Backbone geometry

The first approach has successfully been applied to the study of amorphous as well as to macroscopically ordered solids. Examples of applications include the determination of backbone geometries in fibrous proteins [4] or the determination of protein-backbone, side-chain, and bound-ligand orientation with respect to the membrane normal in membrane-bound proteins [5-8]. Membranes, bilayers, bicelles, or liposomes are neither solid nor liquid systems but have aspects of both and are sometimes liquid crystalline. In most of these systems, time-independent anisotropic interactions play an important role,... 

Other structural variations on the rigid-rod PBZXs have encompassed a variety of changes that affect the backbone geometry. Deviation from 180° para-catenation has been investigated by a number of researchers for improved processability. Solution properties are of particular interest in an effort to determine concentration effects on the ability to form liquid crystalline solutions. Most notable backbone deviations have been the ABPBT, ABPBO and ABPBI systems which are characterized by catenation angles of 162°, 150°, and 150° respectively. They are classified as extended chain systems because of the unrestricted rotation between the repeat units. The polymer backbone can... 

Earlier studies of macromolecules with flexible, non-mesogenic side-chains had revealed that the transition properties change with increasing side-chain length from typical polymeric behavior to that of the small molecule which corresponds to the side chain 72,73). With short side-chains and proper backbone geometry (tacticity),... 

We have also carried out Huckel calculations on the various backbone geometries considered in this paper, rfuckel theory only considers nearest neighbor overlap integrals, p, for the backbone carbon atoms and has no sensitivity to bond angles. The... 

Figure 5. Huckel results for polymer bandgap. Eg, versus corresponding results from VEH theory for various backbone geometries (See Table I). All energies are given in eV. The three dates sets represent three different choices for the p-bond length relationship in Huckel theory reference 19 (x), reference 18 (e), and reference 26 (o).

The abilities of different monomeric units of the copolymer to cocrystallize into the same lattice should depend on the degree of structural similarity between them. The minor component should at least have the chemical structure causing no significant distortion in the backbone geometry of the homopolymer chain of the major component. 

H. Kono, J. Doi. Energy minimization method using automata network for sequence and side-chain conformation prediction from given backbone geometry. Proteins. 1994, 19, 244-255. 

In the case of the type VI / -turn competent replacements for the backbone geometry of the central residues with a ds-amide bond are obtained by tethering the Ca of the N-terminal amino acid residue to the proline Ca in a dipeptide lactame (Fig. 11.10). Again azabicycloalkane amino acids are obtained which may contain additional heteroatoms and differ in the ring sizes of the fused bicyclic framework. Selected examples are shown in Fig. 11.12. 

A review on the determination of the backbone geometry of single-stranded nucleic acids in aqueous solution has appeared. A method for assigning n.m.r. signals of and P nuclei in the oligonucleotide backbone by 2-D n.m.r. plots using homonuclear and heteronuclear ( H- P) spin-spin... 

Mimicking a p-tum consists in constraining correctly four torsional angles (4>,4>2, P, P2) and four bonds (bonds a-d, cf. Fig. 2.3.3). Bonds a and d direct the entry and the exit of the peptide chain through the turn, respectively, whereas bonds b and c are responsible for the spatial dispositon of the amino acid side chains at position i+1 and i+2 of a turn. The torsional angles determine the backbone geometry of the turn and consequently the shape of the turn hydrogen... 

There have been a number of recent investigations in the field of normal Raman spectroscopy with laser excitation of proteins in aqueous solutions . Raman spectroscopy uncovers information of the peptide backbone, geometry of... 

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