Phase living systems

The phase of science fiction stories about little green men from Mars is hopefully over, and the question can only be are there, or were there ever, real living systems there, or can we find traces of precursors of life in the form of biomolecules ... 

There has been considerable interest in using fluorescence anisotropy to detect multiple environments in membranes as with fluorescence lifetimes (see above). For example, if a fluorophore is located in two environments with long and short lifetimes, then the fluorescence anisotropy decay process at longer times after excitation will be dominated by the long-lived fluorescent species. This occurs with parinaric acids, and this situation has been explored for a number of theoretical cases. 60 A similar situation has been found for DPH in two-phase lipid systems by collecting anisotropy decay-associated spectra at early and late times after excitation. 61 Evidence was found for more than one rotational environment in vesicles of a single lipid of it is at the phase transition temperature. It is important to identify systems showing associated anisotropy decays with more than one correlation time, each of... 

The Bromine Industry in particular, points out that non-brominated chemical flame retardants may be very hazardous and that the phase-out of BFRs may not be safe. The non-brominated alternatives listed in the above case studies are likely to be safer if they exhibit less persistence and bioaccumulation in living systems, but some do possess significant toxicity. In the last few years, some agencies have therefore investigated the relative merits of alternatives to BFRs. 

Lyotropic liquid-crystalline nanostructures are abundant in living systems. Accordingly, lyotropic LC have been of much interest in such fields as biomimetic chemistry. In fact, biological membranes and cell membranes are a form of LC. Their constituent rod-like molecules (e.g., phospholipids) are organized perpendicularly to the membrane surface yet, the membrane is fluid and elastic. The constituent molecules can flow in plane quite easily but tend not to leave the membrane, and can flip from one side of the membrane to the other with some difficulty. These LC membrane phases can also host important proteins such as receptors freely floating inside, or partly outside, the membrane. 

Looking at the literature in the field of biomineralization, one notices, that the majority of articles is descriptive in nature. On the basis of electron micrographs or thin section studies, the intricate relationships between mineral phase and organic matrix are investigated. Other papers deal with the chemical composition of the mineralized tissue and the minerals. Only a few authors address themselves to the question of metal ion transport mechanisms in cellular systems and the solid state principles involved in mineral deposition on organic substrates. All three sets of information, however, are essential to understand calcification processes. It appears, therefore, that information on the functionality of metal ions in living systems and their role in mineral deposition are particularly desired in this area of research. 

Example 11.1 Cell electric potentials In living systems, ions in the intracellular phase and the extracellular phase produce a potential difference of about 80 mV between the two phases. The intracellular phase potential is negative (Garby and Larsen, 1995). Determine the difference in electrical potential energy per mole positive monovalent ion, e.g., Na+, between the two phases. 

There are striking similarities between the anaesthetic effect discussed above and anti-microbial effects. Thus gases tiiat are general anaesthetics, even die inert noble gases, exhibit an anti-microbial effect. Furthermore this is correlated to the anaesthetic potency [57]. Moreover, it is possible to reverse this effect by hydrostatic pressiue. As discussed above there is an opposing effect of temperature on lipid phase transitions as compared to that of pressure, and this is also reflected in living systems. At 1,000 bar for example certain orgaiusms can survive at 104 C [57]. 

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