ペプチド修飾サービス

生物学研究および産業用途を目的としており、個人の臨床用途または医療用途を意図したものではありません。

安定性、溶解性、活性、デリバリー性能を高めるためのオーダーメイドのペプチド修飾。

プロジェクト相談

目的配列、純度、スケール、修飾、納品形態、必要書類をお知らせください。Quantai が実現性を確認し、実務的な見積ルートをご提案します。

中核技術

N 末端・C 末端修飾

The two ends of a peptide are the most common places to intervene, because both are exposed to the exopeptidases that clear peptides in biological media. Acetylating the N-terminus removes the free amine and its positive charge; amidating the C-terminus removes the free acid. Together they make the peptide look less like a substrate for those enzymes and often bring the termini closer to how the sequence appears within a parent protein. Other terminal groups, including fatty acyl chains and labels, are installed at the same positions.

PEG 化・脂質化・環化

These three change how long a peptide survives and where it goes. A polyethylene glycol chain increases hydrodynamic size, which slows renal clearance and shields the peptide from proteases; the effect scales with chain length and with whether the PEG is linear or branched. Lipidation attaches a fatty acid so the peptide binds reversibly to serum albumin and is released slowly, the approach used in several long-acting peptide drugs. Cyclisation instead removes the flexible ends altogether and locks the conformation. The right choice depends on whether the problem is clearance, stability, or loss of the active conformation.

蛍光・同位体・ビオチン標識

Labels are added to observe a peptide rather than to change it, so the aim is the smallest perturbation that still gives a usable signal. Fluorophores such as FITC, TAMRA, FAM and cyanine dyes are attached at a terminus or to a lysine side chain, often through a short spacer that keeps the dye away from the binding face. Paired fluorophore and quencher labels make protease substrates that report cleavage directly. Biotin allows capture on streptavidin. Stable isotope labels give a mass shift for quantitative mass spectrometry without changing chemistry at all.

カスタム官能基とリンカー設計

A handle is a group placed on the peptide so that something can be attached later, under conditions the peptide will tolerate. A free cysteine thiol pairs with maleimide; an azide or alkyne enables click chemistry that ignores the other functional groups present. The linker between handle and peptide is a design decision in its own right: its length sets how far the payload sits from the peptide, and whether it is cleavable determines if the two ever separate again.

標準的な流れ

1要件確認

2技術的実現性

3見積とスケジュール

4合成またはプロセス実行

5QC 文書

6出荷とフォローアップ

開発段階	ペプチドサポート
コンセプトと実現性	ペプチド設計戦略、配列最適化、実現性評価
探索研究	カスタムペプチド合成、ターゲティングペプチド設計、機能スクリーニング支援
リード最適化	ペプチド修飾、コンジュゲーション戦略、構造活性最適化
プロセス開発	合成ルート最適化、プロセス頑健性、不純物管理戦略
GMP 製造	GMP 準拠のペプチド合成、品質文書、バッチ出荷判定の支援

技術ノート

Choosing where to modify

A modification is only useful if it does not sit on the part of the peptide that does the work. Where the binding face is unknown, the practical approach is to prepare a small series with the modification at different positions and test them, rather than to commit to one position and explain a loss of activity afterwards. Terminal positions are the usual first choice because they are least often involved in binding, and because they are straightforward to address during synthesis.

PEG chain length and architecture

PEG molecular weight is the main lever on half-life, and it is a trade: larger PEG slows clearance further but also shields more of the peptide, which can reduce potency. Branched PEG gives a larger hydrodynamic radius than a linear chain of the same mass, so it can buy the same clearance benefit with less linear length. Because the effect is sequence-dependent, a short series of chain lengths is often more informative than reasoning from a single value.

Lipidation chemistry

Fatty acid modification usually attaches a palmitoyl, myristoyl or diacid chain to a lysine side chain, frequently through a spacer such as a gamma-glutamate or short PEG unit. The spacer keeps the peptide from being pulled flat against albumin and generally preserves more activity than direct attachment. Chain length, whether the acid is mono- or di-functional, and the spacer are the variables that set the balance between binding to albumin and remaining available.

Cyclisation routes

A disulfide bridge between two cysteines is the mildest route and is reversible in a reducing environment, which may be an advantage or a problem depending on where the peptide has to work. A lactam bridge between a glutamate and a lysine side chain is not reducible. Head-to-tail cyclisation removes both termini and with them the exopeptidase route entirely. Hydrocarbon stapling by ring-closing metathesis stabilises a helix rather than closing the whole ring. Multiple disulfides require an orthogonal protection scheme so that the pairs form in the intended combination rather than at random.

Confirming the modification

Every modification changes the mass, so mass spectrometry confirms both that it happened and that it happened once. Where the same residue type appears more than once, the mass alone does not say which copy carries the label, and positional confirmation needs fragmentation data or a digest. Fluorescent labels are additionally checked by their absorbance so that the dye-to-peptide ratio is known rather than assumed.

納品物

Modified peptide purified after the modification step
Mass spectrometry data confirming the mass shift expected from the modification
HPLC purity of the final modified material, not of the precursor
Label ratio data where a fluorophore or biotin is attached
Summary of the modification chemistry and attachment position as executed

主な用途

Extending circulating half-life — PEGylation or lipidation where a peptide is cleared too quickly to reach a useful exposure, with chain length and spacer treated as variables to be tested.

Imaging and localisation — Fluorescent labelling for microscopy, flow cytometry and binding studies, with the dye placed away from the active face and the ratio characterised.

Protease substrates — Paired fluorophore and quencher constructs that generate signal only on cleavage, used to measure enzyme activity continuously.

Conformational constraint — Cyclisation and stapling where a linear peptide loses its active conformation in solution, or where terminal degradation is the limiting factor.

よくあるご質問

Which modification should I use to extend half-life?

It depends on why the peptide disappears. If it is cleared renally because it is small, PEGylation addresses that directly. If it is degraded by proteases, terminal capping or cyclisation may be enough on their own. If a long duration is the goal, lipidation with albumin binding is the approach behind several marketed long-acting peptides. Establishing which mechanism dominates is worth doing before choosing.

Will a modification reduce activity?

It can, and that is the main reason to place it deliberately. Any group large enough to change clearance is large enough to interfere with binding if it sits on the wrong face. Preparing two or three positional variants is usually faster than committing to one and investigating a disappointing result.

Can several modifications be combined on one peptide?

Yes, and it is common, for example a cyclised peptide that also carries a label. Combinations need an orthogonal protection scheme so each step happens at the intended site, which is a synthesis planning question rather than an afterthought. Tell us the full set of modifications at the enquiry stage rather than adding one later.

Do you supply peptides with multiple disulfide bridges?

Yes. Where more than one pair is present, the cysteines are protected orthogonally so the bridges form in the specified pairing rather than by chance, and the resulting connectivity is confirmed analytically. State the intended pairing with the sequence, because a given set of cysteines can fold into several distinct products.

What spacer should sit between the peptide and a label?

A short spacer, commonly an aminohexanoic acid or a small PEG unit, is usual. It keeps the label from interacting with the binding face and, for fluorophores, reduces quenching by nearby residues. Longer spacers give more separation but add flexibility, which can matter where the construct has to be presented on a surface.

How do I know the label went where I asked?

Mass spectrometry confirms that a single label was added and gives the expected mass shift. If the peptide has more than one residue of the type being labelled, positional assignment needs fragmentation data or an enzymatic digest, which is worth specifying up front where the position matters to the experiment.