Technical Support

Frequently asked questions

Please contact us for additional details regarding these and other questions.

120401-662

Which bifunctional ligand should I use?

The choice of bifunctional ligand depends on the type of functional group that you plan to use for covalent attachment. We currently offer isothiocyanate and NHS-esters for attachment to primary amines, maleimides for attachment to thiols, and amine functionalized bifunctionals that can be attached to electrophilic groups. For conjugation reactions performed under aqueous conditions B-205, B-305, and B-280 are representative examples of some very popular bifunctional ligands based on isothiocyanates and NHS-ester linkages: We also carry a variety of other bifunctional ligands that are specifically designed for optimal performance with different metals and for use in solid phase and organic solvent applications.

What are typical conditions for preparing lanthanide complexes?

Typically, the bifunctional ligand is first conjugated to a protein, peptide, or an antibody prior to complexation. The key to successful complexation is to make sure the conjugate is adequately buffered at a slightly acidic pH prior to introduction of the lanthanide. If the metal experiences a basic pH upon addition, it is likely to form the hydroxide species Ln(OH)3 which undergoes complexation at a much slower rate relative to the LnCl3 species. Formation of the hydroxide can be detected visually by the appearance of a slightly turbid suspension. Ultimately this condition leads to a reduce percentage of complexation.

What can I do to increase conjugation efficiency?

Isothiocyanate bifunctional ligands react quickly with primary amines at neutral to moderately basic conditions whereas the NHS-ester begins to react under slightly acidic conditions. Both will undergo competitive hydrolysis under these same conditions which reduces conjugation efficiency. For this reason it is important to combine the bifunctional ligand with the targeting vector in a properly buffered medium and to avoid preparing the bifunctional ligand solution too far in advance. It is also advantageous to use an excess of bifunctional ligand as some degree of hydrolysis is unavoidable.

How should I store Macrocyclics products?

Macrocyclics ships all products by overnight, two-day air, or FedEx international. In all cases our products are stable during transit and do not require refrigerated packaging. However, for long term storage we recommend that reactive isothiocyanates and NHS-esters be stored at -20ºC upon receipt by the customer.

Please contact us for additional product information related to:

  • Conjugation and Labeling Procedures for Isothiocyanato Derivatives
  • Analytical Methods, Chelation and Stability Measurements
  • Application of DOTA-tris(tert-Bu) in the Synthesis of DOTA- peptides
  • Coupling with DOTA and Activated Esters of DOTA
  • TmDOTP as an in vivo Temperature Probe
  • Product MSDS sheets
  • Certificate of Analysis
  • Product application references

Talk To An Expert

  • Macrocyclics is committed to providing unsurpassed technical support. Our experts are eager to help and can be reached by phone during working hours (8 AM-5 PM CDT) or by email.
  • For more information on Macrocyclics’ cGMP quality system, please contact our Head of Quality Assurance, Alicia Staz, (469) 786-6060.

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