Hybrid amino acid

Eigure 3 represents an illustrative biological application an Asp Asn mutation, carried out either in solution or in complex with a protein [25,26]. The calculation uses a hybrid amino acid with both an Asp and an Asn side chain. Eor convenience, we divide the system into subsystems or blocks [27] Block 1 contains the ligand backbone as well as the solvent and protein (if present) block 2 is the Asp moiety of the hybrid ligand side chain block 3 is the Asn moiety. We effect the mutation by making the Asn side chain gradually appear and the Asp side chain simultaneously disappear. We choose initially the hybrid potential energy function to have the form... 

We saw in Sections 20.3 and 24.5 that a carboxyl group is deprotonated and exists as the carboxylate anion at a physiological pH of 7.3, while an amino group is protonated and exists as the ammonium cation. Thus, amino acids exist in aqueous solution primarily in the form of a dipolar ion, or zwitterion (German zwitter, meaning "hybrid"). 

Clays have long been used as fillers in polymer systems because of low cost and the improved mechanical properties of the resulting polymer composites. If all other parameters are equal, the efficiency of a filler to improve the physical and mechanical properties of a polymer system is sensitive to its degree of dispersion in the polymer matrix (Krishnamoorti et ah, 1996). In the early 1990s, Toyota researchers (Okada et ah, 1990) discovered that treatment of montmorillonite (MMT) with amino acids allowed dispersion of the individual 1 nm thick silicate layers of the clay scale in polyamide on a molecular. Their hybrid material showed major improvements in physical and mechanical properties even at very low clay content (1.6 vol %). Since then, many researchers have performed investigations in the new field of polymer nano-composites. This has lead to further developments in the range of materials and synthesizing methods available. 

Most of the aforementioned efforts are based on the nonsense suppression methodology as the method for peptide altering [100]. In this approach, a nonsense codon is introduced into the enzyme-coding mRNA in the site that has to be altered. Simultaneously, the tRNA-noncoded amino acid hybrids are prepared with nonsense anticodons. Finally, the translation of modified mRNA is performed in vivo [101] or in vitro [102]. 

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],... 

Table IV. Amino Acid Sequences of Sea Snake Neurotoxins (Hybrid Type)...

Bifunctional adamantyl, as a hydrophobic central core, can be used to construct peptidic scaffolding [151], as shown in Fig. 27. This is the reason why adamantane is considered one of the best MBBs. This may be considered an effective and practical strategy to substitute different amino acids or DNA segments on the adamantane core (Fig. 28). In other words, one may exploit nucleic acid (DNA or RNA) sequences as linkers and DNA hybridization (DNA probe) to attach to these modules with an adamantane core. Thus a DNA-adamantane-amino acid nanostructure may be produced. 

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