Emerging Complexity in Supramolecular Systems

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Strasbourg Complex Systems Roadmap (January 2012)

Participants

Keywords

Hierarchical structures, Dynamic systems, Adaptive behaviour, Molecular evolution, Smart functional systems, Information-gaining systems

Introduction

Complexity can be defined as C = M*I*I

M: Multiplicity

  1. One single molecule can present several properties e.g. Multiplicity of binding sites, number of energy levels....
  2. Mutiplicity of components: number of components (molecular) /constituents (supramolecular) in the system

I: Interaction

  1. Complentaries of shapes, of charges, of energy levels (Program writing / reading)
  2. Thermodynamic and kinetic of the interaction (reversibility, lability), covalent / non-covalent bonds, short-range/long-range
  3. Interactions of molecules with their environments (possibly in flux of energies far from equilibrium)

I: Integration

  1. Collective structuring
  2. In space: From sub-nano, to meso, to macro
  3. In time: Modulation of structures, oscillations
  4. Emergence of new properties because of the network topologies (feedback loops)
  5. Emergence of new functions


Grand Challenges

  1. Designing supramolecular systems able to generate complexity
  2. Reaching emergent properties in complex supramolecular systems
  3. Producing applications from complex supramolecular systems – societal implications
  4. Teaching complex systems in chemistry (Strasbourg Erasmus Mundus)



1. Designing supramolecular systems able to generate complexity

The conception of these complex supramolecular systems require first to understand and engineer specific tools before bringing them all together.

Specificity of interactions and integrations

Synthetic chemistry - often supported by modelling - remains the prerequisite to design any molecular and supramolecular systems. Because of the specificity of supramolecular objects which leads to hierarchical structuring, the information contained in the basic building blocks should be precisely tailored. This remains true for small host-guest complexes with a high degree of organization, but also for softer objects with long range organizations.

Spatio-temporal dynamics at the Multiplicity, Interaction, and Integration levels

Thermodynamics governs (supra)molecular systems at a number of levels and in particular, the transient conformations of individual molecules can affect their interactions with the other constituents of the system. The constitutional dynamic, which refer to objects reversibly connected by one another in larger aggregates, is also under thermodynamic control, although they can be pushed far from equilibrium when crossed by flux of energies, including photochemical and electrochemical triggers, electric and magnetic fields, shearing forces, gradients of chemical species. Dynamics is also a crucial property of chemical networks of reactions, and the relative ratii of concentrations and kinetic rates, depending on the network topologies, provide new properties such as stability, robustness, spatial and temporal organization such as patterns, oscillations, and waves. Together, the dynamics occuring at the molecular, supramolecular and network levels are merged to allow adaptation processes.

  1. Conformational Dynamic
  2. Constitutional dynamic: reversibility of the structure of the systems components
  3. Network dynamics in coupled reactions
  4. Reversible dynamics at the three levels allow adaptation


Chemical reversibility as a requirement for evolvability

The reversibility of chemical reactions and supramolecular interactions is mandatory for two main aspects. The first one concerns the necessity to explore the whole combinatorial space containing all the potential structures. These species are not necessary expressed by the system, but should be able to emerge when necessary (virtuality). The second aspect, which is a consequence of the first one, is that reversible systems will be able transiently to express an object which will then be destructed to express another one for other environmental conditions.

  1. Creates stochastic behavior for exploration of phenotypes
  2. Generate adaptativity by "mutations" which are driven by internal, or environmental parameters (e.g. stimuli, effectors)


Cooperativity is part of the integration processes which is important for modulations

  1. Allosteric effects (activation/inhibition)
  2. Long range interactions and colective behaviors (e.g. phase transitions)
  3. Auto-catalysis and cross-catalysis (positive / negative feedback loops)
  4. Cooperativity allows emergence


2. Reaching emergent properties in complex supramolecular systems

Diversity

The diversity results from the multiplicity of the systems in terms of number of components, of number and nature of interactions they can generate one another, and of reversiblity of these interactions which allow a full exploration of the combinatorial space.

Selection

The selection results from the specificity of the interactions, from the topology of the reaction networks (random, scale free, auto-catalytic pathways), from the kinetics of diffusion, from the overall reversibility of the system, and from the interactions with the environment possibly far from equilibrium in open systems

Evolution

Supramolecular systems will be ultimately able to evolve if they can generate the components necessary to sustain their own structures, if they can perform mutations in relation to their environment (adaptation), and if they can self-replicate to grow their population.

New functions

Complex supramolecular systems are by essence multi-functional systems which are able to produce several functions from a common set of basic constituents. The expression of these functions can vary in space and time, depending on the internal parameters of the systems, and on the external pressure of environment. In addition, emergence of new functions can appear from these systems, although they were not contained within their individual components. This is allowed by numerous synergistic effects in multi-component systems and networks, including allostery, short and long range spatial couplings, compartmentalization, and feedback loops.

Open questions

  1. Is supramolecular complexity (one of the) the support to produce thinking matter?
  2. If yes, is this pathway continuous or does it present at one point a strong nonlinearity in evolution? Information/consciousness?


3. Producing applications from complex supramolecular systems – societal implications

Medicine

  1. Drugs
  2. Transfections - Delivery
  3. Imaging


Cellular biology

  1. Understanding of the construction of molecular networks
  2. Understanding protein foldings
  3. Biomimetic behaviors


Environmental sciences

  1. CO2 capture
  2. Water purification


Chemistry and materials

  1. Catalysis
  2. Organic electronics
  3. Solar cells
  4. Self-healing materials
  5. Smart materials (responsive/adaptive)
  6. Molecular motors
  7. Information processing and engineering


4. Teaching complex systems in chemistry (Strasbourg Erasmus Mundus)

Notes

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