Oligopeptides, chemical structure

Chemical Name Cyclic oligopeptide (See Structural Formula)... 

Once we have this library, fragment-condensation procedures might link the oligopeptides to one another so as to build longer chains. Prebiotic methods for fragment condensation are not really known. Kent s synthesis comes close to the target (Kent, 1999) but is restricted to particular chemical structures and cannot be seen as a generalized prebiotic method. 

In spite of Its power, ICC is a technique with certain limitations in its specificity (6,7), and in most cases, the technique needs to be supplemented with rigorous specificity testing and independent nonimmunological assay techniques. Neuropeptides, like other peptides and proteins, because of their complex chemical structure, are especially problematic to detect specifically. The antigens used for immunization to obtain neuropeptide antibodies are commonly synthetic oligopeptides coupled to larger carrier proteins. It is known... 

Chart 5.21 Chemical structure of oligopeptides with good optical storage properties. 

Figure 10.11 Chemical structure of antifouling peptoids with ethylene glycol (A) and zwitterionic (B) side chains. Petoids are end-functionalized with oligopeptides containing repeating DOPA and lysine units (C).

Arai, S., M. Yamashita, H. Kato, M. Fujimaki, Applying proteolytic enzymes on soybean Part V. A nondialzable bitter peptide hydrolyzate of soybean protein and its bitterness in relation to the chemical structure, Agric. Biol. Chem., 34, p. 729, 1970. Arai, S., The bitter flavor due to peptides or protein hydrolysates and its control by bitterness — masking with acidic oligopeptides, in The Analysis and Control of Less Desirable Flavors in Foods and Beverages, G. Charalambous, Ed., Acad. Press, New York. p. 1, 1980. 

Figure 6.17 Chemical structures of PEG-based hydrogels. A. Chemical structures of a 3-arm PEG (a), 4-arm PEG (b), 8-arm PEG (c), and an oligopeptide with an MMP-specific cleavage site (d). B. Chemical reaction of 3-arm PEG hydrogels (a), 4-arm PEG hydrogels (b), and 8-arm PEG hydrogels (c). Reproduced with permission from [2] Copyright 2014 Elsevier Inc.

Fig. 5 A Chemical structure of the amphiphilic diblock-type oligopeptide, LK16, and its molecular dimension in a-helical form. B Tapping-mode AFM image of the self-assembled nanoparticle obtained from LK16. C Proposed model of the nanoparticle from a-helical LK16...

In addition to the last example, in which H-Hg couplings were measured, 199Hg NMR has been used to investigate the solution structure of Hg11 complexes of oligopeptides containing cysteine and histidine residues. In this work it was shown that the magnitude of the chemical shift is dependent upon the amino acid sequence of the peptide (Adachi et al., 1992). 

Recently, the difference in structure and chemical reactivity between 2-D racemic and enantiomorphous crystallites has been used to generate enan-tiopure homochiral oligopeptides from non-racemic mixtures of amphiphilic a-amino acid NCAs. The racemic N"-carboxyanhydridc of y-slcaryl-glutamic acid (Cis-Glu-NCA) self-assembles on water to form racemic 2-D crystallites (Fig. 16a,b), as proved by GIXD. 

The elements of protein structure are divided into four classes primary, secondary, tertiary, and quaternary. Primary structure refers to the linear sequence of amino acids linked by amide bonds along protein chains. These polymer chains vary in length from a few amino acid residues (oligopeptides) to molecules containing 2000 or more amino acids. Most proteins are from 100 to 500 amino acid residues in length. One or more of each of 20 natural amino acids may be present in each protein molecule. In some cases the amino acids undergo posttranslational chemical modification, which introduces still more variety into protein structure. 

The first example of chemical communication in low-GC Gram-positive bacteria was discovered in 1978 by Dunny, Clewell and their colleagues.93 It was found that conjugative plasmid transfer of Enterococcus faecalis was induced by a chemical substance, termed sex pheromone, which is secreted from plasmid-free recipient cells. Several years later, the structure of the sex pheromone was elucidated to be an oligopeptide by Suzuki et al Since this discovery, a variety of cell-to-cell communication events in Gram-positive bacteria have been found to be mediated by peptidic substances.95-97... 

Accurate 13C-15N interatomic distances have been measured by means of rotational echo double resonance (REDOR) experiments for oligopeptides [50]. The interatomic 13C-15N distance in the hydrogen bonded fragment was measured to be 4.5 0.1 A in five different samples studied. This finding is consistent with an a-helix structure, in agreement with conformation-dependent 13C chemical shift data. 

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