Metal-chelating amino acids as building blocks for synthetic receptors sensing metal ions and histidine-tagged proteins

Protein structure and function rely on a still not fully understood interplay of energetic and entropic constraints defined by the permutation of the twenty genetically encoded amino acids. Many attempts have been undertaken to design peptide-peptide interaction pairs and synthetic receptors de novo by using this limited number of building blocks. We describe a rational approach to creating a building block based on a tailored metal-chelating amino acid. Nepsilon,Nepsilon-bis(carboxymethyl)-L-lysine can be flexibly introduced into peptides by 9-fluorenylmethoxycarbonyl solid-phase chemistry. The corresponding metal-chelating peptides act as metal sensors and synthetic receptors for histidine-tagged proteins. These biochemical tweezers will open new ways to control protein-protein interactions, to design peptide-based interaction pairs, or to generate switchable protein function.     

Identification of new homoterpene esters from Dufour's gland of the ponerine ant Gnamptogenys striatula

Extracts of Dufour's gland of the ponerine ant, Gnamptogenys striatula, were analyzed by using the combination of gas chromatography and mass spectrometry. Series of esters of the new homoterpenoids (2E,6)-3,4,7-trimethyl-2,6-octadiene-1-ol (4-methylgeraniol) and (2E,6)-3,4,7-trimethyl-2, 6-nonadiene-1-ol (bishomogeraniol) with unbranched medium-chain fatty acids were identified. Transformation of the chiral natural products into 1,4-di(trifluoroacetoxy)-3-methylpentane and comparison of its gas chromatographic retention time on a modified cyclodextrin phase with that of synthetic optically active reference samples proved the stereogenic center to keep (S)-configuration. (2E,4S,6)-3,4,7-Trimethyl-2,6-octadien-1-yl decanoate and the corresponding dodecanoate are the main volatiles in the extracts.     

Strategy Alignment of Mobile Solutions in Customer-Oriented Processes

In this paper we analyze how companies define their strategy, especially how they interact with and appear to the customer. Based on a framework of five goals in customer oriented strategy, we classify seven cases. Analyzing the strategic premises and the processes chosen to be supported by mobile solutions, we show interdependencies between the strategic premises and the selected processes, resulting in typical properties which qualify processes for mobilization.     

Pulsed magnetization transfer for imaging and spectroscopic applications on whole-body imagers

Magnetization transfer contrast is a tool to obtain additional information on tissue using standard whole-body magnetic resonance (MR) units without any hardware extension. Short hard pulse sequences with a total duration of about 1 ms can provide selective saturation of protons with very short relaxation timesT ₂ of 1–10 µs. Comparatively high amplitude of the radio-frequency field is advantageous; on the other hand, this amplitude is limited for whole-body units. The presented approach to achieve adapted hard pulse sequences is mainly based on maximum RF amplitudes corresponding with pulse angles per millisecond of 360 °, or 720°. The pulse sequences must not influence the magnetization of free protons with longer relaxation timesT ₂>10 ms in a frequency range that depends on the circumstances of the application. This frequency range has to be markedly broader for imaging techniques than for localized spectroscopy. The number of pulses, the pulse durations and pulse angles, and the interpulse delays were systematically varied. The time intervals between repetitions of the hard pulse sequences in order to obtain stronger magnetization transfer contrast were also optimized experimentally for human skeletal muscle and brain.Additional reprints of this chapter may be obtained from the Reprints Department, Chapman & Hall, One Penn Plaza, New York, NY 10119.     

Synthesis and characterization of polyvinylpyridine macromonomers

Summary Macromonomers of polyvinylpyridine were obtained anionically, by reacting unsaturated electrophiles onto a living polyvinylpyridine solution. The end-standing unsaturation is either a methacrylic ester function or an -methylstyrene group. Several experimental problems had to be solved to get polymers of adequate and predetermined molecular weight and of low polydispersity, and to have the molecules fitted quantitatively with unsaturation at chain end. A careful characterization procedure was used to check the ability of the method to yield well defined macromonomers.     

Developing low temperature,impact-resistant PVC—a new testing approach

Concern over making end-use predictions from milled/notched Izod test data for applications where product manufacturing techniques differ greatly from Izod test sample preparation brought on this study of the use of Gardner-type impact tests on commercial and laboratory extruded PVC sheet. By notching the test sample, the standard Gardner and Izod impact tests at low temperatures could be predicted at room temperature in the Gardner test equipment.     

Copolymerization of polyvinylpyridine macromonomers with styrene

Summary Free radical Copolymerization of ( -methylstyryl) poly (2-vinylpyridine) macromonomers with styrene was performed. After separation of residual macromonomer the graft copolymers were submitted to a careful characterization.The copolymers were generally of rather low molecular weight and the average number of grafts per backbone chain was found close to unity. Nevertheless, these polymeric species tend to give aggregates and/or emulsions in selective solvents of the grafts, a typical behaviour of graft copolymers.     

Exact solutions for evolutionary strategies on harmonic landscapes

In this paper two different evolutionary strategies are tested by means of harmonic landscapes. Both strategies are based on ensembles of searchers, spreading over the search space according to laws inspired by nature. The main difference between the two prototypes is given by the underlying selection mechanism, governing the increase or decrease of the local population of searchers in certain regions of the search space. More precisely, we compare a thermodynamic strategy, which is based on a physically motivated local selection criterion, with a biologically motivated strategy, which features a global selection scheme (i.e., global coupling of the searchers). Confining ourselves to a special class of initial conditions, we show that, in the simple case of harmonic test potentials, both strategies possess particular analytical solutions of the same type. By means of these special solutions, the velocities of the two strategies can be compared exactly. In the last part of the paper, we extend the scope of our discussion to a mixed strategy, combining local and global selection.     

Composite organic-inorganic nanoparticles as Raman labels for tissue analysis

Composite organic-inorganic nanoparticles (COINs) are novel optical labels for detection of biomolecules. We have previously developed methods to encapsulate COINs and to functionalize them with antibodies. Here we report the first steps toward application of COINs to the detection of proteins in human tissues. Two analytes, PSA and CK18, are detected simultaneously using two different COINs in a direct binding assay, and two different COINs are shown to simultaneously label PSA in tissue samples.