Sidechain structure structural properties

Typical Lewis acids such as AlCl3 and ZnCl2 display excellent catalytic activity in most Friedel-Crafts type reactions (9, 10) and are also known to catalyze coal liquefaction and solubilization (11-26). Because of this latter property, acid-catalyzed depolymerization has become a useful method for structural investigation of coal (27). The rationale for solubilization is interpreted either in terms of depolymerization via rupture of the bridges or, since the overall reaction in general is that of Friedel-Crafts alkylation or acetylation, in terms of the effect of the sidechains introduced on the aromatic ring system. 

The twenty basic units of differing chemical properties, their random order and variable abundance in the polymer, and the variable length of proteins provide a tremendous diversity to proteins as a class. For example, there are 400 possible dipeptides (20x20) and 8000 (20 ) possible tripeptides, and the numbers become astronomical (20 ) when even moderately small proteins of as few as 100 amino acids are considered. Superimposed on this diversity are further modifications such as intrachain and interchain disulfide linkages, which are covalent linkages between cysteines, and other covalent modifications of the sidechains of individual amino acids (discussed below). The linear amino acid sequence together with further covalent modifications is known as the primary structure of a protein. 

On the subnanosecond time scale our basic knowledge of protein motions is almost complete that is, the types of motion that occur have been determined, their characteristics evaluated and the factors responsible for their properties delineated. Simulation methods have shown that the structural fluctuations in proteins are sizable particularly large fluctuations are found where steric constraints due to molecular packing are small (e.g., in the exposed sidechains and external loops), but substantial mobility is also found in the protein interior. Local atomic displacements are correlated in a manner that tends to minimize disturbances of the global structure of the protein. This often leads to fluctuations larger than would be permitted in a rigid polypeptide matrix. 

The helioporins, a group of marine diterpenes with antiviral and cytotoxic properties, are structurally closely related to the (seco-) pseudopterosins and all possess a characteristic benzodioxole unit [29]. Their stereostructure was assigned as shown in Fig. 4 with a cfs-relationship of the two benzylic sidechains at the tetralin nucleus. 

An antimicrobial class comprises compounds with a related molecular structure and generally with similar modes of action. Variations in the properties of antimicrobials within a class often arise as a result of the presence of different sidechains of the molecule, which confer different patterns of PK and PD behavior on the molecule. The major classes of antimicrobial drugs are discussed below. 

Structural descriptors at the secondary level (mesoscale) are topology and domain size of polymeric aggregates (persistence lengths and radius), effective length and density of charged polymer sidechains on the surface, properties of the solution phase (percolation thresholds and critical exponents, water structure, proton distribution, proton mobility and water transport parameters). Moreover, -point correlation fimctions could be defined that statistically describe the structme, containing information about surface areas of interfaces, orientations, sizes, shapes and spatial distributions of the phase domains and their connectivity [65]. These properties could be... 

This coarse-grained molecular dynamics model helped consolidate the main features of microstructure formation in CLs of PEFCs. These showed that the final microstructure depends on carbon particle choices and ionomer-carbon interactions. While ionomer sidechains are buried inside hydrophilic domains with a weak contact to carbon domains, the ionomer backbones are attached to the surface of carbon agglomerates. The evolving structural characteristics of the catalyst layers (CL) are particularly important for further analysis of transport of protons, electrons, reactant molecules (O2) and water as well as the distribution of electrocatalytic activity at Pt/water interfaces. In principle, such meso-scale simulation studies allow relating of these properties to the selection of solvent, carbon (particle sizes and wettability), catalyst loading, and level of membrane hydration in the catalyst layer. There is still a lack of explicit experimental data with which these results could be compared. Versatile experimental techniques have to be employed to study particle-particle interactions, structural characteristics of phases and interfaces, and phase correlations of carbon, ionomer, and water in pores. 

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