Biological molecules, proton

Although the oldest type of columns, these are presently the most popular nonpartition columns because they can separate large biological molecules such as proteins and nucleic acids. By means of controlled pore sizes, they separate compounds by their molecular size and shape. The resolution achieved by a size resolution column is not nearly as great as that shown by ion exchange or by partition. You will need a 100% difference in molecular weights to achieve a clean separation. Partition can separate on the basis of a proton up or down out of 13 protons on a compound. 

Examples Acid salts, acids, proton sponges, HF complexes Acids, alcohols, hydrates, phenols, biological molecules Weak base, basic salts C-H- O/N O/N-H- ji... 

Because of the ease with which molecular mechanics calculations may be obtained, there was early recognition that inclusion of solvation effects, particularly for biological molecules associated with water, was essential to describe experimentally observed structures and phenomena [32]. The solvent, usually an aqueous phase, has a fundamental influence on the structure, thermodynamics, and dynamics of proteins at both a global and local level [3/]. Inclusion of solvent effects in a simulation of bovine pancreatic trypsin inhibitor produced a time-averaged structure much more like that observed in high-resolution X-ray studies with smaller atomic amplitudes of vibration and a fewer number of incorrect hydrogen bonds [33], High-resolution proton NMR studies of protein hydration in aqueous... 

Due to proton deficiency, crystal structures of amino acids display a much higher proportion of three-center hydrogen bonds. Their geometries, given in Th-bles 8.6 and 8.7, are based on neutron diffraction data, of which a relatively large number is available for this class of biological molecules. 

The three-center bonds represent — 70% of the total number of hydrogen bonds in the crystal structures surveyed (Thble 2.3). This is a significantly higher proportion than in the other biological molecules, and was attributed to proton deficiency, which occurs because the amino acids form zwitterionic crystal structures where the predominant hydrogen bonding is between the -NH3 and the... 

On the other hand, Kihara s group reported interesting ET systems for biological molecules including L-ascorbic acid [13], flavin mononucleotide (FMN) [14] and 3-nicotinamide adenine dinucleotide (NADH) [15]. While these ET systems are very important from a biological viewpoint, their reaction mechanisms are often complicated by the coupling of ET and proton or ion transfer. 

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