Eosin-Y-lysine-dextran 500

Eosin-Y-lysine-dextran 500

CAS Number: N/A
Alternative Name: EYLD500
Eosin-Y-lysine-dextran 500 (EYLD500) is a dextran derivative that is labelled with the Eosin Y dye and it is currently produced at a molecular weight of 500kDa.

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Structure and physical properties
Eosin-Y-lysine-dextran 500 (EYLD500) is a dextran-based derivative labeled with the dye Eosin Y (2-(2,4,5,7-tetrabromo-6-oxido-3-oxo-3H-xanthen-9-yl) benzoate; CAS No: 17372-87-1). Lysine-dextran is marked using a special technique created by TdB Labs, which enables a significant level of functionalization (Fig. 1). The method utilizes the amino groups of lysine dextran to achieve the formation of a linker that involves amide groups. The latter provides substantial spacing between the substrate and the fluorophore, and at the same time offers H-bonding opportunities (intramolecular and/or intermolecular, e.g., with solvent molecules or biomolecules e.g. proteins). The method is highly customizable, which allows for precise control over the labeling process. This way, different degrees of labeling can be achieved by making simple modifications.

EYLD structure

Fig. 1 Structure of Eosin-Y-lysine-dextran 500 kDa (ratio x/(y+z) depends on the load of fluorescent labelling; R bulky substituent not displayed).

Owing to the presence of Eosin Y, EYLD500 exhibits strong orange fluorescence (excitation max. at λ=530 nm and fluorescence max. at λ=548 nm in water; see Fig. 2). The fluorescence quantum yield for EYLD500 sample with a degree of fluorescent labelling of 0.002 mmol EY/g sample has been determined to be Φ=0.91.


EYLD excitation and fluorescence spectra

Fig. 2 Excitation and fluorescence spectra of EYLD500 recorded in borate buffer (pH=7.0). 

EYLD500 is sensitive to pH due to the presence of Eosin Y, a tetrabrominated derivative of fluorescein that exhibits a similar dependency on pH like its parent compound. A gradual decrease in the absorbance band of EYLD500 is observed when lowering the pH from 9 to 1. Similarly, the fluorescence of EYLD500 drops by a factor of approximately 7 upon the decrease of pH from 9 to 1. The optical behavior of EYLD500 against pH is reflected through the sigmoidal curve shown in Fig. 3.


EYLD sigmoidal curves

Fig. 3 Sigmoidal curves obtained from the results of titration experiments on EYLD500 indicating a high sensitivity to pH (absorbance: orange dots, emission: blue dots) in the range from 1 to 4 (Y-axis corresponds to the product of maximal absorbance or maximal emission intensity of EYLD500).

Storage and stability
EYLD500 should be stored in a well-sealed container in the dark, at room temperature, and has a shelf-life of 6 years under these conditions.

EYLD500 is delivered as a pink amorphous powder readily soluble at concentrations close to 100 mg/ml in water and 50 mg/ml in DMSO, where mild heating (up to max 60oC) might be required. However, it is insoluble in methanol and ethanol.

EYLD500 is part of a family of fixable fluorescent labeled lysine-dextran derivatives that has a range of potential applications in cell permeability studies, tissue and cell imaging, as a fluorescent nanocarrier for drug delivery applications, and as a pH indicator due to the pH-dependent fluorescence of the fluorophore (Eosin Y).


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