Structure dipeptide amide

Hinspach M, Li H, Jamal J, Yang W, Huang H, Hah J-M, Gomez-Vidal JA, Litzinger EA, Silverman RB, Poulos TL. Structural basis for dipeptide amide isoform-selective inhibition of neuronal nitric oxide synthase. Nature Struct. Mol. Biol. 2004 11 54— 59. 

Peptidomimetic ligands for opioid receptors have also been identified from combinatorial libraries. Screening of an N-(substi-tuted)glycine peptoid library for affinity for ix opioid receptors yielded novel structures (251) with high affinity for these receptors (K = 6-46 nM) (953). A library of dipeptide amides with alkyl substituents on both the interior and C-terminal amides were prepared, and high affinity agonists for all three opioid receptors identified from the library (see Ref 946). Peptide libraries can also be further modified ["libraries from libraries" (954)] to yield new potential ligands for receptors. Thus an acety-... 

Fig. 3. Structure—activity summary of dipeptide sweeteners, where n may be 0 or 1 (62). There are no known replacements for the acid or amide groups denoted by arrows, although thioamide has some sweetness. If the NH2 is replaced by NHC(0)R, the potency is increased when...

The structural versatility of pseudopoly (amino acids) can be increased further by considering dipeptides as monomeric starting materials as well. In this case polymerizations can be designed that involve one of the amino acid side chains and the C terminus, one of the amino acid side chains and the N terminus, or both of the amino acid side chains as reactive groups. The use of dipeptides as monomers in the manner described above results in the formation of copolymers in which amide bonds and nonamide linkages strictly alternate (Fig. 3). It is noteworthy that these polymers have both an amino function and a carboxylic acid function as pendant chains. This feature should facilitate the attachment of drug molecules or crosslinkers,... 

Cyclic structures can form as a result of side reactions. One of the most common examples is the formation of diketopiperazines during the coupling of the third amino acid onto the peptide chain (Fig. 7). Intramolecular amide bond formation gives rise to a cyclic dipeptide of a six-membered ring structure, causing losses to the sequence and regeneration of the hydroxyl sites on the resin. The nucleophilic group on the resin can lead to fiuther unwanted reactions [14]. 

Schafer, L., C. Van Alsenoy, and J. N. Scarsdale. 1982. Ab Initio Studies of Structural Features Not Easily Amenable to Experiment. 23. Molecular Structures and Conformational Analysis of the Dipeptide N-acetyl-N -methyl Glycyl Amide and the Significance of Local Geometries for Peptide Structures. J. Chem. Phys. 76, 1439-1444. 

Siam, K., V. J. Klimkowski, C. Van Alsenoy, J. D. Ewbank, andL. Schafer. 1987. Ab Initio Geometry Refinement of Some Selected Structures of the Model Dipeptide N-Acetyl N -Methyl Serine Amide. J. Mol. Struct. (Theochem) 152, 261-270. 

Amides. Metal ions catalyze the hydrolysis of a variety of amides, including acylamino acids, dipeptides and tripeptides, and amino acid amides. In all these compounds it is possible for a metal ion to complex with one or more ligand groups, either amine or carboxylate ion functions, in addition to the amide group. Thus the structural prerequisites for the metal ion catalysis of amide hydrolysis are the same as those for ester hydrolysis. 

Marraud et alJ31 demonstrated that incorporation of an A-hydroxy amide into model dipeptides induced a y-turn-like structure 4, as do hydrazino peptides 5 (Scheme 5). 

Scheme 5 Incorporation of an /V-Hydroxy Amide and a Hydrazine into Model Dipeptides to Induced y-Turn-Like Structures 31 ...

Worked Example 24.3 Draw the structure of the dipeptide Ala-Ser. Strategy First, look up the names and structures of the two amino acids, Ala (alanine) and Ser (serine). Since alanine is N-terminal and serine is C-terminal, Ala-Ser must have an amide bond between the alanine -C02H and the serine -NH2. Solution N terminal q q C terminal V, ii i J H2NCHC — NHCHCOH 1 1 ch3 ch2oh Alanine Serine Ala-Ser... 

The dependence of the principal components of the nuclear magnetic resonance (NMR) chemical shift tensor of non-hydrogen nuclei in model dipeptides is investigated. It is observed that the principal axis system of the chemical shift tensors of the carbonyl carbon and the amide nitrogen are intimately linked to the amide plane. On the other hand, there is no clear relationship between the alpha carbon chemical shift tensor and the molecular framework. However, the projection of this tensor on the C-H vector reveals interesting trends that one may use in peptide secondary structure determination. Effects of hydrogen bonding on the chemical shift tensor will also be discussed. The dependence of the chemical shift on ionic distance has also been studied in Rb halides and mixed halides. Lastly, the presence of motion can have dramatic effects on the observed NMR chemical shift tensor as illustrated by a nitrosyl meso-tetraphenyl porphinato cobalt (III) complex. 

---