The origin of life

The most remarkable aspect of life is its mysterious origin.

Although chemists are now able to create the building blocks of life in the lab, the magic spark that makes these molecules self-assemble into something living could not be observed yet. And indeed, a basic law of physics dictates that man made constructs are prone to decay when left to themselves. Our new insights reveal that first replicating entities on our planet were not entirely alone though, but taken care of by heat driven micro-reactors inside submarine volcanic rocks. In these little compartments genetic molecules get trapped and find optimal conditions for replication. Additionally they are selected towards ever increasing complexity, reversing the usual one-way route from living organisms to dead matter.

Reference: Moritz Kreysing, Lorenz Keil, Simon Lanzmich, and Dieter Braun
Nature Chemistry (2015) doi:10.1038/nchem.2155 (see 'publications' for PDF version of this paper)

More recently, we found that also phase separated protocells can be assembled in this setting, and we are looking forward to study the implications of this finding supported by a 5-year collaborative grant that we received from the Volkswagen Foundation (see jobs section in case of interest).

Optical constraints on retinal architecture

The first part of our research addresses one of the vertebrate retina's most surprising, but least investigated characteristics, its optical architecture: since the sensitive portions of the photoreceptor cells are found on the back of the retina, light needs to travel through several layers of living neuronal tissue before being detected. What is usually regarded as being a problem of neuronal activity is complemented from the perspective of optics, focusing on one key question: how does the retina deal with incident light?

When looking through a piece of freshly excised retinal tissue, in front of a dark background, it appears slightly opaque and silky (Fig.1, left). Any attempt to see through this retina is only successful as long as the object behind it is in the closest proximity to this tissue, clearly indicating strong interaction of light with the tissue, that would not occur in a truly transparent medium, such as the homogeneous and isotropic vitreous humor (Fig. 1, right). Quantitative measurements on the inner retina reveal that despite being scattering in the far-field, retinal tissue possesses a high ability to transfer an image from its inner surface to the back of the outer nuclear layer.

Using custom design microscopes we are aiming to gain a detailed understanding of optical constrains on retinal development that have previously been shown to be present down to the level of the chromatin organization. Apart from its importance for the initiation of the visual process, light propagation in neuronal tissues is also key to the optical observation of brain activity over large scales. Our experimental research is accompanied by theoretical and computer modeling of light tissue interaction.

Advanced laser manipulation of biological cells

In the past, we developed a tool for the contact-free manipulation of biological samples. The optical cell rotator technology is able to orient individual cells under any microscope thus paving the way for optical tomography of suspended cells.

Furthermore, we are interested in the manipulation and perturbation of self organizing systems with well defined physical stimuli. These include spatially varying temperature distributions (i.e. to locally trigger gene expression or concentration changes) as well as mechanical stimuli to interfere with biological reaction-diffusion systems.