Bioactive composites fabricated by freezing‐thawing method for bone regeneration applications

Hydrogels are widely used for controlled delivery of therapeutic agents. However, hydrogels lack bioactivity to encourage bone formation and mechanical integrity. Moreover, chemically crosslinked hydrogels exhibit cytotoxic effect. To overcome these limitations poly‐vinyl alcohol (PVA) and poly‐acrylic acid (PAA) blends were combined with ceramic materials based on β tricalcium phosphate, wollastonite, and magnesium silicate with different pore size distributions. The final 3D matrix was physically crosslinked using various freeze thawing (F/T) cycles. FTIR and SEM analysis showed that ceramics were dispersed within the polymer matrix and formed hydrogen bonds. Swelling studies in buffer solution pH 7.4 showed an increase in polymer swelling when ceramic was added. Furthermore, rheological testing demonstrated that incorporation of ceramics caused an increase in mechanical properties which varies with different pore size distributions of ceramics grains added. DSC thermograms showed increased T_g values for samples containing ceramics. Antimicrobial activity containing ciprofloxacin was tested against a pathogen associated with osteomyelitis and presented positive results with ciprofloxacin. The combination of increased strength and ability to encapsulate a clinically relevant antimicrobial agent indicates that the composite tested in this study has potential for the treatment of osteomyelitis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 761–773     

Are nuclei withN∼43 deformed?

The level schemes of⁷⁵Se and⁷⁹Kr have been established through gamma ray and conversion electron spectroscopy following⁷⁵As (p, nγ ^?e) and⁷⁹Br (p, nγe^?) reactions. The data on these nuclei and the nuclei in the neighbourhood of this mass region are discussed and evidence is presented to show that the nuclei withN～43 are deformed.     

An efficient chemoenzymatic approach to (S)-gamma-fluoroleucine ethyl ester

[reaction: see text] An asymmetric synthesis of (S)-gamma-fluoroleucine ethyl ester 1 is described. The key transformation involves a lipase-catalyzed dynamic ring-opening of 2-(3-butenyl)azlactone 7b with EtOH to give amide ester (S)-6b in 84% enantiomeric excess. Removal of the N-pentenoyl group with N,N'-dibromodimethylhydantoin in the presence of trifluoroacetic acid afforded the titled compound, which was isolated as its hydrogen sulfate salt in 75% yield and >97% ee.     

Palladium-catalyzed carbene insertion and trapping with carbon nucleophiles

Palladium catalysts are shown to catalyze the three-component coupling of vinyl halides, trimethylsilyldiazomethane, and stabilized carbon nucleophiles. The reaction is believed to proceed through a palladium-carbene intermediate LX(R)PdCHSiMe 3 that undergoes migration of the vinyl substituent to the electrophilic carbene center to generate an eta 3-allylpalladium intermediate. The allylpalladium intermediate is attacked by the carbon nucleophile to generate a vinylsilane product.     

Synthesis of a tertiary carbinamide via a novel Rh-catalyzed asymmetric hydrogenation

Asymmetric hydrogenation of allylic dimethylcarbinamide 2 with 1 mol % of cationic Rh(I)-Josiphos complex in THF under 500 psi of H2 generated the corresponding tertiary carbinamide 1 in 98.5% assay yield and a 94:6 enantiomeric ratio. Upon crystallization, the product was isolated in 91% isolated yield and 95:5 enantiomeric ratio.     

Observation of anomalous transmission modes in nickel at microwave frequencies

A study has been made of the transmission of energy through nickel crystals in magnetic fields up to 13 kG using incident microwave power at 9.37 GHz. The transmission spectrum has been studied as a function of temperature and magnetic field orientation relative to the sample surface. A new set of anomalous transmission modes has been observed with the field perpendicular to the sample plane; these modes cannot be explained within the framework of existing theoretical models describing the resonance excitation of sound in ferromagnetic metals by electromagnetic waves.     

Analysis of novel streptavidin-binding peptides,identified using a phage display library,shows that amino acids external to a perfectly conserved consensus sequence and to the presented peptides contribute to binding

Summary Streptavidin-binding peptides containing the consensus amino acid sequence motif EPDW were identified using a phage display library. Phage presenting peptides containing these sequences bound streptavidin in a biotin-sensitive fashion and could be eluted with biotin. The previously identified streptag peptide sequence (AWRHPQGG) competed with phage presenting the EPDW consensus sequence for streptavidin binding. Furthermore, the EPDW sequence has two amino acids in common with yet another previously identified streptavidin-binding sequence, GDWVFI, which has similar biochemical properties. Binding inhibition studies revealed that residues flanking EPDW, as well as residues of the modified phage pIII product to which displayed peptides are fused, contributed to streptavidin binding. The derivation of small molecules based on the structure of peptides selected using display methods is a potentially important application of phage display technology. The relevance of the observations made here for that application are discussed. Finally, a group of nuisance peptides of the consensus sequence WHWWXW, whose binding specificity has not been fully elucidated, but which have been isolated in a number of biopanning experiments, including those that do not utilize streptavidin, are also described.     

Bestimmung von Schwefel in organischen Verbindungen

Ohne Zusammenfassung     

Observation of the paramagnetic resonance of Fe in Pd

The observation of the paramagnetic resonance of Fe in Pd is reported. The ion is found to be in an S tate. We deduce the s wave exchange parameter to be 0.056 ± 0.046 eV and the d wave parameter to be 0.0025 ± 0.0002 eV in good agreement with results for Mn in Pd and with resistivity results for Fe in Pd.     

Separation of 5d and 4f contributions to the electric field gradient in heavy rare-earths

We calculate the conduction electron contribution to the electric field gradient in heavy rare earth metals assuming 5d virtual bound state character present. The results are in better agreement with experiment than found previously and predict antishielding parameters for Er and Tm in good agreement with those calculated directly.