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Abstract: Hydrophilic carotenoids, unusual members of an intrinsically hydrophobic family, and their radical ions are important reactants. An all-optical method for generating singly charged radical ions of a hydrophilic carotenoid (Car) is described. It relies on photolyzing an aqueous mixture of Car and a photoionizable auxiliary solute (A), and making conditions conducive to the capture, by Car, of the hydrated electron (e?aq) or the positive hole in A?+ or both. When A is Trolox (TOH), only e?aq can be captured, since TOH?+ deprotonates too rapidly to be a hole donor; when A is Trolox methyl ether (TOMe), both Car?? and Car?+ are formed, since TOMe?+ lives long enough to transfer its positive hole to Car; formation of Car?? is prevented under aerobic conditions.

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Abstract: Eukaryotic signal transduction involves the assembly of transient protein-protein complexes mediated by modular interaction domains. Specific Pro-rich sequences with the consensus core motif PxxP adopt the PPII helix conformation upon binding to SH3 domains. For short Pro-rich peptides, little or no ordered secondary structure is usually observed before binding interactions. The association of a Pro-rich peptide with the SH3 domain involves unfavorable binding entropy due to the loss of rotational freedom on forming the PPII helix. With the aim of stabilizing the PPII helix conformation in the Pro-rich HPKI decapeptide PPPLPPKPKF (P2), a series of P2 analogues was prepared, in which specific Pro positions were alternatively occupied by 4(S)- or 4(R)-4-fluoro-L-proline. The interactions of these peptides with the SH3 domain of the HPK1-binding partner HS1 were quantitatively analyzed by the NILIA-CD approach. A CD thermal analysis of the P2 analogues was performed to assess their propensity to adopt the PPII helix conformation. Contrary to our expectations, the K-d values of the analogues were lower than that of the parent peptide P2. These results clearly show that the induction of a stable PPII helix conformation in short Pro-rich peptides is not sufficient to increase their affinity toward the SH3 domain and that the effect of 4-fluoroproline strongly depends on the position of this residue in the sequence and the chirality of the substituent in the pyrrolidine ring. Copyright (c) 2006 European Peptide Society and John Wiley & Sons, Ltd.

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Abstract: The search for effective drug delivery systems is one of the major challenges in drug formulation especially for biopharmaceuticals Such as proteins, and peptide-based drugs and vaccines. A procedure has been developed whereby human serum albumin (HSA) call be Used as a delivery vehicle for these biomolecules using its role as main ratty acid carrier. Using essentially fatty acid free HSA (HSAff) it is possible to form stable complexes with lipidic chain compounds (lipo-compounds). Two lipo-compounds have been used to develop this system, a novel antimicrobial lipopeptide and gamma-amino-n-butyric acid, GABA. conjugated with an alkyl chain, lipo-GABA, in both cases C8 and C14 alkyl chain lengths were evaluated. The HAS-lipo compound complex had a mutual stabilizing effect on both the HSA and the lipo-compound. The protease enzyme study showed that the alkyl chains of these lipo-compounds bound to HSAff confer a similar if not greater biostability than caprylic acid shown by CD and importantly, the bound lipopeptide was stabilized by the HSA shown by mass spectrometry. Heat stability studies at 60 degrees C over 10 h also confirmed that the lipo-HSA complexes confer stability and provide a method of preparing sterile formulation for therapeutic use. No further increased in stability of the lipo-compounds when HSA containing fatty acid (HSAfa) Was used. With the antimicrobial lipopeptide, there was enhanced activity with HSAff formulation suggesting increased biostability and bioavailability of compounds. These finding allowed us to develop a simple and effective way of delivering lipo-compounds using fatty acid free HSA as the carrier.

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Abstract: Ultrathin films of magnetite (Fe3O4) have been grown epitaxially on wurtzite wide bandgap semiconductor GaN(0001) surfaces using molecular-beam epitaxy. Reflection high-energy electron-diffraction patterns show a (111) orientation of the Fe3O4 films and in-plane epitaxial relationship of < 1 (1) over bar0 >(Fe3O4)parallel to < 11 (2) over bar0 >(GaN) and < 11 (2) over bar >(Fe3O4)parallel to < 1 (1) over bar 00 >(GaN) with the GaN(0001). X-ray photoelectron spectroscopy and x-ray magnetic circular dichroism confirm the growth of stoichiometric Fe3O4, instead of gamma-Fe2O3. The magnetic hysteresis loops and saturation magnetization M-s obtained by superconducting quantum interference device at room temperature show fast saturation of the Fe3O4 films with the magnetization close to that of the bulk single-crystal value. In-plane magnetoresistance (MR) measurements reveal negligibly small MR effects, further indicating that the films are free from antiphase boundaries.