[en] Peptide labelling with radioactive isotopes is always a compromise between peptide chemistry, labelling chemistry, and biological receptor tolerance. Therefore new ways for isotope introduction are always useful. The present contribution describes the introduction of iodine isotopes onto synthetic polypeptides by means of the Gattermann/ Sandmeyer reactions. Peptides containing the nitrophenylalanyl residue are reduced to the corresponding aminophenylalanyl, diazolized to the diazonium phenylalanyl peptide and converted to the iodophenylalanyl peptide in the presence of copper. Two examples are presented: angiotensin II and enkephalin. In both cases, the iodophenylalanyl residue is well accepted by the biological target. (author). 13 refs.; 4 figs

No abstract available

[en] The extensive collection of NOE constraint data involving the aromatic ring signals is essential for accurate protein structure determination, although it is often hampered in practice by the pervasive signal overlapping and tight spin couplings for aromatic rings. We have prepared various types of stereo-array isotope labeled phenylalanines (ε- and ζ-SAIL Phe) and tyrosine (ε-SAIL Tyr) to overcome these problems (Torizawa et al. 2005), and proven that these SAIL amino acids provide dramatic spectral simplification and sensitivity enhancement for the aromatic ring NMR signals. In addition to these SAIL aromatic amino acids, we recently synthesized δ-SAIL Phe and δ-SAIL Tyr, which allow us to observe and assign δ-¹³C/¹H signals very efficiently. Each of the various types of SAIL Phe and SAIL Tyr yields well-resolved resonances for the δ-, ε- or ζ-¹³C/¹H signals, respectively, which can readily be assigned by simple and robust pulse sequences. Since the δ-, ε-, and ζ-proton signals of Phe/Tyr residues give rise to complementary NOE constraints, the concomitant use of various types of SAIL-Phe and SAIL-Tyr would generate more accurate protein structures, as compared to those obtained by using conventional uniformly ¹³C, ¹⁵N-double labeled proteins. We illustrated this with the case of an 18.2 kDa protein, Escherichia coli peptidyl-prolyl cis-trans isomerase b (EPPIb), and concluded that the combined use of ζ-SAIL Phe and ε-SAIL Tyr would be practically the best choice for protein structural determinations.

[en] Reduction of (s)-pinanediol (S)-[(phenyl) (chloro)-methyl]boronate (1) with lithium triethylborodeuteride yielded (s)-pinanediol (R)-[(phenyl)methyl]boronate-α-²H (2). The chiral purity of 2 was measured via peroxidic oxidation to (S)-benzyl alcohol-α-²H (3), which was analyzed with an NMR chiral shift reagent. (Dichloro-methyl)lithium converted 2 to (s)-pinanediol (1S, 2S)-1-chloro-2-phenylethylboronate-2-²H (4), which with sodium azide yielded (s)-pinanediol (1R, 2S)-1-azido-2-phenylethylboronate-2-²H (5). (Dichloromethyl)lithium with 5 yielded (s)-pinanediol (1S, 2S, 3S)-1-chloro-2-azido-3-phenylpropylboronate-3-²H (6), which was oxidized by sodium chlorite to (2S, 3S)-2-azido-3-phenylacetic acid-3-²H (7). Hydrogenation of 7 yielded (2S, 3S)-phenylalanine-3-²H in high diastereomeric and enantiomeric purity. (author)

[en] The envelope glycoprotein (GP) of Ebolavirus (EBOV) mediates viral entry into host cells. Through mutagenesis, we and other groups reported that two phenylalanines at positions 88 and 159 of GP are critical for viral entry. However, it remains elusive which steps of viral entry are impaired by F88 or F159 mutations and how. In this study, we further characterized these two phenylalanines through mutagenesis and examined the impact on GP expression, function, and structure. Our data suggest that F159 plays an indirect role in viral entry by maintaining EBOV GP's overall structure. In contrast, we did not detect any evidence for conformational differences in GP with F88 mutations. The data suggest that F88 influences viral entry during a step after cathepsin processing, presumably impacting viral fusion.

