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Chromeo™ Py-Dyes

simple and effective fluorescent dyes for protein labeling

Virtually all fluorescent labels developed so far do not undergo significant changes in their spectral properties when conjugated to protein. In contrast, Chromeo™ Py-Dyes are a new class of amine-reactive fluorescent labels that undergo a shortwave spectral shift as well as a large increase in quantum yield upon binding to primary amines. This effectively eliminates background from any unbound dye (Figure 1 and Table 1). Py-Dyes are stable in aqueous solvents and are suitable for a variety of applications, such as labeling proteins or as stain of proteins in electrophoresis.

Chromeo™ Py-Dye Advantages

Labeling proteins with conventional fluorescent dyes has tended to suffer from many limitations, such as the requirement for toxic co-factors, high rates of hydrolysis or unsuitable spectral properties. Most common procedures also require the time-consuming purification of the conjugated proteins. The Chromeo Py-Dyes from Active Motif Chromeon overcome these limitations. The dyes are supplied ready to use with a single reactive group that conjugates to a primary amine in a simple one-step, room-temperature incubation. This eliminates the need to activate the dye prior to conjugation. And, because Py-Dyes have only one reactive group, problems associated with crosslinking are avoided. In addition, the positive charge of the amine group is maintained after Py-Dye conjugation, so labeled protein maintains the same ionic character as the native protein (Figure 2).

Figure 1: Absorption and emission spectra of free vs. bound dye.

Normalized absorption and emission spectra of Chromeo P503 when the dye is free (solid, purple lines) and conjugated (dotted, copper lines). As free dye and bound dye absorb at different wavelengths (612 nm vs. 503 nm) and the quantum yield of bound dye is 50-fold greater than that of free dye, background from free dye is effectively eliminated.

Figure 2: Labeling with Py-Dyes maintains each protein's natural charge.

Chemical equation depicting the chemistry of Py-Dye labeling, which demonstrates the preservation of the positive charge of the lysine residue of a protein. R stands for the respective chromogenic/fluorogenic group.

Why use Py-Dyes?

• Broad Stokes shifts improve sensitivity
• Large increase in quantum yield upon binding eliminates background
• Excellent photostability (no bleaching)
• Fast and simple procedure
• No change in net charge of the biomolecule

Contents & Storage

Each Chromeo Py-Dye is supplied as a dry powder. Guaranteed stable for 6 months when stored properly.