Introduction

Information and Noise:
Chemistry, Biology and Evolution
Creating Complex Systems

When do chemical systems become biological ones? What needs to happen for molecules behaving stochastically to join in networks and cooperate to produce non-random or directed chemical pathways? Biological systems consist of networks of interacting molecules over a large number of time and length scales, and with error tolerance: The larger and more organized the molecules, the more they behave cooperatively. The evolution of biological systems results in interconnected networks optimized for robustness. Such systems are often not the optimal solution, but rather an adjacent one, stable to perturbations. Indeed, before the first genetically regulated ones, such systems had to self-encode into a replicating system. What mechanism led to self-encoding chemistry and was this the seed for biological evolution? This question is perhaps the most important. Finding the first system that is able to evolve is a big challenge.

The first evolving systems started without all the error-correction mechanisms of biology, and chemical reactions do not proceed with 100% yield; they are inherently noisy. Sometimes the reaction produces byproducts, other times, small changes in the conditions lead to changes in products.

 

Biological systems are also noisy. Noise can be described in terms of apparently undirected activity such as Brownian molecular movement in cells, or even in terms of unspecific, promiscuous enzyme catalysis of chemical reactions involving unusual or uncommon substrates. Information transfer in networks can be facilitated by noise. What is the nature and meaning of the information that we are transferring in chemical and biochemical reactions and what types of noise play a role in signaling and information transfer in biological systems?

Complex molecules found in nature are the results of chemical reactions in biological systems, i.e. living systems. But what is the maximum complexity that can be found abiotically without the use of a biological system and is there a limit to the complexity that biological systems can produce (or humans can understand)? Is the chemical variation of life on earth the most robust form potentially evolvable, or just robust enough? Is it efficient to mimic biological synthesis pathways by means from the organic chemistry toolbox?