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Doctoral dissertation on the colour of molecules

Physicist Steen Brøndsted Nielsen has obtained his higher doctoral degree at Aarhus University. His doctoral dissertation investigates the colour of molecules when they are not under the influence of their surroundings. The aim is to develop better fluorescent markers for medical examinations.

2019.11.07 | Christina Troelsen

Steen Brøndsted Nielsen, Department of Physics and Astronomy, Aarhus University, defended his doctoral dissertation on the colour of molecules on the 28 October 2019. Photo: Melissa Yildirim, AU Foto

Steen Brøndsted Nielsen is an associate professor at the Department of Physics and Astronomy at Aarhus University, and after defending his doctoral dissertation - Photophysical Properties of Molecular ions – The impact of a microenvironment - on 28 October 2019, he can now call himself ‘Doctor Nielsen’.

Steen Brøndsted Nielsen’s research was about investigating the colour of molecules in nature when they are completely isolated; i.e. when they are not in a protein or in an aqueous solution such as chlorophyll, which gives plants their green colour. He is particularly interested in finding out how a molecule’s surroundings, for example a water molecule, affect electronic transitions, and how proteins can 'turn on’ a light-absorbent molecule, so that it becomes fluorescent.

In the field of cell biology and molecular biology, fluorescent marker proteins are often used to find out about the growth of a tumour, for example. The most well-known example is probably Green Fluorescent Protein (GFP), which converts blue light into green light. However, proteins that emit red light are best because red light penetrates tissue more easily than green and blue light. A number of these proteins have been developed, but the problem is that they are all only weak light sources. Steen Brøndsted Nielsen hopes that a fundamental understanding of how a microenvironment (e.g. water or amino acids) influences the colour of a light-absorbent molecule will make it easier to design new and better fluorescent proteins for medical examinations.

Steen Brøndsted Nielsen was born in Grenå (1972). He has a Master's degree in chemistry and physics from the University of Southern Denmark (1997) and a PhD degree in chemistry from the University of Copenhagen (2000). After research stays abroad (Yale and Princeton), he came to Aarhus University in 2002. Since 2007, he has been an associate professor at the Department of Physics and Astronomy

Steen Brøndsted Nielsen is married and has three children. The family lives in Risskov near Aarhus.

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