Amino acids structures, Table

Name the amino acids in Table 19.4 that contain side groups capable of forming hydrogen bonds. This interaction contributes to the tertiary structure of a protein. 

Crystal structures are available for many (N)4Co-amino acid complexes (Table I). Many of the diastereomers (AS, AS) in the bis-en series have been resolved using classic crystallization (usually via bromocamphor sulfonate, arsenyl-, or antimonyl-tartrate salts) or ion exchange methods (Table II). Reversed-phase ion-pair HPLC, using aryl phosphate or aryl/alkyl sulfonate ion pairing reagents in MeOH/ H20 eluent, has allowed diastereomer separations to be carried out on analytical amounts (28) (Table II). 

Extractions of aqueous solutions of racemic amino-acid ester salts with solutions of / -6/s(dinaphthyl)-22-crown-6 [284] in chloroform revealed the dependence of the enantiomeric distribution constant on the structure of the amino acid ester (Table 64). In order to limit the concentrations of complex in the aqueous phase, inorganic salts were added. In the case of tyrosine, serine and alanine no extraction of salt was observed obviously these salts form very hydrophilic complexes. The highest degree of chiral recognition was found with [284] and p-hydroxyphenylglycine methyl ester hexafluorophosphate [A(AG°)... 

AMINO ACIDS, PEPTIDES AND PROTEINS Table 13.1 Amino acids structures and standard abbreviations... 

Write the general structure of an amino acid. Why do some amino acids in Table 10-1 have two pK values and others three ... 

There are several levels of peptide structure. The primary structure is the amino acid sequence plus any disulfide links. With the 20 amino acids of Table 27.1 as building blocks, 202 dipeptides, 203 tripeptides, 204 tetrapeptides, and so on, are possible. Given a peptide of unknown structure, how do we determine its amino acid sequence ... 

Exercise 25-2 Which of the amino acids in Table 25-1 are acidic amino acids and which basic amino acids Which of the structures shown would have the most basic nitrogen The least basic amino nitrogen Give the reasons for your choices. (Review Section 23-7.)... 

The CBH I (D) is identical in composition and activity to the CBH I (D) previously described (2) from T. reesei QM 9123. The close correspondence of their amino acid contents (Table VI), the nearly identical content of neutral carbohydrate 6.8% by weight for the CBH I (D) produced in the presence of sophorose and 6.7% for T. reesei QM 9123 CBH I (D) grown on cellulose (2), and identical electrophoretic properties clearly argue for a common molecular structure for these CBH s I (D). The CBH II is clearly different from all other CBH s in electrophoretic mobility (Figure 12) and amino acid composition (41), but is devoid of endoglucanase activity and produces predominantly cellobiose (>90% by weight of soluble products) from cellulose. It has a sedimentation coefficient of 3.71 in comparison to CBH I (D), for which a value of 3.66 was obtained. 

The amino acids in Table 27.1 that have more than one stereogenic center are isoleucine and threonine. The stereogenic centers are marked with an asterisk in the structural formulas shown. 

By convention, peptides are written so that the end with the free amino group, called the N-terminus, is on the left and the end with the free carboxyl group, the C-terminus, is on the right. Because it takes considerable space to show the structure of even a small polypeptide like this one, it is common to represent the structures of peptides and proteins by using the three-letter abbreviation for each amino acid (see Table 26.1). Thus tuftsin, with a threonine N-terminal amino acid, followed by lysine, proline, and, finally, arginine as tire C-terminal amino acid, is represented as... 

The isoelectric points of the standard amino acids are given in Table 24-2. Notice that the isoelectric pH depends on the amino acid structure in a predictable way. 

Table 24 contains data on approximately half the known structures, and a similar story emerges from the amino acid structures.253 Monomers are known and there is the first example of a transition metal conipound [M(RC00)(H20)s]RC00 but most structures involve carboxylate bridging of three basic types (82 (84), although one structure has cw-unidentate carboxylates and chooses to polymerize on a single bridging water molecule. The Mn polyhedron in the tetrahydrate for R = (89) is the only one to depart from the pattern of [MnOs] octahedra. It has trans-H20 molecules at relatively normal distances of 2.28 and 2.31(2) A, and in the plane normal to these are three... 

MFB2 is the first structure to be determined wherein the highly conserved tryptophan at position 8 is not conserved. In MFB2, the spatially equivalent residue is a tyrosine. The N terminus is two residues shorter than in ALBP, and to align the strictly conserved Gly-6 requires an insert in amino acid sequence (Table III) between the usual G-X-W motif. In the MFB2 structure, the N terminus differs somewhat from the other structures in the family and is the outlier in Fig. 5. Lys-5 (MFB1 numbering) is in fact spatially equivalent to the position of Gly-6 (ALBP/P2... 

The a-helix is one of the best-known regular conformational features as a subheading within the secondary structure of polypeptides and is frequently adopted in chains of six or more helicogenic amino acids (see Table 2.1 for a definition of terms and examples). The (3-sheet is another classic conformational structure that has been detected from the earliest days of X-ray crystallography of proteins. Local... 

The Hydrophobic Effect - interactions between hydrophobic regions of a protein, which actually increase entropy by destroying the ordered clathrate structures of water around these residues in the unfolded state. The hydrophobic effect is sometimes incorrectly called hydrophobic bonding. Table 6.4 shows numerical values assigned to the relative hydrophobicities of the amino acids. In Table 6.3, the hydrophobic effect can be seen by the more positive AS values for cytochrome c and myoglobin. 

Topham, C.M., McLeod, A., Eiserunenger, F., Overington, J.P., Johnson, M.S., et al. (1993) Fragment ranking in modelling of protein structure. Conformationally constrained environmental amino acid substitution tables. J. Mol. Biol. 229 194-220. 

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