Terminal Deoxynucleotidyl Transferase (TdT)

What it means: Target is the identity of the recombinant protein you are purchasing. The target on this page is TDT.

How to interpret here: Use TDT as your “construct match” checkpoint—confirm it is the exact antigen/standard you need for your antibody validation, binding assay, or functional study. The expressed construct/region is X04122, Mer1-Ala520—use it to verify your epitope/domain is included. The expression system is E. coli, which can affect folding and post‑translational modifications. Tag status is No tag—use this to plan capture/immobilization (or to avoid tag interference). Purity is listed as > 90 % as determined by SDS-PAGE, which helps you judge background tolerance for your assay. Choose this when target + origin + construct details align with your experiment; consider another construct if you need full‑length protein, a different domain, a tag‑free format, or native PTMs.

Why it matters for buying:

• Specificity and binding: Closely related family members, isoforms, or fragments can change antibody/ligand binding.
• Assay validity: The same target produced in different systems or constructs can behave differently in ELISA coating, BLI/SPR, pull‑downs, or activity assays.
• Reproducibility: Documented construct details reduce surprises between batches and between publications.

Helpful selection notes for this listing:

• Accession cross‑check: TDT is linked to accession P06526 for sequence/domain verification when needed.
• Protein length: The recombinant bovine TdT consists of 520 amino acids and migrates with an apparent molecular mass of 58.3 kDa as estimated in SDS-PAGE under reducing conditions. (useful for confirming full‑length vs fragment).
• Synonyms: DNA nucleotidylexotransferase, Terminal addition enzyme, Terminal deoxynucleotidyltransferase, Terminal transferase, TdT.

Practical guidance:

• Confirm your binding site: Map your antibody epitope or functional domain to the expressed region before ordering for a critical assay.
• Plan a pilot: Test a small amount first to confirm binding/activity under your exact buffer and immobilization conditions.
• Use controls: Include buffer‑only and an unrelated protein control to detect non‑specific binding.
• Buffer awareness: Formulation is Liquid in sterile 50 mM K2HPO4, 100 mM NaCl, 1 mM DTT, 0.1% Tween20, 1% BSA, 50% Glycerol, pH 6.5.—confirm compatibility with your downstream chemistry.
• Stability planning: Storage is Stored at -20°C.—aliquot to avoid repeated freeze–thaw.

What to watch out for:

• PTM‑dependent epitopes: Some antibodies/ligands require glycosylation or native folding—confirm the expression system supports what you need.
• Tag interference: Tags can introduce extra epitopes or steric effects; use tag‑controls when interpreting binding data.
• Construct mismatch: A protein fragment can be excellent for epitope mapping but may not reproduce full‑length functional behavior.

What it means: Expression Region describes the exact construct that was expressed and purified (full‑length vs fragment, domains, and sometimes built‑in tags). The value on this page is X04122, Mer1-Ala520.

How to interpret here: Treat X04122, Mer1-Ala520 as the “what you actually get” definition. For TdT, confirm this region includes your epitope/domain of interest. Use accession P06526 to map domains/isoforms in sequence databases. The region suggests an amino‑acid span of Mer1–Ala520, which can help you verify coverage and expected size. Protein length (The recombinant bovine TdT consists of 520 amino acids and migrates with an apparent molecular mass of 58.3 kDa as estimated in SDS-PAGE under reducing conditions.) provides an additional check for full‑length vs fragment. Pair this with the expression system (E. coli) when assessing PTM/conformation requirements. Choose this when the construct definition matches your assay design; avoid mismatches when your antibody/ligand targets a domain that may be missing.

Why it matters for buying:

• Epitope inclusion: Many binding failures come from ordering a fragment that does not contain the epitope.
• Functional relevance: Full‑length and fragments can behave differently in activity assays or conformational binding.
• Immobilization and detection: Built‑in tags or fusion regions can change how the protein coats plates or binds capture surfaces.

Practical guidance:

• Map the domain: If you know the domain/epitope, verify overlap with the region before ordering for a key experiment.
• Plan QC on arrival: Verify size and major species by SDS‑PAGE/Western for critical work.
• Control for constructs: If comparing variants, use the same region/expression system to reduce confounding.

What to watch out for:

• Signal peptide/TM removal: Many constructs omit signal peptides or transmembrane regions; this can change conformation.
• PTM‑dependent sites: Fragments expressed in bacteria may not reproduce native glycosylation/disulfide patterns.
• Tag assumptions: Do not assume tags are cleavable or positioned at a specific terminus unless stated.

What it means: Expression System is the production host used to express the recombinant protein. The expression system listed here is E. coli.

How to interpret here: Use E. coli to predict whether the protein will be “native‑like” for your application (folding, disulfides, and post‑translational modifications). E. coli expression is fast and common, but typically lacks mammalian glycosylation and some native PTMs—important if your antibody/ligand is PTM‑ or conformation‑dependent. For TdT, choose an expression system compatible with your binding or functional requirements. Pair host choice with formulation (Liquid in sterile 50 mM K2HPO4, 100 mM NaCl, 1 mM DTT, 0.1% Tween20, 1% BSA, 50% Glycerol, pH 6.5.) when planning downstream chemistry and stability. Follow the listed storage conditions (Stored at -20°C.) to preserve structure after reconstitution. Choose this when host limitations do not conflict with your assay; consider mammalian/insect expression when native PTMs or complex folding are critical.

