Membrane potentials molecular environments

Other molecular sieve membranes are prime candidates as well. Molecular sieve carbon membranes exhibits very high separation factors in the laboratory. Their microstnictuies can be tailored by adjusting the synthesis and calcination conditions however, the issues of their mechanical, chemical and thermal stabilities under various potential application environments have not been addressed. 

Nasal Administration. A route that has gained increasing popularity of late for pharmaceutical administration in humans is the intranasal route. The reasons for this popularity are the ease of use (and, therefore, ready patient acceptance and high compliance rate), the high degree and rate of absorption of many substances (reportedly for most substances up to 1000 molecular weight McMartin et al., 1987), and the avoidance of the highly acid environment in the stomach and first-pass metabolism in the liver (particularly important for some of the newer peptide moieties) (Attman and Dittmer, 1971). The only special safety concerns are the potential for irritation of the mucous membrane and the rapid distribution of administered materials to the CNS. 

Bennet, W.F.D., MacCallum, J.L., Hinner, M., Marrink, S.J., Tieleman, D.P. A molecular view of cholesterol flip-flop and chemical potential in different membrane environments. J. Am. Chem. Soc. 2009, in press. 

Molecular mechanisms in biology, too, depend to a great extent on electrified interfaces. Thus, the mechanism by which nerves carry messages from brain to muscles is based on the potential difference across the membrane that separates a nerve cell from the environment. What are the laws that apply to this electrified interface If this question is answered, then the mechanism by which nerves transmit messages may be determined at the molecular level and the process concerned may become controllable. 

This expression, however, only deals with a single molecular dipole and as many such dipoles would be required to describe the overall membrane dipole potential but as a mean-field expression, this term is practical and culmulatively offers the approximation of the estimated dipolar organisation shown in Fig. 4. A further complication, however, involves the solvent environment and this too is also often dealt with as a mean field or in a continuum manner. But the relative permittivity (or dielectric constant) (sr) cannot be considered to possess the same value throughout the multiphase system represented by a membrane in an aqueous medium. The permittivity profile has been measured to vary from about 78.5 in the bulk aqueous... 

An alternative source of prebiotic molecules on the early Earth is from meteorites. Carbonaceous chondrite meteorites contain abundant carbon, present in a variety of molecular forms, including amino acids, polyols such as sugars and sugar-alcohols. These molecules are all important to life and form key components of nucleic acids and cell membranes (Cooper et al., 2001). Similar molecular evidence for amino acids is found in even more ancient fragments of the early Universe -IDPs. These molecules formed either in the solar nebula or in an interstellar environment (Flynn et al., 2003). Comets have also been considered a viable potential source of prebiotic molecules although currently the view is that most organic material was delivered by asteroids rather than by comets (Dauphas Marty, 2002). 

Molecular modeling and computer simulation with empirical potential energy function (force field) are now routinely carried out to help understand and predict structures and dynamics of proteins and other macromolecules of biological relevance in water and membrane environments. After over 40 years of development, popular force fields such as AMBER, CHARMM, OPLS and GROMOS have been widely employed in biomolecular simulations. These force fields are used dominantly in highly optimized molecular dynamics... 

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