Glycine, structure

Glycine, structure of, 110 Gradient methods, see Conjugated gradient methods... 

Determine the geometry around each interior atom in the glycine structure and make a three-dimensional sketch of the molecule. 

New problems on structure of cisplatin from number of known isomers, resonance structures of acetylacetonate and glycinate, structures of glycinato complexes, complexes of the ambidentate thiocyanato complexes, structure of a trien complex, and names of the Figure 3.18 complexes... 

Crystalline Structures. Crystal shape of amino acids varies widely, for example, monoclinic prisms in glycine and orthorhombic needles in L-alanine. X-ray crystallographic analyses of 23 amino acids have been described (31). L-Glutamic acid crystallizes in two polymorphic forms (a and P) (32), and the a-form is mote facdely handled in industrial processes. The crystal stmeture has been determined (33) and is shown in Figure 1. 

Observed values for all residue types except glycine. Each point represents (j) and values for an amino acid residue in a well-refined x-ray structure to high resolution, (c) Observed values for glycine. Notice that the values include combinations of (j) and that are not allowed for other amino acids. (From J. Richardson, Adv. Prot. Chem. 34 174-175, 1981.1... 

Glycine residues have more conformational freedom than any other amino acid, as discussed in Chapter 1. A glycine residue at a specific position in a protein has usually only one conformation in a folded structure but can have many different conformations in different unfolded structures of the same protein and thereby contribute to the diversity of unfolded conformations. Proline residues, on the other hand, have less conformational freedom in unfolded structures than any other residue since the proline side chain is fixed by an extra covalent bond to the main chain. Another way to decrease the number of possible unfolded structures of a protein, and hence stabilize the native structure, is, therefore, to mutate glycine residues to any other residue and to increase the number of proline residues. Such mutations can only be made at positions that neither change the conformation of the main chain in the folded structure nor introduce unfavorable, or cause the loss of favorable, contacts with neighboring side chains. 

Now, it is seen that polar groups dominate the molecular structure, resulting from hydroxyl groups from the two serine and threonine fragments in addition to the peptide bonds themselves. Only weak dispersive interactions will be contributed by glycine fragments (CH2 groups). 

Collagen Collagen is an extracellular structural protein 1052 amino acid residues. Collagen has an minsnal amino acid composidon it is about one-third glycine and is rich in proline. Note diat it also lacks Cys and Trp and is deficient in aromadc amino acid residues in general. 

---