S-Amino-acids

Y-Amino-acids. - A total synthesis of the amino-acid (514), a component of the anti-tumour antibiotic carzinophilin, features a one-pot Payne rearrangement-azide opening of the chiral epoxide (512) in which the use of phase-transfer conditions is crucial to force the equilibrium over to the primary azideadduct (513).  

A simpler member of this series, y-amino-3 hydroxybutyric acid, a 

GABA series neuromodulator, has been prepared in either 

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Sickle-cell anemia is the classic example of an inherited disease that is caused by a change in a protein s amino acid sequence. Linus Pauling proposed in 1949 that it was caused by a defect in the hemoglobin molecule he thus coined the term molecular disease. Seven years later Vernon Ingram showed that the disease was caused by a single mutation, a change in residue 6 of the P chain of hemoglobin from Glu to Val. 

Figure S.S Amino acid sequence of p strands 2 3 4 in human plasma retinol-binding protein. The sequences are listed in such a way that residues which point into the barrel are aligned. These hydrophobic residues are arrowed and colored green. The remaining residues are exposed to the solvent.

Phenols and phenol ethers can be acylated with y- or S-amino acids in the presence of polyphosphoric acid to form 2-aryl-2d -pyrrolines (11, = 1) or 2-aryl-/l -piperideines (11, n = 2), respectively (13). 

Proteins have four levels of structure. Primary structure describes a protein s amino acid sequence secondary structure describes how segments of the protein chain orient into regular patterns—either a-helix or /3-pleated sheet tertiary structure describes how the entire protein molecule coils into an overall three-dimensional shape and quaternary structure describes how individual protein molecules aggregate into larger structures. 

Except for cysteine, only S amino acids occur in proteins. Several R amino acids are also found in nature, however. (ft)-Serine is found in earthworms, and (R)-alanine is found in insect larvae. Draw Fischer projections of (fl)-serine and (J )-alanine. Are these Don amino acids ... 

In addition to the enzyme s amino acid sequence, other parameters can affect the outcome of a biocatalytic process. For instance, a similar outcome in the aforementioned DERA-catalyzed statin synthesis was achieved by process improvements [21]. Using a thermostable variant of DERA (thermostability generally correlates well with tolerance to high concentrations of organic reagents or cosolvents), and fed-batch conditions, an efficient process that overcame sensitivity to high concentrations of chloroacetaldehyde was developed. 

Dallas WS, Falkow S Amino acid sequence homology between cholera toxin and Escherichia coli heat-labile toxin. Nature 1980 288 499-501. 

Upon biosynthesis, a polypeptide folds into its native conformation, which is structurally stable and functionally active. The conformation adopted ultimately depends upon the polypeptide s amino acid sequence, explaining why different polypeptide types have different characteristic conformations. We have previously noted that stretches of secondary structure are stabilized by short-range interactions between adjacent amino acid residues. Tertiary structure, on the other hand, is stabilized by interactions between amino acid residues that may be far apart from each other in terms of amino acid sequence, but which are brought into close proximity by protein folding. The major stabilizing forces of a polypeptide s overall conformation are ... 

Infergen (interferon alfacon-1 or consensus interferon) is an engineered interferon recently approved for the treatment of hepatitis C (Table 8.8). The development of infergen entailed initial sequence comparisons between a range of IFN-as. The product s amino acid sequence reflects the most frequently occurring amino acid residue in each corresponding position of these native interferons. A DNA sequence coding for the product was synthesized and inserted into E. coli. The recombinant product accumulates intracellularly as inclusion bodies. 

The synthesis of 3-aryltetrahydroisoquinolines was accomplished by electrophilic aromatic substitution of polysubstituted phenols and phenyl ethers with Lewis acid-generated tosyliminium ions of 2-tosyl-3-methoxytetrahydroisoquinoline derivatives <00SL801>. In addition isoquinoline was reported to react with N-tosylated (R)- or (S)-amino acid fluorides to afford optically active dihydroimidazoisoquinolinones. The reaction proceeds via acylation followed by attack of the tosylamino group at Cl of the intermediate 2-tosylaminoacylisoquinolinium salt <00TL5479>. 

Oshikawa, T. and Yamashita, M., Preparation of optically active (S)-2-ami-noalkylphosphonic acids from (S)-amino acids without racemization, Bull. Chem. Soc. Jpn., 63, 2728, 1990. 

At the time the hormone is introduced into the LBD (Fig. 1.4), a conformational change is produced in the three-dimensional structure of the receptor, a change that is key to the subsequent steps in hormonal action. This change is produced by a few contacts (between 6 or 7 and 15) of the receptor s amino acids with related groups from the hormone s structure. Some basic amino acid residues, particularly from arginine, which are preserved virtually intact among receptors, are critical in the execution of this function (Quingley et al. 1995). 

The P-cluster and M centers are about 14 A apart therefore, electron transfer between them is not easy to explain. Electron transfer is believed to take place through electron tunneling involving the protein s amino acid side chains. Each... 

Yield TON enzyme (S)-Amino acid (R)-Amino acid [%] Yield [%] ee Yield [%] ee... 

When platelike crystals of gly with well-developed 010 faces were partially dissolved in solvents containing variable amounts of resolved R a-amino acids, well-defined etch pits were formed only on the (010) face (Figure 30a). These pits exhibited twofold morphological symmetry with surface edges parallel to the a and c axes of the crystal. The enantiotopic (010) face dissolved smoothly (Figure 30b), exactly as it does when the crystal is dissolved in a solution of pure gly. As expected, S amino acids induced etch pits on the (010) face. Racemic... 

Hartley, B. S. Amino acid sequence of bovine chvmotrypsinogon A. Nature 201, 1284-1287 (1964). 

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