Phenylalanine complexes

Boehm et al.100 have synthesised and studied a series of half-sandwich rhodium (III) and iridium (III) complexes, derivatives of salicylaldehyde and L-amino acid esters. The diastereoselectivity has shown strong dependence on the type of metal as well as amino acid residue. The labile configuration of the metal atoms was suggested because of changes in the diastereomers ratio with increasing temperature. Fast epimerisation at the metal atom was suggested for some S-phenylalanine complexes. 

An analogous stmcture was observed in the polymers derived from a- and j3-naphthoftiran in the presence of the AlCl3-phenylalanine complex (337) their rotations are [a]o = 41 and 145°, respectively. This latter value has, for a long time, been the highest specific rotation obtained by asymmetric polymerization. Unfortunately, in this and many other examples, it is not possible to correlate the values of optical activity with corresponding ones of optical purity. Difficulties exist, both on the experimental and on the theoretical level, in making such correlations, especially when the polymer microstmcture is not exactly known. 

Recognition of amino acids has been attempted more frequently with receptors that are likewise zwitterionic in nature (compare 35). Some early studies include the transport of phenylalanine by a merocyanine dye through a liposomal bilayer [53]. Rebek s dicarboxylate-complexing cleft 9 (see Sect. 2) turned out to be a selective (though achiral) binder of trypthophane, phenylalanine, and tyrosine methyl ether [54]. A reasonable structure for a phenylalanine complex of 2 1 stoichiometry, as deduced from NMR studies, is schematically represented in formula 39 [55]. 

Figure 8 shows the MCD spectra for these two complexes. The spectra of the model complexes resemble well the Co2+-thermolysin spectra. Substitution of 2-methylimidazole for imidazole produces a spectrum similar to that for the Co2+-thermolysin-/J-phenylpropionyl-6-phenylalanine complex, while the spectrum with imidazole resembles closely that of the Co2+-thermolysin spectrum without inhibitor. 

Fia. 16. Dreiding model of a hypothetical enzyme-substrate-n-phenylalanine complex. 

Gapeev A, Dunbar RC. Cation-ir interactions and the gas-phase thermochemistry of the Na+/phenylalanine complex. JAm Chem Soc. 2001 123 8360-5. 

Tryptophan Tyrosine Phenylalanine Complex Tyrosine Tryptophan Phenylalanine Tryptophan... 

D, J Sturzebecher and WBode 1991. Geometry of Binding of the N-Alpha-Tosylated Piperidides of weffl-Amidino-Phenylalanine, Para Amidino-Phenylalanine and para-Guanidino-Phenylalanine to Thrombin and Trypsin - X-ray Crystal Structures of Their Trypsin Complexes and Modeling of their Thrombin Complexes. FEBS Letters 287 133-138. 

Recent investigation of the effect of substituents in the para position of the phenylalanine ligand on the stability of the ternary complexes has revealed the secpience Br > OH > Q NH2 > H > F". Interestingly, analysis of CD spectra indicates a reduction of the arene-arene interaction" upon addition of 1,4-dioxane to aqueous solutions of the mixed-ligand complexes, in disagreement with previous observations by Sigel" . 

The principle of this method depends on the formation of a reversible diastereomeric complex between amino acid enantiomers and chiral addends, by coordination to metal, hydrogen bonding, or ion—ion mutual action, in the presence of metal ion if necessary. L-Proline (60), T.-phenylalanine (61),... 

For the separation of amino acids, the applicability of this principle has been explored. For the separation of racemic phenylalanine, an amphiphilic amino acid derivative, 1-5-cholesteryl glutamate (14) has been used as a chiral co-surfactant in micelles of the nonionic surfactant Serdox NNP 10. Copper(II) ions are added for the formation of ternary complexes between phenylalanine and the amino acid cosurfactant. The basis for the separation is the difference in stability between the ternary complexes formed with d- or 1-phenylalanine, respectively. The basic principle of this process is shown in Fig. 5-17 [72]. 

Hayama et al.132 discussed the catalytic effects of silver ion-polyacrylic add systems toward the hydrolyses of 2,4-dinitrophenylvinylacetate 84 (DNPVA) by using the weak nudeophilicity of carboxylic groups and the change-transfer interactions between olefinie esters and silver ions133Metal complexes of basic polyelectrolytes are also stimulating as esterase models. Hatano etal. 34, 13S) reported that some copper(II)-poly-L-lysine complexes were active for the hydrolyses of amino acid esters, such as D- and L-phenylalanine methyl ester 85 (PAM). They... 

Phenol-4-sulfonic acid, 2-(2-hydroxynaphthyl-l-azo)-copper complexes, 6, 55 Phenolysis metal sulfides, 2, 342 Phenylalanine... 

More complex detective work is required to analyze large biomolecules and drugs. However, fragmentation generally follows predictable patterns, and one compound can be identified by comparing its mass spectrum with those of other known compounds with similar structures. In Fig. 2, we see the spectrum of a sample of blood from a newborn infant. The blood is being analyzed to determine whether the child has phenylketonuria. The presence of the compound phenylalanine is a positive indication of the condition. Some... 

Only a few residues show more than 75% sequence identity, including four glycine residues, a proline residue at the beginning of the Pro loop, and a phenylalanine residue in a position corresponding to the conserved residue Tyr 165 of the bovine heart Rieske protein. However, structure prediction and sequence comparison with Rieske proteins from bci complexes suggests that the fold will be very similar in all Rieske-type ferredoxins, as in the other Rieske or Rieske-type proteins (see Section III,B,1). 

The Jing group investigated their poly(L-lysine)-6-poly(L-phenylalanine) vesicles for the development of synthetic blood, since PEG-lipid vesicles were previously used to encapsulate hemoglobin to protect it from oxidation and to increase circulation time. They extended this concept and demonstrated that functional hemoglobin could be encapsulated into their vesicles. The same polypeptide material was also used to complex DNA, which caused the vesicles to lose their... 

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