What is Orexin B??
Orexin B (Hypocretin-2, CAS 205640-91-1) is a 28-amino acid C-terminally amidated linear neuropeptide co-produced with Orexin A from the same prepro-orexin precursor. Sequence: Arg-Ser-Gly-Pro-Pro-Gly-Leu-Gln-Gly-Arg-Leu-Gln-Arg-Leu-Leu-Gln-Ala-Ser-Gly-Asn-His-Ala-Ala-Gly-Ile-Leu-Thr-Met-NH2. Unlike Orexin A, Orexin B lacks the N-terminal pyroglutamyl residue and disulfide bridges – giving it a linear, more flexible structure. This structural difference underlies its selective binding to OX2R over OX1R (approximately 5-100-fold preference), making it the ideal pharmacological tool for dissecting OX2R-specific functions from dual OX1R/OX2R effects. OX2R is expressed prominently in the tuberomammillary nucleus (histaminergic arousal) and the dorsal raphe (serotonergic), and OX2R-selective compounds are the mechanistic basis for the insomnia drug suvorexant.
Research Applications
OX2R-Selective Pharmacology
OX2R vs. OX1R selectivity profiling – Gq signalling, receptor internalisation, competitive binding vs. Orexin A
Sleep Architecture & NREM
OX2R role in non-REM sleep stability, histaminergic arousal pathway – TMN activation, REM/NREM balance
Histaminergic Arousal System
Tuberomammillary nucleus OX2R – histamine release, H1 receptor arousal pathway downstream of OX2R activation
Insomnia & Hypersomnia Models
OX2R antagonist comparison (suvorexant), sleep onset, maintenance, receptor occupancy/dose-response studies
Orexin A vs. B Comparison
Selectivity, potency, and functional dissection – identify OX1R-specific (addiction, analgesia) vs. OX2R-specific (sleep, arousal) biology
Quick Specs
| Form | Lyophilized powder |
| Purity | >=99% by HPLC – every batch |
| CAS Number | 205640-91-1 |
| Molecular Weight | MS molecular weight confirmed – every batch |
| Specification | >=99% by HPLC – every batch |
| Shelf Life | 24 months unopened |
| Storage | -20C sealed | 2-8C reconstituted (2-4 weeks) |
| Manufacture | In-house Fmoc SPPS – Qingdao, China |
| Brand | Asia |