Amino acids artificial

Design and development of unnatural peptides based on D-amino acids, /1-amino acids, artificial amino acids, etc. 

Material Conversion - Natural and Artificial Enzymes Enzymes perform highly selective and highly efficient molecular conversion based on sophisticated three-dimensional arrangements of amino acids. Artificial enzyme mimics can be constructed using cyclodextrins and Hpid bilayer membranes. 

There are numerous further appHcations for which maleic anhydride serves as a raw material. These appHcations prove the versatiHty of this molecule. The popular artificial sweetener aspartame [22839-47-0] is a dipeptide with one amino acid (l-aspartic acid [56-84-8]) which is produced from maleic anhydride as the starting material. Processes have been reported for production of poly(aspartic acid) [26063-13-8] (184—186) with appHcations for this biodegradable polymer aimed at detergent builders, water treatment, and poly(acryHc acid) [9003-01-4] replacement (184,187,188) (see Detergency). 

Amino acid polymers like poly(y-methyl-L-glutamate) [29967-97-3] h.a.ve been developed as raw materials for artificial leathers (see Leatherlike materials). Derivatives of amino acids are now finding new appHcations in industry and agriculture. 

Much of what is known about the chymotrypsin mechanism is based on studies of the hydrolysis of artificial substrates—simple organic esters, such as /Miitrophenylacetate, and methyl esters of amino acid analogs, such as... 

Formation of helical-like peptides stabilized due to heterocyclic bridges formed between coils by natural and artificial amino acids 99T11711. 

Different optical enantiomers of amino acids also have different properties. L-asparagine, for example, tastes bitter while D-asparagine tastes sweet (see Figure 8.3). L-Phenylalanine is a constituent of the artificial sweetener aspartame (Figure 8.3). When one uses D-phenylalanine the same compound tastes bitter. These examples clearly demonstrate the importance of the use of homochiral compounds. 

Neotame is an artificial sweetener designed to overcome some of the problems with aspartame. The dimethylbutyl part of the molecule was added to block the action of peptidases, enzymes that break the peptide bond between the two amino acids aspartic acid and phenylalanine. This reduces the availability of phenylalanine, eliminating the need for a warning on labels directed at people who cannot properly metabolize phenylalanine. 

The —CO—NH - link shown in the red box is called a peptide bond, and each monomer used to form a peptide is called a residue. A typical protein is a polypeptide chain of more than a hundred residues joined through peptide bonds and arranged in a strict order. When only a few amino acid residues are present, we call the molecule an oligopeptide. The artificial sweetening agent aspartame is a type of oligopeptide called a dipeptide because it has two residues. 

Fig. 15 Amino acid sequences of artificial extracellular matrix (aECM) proteins. Each protein contains a TV tag, a histidine tag, a cleavage site, and elastin-like domains with lysine residues for crosslinking. The RGD cell-binding domain is found in aECM 1, whereas aECM 3 contains the CS5 cell-binding domain. aECM 2 and aECM 4 are the negative controls with scrambled binding domains for aECM 1 and aECM 3, respectively. Reprinted from [121] with permission from American Chemical Society, copyright 2004...

Methodologies for the de novo design and synthesis of polypeptides were recently developed. The preparation of periodic polypeptides, polypeptides containing artificial amino acids, polypeptides exhibiting rodlike structures, and hybrids of natural and artificial polypeptide segments was recently described [33],... 

Cyclic artificial polypeptides comprised of alternating d and l amino acids were recently synthesized and self-assembled into nanotubes exhibiting lengths of 1000-1500 A, formed at an air-water interface [34,35],... 

Adamantane can be used to construct peptidic scaffolding and synthesis of artificial proteins. It has been introduced into different types of synthetic peptidic macrocycles, which are useful tools in peptide chemistry and stereochemistry studies and have many other applications as well. Introduction of amino acid-functionalized adamantane to the DNA nanostmctures might lead to construction of DNA-adamantane-amino acid nanostmctures with desirable stiffness and integrity. Diamondoids can be employed to constmct molecular rods, cages, and containers and also for utilization in different methods of self-assembly. In fact, through the development of self-assembly approaches and utilization of diamondoids in these processes, it would be possible to design and constmct novel nanostmctures for effective and specific carriers for each dmg. 

