N loops

So we can decide weak equivalence for Ianov schemas we can decide whether they ever halt with different answers. If they are weakly equivalent, the only way they can fail to be strongly equivalent is for one to halt and the other loop for the same interpretation and input. We now show that this situation is detectable. We use a somewhat more complex version of the previous argument. Call a node n "loop-alive" if there is any path from n to STOP passing twice through the same node. 

Vangelista L, Longhi R, Sironi F et al (2006) Critical role of the N-loop and betal-strand hydrophobic clusters of RANTES-derived peptides in anti-HIV activity. Biochem Biophys Res Commun 351 664-668... 

Bond Distances N-N = [1.2301 Bond Angle D-N-N = [lOOp Product of Moments of Inertia ... 

Additional hydrophobic residues between the second cysteine and a 3-10 helix in the "N-loop" have also been shown to be important for chemokine binding. The N-loop in... 

Figure 1 Representative chemokines of CC (A), CXC(B), CX3C (C), and XC (D) families. The conserved cysteine pattern is shown in yeiiow (gray in the print version) sticks residues separating the two N-terminai cysteines are shown as magenta balls (B and C). Loops believed to be involved in coordinating the N-terminus of the receptor (N-loop and 40s-loop) are colored blue (dark gray in the print version) and charged residues in these regions are shown as sticks.

The chemokine fold (Fig. 1C) consists of a flexible N-terminus, an N-loop, occasionally a 3io helix, an antiparallel three-stranded P-sheet, and a C-terminal a-hehx. Within the antiparallel three-stranded P-sheet, the pi-strand is connected to P2-strand by the 30s loop and p2-strand is... 

The structural elements involved in the binding of chemokine ligands to chemokine receptors have been mainly obtained from mutational analyses [23]. The N-loop... 

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