Fi- Turns

The paper also proves that the fluid region where turbulent motion occurs expels the external magnetic field like a diamagnetic body with low magnetic permeability /i. In the two-dimensional case considered in this paper, fi turns out to be of order (Rem)-1. However, the assertion regarding the diamagnetic properties of the turbulent motion is valid for the three-dimensional case as well. Here we find p (Rem)-1 (see review ). The next article in this collection is devoted to further development of the results obtained in this paper. 

Banfi, L. Anthoine-Dietrich, S. Basso, A. Guanti, G. Riva, R. Synthesis of mesocyclic fi-turn scaffolds hy tandem U-MCRj RCM methodology, Poster26, MCR2003, April 11-14, 2003, Genoa, Italy. 

The existence of a Pro residue in the pyrokinins raises the possibility of the presence of a turn structure in the active core region. Indeed, a fi-turn is predicted by Chou-Fasman ( ) rules for the sequence Thr-Pro-Arg-Leu within the active core. The significant activity of the cyclic LPK analog cvclo-FAsn-Thr-Ser-Phe-Thr-Pro-Arg-Leu] (Figure 6), in which the N- and C-termini are linked by an amide bond, is consistent with the presence of a )8-turn. This cyclic analog demonstrated a threshold concentration value of 3.5 x 10 M or a significant 4% of its linear counterpart. 

From the investigations on APhe-based peptides, it is clear that the 3-D disposition largely preferred by this residue is the hehcal conformation (23, 24). Therefore, most corner positions of the various types of fi-turns and aU positions of 3io-/a-helices are accessible easily to this residue. Fig. (4) shows the right-handed 310-helix generated by a double repetition of the model triplet -(A Phe-A Phe-L-Ala)-. Aromatic amino acid residues, which include A Phe (25), are known to... 

Type II fi turns are occasionally found with a residue other than Gly in the third position. A calculation was therefore also done for a type II turn with Ala in the third position. The dihedral angles were (0, 0)2 = -72°, 119° and (0, 0)3 = 77°, 16°, based on average values from protein structures, and (0, 0)i = (0, 0)4 = -139°, 135°. 

The complete normal-mode frequencies for standard fi turns of types... 

Observed and Calculated Amide Modes of Type II fi Turns in cyclo(L-Ala—D-Ala-Aca)... 

Many globular proteins contain combinations of a-helix and /Tpleated sheet secondary structures (Figure 5.20). These patterns are called supersecondary structures. In the /la/1 unit, two parallel /Tpleated sheets are connected by an a-helix segment. In the fi-meander pattern, two antiparallel /1-sheets are connected by polar amino acids and glycines to effect an abrupt change in direction of the polypeptide chain called reverse or fi-turns. In aa-units, two successive a-helices separated by a loop or nonhelical segment become enmeshed because of compatible side chains. Several j8-barrel arrangements are formed when various... 

A class of zinc ion (Zn2+) sensors, which utilized an unnatural amino acid that included the chelation-sensitive fluorophore, 8-hydroxy-4-(Af,Af-dimethylsulfonamido)-2-methylquinoline (sulfonamido oxine (Sox), Figure 1.3a), provided inspiration for a second class of kinase activity sensors [12-14]. The Sox amino acid was prepared via asymmetric synthesis and converted to the fluorenylmethyloxycarbonyl (Fmoc)-protected derivative and incorporated via SPPS into a peptide containing a proline-mediated fi-turn sequence [13]. The fl-turn was flanked by both Zn-chelating amino acids and the Sox fluorophore (Figure 1.3b). In this case, the fi-turn was included to provide preorganization... 

Figure 10.3 Copper(l)-catalyzed azide-alkyne cycloadditions were used to incorporate triazoles into a-helical structures 25 and fi-turn mimics 26, respectively, and the secondary structures were spectroscopically verified...

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