Biological coherent processes

The theory of autopoiesis is based on the observation of the actual behavior of a living cell. As such, it is not an abstract theoretical model for life - there are many of these - but a deductive analysis of life as it is on Earth. It is in a way a picture of the blue-print of cellular life, and it is fascinating to see how many concepts related to the process of life - emergence, homeostasis, biological autonomy, interactions with the environment, cognition, evolutionary drift, etc. - pour forth from this analysis in a coherent way. 

To understand a complex biological process, a biochemist isolates and studies the individual components in vitro, then pieces together the parts to get a coherent picture of the overall process. A major source of molecular insights is the cell s own information archive, its DNA. The sheer size of chromosomes, however, pres-... 

Since many of these developments reach into the molecular domain, the understanding of nano-structured functional materials equally necessitates fundamental aspects of molecular physics, chemistry, and biology. The elementary energy and charge transfer processes bear much similarity to the molecular phenomena that have been revealed in unprecedented detail by ultrafast optical spectroscopies. Indeed, these spectroscopies, which were initially developed and applied for the study of small molecular species, have already evolved into an invaluable tool to monitor ultrafast dynamics in complex biological and materials systems. The molecular-level phenomena in question are often of intrinsically quantum mechanical character, and involve tunneling, non-Born-Oppenheimer effects, and quantum-mechanical phase coherence. Many of the advances that were made over recent years in the understanding of complex molecular systems can therefore be transposed and extended to the study of... 

The next two chapters are devoted to ultrafast radiationless transitions. In Chapter 5, the generalized linear response theory is used to treat the non-equilibrium dynamics of molecular systems. This method, based on the density matrix method, can also be used to calculate the transient spectroscopic signals that are often monitored experimentally. As an application of the method, the authors present the study of the interfadal photo-induced electron transfer in dye-sensitized solar cell as observed by transient absorption spectroscopy. Chapter 6 uses the density matrix method to discuss important processes that occur in the bacterial photosynthetic reaction center, which has congested electronic structure within 200-1500cm 1 and weak interactions between these electronic states. Therefore, this biological system is an ideal system to examine theoretical models (memory effect, coherence effect, vibrational relaxation, etc.) and techniques (generalized linear response theory, Forster-Dexter theory, Marcus theory, internal conversion theory, etc.) for treating ultrafast radiationless transition phenomena. 

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