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[D-Ala4]-Substance P (4-11) is an eight-residue C-terminal Substance P fragment in which residue 4 is D-alanine.
The peptide preserves the Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2 C-terminal sequence while reversing stereochemistry at the N-terminal residue of the fragment.
Product Information
| Product Name | [D-Ala4]-Substance P (4-11) |
| Catalog No. | AS2536 |
| CAS No. | 81381-50-2 |
| Sequence | D-Ala-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2 |
| Peptide Length | 8 residues |
| Molecular Formula | C44H65N11O10S |
| Molecular Weight | Approximately 940.1 Da |
| Key Modification | D-Ala4 |
| C-Terminus | Amidated |
D-Ala4 Changes Stereochemistry Without Adding Side-Chain Bulk
Alanine has a small methyl side chain. Using D-Ala therefore changes residue orientation while minimizing additional steric complexity.
This makes the analog useful for separating stereochemical effects at the N-terminal boundary of SP(4-11) from larger changes in side-chain size or aromaticity.
Reported Tachykinin Binding Activity
In rat cerebral cortex membrane assays, [D-Ala4]-SP(4-11) has been reported to inhibit binding of radiolabeled Substance P with an IC50 of approximately 0.15 μM and radiolabeled eledoisin with an IC50 of approximately 0.5 μM.
These values are assay-specific competition data and should not be interpreted as universal human NK1 affinity constants.
Research Applications
The peptide can support tachykinin receptor binding, Substance P fragment SAR, stereochemical scanning and comparison of C-terminal SP pharmacophores.
Frequently Asked Questions
What is modified?
The N-terminal residue of SP(4-11) is D-Ala.
What binding IC50 values have been reported?
Approximately 0.15 μM for radiolabeled Substance P competition and 0.5 μM for radiolabeled eledoisin competition in rat cerebral cortex membranes.
Does it retain Met11?
Yes. The peptide terminates in Met-NH2.