Why it matters for buying:

• PTMs and conformation: Host affects glycosylation, disulfide bonding, folding, and oligomerization—key for many epitopes and receptors.
• Assay background: Host-related impurities can influence low-signal assays; bacterial systems may also introduce endotoxin relevant to cell-based work.
• Comparability: Use the same expression system when comparing binding across constructs to reduce confounding.

Practical guidance:

• Validate early: Run a small pilot with your antibody/ligand under your exact buffer and immobilization conditions.
• Consider PTM sensitivity: If your reagents recognize glycosylated or conformational epitopes, verify the host can reproduce them.
• Use controls: Include an unrelated protein produced in the same host to help interpret host-driven background.

What to watch out for:

• “Works in cells” assumptions: A recombinant protein may be suitable for binding assays but not necessarily for cell stimulation without additional validation.
• Aggregation risk: Some proteins aggregate depending on host and buffer—reconstitute gently and avoid repeated freeze–thaw.
• Activity expectations: Do not assume enzymatic or receptor activity unless explicitly validated in the datasheet.

What it means: Conjugate/Tag describes whether the protein includes an affinity or fusion tag. The tag value shown here is No tag.

How to interpret here: Use No tag to decide how you will capture, detect, purify, or immobilize the protein in your workflow. Tag‑free proteins can reduce assay interference and better mimic native termini, but you lose tag-based capture convenience. For TdT, consider whether tag placement could overlap the functional/binding region. Purity (> 90 % as determined by SDS-PAGE) influences background; tag-based capture can sometimes reduce non-specific adsorption compared to passive coating. Choose this when the tag strategy supports your downstream method; choose tag‑free when native-like behavior is more important than convenience.

Why it matters for buying:

• Workflow integration: Tags enable affinity capture, standardized immobilization, and sometimes simpler QC.
• Assay interference: Tags can drive non‑specific binding or mask epitopes; controls are essential in sensitive assays.
• Comparability: Comparing tagged vs tag‑free proteins can change apparent binding/kinetics even with the same target.

Practical guidance:

• Control for tag: Include an unrelated protein with the same tag, or a tag-only control, to detect tag-driven background.
• Prefer oriented capture when possible: Tag capture can improve reproducibility versus random passive adsorption on plates/surfaces.
• Confirm tag location: N- vs C-terminal tags can influence different binding sites—check the datasheet if critical.

What to watch out for:

• Anti-tag cross-reactivity: If you use anti-tag antibodies, ensure they do not bind other assay components.
• Surface overloading: Too much protein on a capture surface can cause steric crowding and reduced apparent binding.
• Tag removability assumptions: Do not assume the tag is cleavable unless stated.

What it means: Purity indicates how clean the preparation is (often estimated by SDS‑PAGE). The purity statement shown here is > 90 % as determined by SDS-PAGE.

How to interpret here: Use > 90 % as determined by SDS-PAGE to judge whether the protein is suitable for your assay’s background tolerance and sensitivity. For TdT, higher purity is especially helpful when using the protein as a quantitative standard or in low-signal binding experiments. Tag status (No tag) can influence background; tag‑capture approaches may reduce non‑specific adsorption compared with passive coating. Also consider formulation (Liquid in sterile 50 mM K2HPO4, 100 mM NaCl, 1 mM DTT, 0.1% Tween20, 1% BSA, 50% Glycerol, pH 6.5.), which can influence non‑specific binding and stability. Follow storage guidance (Stored at -20°C.) to preserve integrity after reconstitution. Shipping (Gel pack with blue ice.) can affect thermal exposure; inspect and aliquot promptly after receipt. Choose this when the stated purity meets your use-case; consider higher purity/extra QC for quantitative standards, kinetics, or cell-based assays.

Why it matters for buying:

• Lower background: Impurities can increase non‑specific binding in ELISA coating and surface binding assays.
• Reproducibility: Cleaner preparations generally reduce variability across runs and lots.
• Downstream compatibility: Contaminants can confound functional assays or create false binding signals.

Practical guidance:

• Match purity to application: Screening may tolerate lower purity; quantitative standards and kinetics benefit from cleaner prep.
• QC on arrival: For critical work, confirm band size and major species by SDS‑PAGE/Western.
• Use controls: Include buffer and unrelated protein controls to interpret background binding.

What to watch out for:

• Purity method differences: SDS‑PAGE estimates do not guarantee a single molecular species (aggregates/fragments may exist).
• Aggregation: Purity does not report aggregation—reconstitute gently and inspect solubility if binding looks inconsistent.
• Cell-based sensitivity: For cell assays, confirm endotoxin/host contaminants if unexpected responses occur.