Apolipoprotein A-I (ApoA-I) is the dominant structural protein of HDL. It interacts with ABCA1 and SR-BI at the cell surface to acquire phospholipid and free cholesterol, and it activates LCAT (lecithin : cholesterol acyl-transferase) to esterify cholesterol within the maturing HDL particle. Plasma ApoA-I concentration, and the ApoA-I / ApoB ratio, are widely used cardiovascular risk indices that often outperform HDL-C and total cholesterol alone (AMORIS, INTERHEART).
YO Proteins cat. 789 is full-length native human ApoA-I, isolated from pooled healthy donor plasma by density-gradient ultracentrifugation, organic-solvent delipidation (diethyl ether / ethanol), and Sephacryl S-300 gel filtration — a non-denaturing protocol that preserves the amphipathic a-helical architecture and the lipid-binding competence that recombinant E. coli ApoA-I frequently loses through denatured / refolded production. The donor plasma is screened negative for HBsAg, HBc, HIV-I, HIV-II and HCV antibodies, and the preparation is supplied at = 90 % SDS-PAGE purity in a 0.5 mg lyophilised vial.
The 0.5 mg unit size is chosen to support standard-curve ladders for ApoA-I sandwich ELISA, antigen coating for phage-display anti-HDL antibody discovery, immunisation antigen production, and HDL-particle reconstitution work without forcing labs to pay for bulk material they will not consume. Cat. 789 is the published-validated antigen used in the Lund University cardiovascular-immunity programme (Engelbertsen et al. 2014) and the Turku University antibody-discovery platform (Negi et al. 2015 / 2016)
SPECIFICATIONS
Catalogue number: 789
Product name: Apolipoprotein A1 (human) — full-length native protein
Source: Human plasma. Donors tested negative for HBsAg, HBc, HIV-I, HIV-II and HCV antibodies
Molecular weight: ~28 kDa (243 amino acids, monomer)
Gene symbol: APOA1
UniProt: P02647
Purity: At least 90 % (SDS-PAGE)
Format: Lyophilised from 0.05 M NaCl, 0.01 M Na2CO3, pH 10.0
Purification: Density-gradient ultracentrifugation ? delipidation with diethyl ether and ethanol ? Sephacryl S-300 gel filtration
Package size: 0.5 mg
Grade: Research use only (not for diagnostic or therapeutic use)
STORAGE / RECONSTITUTION
Reconstitute in sterile pure water or PBS. Centrifuge the vial briefly before opening. Use gentle pipetting; do not vortex. The supplied lyophilisation buffer (0.05 M NaCl, 0.01 M Na2CO3, pH 10.0) is compatible with standard ELISA alkaline-coating protocols — dilute the reconstituted protein to 1–10 µg/mL in carbonate / bicarbonate coating buffer (pH 9.6) immediately before use. For Western-blot positive-control loading, use 25–100 ng per lane.
For HDL-particle reconstitution and lipid-binding assays, dialyse against the user's working buffer (commonly 10 mM Tris pH 8.0 or PBS) before use; ApoA-I tolerates buffer-exchange and the native fold is robust to physiological pH. For phage-display antibody-discovery selections, the reconstituted antigen can be biotinylated through surface lysines with standard NHS chemistry without significant loss of structural integrity.
Avoid repeated freeze–thaw of the reconstituted material. Prepare single-use aliquots immediately after reconstitution.
Storage
Lyophilised product: store up to 2 years at -20 °C.
Reconstituted product: 1 month at +4 °C, 1 year at -20 °C or lower.
Avoid multiple freeze–thaw cycles.
APPLICATIONS
- ELISA standard / reference protein for absolute quantification of plasma ApoA-I
- ELISA coating antigen for sandwich detection of anti-ApoA-I IgG / IgM autoantibodies
- Immunisation antigen for polyclonal and monoclonal anti-ApoA-I antibody production (published — Engelbertsen 2014)
- Screening / panning antigen for phage-display synthetic-antibody libraries targeting HDL (published — Negi 2015 / 2016)
- HDL-particle reconstitution work — assembly of synthetic HDL (sHDL / reconstituted HDL / rHDL) nanoparticles for drug-delivery, atherosclerosis-therapy, and HDL-functional research
- LCAT-activation enzymatic assays — ApoA-I is the canonical activator and is required as a cofactor
- ABCA1 and SR-BI receptor-binding assays — surface plasmon resonance, BLI, microscale thermophoresis
- Western-blot positive control and migration marker for ApoA-I (~28 kDa)
- Cardiovascular biomarker panel building — ApoA-I / ApoB ratio panels alongside YO cat. 650 (ApoB) and cat. 226 (CRP)
- Coating substrate for cell-culture studies of HDL-cell interactions
APPLICATION HIGHLIGHTS — HIGH-VALUE RESEARCH NICHES
- Native, non-denatured human ApoA-I — delipidated from donor plasma, retaining the amphipathic helical fold and lipid-binding competence that refolded recombinant material often loses.
- Reconstituted-HDL nanoparticle engineering — defined scaffold protein for sHDL / rHDL assembly and drug-delivery work.
- Cardiovascular biomarker panels — ApoA-I / ApoB ratio assays, pairing with ApoB-100 cat. 650.
- Reverse-cholesterol-transport mechanism studies — ABCA1 / SR-BI binding and LCAT-activation assays.
- Antibody development and immunoassay QC — immunogen and coating antigen for the anti-ApoA1 panel cat. 553 and cat. 851.
- Anti-ApoA-I autoantibody research — coating antigen in autoimmune and cardiovascular-risk serology.
REFERENCES
The following peer-reviewed publications use YO Proteins human Apolipoprotein A1 (cat. 789) as the antigen / standard of record.
1. Engelbertsen D, Rattik S, Knutsson A, Björkbacka H, Bengtsson E, Nilsson J. Induction of T helper 2 responses against human apolipoprotein B100 does not affect atherosclerosis in ApoE?/? mice. Cardiovascular Research. 2014 Jul 15;103(2):304–12. doi: 10.1093/cvr/cvu131. PMID 24866382.
Lund University (Jan Nilsson cardiovascular-immunology programme). YO ApoA-I was used as a control / comparator antigen in an ApoB100-peptide vaccination study in ApoE-knockout atherosclerosis models. Published validation of cat. 789 as an immunisation-grade reference antigen in murine atherosclerosis research.
2. Negi P, Lövgren J, Malmi P, Sirkka N, Metso J, Huovinen T, Brockmann EC, Pettersson K, Jauhiainen M, Lamminmäki U. Identification and analysis of anti-HDL scFv-antibodies obtained from phage display based synthetic antibody library. Clinical Biochemistry. 2016 Apr;49(6):472–479. doi: 10.1016/j.clinbiochem.2015.11.020. PMID 26656638.
Turku University (Lamminmäki / Pettersson antibody-discovery platform with Jauhiainen). YO ApoA-I was the immobilised target antigen used to pan a synthetic phage-display scFv library; characterised anti-HDL scFv clones were subsequently profiled against the cat. 789 antigen. Published validation of cat. 789 as a screening antigen for in-vitro antibody-discovery workflows.
