Biological systems macroscopic properties

Systems of coupled nonlinear oscillators are nsed to explain the dynamics of various biological and physiological systems. This is because most of the interesting phenomena in biological systems occur as a result of the collective behavior of the entities in the system and also becanse we are more interested in the collective dynamics of the systems (macroscopic properties), instead of the dynamics of individual entities. 

Abiotic forces will not be in the focus of the discussion, but it is obvious that a polymeric material like PVAc or PVA exposed to outdoor conditions will undergo different alterations at the macroscopic and microscopic scales. Depending on its interaction with mechanical forces, thermal stress, radiation or chemical attack, the polymer properties might be changed in a way that is relevant for its interaction with biological systems. 

Interest in thermotropic liquid crystals has focussed mainly on macroscopic properties studies relating these properties to the microscopic molecular order are new. Lyotropic liquid crystals, e.g. lipid-water systems, however, are better known from a microscopic point of view. We detail the descriptions of chain flexibility that were obtained from recent DMR experiments on deuterated soap molecules. Models were developed, and most chain deformations appear to result from intramolecular isomeric rotations that are compatible with intermodular steric hindrance. The characteristic times of chain motions can be estimated from earlier proton resonance experiments. There is a possibility of collective motions in the bilayer. The biological relevance of these findings is considered briefly. Recent similar DMR studies of thermotropic liquid crystals also suggest some molecular flexibility. 

Below, the interdependence of macroscopic properties on these microscopic features is described briefly for 0H---0 hydrogen-bonded crystals. The bistable homonuclear hydrogen bonds are convenient examples to explain the structure-property relations, because the H atom is readily locatable in the structure in this way the mechanism of microscopic transformations can be followed. At the same time, H-bonded systems are important for understanding transformations of molecular and biological systems, or for prospective practical applications. At present there appear to exist no practical applications of electronic devices based on hydrogen-bonded materials. 

In many ways, analysis of the factors influencing biological electron transfer is analogous to the study of electric conduction in macroscopic systems. The properties of conducting systems may be described by Ohm s law ... 

Microemulsions and most surfactants in dilute solutions and dispersions self-assemble into a variety of microstructures spherical or wormlike micelles, swollen micelles, vesicles, and liposomes. Such systems are of biological and technological importance, e.g., in detergency, drug delivery, catalysis, enhanced oil recovery, flammability control, and nanoscale particle production. The macroscopic properties—rheology, surface tension, and conductivity—of these systems depend on their microstructure. As these microstructures are small (1-1000 nm) and sometimes several microstructures can coexist in the same solution, it is difficult to determine their structure. Conventional techniques like radiation scattering, although useful, provide only indirect evidence of microstructures, and the structures deduced are model-dependent. 

We have demonstrated how electro-optical and non-linear optical techniques can be utilized to characterize the structure/function relationship in biologically as well as in technically important supramolecular systems. In both cases, interaction of the molecules under investigation with a liquid interface can be used to bring about system orientation, which is utilized to enhance the performance of the spectroscopic experiment, or to induce the desired macroscopic properties. 

One of the central issues of the molecular approach is to devise adequate force fields that accurately describe the properties of real systems. Depending on the application field, different requirements need to be fulfilled. In biology, for instance, to study protein folding in aqueous environments, typically rather complex force fields are used to determine microscopic molecular structures. In the chemical industry, much more aggregated macroscopic properties are needed, but the quantitative correctness of the data is essential. 

Many models are used to include the microscopic effects of water molecules on biological systems, and most of them are based on parameterized force field schemes that are tuned to reproduce some bulk macroscopic properties of the solvent. For a given system, the choice of a specific water model is based on the usual tradeoff between accuracy and computational complexity. Furthermore, even if a particular model fits a type of data better than another— for example, dielectric constant better than density versus temperature—the choice of which model to use is not obvious. 

The elucidation of the mechanisms that determine the complex interactions structure-properties has as result the discovering of the technical potential of biological systems, and its materialisation in performance applications. Such interactions are practically released at all levels of structural organisation, starting to the molecular one, and overlap and interfere between them, thus generating qualitatively new macroscopic effects. 

---