Model peptide‐based system used for the investigation of metal ions binding to histidine‐containing polypeptides

The reaction of histidine‐containing polypeptides with toxic and essential metals and the molecular mechanism of complexation has yet to be determined, particularly with respect to the conformational changes of the interacting macromolecules. Therefore, a system of oligopeptides containing histidine residues in various positions of Ala or Gly sequences has been designed and used in heavy metal comparatively binding experiments. The role of spacing residues (Gly and Ala repeats) in selecting the various conformations was investigated. The newly synthesized peptides and metal ion adducts have been characterized by Fourier transform infrared spectroscopy (FTIR) as well as electrospray ion trap mass spectrometry (ESI–MS) and circular dichroism (CD). The analysis of CD‐spectra of the four peptides in water revealed that the secondary structure depends much on the position of each amino acid in the peptide backbone. Our peptides system reveals various binding mechanisms of metal ions to peptides depending on the position of histidine residue and the corresponding conformations of Ala or Gly sequences. Biological and medical consequences of conformational changes of metal‐bound peptides are further discussed. Thus, the binding of heavy metals to four peptides may serve as a model system with respect to the conformational consequences of the metal addition on the amino acid repeats situated in prion protein. © 2010 Wiley Periodicals, Inc. Biopolymers 93:497–508, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Opinions of Youngsters with Congenital Below-Elbow Deficiency,and Those of Their Parents and Professionals Concerning Prosthetic Use and Rehabilitation Treatment

Background

Youngsters with unilateral congenital below-elbow deficiency (UCBED) seem to function well with or without a prosthesis. Reasons for rejecting prostheses have been reported earlier, but unfortunately not those of the children themselves. Furthermore, reasons for acceptance are underexplored in the literature.

Objectives

To investigate opinions of children and early and late adolescents with UCBED, and those of their parents and healthcare professionals, concerning (1) reasons to wear or not to wear prostheses and (2) about rehabilitation care.

Methods

During one week of online focus group interviews, 42 children of 8–12 y/o, early and late adolescents of 13–16 and 17–20 y/o, 17 parents, and 19 healthcare professionals provided their opinions on various topics. This study addresses prosthetic use or non-use of prosthetics and rehabilitation care. Data were analyzed using the framework approach.

Results

Cosmesis was considered to be the prime factor for choosing and wearing a prosthesis, since this was deemed especially useful in avoiding stares from others. Although participants functioned well without prostheses, they agreed that it was an adjuvant in daily-life activities and sports. Weight and limited functionality constituted rejection reasons for a prosthesis. Children and adolescents who had accepted that they were different no longer needed the prosthesis to avoid being stared at. The majority of participants highly valued the peer-to-peer contact provided by the healthcare professionals.

Conclusions

For children and adolescents with UCBED, prostheses appeared particularly important for social integration, but much less so for functionality. Peer-to-peer contact seemed to provide support during the process of achieving social integration and should be embedded in the healthcare process.     

Synthesis and characterization of novel organic/inorganic hybrid material with short peptide brushes generated on the surface

A novel route to synthesize an organic/inorganic hybrid material containing short peptide chains attached on the surface (e.g., oligo(S-benzyl-L-cysteine)) was developed. Poly[N-(beta-aminoethylene)acrylamide] (PAEA) adsorbed onto silica particles surface (main diameter between 15 and 40 microm) was irreversibly fixed by the reaction between the accessible primary amino groups of the PAEA and 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTCDA). After the deposition of PAEA from a salt-free aqueous solution onto microporous silica particles and stabilization by a cross-linking reaction with BTCDA, five repeated coupling reactions of boc-S-benzyl-L-cysteine were performed. Changes in surface charges during the polyelectrolyte adsorption were studied by electrokinetic measurements. The cross-linking degree was a tool to control the surface charge of the PAEA/silica hybrid particles. X-ray photoelectron spectroscopy (XPS) was employed to obtain information about the amount of the adsorbed polyelectrolyte as well as the amount of the amino acid S-benzyl-L-cysteine that was covalently bound to the hybrid particle surface and polycondensed there. In the XPS spectra, the sulfur peaks (S 2p3/2, S 2p1/2, and S 2s) qualitatively and quantitatively indicated the presence of the amino acid on the hybrid material surface. After each step of coupling, the intensity of the S 2s peak was increased by a constant value. This indicates the oligopeptide growth. The novel hybrid material offers possibilities for subsequent derivatization reactions such as coupling other amino acids, peptides, obtaining hybrid ion exchange resins, and so forth.     

