Globular conformation

When the polypeptide chains of protein molecules bend and fold in order to assume a more compact three-dimensional shape, a tertiary (3°) level of structure is generated (Figure 5.9). It is by virtue of their tertiary structure that proteins adopt a globular shape. A globular conformation gives the lowest surface-to-volume ratio, minimizing interaction of the protein with the surrounding environment. 

The subunits of an oligomeric protein typically fold into apparently independent globular conformations and then interact with other subunits. The particular surfaces at which protein subunits interact are similar in nature to the interiors of the individual subunits. These interfaces are closely packed and involve both polar and hydrophobic interactions. Interacting surfaces must therefore possess complementary arrangements of polar and hydrophobic groups. 

Attempts were also made to design non-protein polymers able to collapse to a globular conformation with properties complying (at least in part) with the given requirements e.g., having an active center [87]. The review of the research performed in this direction can be found in [88-92]. 

Charged polysoaps (polymer micelles) combine within a molecule structural characteristics of the conventional micelles and polyelectrolytes, and supposedly adopt globular conformations in aqueous media with the hydrophobic region inside and charged groups outside as in water-soluble proteins. Thus,... 

The intron group I ribozymes feature common secondary structure and reaction pathways. Active sites capable of catalyzing consecutive phosphodi-ester reactions produce properly spliced and circular RNAs. Ribozymes fold into a globular conformation and have solvent-inaccessible cores as quantified by Fe(II)-EDTA-induced free-radical cleavage experiments. The Tetrahy-mem group I intron ribozyme catalyzes phosphoryl transfer between guanosine and a substrate RNA strand—the exon. This ribozyme also has been proposed to use metal ions to assist in proper folding, to activate the nucleophile, and to stabilize the transition state. ... 

Figure 11.2. Globular conformations of an A-type duplex (left) and a B-type duplex (right), generally seen for RNA RNA and DNA DNA duplexes, respectively. Charge and shape complementarity of neomycin to the A-form major groove Computer models of (left) neomycin docked in the major groove of A-form DNA, and (right) neomycin buried in the B-form major groove. See color plates.

Figure 11.2. Globular conformations of an A-type duplex (left) and a B-type duplex (right), generally seen for RNA-RNA and DNA-DNA duplexes, respectively. See text for full caption.

Type of crystal comprised of macromolecules having globular conformations. 

When a more globular conformation is enforced by functionaUzing the PPI dendrimers with bulky adamantyl terminal groups, or at higher generations (G4 and G5) of the PAMAM system, the dendrimers behave like nonamphiphUic, hydro-phobic spheroids. 

Molecular dynamic and NMR studies have shown that only the extended conformation of CF3-acetyldocetaxel (i.e., in which the isoserine side chain is distant from the baccatine moiety) is independent of the hydrophilic or hydrophobic nature of the medium. In the other derivatives of Taxol, the globular conformation is largely favored by a protic medium. " Thus, it would be interesting to perform studies of complexes with tubuhnes in the solid phase to determine if the cytotoxic activity is connected with the conformation. 

Typically, proteins fold to organize a very specific globular conformation, known as the protein s native state, which is in general reasonably stable and unique. It is this well-defined three-dimensional conformation of a polypeptide chain that determines the macroscopic properties and function of a protein. The folding mechanism and biological functionality are directly related to the polypeptide sequence a completely random amino acid sequence is unlikely to form a functional structure. In this view, polypeptide sequence... 

Apparently, this is due to some memory effect the core, which existed in the parent globular conformation (Fig. lb), was simply reproduced upon refolding caused by the attraction between H units. One may say that the features of the parent conformation are inherited by the protein-like copolymer. Looking at the conformations of Fig. 3, it is natural to argue that proteinlike copolymer globules could be soluble in water and thus they are open to... 

Fig. 3 Typical snapshots of the globular conformations of a protein-like, b random, and c random-block copolymers of the same length (N = 512). Hydrophobic segments are shown in light gray and hydrophilic segments in dark gray. Adapted from [18]...

The idea of conformation-dependent sequence design via polymer-analogous transformation can be generalized in many respects [23]. Indeed, a special chemical sequence can be obtained not only from a globular conformation any specific polymer chain conformation can play the role of parent. 

Moreover, the thorough analysis of globular conformations shows that this layer is almost absent near the faces of the cylinder [212]. This facilitates the formation of multiglobular aggregates in the solution of regular copolymers. 

A new way of obtaining nanostructures in systems of thermosensitive polymers by combining them with hydrophilic species was proposed by Bron-stein et al. [54]. The core-shell nanoparticles were obtained by stabilization of the globular conformation of PVCL in aqueous solutions at 45 °C on add-... 

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