Name: XFD660 NHS Ester
Brand: AAT Bioquest
SKU: 1834
Availability: InStock

XFD660 NHS Ester

XFD660 NHS Ester Equivalent To Alexa Fluor 660 NHS Ester is an amine-reactive, far-red fluorescent dye with an excitation/emission of 663/691 nm that is used for flow cytometry and microscopy applications.

Easy Conjugation: Efficiently labels primary amines on proteins, ligands, and amine-modified oligonucleotides
Bright & Stable: Delivers intense fluorescence with resilience to photobleaching and pH variations from 4 to 10
Hydrophilic: Minimizes aggregation, enhancing signal clarity for advanced imaging and live-cell studies

Schematic illustrating the NHS ester–amine coupling between an NHS ester‐activated dye and an amine‐modified biomolecule. NHS esters react readily with lysine side‐chain amines or N‐terminal amines on proteins, peptides, and amine‐modified oligonucleotides under mild conditions (pH 7–9). The resulting amide bond is stable and physiologically compatible.

Protocol

SDS

Catalog	Size	Price	Quantity
1834	1 mg	Price

Overview

XFD660, synthesized by AAT Bioquest, shares a similar chemical structure with Alexa Fluor® 660 (a Thermo Fisher trademark). This far-red dye is optimized for excitation by the 633 or 647 nm laser lines, making it well-suited for applications in imaging and flow cytometry where bright and photostable signal generation is critical. XFD660 is water-soluble and demonstrates pH stability within a range from 4 to 10. The NHS ester derivative of XFD660 is predominantly employed for conjugation to proteins or antibodies. This functionality allows the NHS ester to covalently attach to the primary amines present in proteins, amine-modified oligonucleotides, and other amine-bearing molecules. Conjugates utilizing XFD660 are noted for their enhanced fluorescence intensity and increased photostability relative to conjugates using other fluorophores with similar spectral characteristics.

Calculators

Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of XFD660 NHS Ester to given concentration. Note that volume is only for preparing stock solution. Refer to sample experimental protocol for appropriate experimental/physiological buffers.

	0.1 mg	0.5 mg	1 mg	5 mg	10 mg
1 mM	92.645 µL	463.225 µL	926.449 µL	4.632 mL	9.264 mL
5 mM	18.529 µL	92.645 µL	185.29 µL	926.449 µL	1.853 mL
10 mM	9.264 µL	46.322 µL	92.645 µL	463.225 µL	926.449 µL

Molarity calculator

Enter any two values (mass, volume, concentration) to calculate the third.

Mass (Calculate)		Molecular weight		Volume (Calculate)		Concentration (Calculate)		Moles
mg	÷	1079.39 g/mol	=	mL	x	mM	=	mmol

Physical properties

Molecular weight	1079.39
Solvent	DMSO

Spectral properties

Correction factor (260 nm)	0.00
Correction factor (280 nm)	0.10
Extinction coefficient (cm ^-1 M ^-1)	132000
Excitation (nm)	663
Emission (nm)	691

Storage, safety and handling

H-phrase	H303, H313, H333
Hazard symbol	XN
Intended use	Research Use Only (RUO)
R-phrase	R20, R21, R22
Storage	Freeze (< -15 °C); Minimize light exposure
UNSPSC	12171501

Documents

Protocol
Safety Data Sheet
Certificate of Analysis
Brochure: Labeling Antibodies & Biopolymers

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Page updated on December 15, 2025