H-Pyr-OH: Properties, Handling & Lab Use Guidelines

H-Pyr-OH is a cyclic amino acid derivative (pyroglutamic acid) widely used as a building block in peptide synthesis and biochemical research due to its unique lactam ring structure and stability.

Chemical Name

Pyroglutamic acid (5-oxoproline)

Molecular Formula

C₅H₇NO₃

Molecular Weight

129.11 g/mol

Appearance

White to off-white crystalline powder

Recommended Storage

Store at room temperature (15–25 °C), in a cool, dry, well-ventilated area away from light

Primary Application

Peptide synthesis building block; biochemical and pharmaceutical research

Chemical Identity and Key Properties

H-Pyr-OH, commonly known as pyroglutamic acid or 5-oxoproline, is a naturally occurring cyclic amino acid formed by the spontaneous cyclization of glutamine or glutamic acid at the N-terminus of peptides. Its defining structural feature is a five-membered lactam ring, which confers resistance to standard aminopeptidase cleavage and contributes to the compound's chemical stability.

The compound has the molecular formula C₅H₇NO₃ and a molecular weight of approximately 129.11 g/mol. It appears as a white to off-white crystalline powder and is freely soluble in water and polar solvents. Both L- and D-enantiomers are available for stereospecific applications in asymmetric synthesis and chiral pharmaceutical development.

Due to its lactam ring, H-Pyr-OH does not possess a free alpha-amino group in the conventional sense, which makes it a unique N-terminal capping agent in peptide chemistry and differentiates its reactivity from standard linear amino acids.

Storage, Stability, and Handling Precautions

Storage: H-Pyr-OH should be stored at room temperature (15–25 °C) in a tightly sealed container, kept in a cool, dry, and well-ventilated location away from direct light and moisture. Refrigeration is generally not required for the solid form, but prolonged exposure to humidity should be avoided to prevent caking or hydrolytic degradation.

Stability: The compound is stable under recommended storage conditions. The lactam ring is susceptible to hydrolysis under strongly acidic or strongly basic aqueous conditions, reverting to glutamic acid or glutamine derivatives. Prepared solutions should be used promptly or stored at 2–8 °C and protected from freeze-thaw cycles where possible.

Handling Precautions: Standard laboratory safety practices apply. Wear appropriate personal protective equipment (PPE) including gloves, safety glasses, and a laboratory coat when handling the compound. Avoid generating dust; if dust is produced, use appropriate respiratory protection. Work in a well-ventilated area or fume hood. Refer to the Safety Data Sheet (SDS) provided by Aladdin Scientific for full hazard information before use.

Laboratory Applications and Experimental Use

Peptide Synthesis: H-Pyr-OH serves as an N-terminal building block in both solid-phase peptide synthesis (SPPS) and solution-phase synthesis. Its incorporation at the N-terminus mimics naturally occurring pyroglutamyl peptides and is particularly relevant for synthesizing analogs of biologically active peptides such as thyrotropin-releasing hormone (TRH) and other neuropeptides that bear a pyroglutamyl N-terminus.

Biochemical and Pharmacological Research: Pyroglutamic acid residues are found at the N-termini of several physiologically important peptides and proteins. H-Pyr-OH is therefore used to study N-terminal pyroglutamylation, enzymatic processing by glutaminyl cyclase, and the stability of pyroglutamyl peptides against proteolytic degradation.

Asymmetric Synthesis: L-Pyroglutamic acid is a valuable chiral synthon in the preparation of complex natural products and pharmaceutical intermediates, exploited for its rigid ring framework and defined stereochemistry.

Dissolution Tips: For aqueous applications, dissolve H-Pyr-OH in water or aqueous buffer at neutral to slightly acidic pH. For organic synthesis, dimethyl sulfoxide (DMSO) or methanol are suitable co-solvents. Prepare stock solutions fresh when possible and confirm complete dissolution before use.

Quality, Purity, and Ordering Information

Aladdin Scientific supplies H-Pyr-OH (SKU: P106003) to research-grade specifications. Researchers should consult the product Certificate of Analysis (CoA) for lot-specific purity data, including HPLC purity, optical rotation (for chiral forms), and water content. These parameters are critical for quantitative peptide synthesis where high enantiomeric excess and defined purity are required.

When ordering, confirm the desired enantiomeric form (L or D), quantity, and any special purity requirements with the Aladdin Scientific sales team. Bulk quantities may be available upon request. For regulatory-sensitive applications, request documentation of synthesis route and quality control records as needed.

All Aladdin reagents undergo quality control testing prior to dispatch. If a received lot does not meet specifications, contact Aladdin Scientific customer service to initiate a return or replacement in accordance with the return and refund policy.

Frequently asked questions

What is H-Pyr-OH and how does it differ from standard amino acids?

H-Pyr-OH (pyroglutamic acid) is a cyclic amino acid derivative featuring a five-membered lactam ring formed by the cyclization of glutamine or glutamic acid. Unlike standard amino acids, it lacks a free alpha-amino group, making it resistant to aminopeptidase digestion and giving it unique reactivity in peptide synthesis as an N-terminal capping or blocking residue.

How should H-Pyr-OH solutions be prepared and stored for peptide synthesis experiments?

Dissolve H-Pyr-OH in water, aqueous buffer (neutral to slightly acidic pH), DMSO, or methanol depending on the application. Prepare solutions fresh whenever possible. If storage is necessary, keep solutions at 2–8 °C in a sealed container away from light and use within a short period to minimize hydrolytic degradation of the lactam ring.

Is H-Pyr-OH available in both L and D enantiomeric forms from Aladdin Scientific?

Customers should contact Aladdin Scientific's sales team to confirm current stock and available enantiomeric forms of H-Pyr-OH. Both L- and D-pyroglutamic acid are commonly used in research; the specific SKU and availability of each form should be verified at the time of ordering.

What safety precautions should be taken when handling H-Pyr-OH in the laboratory?

Wear gloves, safety glasses, and a laboratory coat when handling H-Pyr-OH. Avoid generating and inhaling dust. Work in a well-ventilated area or under a fume hood. Always consult the current Safety Data Sheet (SDS) provided with the product for comprehensive hazard, first-aid, and disposal information before beginning experiments.

What are the primary research applications of H-Pyr-OH?

H-Pyr-OH is primarily used as a building block in peptide synthesis, particularly for constructing pyroglutamyl peptides such as analogs of TRH and other neuropeptides. It is also employed in biochemical studies of N-terminal pyroglutamylation, enzymatic processing research, and as a chiral synthon in asymmetric organic synthesis.

References

1. Barrett GC, Elmore DT. Amino Acids and Peptides. Cambridge University Press; 1998.
2. Schilling S, Wasternack C, Demuth HU. Glutaminyl cyclases from animals and plants: a case of functionally convergent protein evolution. Biol Chem. 2008;389(8):983-992. doi:10.1515/BC.2008.111
3. Aladdin Scientific. Product Data Sheet: H-Pyr-OH, SKU P106003. Aladdin Scientific; [current year].

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.