Quinazoline Derivatives Designed as Efflux Pump Inhibitors: Molecular Modeling and Spectroscopic Studies

Multidrug resistance of bacteria is a worrying concern in the therapeutic field and an alternative method to combat it is designing new efflux pump inhibitors (EPIs). This article presents a molecular study of two quinazoline derivatives, labelled BG1189 and BG1190, proposed as EPIs. In silico approach investigates the pharmacodynamic and pharmacokinetic profile of BG1189 and BG1190 quinazolines. Molecular docking and predicted ADMET features suggest that BG1189 and BG1190 may represent attractive candidates as antimicrobial drugs. UV-Vis absorption spectroscopy was employed to study the time stability of quinazoline solutions in water or in dimethyl sulfoxide (DMSO), in constant environmental conditions, and to determine the influence of usual storage temperature, normal room lighting and laser radiation (photostability) on samples stability. The effects of irradiation on BG1189 and BG1190 molecules were also assessed through Fourier-transform infrared (FTIR) spectroscopy. FTIR spectra showed that laser radiation breaks some chemical bonds affecting the substituents and the quinazoline radical of the compounds.     

Convenient Method for the 3‐Functionalization of Isoindazoles

The C‐3 position of isoindazoles is readily functionalized by metalation with lithium diisopropylamide followed by reaction with a variety of electrophiles.     

The gluon propagator in the Coulomb gauge

We give the results for all the one-loop propagators, including finite parts, in the Coulomb gauge. In the finite parts we find new non-rational functions in addition to the single logarithms of the Feynman gauge. Of course, the two gauges must agree for any gauge invariant function.Received: 14 November 2003, Revised: 20 July 2004, Published online: 24 September 2004     

Renormalization of Wilson operators in the light-cone gauge

We test the renormalization of Wilson operators and the Mandelstam–Leibbrandt gauge in the case when the sides of the loop are parallel to the vectors used in the M–L gauge. Graphs which in the Feynman gauge are free of ultra-violet divergences, in the M–L gauge show double divergences and single divergences with non-local Si and Ci functions. These non-local functions cancel out when we add all graphs together and the constraints of gauge invariance are satisfied. In Appendix C we briefly discuss the problems of the M–L gauge for loops containing spacelike lines. Received: 31 May 2000 / Published online: 23 January 2001     

Carbon-13 magnetic resonance study of lanthanide-substituted muscle calcium binding parvalbumins

High resolution natural abundance carbon-13 NMR has been used previously to examine molecular motions and conformational transitions in the muscle calcium binding parvalbumins isolated from mirror carp. [S. J. Opella, D. J. Nelson, and O. Jardetzky, J. Chem. Phys. 64 , 2533 (1976) and D. J. Nelson, S. J. Opella, and O. Jardetzky, Biochemistry 15 , 5552 (1976).] The carbon-13 NMR spectrum of parvalbumin typically reveals the presence of a number of well-resolved resonances from single-carbon sites in the protein. Since accurate assignment of these resonances to specific carbon atoms in the protein is essential before these resonances can be employed as probes of local conformational events, an investigation of the origin of a number of single-carbon resonances has been performed. Carbon-13 NMR on Tb(III)- and Yb(III)-substituted parvalbumin is the principal spectroscopic technique employed; however, results from terbium fluorescence spectroscopy, γ-ray scintillation spectroscopy, and x-ray difference Fourier analysis all contribute to single-carbon site assignment. The principal conclusions drawn from the combined spectroscopic results are that: (1) the downfield carboxyl resonance at 184.6 ppm, previously attributed to Glu-81, whose carboxyl group is involved in an internal ionic bond, originates rather from a carboxyl function coordinating the solvent exposed metal ion, (2) the carbonyl resonance at 168.9 ppm arises from Lys-96, as was previously suggested; and (3) the 11.2 ppm resonance derives from the δ-methyl carbon of Ile-97, a resonance assignment that could not be made previously.     

A cross-metathesis approach for the synthesis of tedanolide and 13-deoxytedanolide: stereoselective synthesis of the C3-C16 segment

A unified synthetic strategy has been devised for the synthesis of both tedanolide and 13-deoxytedanolide, which involves a cross-metathesis reaction as the key step. We report herein the stereoselective synthesis of the C3-C16 segment (+)-5b and subsequent manipulation of the C12-C13 double bond leading to the preparation of both tedanolides.     

Spectral Properties of Foams and Emulsions

The optical and spectral properties of foams and emulsions provide information about their micro-/nanostructures, chemical and time stability and molecular data of their components. Foams and emulsions are collections of different kinds of bubbles or drops with particular properties. A summary of various surfactant and emulsifier types is performed here, as well as an overview of methods for producing foams and emulsions. Absorption, reflectance, and vibrational spectroscopy (Fourier Transform Infrared spectroscopy-FTIR, Raman spectroscopy) studies are detailed in connection with the spectral characterization techniques of colloidal systems. Diffusing Wave Spectroscopy (DWS) data for foams and emulsions are likewise introduced. The utility of spectroscopic approaches has grown as processing power and analysis capabilities have improved. In addition, lasers offer advantages due to the specific properties of the emitted beams which allow focusing on very small volumes and enable accurate, fast, and high spatial resolution sample characterization. Emulsions and foams provide exceptional sensitive bases for measuring low concentrations of molecules down to the level of traces using spectroscopy techniques, thus opening new horizons in microfluidics.