[en] Herein we have evaluated the uptake of O-(2-¹⁸F-fluoroethyl)-l-tyrosine (¹⁸F-FET) in insulinoma in comparison with those of 6-¹⁸F-fluoro-3,4-dihydroxy-l-phenylalanine (¹⁸F-FDOPA) providing first data from both murine xenograft model and one patient with proved endogenous hyperinsulinemic hypoglycemia.

[en] SARS-CoV entry is mediated by spike glycoprotein. During the viral and host cellular membrane fusion, HR1 and HR2 form 6-helix bundle, positioning the fusion peptide closely to the C-terminal region of ectodomain to drive apposition and subsequent membrane fusion. Connecting to the HR2 region is a Trp-rich region which is absolutely conserved in members of coronaviruses. To investigate the importance of Trp-rich region in SARS-CoV entry, we produced different mutated S proteins using Alanine scan strategy. SARS-CoV pseudotyped with mutated S protein was used to measure viral infectivity. To restore the aromaticity of Ala-mutants, we performed rescue experiments using phenylalanine substitutions. Our results show that individually substituted Ala-mutants substantially decrease infectivity by >90%, global Ala-mutants totally abrogated infectivity. In contrast, Phe-substituted mutants are able to restore 10-25% infectivity comparing to the wild-type. The results suggest that the Trp-rich region of S protein is essential for SARS-CoV infectivity

[en] Poly(ethylene glycol)-phosphatidylethanolamine conjugate (PEG-PE) has been used in preparing long-circulating liposomes. As a substitute for PEG-PE which can also be used in the long-circulating liposome formualtions, but can be prepared more readily with a lower cost, PEG-Phe-Chol was synthesized from PEG, phenylalanine, and cholesterol. The addition of the PEG derivative to distearoylphosphatidylcholine (DSPC) led to the formation of mixed micelles as well as liposomes when the derivative content was 10 mol % or greater. On the other hand, the addition of just 5 mol % PEG-Phe-Chol to dioleoylphosphatidylethanolamine(DOPE) generated mixed micelles as well as liposomes, but the formation of mixed micelles was completely inhibited by the addition of cholesterol. The leakage of entrapped calcein out of DOPE/cholesterol (7/3) liposomes containing 5 mol % PEG-Phe-Chol was about 45 % during the incubation time for 24 h in 50 % rabbit plasma, which was similar to that of the same liposomes containing 5 mol % PEG-dipalmitoylphosphatidyl-ethanolamine (DPPE) under the identical conditions

[en] Highlights: • BPV and HPV E2 proteins interact with different fibroblast growth factor Receptors. • Over-expression of FGFR increased E2 tyrosine phosphorylation and reduced HPV replication, though not mediated through Y102. • Mass spectrometry identified BPV E2 tyrosine phosphorylations. The papillomavirus (PV) E2 protein activates transcription and replication by recruiting cellular proteins and the E1 DNA helicase to their binding sites in the viral genome. We recently demonstrated that phosphorylation of tyrosine 102 in the bovine papillomavirus (BPV-1) E2 protein restricts these activities and that fibroblast growth factor receptor-3 (FGFR3) tyrosine kinase binds PV E2. Expression of FGFR3 decreased viral replication with both wild-type and the phenylalanine substitution at position 102, inferring that another kinase targets Y102. Here we tested FGFR- 1, −2 and −4 for association with PV E2 proteins. FGFR2 but not FGFR1 or FGFR4 co-immunoprecipitated with BPV-1 E2. We found that FGFR2 suppressed replication but did not depend on phosphorylation of BPV-1 Y102. HPV-16 and −31 E2 interacted with FGFR1, −2, and −4. These results imply that the expression and activity of FGF receptors in epithelial cells can regulate the function of E2 in viral replication.

No abstract available