The Dye with the Pumpkin Cuff

Jun 20, 2005

Complexation with a large cuff-shaped molecule stabilizes rhodamine dye fluorescence

When irradiated, fluorescent dyes emit light at a different wavelength; for scientists and engineers, these dyes are extremely important aides, as active media in dye lasers, as markers for biomolecules in diagnostics, or for the detection of single molecules. A team from the International University of Bremen has now succeeded in significantly raising the stability of a rhodamine dye by placing it into a kind of molecular cuff.

Most attempts to improve the properties of rhodamines, one of the most important classes of fluorescent dyes, have not been very successful. A new additive now makes it possible. The wonder-molecule used by Werner Nau and Jyoti Mohanty is cucurbituril. The unusual sounding name is derived from cucurbitaceae, the botanical name for the pumpkin family of plants, because the structure of the molecule is like an open-ended pumpkin that has been hollowed out.

When cucurbituril is added to a solution of rhodamine, one dye molecule slips into the cavity of each of the little "pumpkins". Safely ensconced in this way, the rhodamine displays an amazing stability; even highly diluted solutions of the stabilized rhodamine can be stored for a long time without loss of fluorescence due to adsorption of the dye on the surface of the storage flask. In concentrated solutions, like those used for dye lasers, the main problem is aggregation of the dye molecules with each other. The pumpkin hinders this "stickyness" of the rhodamine molecules like a wrapper. Another problem is bleaching of the dye by longer or more intensive irradiation. This often makes it impossible to observe biological samples stained with fluorescence dyes under the fluorescence microscope for extended periods. The pumpkin provides the necessary protection and because the cuff is transparent like a ball of glass, the dye can capture just as many light particles as before. In contrast to many previous materials used for stabilization, cucurbituril in no way affects the fluorescence of rhodamine.

It is noteworthy that the fluorescence lifetime of the enclosed rhodamine molecules is extended. This is the time that passes before the light energy absorbed by a dye molecule is given off as fluorescence. Various investigative techniques depend on this value, because it allows conclusions to be drawn about the environment of the dye molecule. A higher value raises the contrast in fluorescence microscopy.

Source: International University of Bremen

Explore further: Scientists seek more tombs at ancient Greek site

add to favorites email to friend print save as pdf

Related Stories

Form Devices team designs Point as a house sitter

Nov 22, 2014

A Scandinavian team "with an international outlook" and good eye for electronics, software and design aims to reach success with what they characterize as "a softer take" on home security. Their device is ...

Man pleads guilty in New York cybercrime case

Nov 22, 2014

A California man has pleaded guilty in New York City for his role marketing malware that federal authorities say infected more than a half-million computers worldwide.

Recommended for you

When shareholders exacerbate their own banks' crisis

Nov 21, 2014

Banks are increasingly issuing 'CoCo' bonds to boost the levels of equity they hold. In a crisis situation, bondholders are forced to convert these bonds into a bank's equity. To date, such bonds have been ...

Trouble with your boss? Own it

Nov 21, 2014

Don't get along with your boss? Your job performance may actually improve if the two of you can come to grips with the poor relationship.

Engineers develop gift guide for parents

Nov 21, 2014

Faculty and staff in Purdue University's College of Engineering have come up with a holiday gift guide that can help engage children in engineering concepts.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.