Geometry valine

Pearson JG et al (1997) Predicting the chemical shifts in proteins structure refinement of valine residues by using ab initio and empirical geometry observations. J Am Chem Soc 119 11941-11950... 

Comparison of the data in Tables III and VIII shows that the probability of remaining in the ground state is approximately 3% higher for the valine molecule than for related organic molecules. The reason for this is the distortion of the equilibrium geometry of the valine molecule by the crystalline field. 

Fig- 1 A ball-and-stick model of a triplet of amino acids (valine, tyrosine, alanine) highlighting the geometry of the main chain (lightgray). The main degrees of freedom of the main chain are the two rotatable dihedral angles tp, ip around each Ca. The different side chains (dark gray) give each amino acid its specificity... 

Gould, R. O., Gray, A. M., Taylor, P., and Walkinshaw, M. D. Crystal environments and geometries of leucines, isoleucine, valine, and phenylalanine provide estimates of minimum nonbonded contact and preferred van der Waals interaction. J. Amer. Chem. Soc. 107, 5921-5927 (1985). 

Valence-bond theory, 32—34, 42, 46 Valence electrons, 10 and Lewis structures, 20 Valence-shell electron pair repulsion and molecular geometry, 26-29, 45 L-Valine, 1054, 1059... 

Isoleucine has the same geometry as valine and is one carbon larger. Likewise, heptanal has the same geometry as octanal and is one carbon smaller. It is plausible that these two features may compensate at the active site of the mouse receptor. The extra carbon on Ile-206 could therefore interfere with octanal binding but still nicely accommodate the shorter heptanal. 

The presence of a D-amino acid in the sequence of these peptides or the alternation of L and D residues (cf. malformin) results in preferred conformations (reverse turns) that facilitate ring closure. Geometries conducive to cy-clization are generated also by the presence of a proline residue in the sequence, while glycine, by the absence of an impeding side chain can be similarly helpful. The cyclization promoting effect of bulky side chains, particularly valine and isoleucine with branching at the j -carbon atom, can not be excluded. 

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