Phenylalanine structural model

Fig. 45. Structural models of adsorbed molecules at Pt(100) and Pt(lll) surfaces, (a) L-Dopa (b) L-Tyrosine (c) L-Cysteine (d) L-Phenylalanine (e) L-Alanine (f) Dopamine (g) Catechol. Reprinted from ref. 84.

Figure 3. Structural models of adsorbed molecules at Pt(lOO) and Pt(lll) surfaces. (A) L-dopa (LD) (B) L-Tyrosine (TYR) (C) L-cysteine (CYS) (D) L-phenylalanine (PHE) (E) L-alanine (ALA) (F) dopamine (DA) (G) catechol (CT) (H) 3,4-dihydroxyphenyl-acetic acid (DOPAC).

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. 

Tyrosinase is a monooxygenase which catalyzes the incorporation of one oxygen atom from dioxygen into phenols and further oxidizes the catechols formed to o-quinones (oxidase action). A comparison of spectral (EPR, electronic absorption, CD, and resonance Raman) properties of oxy-tyrosinase and its derivatives with those of oxy-Hc establishes a close similarity of the active site structures in these proteins (26-29). Thus, it seems likely that there is a close relationship between the binding of dioxygen and the ability to "activate" it for reaction and incoiporation into organic substrates. Other important copper monooxygenases which are however of lesser relevance to the model studies discussed below include dopamine p-hydroxylase (16,30) and a recently described copper-dependent phenylalanine hydroxylase (31). 

A similar situation is found in the structure of putrescine diphosphate " (a model system for amine-nucleic acid interactions) which divides into layers of HjPOJ anions bridged by protonated putrescine (1,4-diamino-n-butane) cations. In a real biological system (yeast phenylalanine transfer RNA) phosphate residues are found to be enveloped by the polyamine spermine [NH2(CH2)jNH(CH2)4NH(CH2)jNH2] which again adopts a linear, nonchelating conformation. ... 

Figure 5 shows the modeled structure for the a helix F interface in human 11(3-HSD-1, in which phenylalanine-188 and alanine-189 form an anchor. Alanine-189 is 3.5 A and 4.7 A from alanine-189 and alanine-185, respectively, on the other subunit. The phenylalanine-188 side chain is 3.2 A from glycine-192. There is a hydrogen bond between serine-185 and serine-196, which are 3.2 A apart. Alanine-185 is 4.7 A from phenylalanine-193. There also is a hydrophobic interaction between phenylalanine-193 and alanine-181, which are 3.9 A apart. 

A crystal structure of the all-tram isomer of [Cr2(gly)4(OH)2] has been reported.1162 Its low temperature magnetic susceptibility has been fitted to both the Van Vleck and modified Van Vleck models. The uncorrected model leads to, uef = 3.80BM with 2/= 8.4 cm-1 1162,1163,1164 with the inclusion of quadratic exchange 2/=7.4 cm-1.1162 Related studies of alanine,1153,1163 valine, phenylalanine, leucine,1163,1149 proline1166,1167 and histidine1168 complexes have appeared. The proline complex is unusual in that it is soluble in methanol and DMSO. Circular dichroism spectra have been measured the X-ray structure shows the complex to be the L-bms(N), L-tram(0) isomer.1166 More complicated dimers of unusual stoichiometry have been reported.1169... 

Otagiri et al. (22) used model peptides composed of arginine, proline, and phenylalanine to ascertain the relationship between bitter flavor and chemical structure. They reported that the presence of the hydrophobic amino acid at the C terminus and the basic amino acid at the N terminus brought about an increase in the bitterness of di- and tripeptides. They further noted a strong bitter taste when arginine was located next to proline and a synergistic effect in the peptides (Arg)r(Pro) ,-(Phe) (/ = 1,2 m, n = 1, 3) as the number of amino acids increased. Birch and Kemp (23) related the apparent specific volume of amino acids to taste. 

Gerona-Navarro and coworkers in 2004 have reported the synthesis and the evaluation of a series of new 2-azetidinones (Fig. 50), derived from phenylalanine [281], which were designed on the basis of the structure of the reported (3-lactam inhibitors [367] and the residues implicated in the active site of the HCMV protease [417]. These compounds have been evaluated against HCMV in human embryonic lung cells [418], and the results compared to those obtained for the reference compounds, which were the model (3-lactam la of Fig. 49, the viral DNA polymerase inhibitors DHPG (ganciclovir), and HPMPC (cidofovir). 

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