Bis-(N,N'-PEG4-NHS ester)-Cy5
CAS No.: 2107273-48-1
Cat No.: BP-501657
Purity: 98%
4.5 
Bis-(N,N'-PEG4-NHS ester)-Cy5 is a Cy5 fluorophore conjugated to two terminal N-hydroxysuccinimide (NHS) ester groups connected through PEG4-based linkers. Structurally, it provides a flexible, hydrophilic PEG spacer that separates the dye core from the reactive NHS termini, enabling efficient coupling to primary amines on proteins, peptides, or other amine-bearing PROTAC components via stable amide-bond formation. In targeted protein degradation workflows, this bifunctional linker–dye construct is useful for preparing labeled PROTACs or intermediates, allowing researchers to track conjugation efficiency, monitor cellular uptake or localization, and quantify binding or degradation-related events using fluorescence-based readouts. Its dual NHS functionality supports controlled, stoichiometric labeling and crosslinking strategies, while the PEG4 spacer helps reduce steric hindrance and nonspecific interactions, improving experimental robustness in biochemical and cell-based assays.
Structure of 2107273-48-1
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Bis-(N,N'-PEG4-NHS ester)-Cy5 is a bifunctional PEG-based linker bearing NHS ester groups and a Cy5 fluorophore, designed to enable efficient conjugation in targeted protein degradation workflows. Its dual reactive sites support modular assembly of PROTAC constructs, while the PEG spacer improves solubility and linker flexibility. The Cy5 tag facilitates monitoring of conjugation quality and tracking of intermediates during linker-to-ligand coupling. Detailed structural and reactivity guidance is provided below.
Structure: The molecule contains a Cy5 dye core connected to a PEG4-based scaffold terminated with two N-hydroxysuccinimide ester functionalities. It features amide-forming NHS esters, ether-rich PEG segments, and a conjugated cyanine chromophore, yielding a polar, water-compatible linker with fluorescence for analytical follow-up.
Reactivity: NHS esters react with primary or secondary amines to form stable amide bonds via nucleophilic acyl substitution. For PROTAC assembly, coupling is typically performed under mildly basic conditions using amine-bearing ligands, with anhydrous or low-water organic solvents (often compatible with NHS chemistry) to preserve ester reactivity. Common catalysts are not required; careful pH control and exclusion of competing amines enhance efficiency.
* Our calculator is based on the following equation:
Concentration (start) x Volume (start) = Concentration (final) x Volume (final)
It is commonly abbreviated as: C1V1 = C2V2
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