Ca2+‐complex stability of GAPAGPLIVPY peptide in gas and aqueous phase,investigated by affinity capillary electrophoresis and molecular dynamics simulations and compared to mass spectrometric results

Strong, sequence‐specific gas‐phase bindings between proline‐rich peptides and alkaline earth metal ions in nanoESI‐MS experiments were reported by Lehmann et al. (Rapid Commun. Mass Spectrom. 2006, 20, 2404–2410), however its relevance for physiological‐like aqueous phase is uncertain. Therefore, the complexes should also be studied in aqueous solution and the relevance of the MS method for binding studies be evaluated. A mobility shift ACE method was used for determining the binding between the small peptide GAPAGPLIVPY and various metal ions in aqueous solution. The findings were compared to the MS results and further explained using computational methods. While the MS data showed a strong alkaline earth ion binding, the ACE results showed nonsignificant binding. The proposed vacuum state complex also decomposed during a molecular dynamic simulation in aqueous solution. This study shows that the formed stable peptide–metal ion adducts in the gas phase by ESI‐MS does not imply the existence of analogous adducts in the aqueous phase. Comparing peptide–metal ion interaction under the gaseous MS and aqueous ACE conditions showed huge difference in binding behavior.     

Label-free LC-MS/MS quantitative proteomics for large-scale biomarker discovery in complex samples

Proteomic platforms that enable researchers to profile a high number of proteins across large sets of complex samples hold a great potential for biomarker discovery. LC-MS/MS-based methods can be used to analyse many samples without the need for protein labelling. As the analysis is a sequential process, the performance of the system has to be consistent throughout the entire experiment. In this study we used a set of spiked serum samples as well as a set of 55 clinical serum samples from schizophrenia patients and healthy volunteers to show that the label-free proteomic approach yields reproducible results across a large number of samples and can be used to accurately measure the relative protein abundance. Using this approach, we identified 1709 serum proteins covering a dynamic range of over three orders of magnitude. We believe that label-free quantitative proteomics is especially suited for biomarker discovery in large sample sets.     

Characterization of temperature-dependent iron-imidazole vibrational modes in far infrared

The active site of several oxygen binding proteins can be mimicked with the ferric iron protoporphyrin IX derivative hemin, coordinating two imidazole molecules and embedded in sodium dodecyl sulfate (SDS) micelles; the detergent simulates the hydrophobic cavity of heme proteins. We studied the low-frequency vibrational modes of the porphyrin-iron-imidazole bonding in infrared absorbance spectra. Assignment of the metal-ligand vibrations to signals at 396, 387, and 378 cm(-1) was performed by isotope labeling of the imidazole ligand. These modes were also found to be temperature-dependent and to display a linear increase of signal intensity between 25 and 150 K and, with a different slope, between 150 and 300 K. The modes at 396 and 399 cm(-1) show for 25 K an up-shift about 4 cm(-1) and the signal at 378 cm(-1) a small downshift, indicating the involvement of antisymmetric stretching modes and, in the latter, of bending motions. Anharmonic couplings to doming modes are discussed, and the doming mode and hydrogen-bonding signature spectral range between 300 and 100 cm(-1) is presented.     

Synthesis of 5‐[(4‐phenylpiperazin‐1‐yl)methyl]pyrrolo‐[2,3‐d]pyrimidine derivatives as potential dopamine D4 receptor ligands

A series of pyrrolo[2,3‐d]pyrimidine Mannich bases of type 9, 12, 15 and 16 have been prepared as potential dopamine D4 receptor ligands. The syntheses start from 4‐aminopyrimidin‐6‐one 3 with pyrrole annulations and Mannich reactions with formaldehyde and phenylpiperazines 8 as new amine components.     

PM IRRAS investigation of thin silica films deposited on gold. Part 1. Theory and proof of concept

Polarization modulation infrared reflection absorption spectroscopy (PM IRRAS) was successfully used for the first time to characterize an optically transparent thin oxide film. SiO2 layers of 7 nm thickness were synthesized by plasma enhanced chemical vapor deposition (PECVD) on 200 nm thick gold covered glass slides. Despite the fact that silica is transparent and absorptive to IR radiation when deposited in the form of thin films on a gold surface, it preserves the high metallic reflectivity for the IR light. At grazing angles of incidence of the IR beam, the enhancement of the normal component of the electric field at the interface is comparable to that of Au alone. In addition, the analysis of the structure of a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid monolayer deposited using the Langmuir-Blodgett technique is demonstrated.     

Thermoresponsive coatings strongly adhering to (semi)conducting surfaces

Thermoresponsive brushes have been efficiently grafted onto (semi)conductive surfaces by a two-step process. In the first step, poly(N-succinimidyl acrylate) chains have been chemisorbed onto silicon or stainless steel by the electrografting method. Then, these modified electrodes were immersed in isopropylamine in order to transform the grafted chains to the thermoresponsive poly(N-isopropyl acrylamide). The thermal response of these brushes has been shown by AFM. This straightforward grafting process is quite attractive for surface modification in confined media and is thus promising for microfludics application.