Product Overview

Fmoc-Met-OH (CAS 71989-28-1; catalog AS0730) is N-Fmoc-L-methionine, a sulfur-containing amino acid building block for peptide synthesis. The alpha-amino group is Fmoc-protected and the carboxyl group remains free for coupling. Methionine contains a thioether side chain, not the thiol found in cysteine, and is commonly incorporated without an additional sulfur protecting group in Fmoc-SPPS.

Quality Specifications and Ordering

Purity: Alan Scientific supplies Fmoc-Met-OH at >99% purity.

Catalog pack sizes: 25 g, 100 g, 500 g, and 1 kg.

Quality documentation: See Product Documents below for lot-specific COA request details. Review the analytical methods and results reported for the supplied batch.

Quotation: Email [email protected] with AS0730, the pack size, total quantity, delivery destination, and required date. Confirm availability and dispatch lead time before ordering.

State any project-specific oxidation-related impurity requirements and confirm the available test scope. Review the storage and handling information for the supplied lot when planning a larger purchase.

Methionine Oxidation during Peptide Processing

The methionine thioether can be oxidized to a sulfoxide. Handling, synthesis, cleavage, purification, and storage conditions can therefore affect the composition of a Met-containing peptide. The absence of a side-chain protecting group should not be interpreted as immunity to oxidation.

Addition of one oxygen atom corresponds to an increase of approximately 16 Da in neutral molecular mass. The observed m/z separation depends on ion charge, and a mass shift by itself does not definitively localize an oxidation site. Interpret analytical results in the context of the full sequence and the method used.

Applications and Control of Modification State

Fmoc-Met-OH is used in sequence-defined research peptides, methionine-substitution panels, and projects comparing unoxidized and deliberately modified peptide forms. The supplied building block is intended to introduce methionine, not an already specified methionine-sulfoxide residue.

For oxidation-sensitive experiments, define the required modification state and acceptance criteria in advance. A finished peptide may require an impurity assessment that is different from routine incoming-reagent testing. Follow the supplied handling and safety documentation rather than applying an unsupported universal storage or solution-stability claim.

For a finished Met-containing research peptide, review custom peptide synthesis and include the required modification state and analytical criteria in the project inquiry.

Product Documents

A Safety Data Sheet (SDS / MSDS) is available for this product to support laboratory handling, storage and safety assessment.

MSDS_Fmoc-Met-OH_AS0730

Certificates of Analysis are batch-specific. Please contact us to request a COA, and we will provide it by email.

Frequently Asked Questions

What should I confirm before ordering a larger pack of Fmoc-Met-OH?

Review the lot documentation, recommended storage and handling conditions, and any available retest or shelf-life information. State any oxidation-related impurity requirements explicitly. The 25 g, 100 g, 500 g, and 1 kg catalog sizes do not imply identical suitability for every storage and usage schedule.

Can methionine replace cysteine as a thiol-conjugation site?

No. Methionine has a thioether and does not provide the free sulfhydryl functionality required for ordinary cysteine-thiol conjugation.

Does a +16 Da mass change prove methionine oxidation?

It is consistent with addition of one oxygen, but is not definitive site identification on its own. Charge state and other possible modifications must be considered.

Research Use Only

For research use only. Not for human or veterinary use.