for Bioconjugation Services

For us to better understand your customized project, please complete our Bioconjugation Service Questionnaire. The more our chemists understand your project’s needs, the more accurate your provided feedback will be. Providing us with your project’s details enables us to recommend the best reagents to use for your project. The most useful and readily available tools for bioconjugation projects are cross-linking reagents. A large number of cross-linkers, also known as bifunctional reagents, have been developed. There are several ways to classify the cross-linkers, such as the type of reactive group, hydrophobicity or hydrophilicity and the length of the spacer between reactive groups. Other factors to consider are whether the two reactive groups are the same or different (i.e. heterobifunctional or homobifunctional reagents), spacer is cleavable and if reagents are membrane permeable or impermeable. The most accessible and abundant reactive groups in proteins are the ϵ-amino groups of lysine. Therefore, a large number of the most common cross-linkers are amino selective reagents, such as imidoesters, sulfo-N-hydroxysuccinimide esters and N-hydroxysuccinimide esters. Due to the high reactivity of the thiol group with N-ethylmaleimide, iodoacetate and a-halocarbonyl compounds, new cross-linkers have been developed containing maleimide and a-carbonyl moieties. Usually, N-alkylmaleimides are more stable than their N-aryl counterparts.

In addition to the reactive groups on the cross-linkers, a wide variety of connectors and spacer arms have also been developed. The nature and length of the spacer arm play an important role in the functionality. Longer spacer arms are generally more effective when coupling large proteins or those with sterically protected reactive side-chains. Other important considerations are the hydrophobicity, hydrophilicity and the conformational flexibility. Long aliphatic chains generally fold on themselves when in an aqueous environment, making the actual distance spanned by such linker arms less than expected. Instead, spacers containing more rigid structures (for example, aromatic groups or cycloalkanes) should be used. These structures, however, tend to be very hydrophobic which could significantly decrease the solubility of the modified molecules or even modify some of their properties. In such cases, it is recommended to choose a spacer that contains an alkyl ether (PEO) chain. Bio-Synthesis offers several cross-linkers with PEO chains, such as thiol-binding homobifunctional reagents, heterobifunctional bases and their derivatives.

Within 3-5 days upon receiving your project scope, we will provide you an appropriate quotation. An order can be placed with PO (Purchase Order) or major credit cards ( ). Your credit card will be billed under Bio-Synthesis, Inc.