Lipoamido-dPEG®₈-TFP ester

Lipoamido-dPEG®8-TFP ester, product number 10642, is a monodispersed PEG crosslinker. The spacer length from the disulfide bond in the lipoic acid ring to the carbonyl carbon adjacent to the 2,3,5,6-tetrafluorophenol (TFP) ester is 36 atoms (approximately 42.7 Å). The product joins free amines with metals, most notably gold and silver. Thus, this product is useful for crosslinking and immobilizing peptides and proteins to the surfaces of metal nanoparticles and forming self-assembled monolayers (SAMs) on metal surfaces.

Discrete PEG Products
Quanta BioDesign, Ltd. manufactures and sells monodispersed PEG products under the dPEG® tradename. From our founding, we have pioneered the synthesis of highly pure, monodispersed PEG.

Traditional PEG products are dispersed polymers that contain complex mixtures of different PEG chain lengths and molecular weights in a Poisson distribution. Analysis of conjugates made with these products can be time consuming and expensive. Some producers of monodispersed PEG reagents begin with a PEG polymer mixture and repeatedly purify until the exact chain length desired is isolated. This process is labor-intensive and, in our view, inefficient.

Our dPEG® products are different from traditional PEGylation products and other companies' monodispersed PEG products. First, all of our products are monodispersed. Each product contains a single PEG product with a discrete chain length and molecular weight. Second, instead of purifying our dPEG® products from a polymer mixture, we synthesize them from highly pure starting materials, building them stepwise until we achieve the desired dPEG® spacer or linker. Our processes are scalable from milligrams to multiple kilograms.

Lipoic Acid-containing dPEG® Products
Lipoic acid, also known as alpha-lipoic acid, α-lipoic acid, and thioctic acid, is a naturally occurring antioxidant. It functions as a cofactor in several enzyme systems. The molecule consists of a five-membered ring containing a disulfide attached to a pentanoic (valeric) acid group.

As a bidentate thiol ligand, lipoic acid forms stable dative bonds (coordinate covalent bonds) with gold, silver, and other metals in both the oxidized and reduced states. Because lipoic acid forms two dative bonds with metal, it is more stable than PEGylation reagents that contain a single thiol and thus form only one dative bond per PEG modifier. This increased stability prevents lipoic-acid-functionalized dPEG® products from being oxidized off the metal surface.

Using Lipoamido-dPEG®8-TFP ester
TFP esters react more readily with amines and possess better hydrolytic stability than N-hydroxysuccinimide (NHS). The superiority of PEG-TFP esters over NHS esters is documented in the scientific literature and by Quanta BioDesign's in-house research.

When using this product, it is typical to conjugate the carboxyl end of the dPEG® to an amine to form an amide bond before forming a dative bond between a metal surface and the lipoic acid moiety of Lipoamido-dPEG®8-TFP ester. The TFP ester reacts optimally at pH 7.5 – 8.0, but it will also react with amines at pH values above and below this range.

The lipoic acid group forms dative bonds with metals with or without reduction to dihydrolipoic acid (DHLA). If reduction to DHLA is preferred, Tris(2-carboxyethyl)phosphine (TCEP) will reduce lipoic acid to DHLA rapidly.

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