The formation of propylene fumarate oligomers for use in bioerodible bone cement composites

Poly(propylene fumarate) (PPF) oligomers were synthesized by step polymerization using bis(2-hydroxypropyl fumarate) or propylene bis(hydrogen maleate) as starting materials. Oligomers possessing identical degrees of polymerization (DP), but varying in their end group character (either hydroxyl or carboxyl) were first prepared and characterized, then used as part of a bone cement preparation consisting of oligomer, tricalcium phosphate, calcium carbonate, and methyl methacrylate. Compressive strength of the resulting composite appeared to be dependent on both the degree of polymerization of the PPF, and the nature of the oligomers' end groups.     

Stability study of somatropin by capillary zone electrophoresis

Human Growth Hormone (hGH) is a monomeric 22 kilo Dalton (kDa), 191 amino acid protein with an isoelectric point (pI) close to pH 5, produced in the anterior pituitary gland. High level production of somatropin (recombinant hGH) is done in Escherichia coli (E. coli) to meet the demand and to avoid possible Creutzfeldt-Jacob disease (CJD).The present study was initiated on the basis of results from post-marketing control of all somatropin preparations on the Norwegian market. The samples consisted of preparations presented as somatropin in solution, and some freeze-dried preparations were also included for comparison.The present study showed a significant degree of degradation of somatropin in solution. Deamidation increased over time for preparations in solution, as well as for freeze-dried preparations after dissolution. Preparations in solution showed high content of deamidated and cleaved forms. Freeze-dried preparations after dissolution and storage showed high content of deamidated forms, but low content of cleaved forms. Also, in one preparation, an unknown peak was detected in the electropherogram from capillary zone electrophoresis (CZE), eluting after the principal peak, in front of the Gln-18 somatropin peak.     

Novel biodegradable poly(1,8-octanediol malate) for annulus fibrosus regeneration

A novel elastic scaffold that simulates the deformability of annulus fibrosus (AF) and has good biocompatibility was developed. The scaffold was formed of a malic acid-based polyester poly(1,8-octanediol malate) (POM), which was synthesized by direct polycondensation. The tensile strength of POM gradually increased with the extension of the polymerization time, while the degradation rate decreased. Rat AF cells proliferated on the POM films and maintained their phenotype. The 3D scaffold also supported the growth of the AF cells, as confirmed by Safranin-O and type II collagen staining. POM also demonstrated a good biocompatibility in an in vivo foreign body response assay, an important prerequisite for tissue engineering applications. This study suggests that elastic POM scaffold may be an ideal candidate for AF tissue engineering.     

Prediction of environmental noise from fast electric trains

A model is presented for the environmental noise of fast electric trains on continuous welded rails, based on a consideration of the possible modes of vibration of the wheels. Evidence is presented to support the idea that the wheels are the dominant sources of noise and radiate as resonant dipoles. The model is calibrated by the results of measurements and methods of predicting train noise level and noise energy (per unit area) are developed. The noise intensity is found to increase as the fourth power of the speed. Energy (per unit area) at an observer increases as the third power of the speed and is proportional to train length divided by the distance of the observer from the track. The relevance of the model as a basis for the calculation of train noise in terms of some noise indices is then discussed and it is shown that it can be used to predict the parameters required by some indices which may be relevant to the subjective effects of environmental train noise.     

Resonance-enhanced multiphoton ionisation photoelectron spectroscopy of the ClO radical: the C 2 sigma- state

A (2 + 1) one-colour resonance-enhanced multiphoton ionisation study is carried out on the C 2 sigma- state of the ClO radical in the one-photon energy range 29,500-31,250 cm-1. The ClO radical is produced by one-photon photolysis of ClO2 employing 359.2 nm photons derived from a separate laser. In this way a significant concentration of vibrationally excited ClO in its spin-orbit split X 2 pi omega (omega = 3/2 or 1/2) electronic ground state is produced. In addition to mass-resolved excitation spectra, kinetic-energy resolved photoelectron spectra for the X 3 sigma-(v+)<--C 2 sigma-(v' = 3-5) transitions are measured. These transitions are not completely Frank-Condon diagonal, and indicate a decrease in bond length on removal of the Rydberg electron from the C 2 sigma- state. In addition to an unambiguous assignment of the C 2 sigma- state, valuable information is obtained on the degree of vibrational excitation with which the nascent ClO radical is formed in the photolysis of ClO2. Analysis of the photoelectron spectra is supported by Franck-Condon calculations based on potential energy curves either from experimental spectroscopic parameters, or obtained by theoretical ab initio methods.     

