Ester Carbonyl Vibration as a Sensitive Probe of Protein Local Electric Field

The ability to quantify the local electrostatic environment of proteins and protein/peptide assemblies is key to gaining a microscopic understanding of many biological interactions and processes. Herein, we show that the ester carbonyl stretching vibration of two non‐natural amino acids, L ‐aspartic acid 4‐methyl ester and L ‐glutamic acid 5‐methyl ester, is a convenient and sensitive probe in this regard, since its frequency correlates linearly with the local electrostatic field for both hydrogen‐bonding and non‐hydrogen‐bonding environments. We expect that the resultant frequency–electric‐field map will find use in various applications. Furthermore, we show that, when situated in a non‐hydrogen‐bonding environment, this probe can also be used to measure the local dielectric constant (ε). For example, its application to amyloid fibrils formed by Aβ_16–22 revealed that the interior of such β‐sheet assemblies has an ε value of approximately 5.6.     

Correlation between target–substrate distance and oxygen pressure in pulsed laser deposition of complex oxide thin films

A physico-chemical model is developed to describe a typical pulsed laser deposition (PLD) process. The interaction of atoms in the plume, ejected from the target, with those of the background gas (e.g. oxygen) is specifically considered. The model gives a physical definition of the ‘plume range’, which depends on the particular PLD system, and calculates the range. One prediction is that when the target-to-substrate distance (D) is optimised with respect to the oxygen pressure (P), the plasma dynamics plays an important role in growing high-quality complex oxide thin films. Our model predicts a scaling law PD³=const from thermodynamic data and the experimental volumetric erosion rate of the metallic elements ejected from the target. The volumetric erosion rate was experimentally determined by atomic force microscopy, measuring the dimensions of the crater formed in the target after a number of shots. The model was applied to the growth of three ternary oxides, CdTeO₃, AlVO₄ and PbFe₁₂O₁₉ thin films, and the scaling laws predicted by our model using 420, 400 and 700 °C as substrate temperatures, respectively, were PD³=(3.3086,5.9827,30.3)×10³ mTorr cm³, respectively, for the CdTeO₃, AlVO₄ and PbFe₁₂O₁₉ thin films. In order to grow the thin films, we used an energy density of laser beam of 2 J/cm², and fixed D=4.0, 4.0 and 3.0 cm from our scaling law; the values of P were 51.7, 130.0 and 751.8 mTorr, respectively. X-ray diffraction shows that the films are polycrystalline and the observed peaks in the samples were similar with respect at its JCPDF patterns respectively. PACS 81.05.Dz; 81.15.Fg; 52.40.Hf; 52.25.Fi; 81.15.A; 81.65.Mq     

Structural polymorphism in poly(dodecamethylen‐di‐O‐methyl‐L‐tartaramide)

Structural characterization of poly(dodecamethylen‐di‐O‐methyl‐L‐tartaramide) was carried out with optical microscopy, thermal analysis, X‐ray diffraction, and electron microscopy. Two different crystalline forms were found in accordance with the thermograms, powder and fiber X‐ray diffraction diagrams. The electron microscopy allows corroboration of the morphological and crystallographic differences. Molecular modeling was used to conclude the structural analogies and differences between the two crystalline forms that were related to the chain packing and orientation in the crystal cell, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2523–2530, 2002     

Some particular aspects of the low-temperature oxidation of methane initiated by nitric acid

During methane oxidation initiated by nitric acid or nitrogen dioxide, it is possible to observe, under certain conditions of temperature, initiator content, and flow rates, the formation of an adiabatic “temperature peak.” Because the maximum temperature of the peak does not exceed the initial temperature of the reactor by more than 220°C, the recorded temperature-increase curves were used for a kinetic interpretation. The obtained kinetic parameters (overall n and E) agree with the values reported in the literature for isothermal methane oxidation and suggest that the overall mechanism does not change in the conditions of “temperature peak.”     

Thermal behaviour and spectroscopic investigation of some methyl 2-pyridyl ketone complexes

Pyridine derivative complexes are widely employed as biological active materials especially as antibacterial agents. Five transition metal(II) mpk complexes (mpk = methyl 2-pyridyl ketone) were synthesized and investigated using elemental analysis, spectroscopic techniques (IR and UV–Vis–NIR) and conductometric measurements. The general formulae established from experimental data were found to be [M(mpk)₂(NO₃)₂]·xH₂O (x = 0 for M = Cd(II), Zn(II), x = 2 for M = Cu(II)) and [M(mpk)₂(H₂O)₂](NO₃)₂ (M = Co(II), Ni(II)). These compositions were further confirmed by thermal analysis and their thermal stability in dynamic air atmosphere investigated.     

Guanidination chemistry for qualitative and quantitative proteomics

The application of guanidination chemistry, the conversion of lysine into homoarginine residues, is used to illustrate several important general considerations relating to the use of differential isotope labelling for relative quantification in proteomics. The derivatisation procedure has been optimised for automation using a liquid handling station designed for proteomics. Automated application of the procedure to the analysis of in-gel tryptic digests of multiple spots from the two-dimensional gel electrophoretic (2DE) analysis of proteins from the FDCP-mix cell line shows near-universal improvement in protein identification as a result of derivatisation. This chemistry has been extended for relative quantification, applicable to matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) and also tandem mass spectrometry (MS/MS). It provides a robust method for the quantitative comparison of two samples that have been separated by 2DE. A peptide pair may display poor detection during MS analysis, causing their reliable relative quantification to be difficult. In such circumstances, the additional selectivity of detection provided by MS/MS can substantiate identification and allow relative quantification of these species via product ion signal ratios.