An alternative approach is to synthesize an artificial gene in the test-tube starting with the appropriate deoxyribonucleotides. This approach, which demands that the entire amino acid sequence be known, has been used to clone genes encoding proteins 200 amino acids long. 

Goodacre, R. Edmonds, A. N. Kell, D. B. Quantitative analysis of the pyrolysis-mass spectra of complex mixtures using artificial neural networks Application to amino acids in glycogen. J. Anal. Appl. Pyrolysis 1993, 26, 93-114. 

Poly(HASCL) depolymerases are able to bind to poly(3HB)-granules. This ability is specific because poly(3HB) depolymerases do not bind to chitin or to (crystalline) cellulose [56,57]. The poly(3HB)-binding ability is lost in truncated proteins which lack the C-terminal domain of about 60 amino acids, and these modified enzymes do not hydrolyze poly(3HB). However, the catalytic domain is unaffected since the activity with water-soluble oligomers of 3-hy-droxybutyrate or with artificial water-soluble substrates such as p-nitrophenyl-esters is unaffected [55, 56, 58, 59]. Obviously, the C-terminal domain of poly(3HB) depolymerases is responsible and sufficient for poly(3HB)-binding [poly(3HB)-binding domain]. These results are in agreement ... 

Use of multivariate approaches based on classification modelling based on cluster analysis, factor analysis and the SIMCA technique [98,99], and the Kohonen artificial neural network [100]. All these methods, though rarely implemented, lead to very good results not achievable with classical strategies (comparisons, amino acid ratios, flow charts) and, moreover it is possible to know the confidence level of the classification carried out. 

A similar study has been performed on silk [Howell et al. 2007]. The ToF-SIMS fingerprint of silk exhibits the presence of different amino acid fragments (positive ion mode). In contrast to wool, the effect of artificial ageing is not obvious and no modification appears in the ToF-SIMS spectra. Nevertheless, the study of the cleaning procedures leads to the same conclusion as that in the case of wool. The amount of remaining surfactant increases with artificial ageing. 

Fig. 3 Important 19F-labelled amino acids, (a) Compounds that are wo-steric to native amino acids can be incorporated into proteins biosynthetically, but they possess too many degrees of torsional freedom to be useful for ssNMR structure analysis, (b) In these artificial amino acids the 19F-reporter group is rigidly attached to the peptide backbone. They can be incorporated by solid-phase peptide synthesis, but some problems can arise due to racemisation (4F-Phg, 4CF3-Phg), steric hindrance of coupling (F3-Aib) or HF elimination (fluoro-Ala, F3-Ala). 4F-Phg is additionally problematic due to an ambiguity of the side-chain rotamer. The preferred 19F-labels for ssNMR structure analysis are CF3-Bpg and CF3-Phg (as suitable substitutes for Leu, lie, Met, Val and Ala), as well as F3-Aib and CF3-MePro...

The participation of the nuclear receptors in the machinery of gene transcription takes place by means of specific domains of the molecule known as transactivators (abbreviation for transcription activators). These are made up of sequences of amino acids that interact by means of protein-protein contacts with other transcription factors. The artificial alteration of these sequences has as a consequence the inability of the hormone to induce gene expression (Beato et al. 1996 Klug et al. 1987 Lones et al. 1995). 

New insights into the analysis of hydrophobically post-translational modified proteins could be achieved by the construction of lipidated proteins in a combination of bioorganic synthesis of activated lipopeptides and bacterial expression of the protein backbone (Fig. 19). The physico-chemical properties of such artificial lipoproteins differ substantially from those of the corresponding lipopeptides. The pronounced dominance of the hydrophilic protein moiety (e.g., for the Ras protein 181 amino acids) over a short lipopeptide with one or two hydrophobic modifications provides solubility up to 10 4 mol/1, while the biotinylated or fluorescence labeled lipopeptides exhibit low solubility in aqueous solutions and can be applied in the biophysical experiments only in vesicle integrated form or dissolved in organic solvent. 

The powerful tool of molecular genetics allows the modification of each single amino add in the peptide chain of a protein, e.g. ddetion of side residues necessary for isoprenylation or palmitoylation1361 or introduction of additional charged amino acids for electrostatic interaction with the plasma membrane.1371 Even some artificial modifications can be introduced by means of recombinant enzymes as shown above. 

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