Simulations of nanocylinders self-assembled from cyclic β-tripeptides

This paper examines the self-assembly of cyclic β-tripeptides using density functional theory. On the basis of literature precedents, these cyclic peptides were expected to self-assemble into cylindrical structures by stacking through backbone-backbone hydrogen bonding. Our calculations show that such stacking is energetically favorable, that the association energy per cyclic peptide decreases (becomes more favorable), and that the overall macrodipole moment of the cylindrical assembly increases with the number of stacked rings, for up to eight rings. For a structure in which two peptide ring units are joined through a single side chain-side chain covalent linker, the association energy between the two rings is favorable, albeit less so than for the unlinked rings. Significantly, the association energy in the dimers is only weakly dependent on the length (above a certain minimum) and conformation of the covalent linkers. Finally, as a plausible route for controlling assembly/disassembly of nanocylinders, we show that, for a pair of rings, each bearing a single amino-functionalized side chain, protonation of the amino group results in a strongly positive (unfavorable) association energy between the two rings.     

Capillary Gas Chromatography Coupled with Microplasma Mass Spectrometry – Improved Ion Source Design Compatible with Bench-Top Mass Spectrometric Instrumentation

Capillary gas chromatography was performed with mass spectrometric detection using a novel microplasma ion source for operation in an element-selective mode. The ion source was a 350 kHz radio frequency helium plasma, which was sustained inside the 4 cm end of a 0.32 mm i.d. fused silica capillary column, and located inside the high vacuum chamber of the quadrupole mass spectrometer. Due to the low volume of the ion source, a stable low pressure discharge was produced utilizing only the 2.25 mL min⁻¹ of GC carrier gas (helium) for plasma support. Small amounts of oxygen (0.1–0.2% v/v) were added to the plasma gas in order to prevent carbon deposits and to enhance signal-to-noise ratios. Chlorine and bromine were selectively detected at the 5–20 pg s⁻¹ level (S/N = 2), and both produced a response that was linear within 3 orders of magnitude.     

Simultaneous Element-Selective Detection of C,F, Cl,Br, and I by Capillary Gas Chromatography Coupled with Microplasma Mass Spectrometry

Simultaneous element-selective detection of the halogens and carbon was accomplished with capillary gas chromatography coupled with microplasma mass spectrometry. The microplasma ion source was a radio frequency plasma contained inside the last 4–5 cm of the 0.32 mm i.d. fused silica capillary column. The ion source was located inside the high vacuum housing of the MS, and only the GC carrier gas (2.3 mL min⁻¹ of helium) was used for plasma generation. Atomic ions were detected in the positive mode. Detection limits were in the low picogram area, and the selectivity to carbon ranged from 8×10² for fluorine to higher than 10⁴ for the other halogens. By introduction of both hydrogen and oxygen as reagent gases, peak tailing was avoided by suppression of analyte reactions with the silica walls of the ion source. Special attention was given to the fluorine-selective detection due to an interfering background species at m/z 19, assumed to be H₃O⁺ originating from the reagent gases. The background signal was minimized by careful control of the power level.     

Photoelastic determination of stresses in multiple-pin connectors

The design, fabrication, and testing of photoelastic models of double-lap, multiple-pin connectors are discussed. Interest is in the stresses in the inner laps. These stresses are determined by constructing models with photoelastic inner laps and transparent-acrylic outer laps. The connectors have two pins, in tandem, parallel to the load direction. A photoelastic-isotropic point is shown to permit the evaluation of load sharing between the two pins. A numerical scheme, utilizing the isochromatic- and isoclinic-photoelastic data and a finite-difference representation of the planestress equilibrium equations, is used to compute the stresses around the two pins. Representative stress distributions and stress-concentration factors are shown.     

Phage display-derived inhibitor of the essential cell wall biosynthesis enzyme MurF

Background  

To develop antibacterial agents having novel modes of action against bacterial cell wall biosynthesis, we targeted the essential MurF enzyme of the antibiotic resistant pathogen Pseudomonas aeruginosa. MurF catalyzes the formation of a peptide bond between D-Alanyl-D-Alanine (D-Ala-D-Ala) and the cell wall precursor uridine 5'-diphosphoryl N-acetylmuramoyl-L-alanyl-D-glutamyl-meso-diaminopimelic acid (UDP-MurNAc-Ala-Glu-meso-A2pm) with the concomitant hydrolysis of ATP to ADP and inorganic phosphate, yielding UDP-N-acetylmuramyl-pentapeptide. As MurF acts on a dipeptide, we exploited a phage display approach to identify peptide ligands having high binding affinities for the enzyme.