What is a Dextran Polymer?
Dextrans are polysaccharides consisting of repeating units of D-glucose linked together
in glycosidic bonds with molecular weights ≥1000 dalton. The hydroxylic content
of the dextran sugar backbone makes the polymer very hydrophilic and can be easily
modified for attaching to other molecules. The hydroxyl functional groups of dextran
are present on each monomer in the chain. Each monomer contains of at least 3 hydroxyls
(4 on the terminal units) that may undergo derivatization reactions. This multivalent
nature of dextran allows molecules to be attached at numerous sites along the polymer
chain.
Bio-Synthesis offers dextran modification and conjugation services using various
molecular weight sizes ranging from 3,000 to 2,000,000 daltons. Because unlabeled
dextrans are polydispersed and may become more so during the chemical processes
required for their modification and purification, the actual molecular weights present
in a particular sample may have a broad distribution. For example, our 3,000 MW
dextran preparations contain polymers with molecular weights predominantly in the
range of ~1,5003,000 daltons, including the dye or other labels, while our 70,000
MW dextran preparations contain polymers with molecular weights ranging from 60,000
to 90,000 daltons.
Contact our Technical Service Center at 800.220.0627 or contact us online
with your detailed project specifications. A project manager will be assigned to
help you with the design and development of an appropriate synthetic method for your
specific needs.
Sample Submission Requirement:
Biomolecules supplied by customers should be sufficiently pure. Please provide up
to 3 mgs of starting material with the necessary data for purity assessment. Commercial
available biopolymers can be supplied by customers or synthesize and ordered through
Bio-Synthesis.
Price
The price 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 ordering through Bio-Synthesis from commercial vendors and, if deemed necessary,
biopolymer modification to introduce additional functional groups, extra linkers,
spacers, etc. Please contact us for a quote.
Service Descriptions
Chemistry:
Reaction of aldehyde with amine, hydroxyl amine or hydrazine
containing compounds.
Service Specification:
After standard desalting or purification,
a small percent of heterogeneous products containing single or multi-site conjugate
per molecule may exist.
Procedure:
After labeling, final conjugates must first be isolated
from excess or unreacted reagent by gel filtration or dialysis. In many cases, simple
dialysis may suffice to remove unreacted reagent from the reaction solution. Additional
purification techniques such as stirred cell filtration, tangential flow filtration
(TFF), and gel filtration chromatography may also be used to either remove excess
reagent or isolate and characterized the cross-linked product. With exception of
dialysis, additional purification techniques are usually recommended if the protein/antibody
is significantly larger (>3-fold) than the modifying or coupling reagent. For reagents
(mostly protein and other biological molecules) that are similar in size or larger
than the antibody, one must resort to other purification techniques such as affinity
chromatography, ion-exchange chromatography, and hydrophobic interaction chromatography.
Cross-linked target molecules may then be further characterized by gel electrophoresis.
It may be subject to additional analyses with an additional fee. This includes spectroscopic
(MALDI-TOF, ESI, LC-MS Fluorescence), electrophoresis, immunochemical biochemical,
enzymatical analysis, and TLC. QC (quality control) and QA (quality assurance) procedures
are also followed independently to offer you double guarantee for the highest quality
possible. Moreover, our dedicated technical account managers will guide you through
every step of the process and constantly keep you informed of the latest project
progress.
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.