Interaction of β-amyloid(1-40) peptide with pairs of metal ions: An electrospray ion trap mass spectrometric model study

The stoichiometries and the affinity toward simple and paired metal ions of synthetic amyloid-β(1-40) peptide (Aβ1-40) were investigated by electrospray ion trap mass spectrometry (ESI-MS), circular dichroism (CD), and atomic force microscopy (AFM). The results lead to the working hypothesis that pH-dependent metal binding to Aβ1-40 may induce conformational changes, which affect the affinity toward other metals. A significant copper and zinc binding to Aβ1-40 peptide at pH 5.5 was found, whereas nickel ions commonly bind to each molecule of β-amyloid peptide. Some complexes of Aβ1-40 with more than one nickel ion were identified by ESI-MS. In addition, nickel ions proved to enhance Aβ oligomerization. On increasing pH, up to 12 ions of zinc may bind to a single Aβ molecule. Under the same pH and concentration conditions, the binding pattern of the independent copper and silver ions to Aβ1-40 was different from that of the equimolecular mixture of the two metal ions. One might assume that some conformational changes due to water loss altered the capacity of Aβ peptide to bind certain heavy metal ions. As a consequence, copper–silver interaction with the binding process to Aβ1-40 became highly complex. A competition between silver and nickel ions for Aβ1-40 binding sites at high pH was also observed. New strategies were proposed to identify the characteristic signals for some important metal ion–peptide complexes in the spectra recorded at high pH or high concentrations of metal ions. To explain the formation of such a large number of high metal ion–Aβ complexes, we took into consideration the participation of both histidine residues and free amino groups as well as carboxylate ones in the binding process. Finally, CD and AFM studies supported the mass spectrometric data.     

Influence of genotype and some ecological factors on volatile oil production of camomile plants

Abstract

Working with spontaneous and meliorated camomile plants (Chamomilla recutita (L.) Rausch.) cultivated in different pedo-climatic conditions, a quantitative and qualitative variation of active principle was registered. The different expression of the biosynthetic potential varied from a genotype to another, being influenced by the growing sites, precipitation regime and light intensity. Diurnal oscillations of active principle accumulation and monthly differences of essential oil and chamazulene content were evidentiated. An important stimulation of volatile oil synthesis was obtained by gamma ray fruit irradiation.     

Synthesis and mass spectrometric characterization of a metal-affinity decapeptide: copper-induced conformational changes

A decapeptide with high affinity toward heavy metal ions (RCHQYHHNRE) has been prepared by Fmoc strategy using TGR resin as solid support. The model peptide provides a simple system that can be used for a systematic study of the impact of different metal ions on peptide secondary structure on a molecular level; histidine residues were incorporated into the peptide in a sequence similar to beta-amyloid peptide (Abeta1-40) to generate possible complexation sites for Cu (2+) ions. The peptide secondary structure, as investigated by circular dichroism, and self-assembled nanostructures were observed to depend strongly on the presence of copper and sodium dodecyl sulfate (SDS). Atomic force microscopy (AFM) revealed also that copper and SDS affected slightly the Abeta1-40 nanostructures. An explanation for the effect of metal ions and SDS on the self-assembly of peptides was proposed. The extensive beta-sheet formation may further promote peptide self-assembly into longer fibers.     

IR, MS and CD Investigations on Several Conformationally-Different Histidine Peptides

Solid phase synthetic methodology has been used to prepare four peptides which form a system able to monitor metal ion binding to conformationally different peptides. The 19-residues oligopeptides containing histidine residues in various positions of Ala or Gly sequences, namely GGGGHGGGGHGGGGHGGGG, GGGHGGGHGGGHGGGGGGG, AAAAHAAAAHAAAA-HAAAA, and AAAHAAAHAAAHAAAAAAA have been synthesized by Fmoc strategy and characterized by Fourier transform infrared spectroscopy (FT-IR) as well as electrospray ion trap mass spectrometry (ESI-MS) and circular dichroism (CD). The analysis of CD-spectra of the four peptides revealed that the secondary structure depends much on the amino acid sequence. Biological and medical consequences of conformational changes of metal-bound peptides are further discussed.