A mild and efficient one pot synthesis of 1,3,4-oxadiazoles from carboxylic acids and acyl hydrazides

A convenient one pot method for the synthesis of 2,5-disubstituted 1,3,4-oxadiazoles from acids and acyl hydrazides is reported. Acid activation with CDI, followed by coupling with the desired acylhydrazide and dehydration in the same pot with Ph₃P and CBr₄ affords the corresponding 1,3,4-oxadiazoles in good yield. The scope of the acid and acylhydrazide components is presented.     

Impact of deglycosylation methods on two-dimensional gel electrophoresis and matrix assisted laser desorption/ionization-time of flight-mass spectrometry for proteomic analysis

Glycosylation is a common post-translational modification that can add complexity to the proteome of many cell types. We used enzymatic and chemical methods of deglycosylation to treat a heavily glycosylated exoproteome sample from the filamentous fungus Trichoderma reesei. Deglycosylated samples were resolved on one-dimensional (1-D) and two-dimensional (2-D) gels in order to determine the effect of deglycosylation on the electrophoresis patterns and on the ability to identify proteins by peptide mass matching using matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) analysis of in-gel tryptic digests. We found that deglycosylation of the protein sample resulted in different protein patterns on 1-D and 2-D gels, reduced the complexity of gel patterns, and enhanced the protein identification of some proteins via MALDI-TOF-MS. Deglycosylation with trifluoromethanesulfonic acid (TFMS) was found to be more effective than enzymatic treatments. These deglycosylation techniques may be employed in whole proteome analysis to locate glycosylated proteins and assist in their identification by MS.     

Spectroscopic study of chloranil charge-transfer complexes of amino acids and related compounds

The absorption maxima, molar absorptivities, infrared spectra, compositions, formation constants, and pH dependence of amino acid—chloranil complexes have been determined with purified chloranil The n-π charge-transfer interaction depends on the presence of an unprotonated amino group; pH 9 is optimal for complex formation, but once formed, the complex is stable in a highly acidic medium and may be quantitatively extracted by hexanol. The molar absorptivities of the chloranil complexes of glycine, iminodiacetic acid, NTA, EDTA, DTPA and TTHA were measured. There is a linear relationship between the logarithm of the molar absorptivities of their chloranil complexes and the number of carboxylic groups in the molecule. There is an inverse linear relationship between the molar absorptivities of chloranil—metal—EDTA complexes and the logarithm of the stability constants of the EDTA chelates. This leads to a new method of determining the stability constants of complexes involving a nitrogen-donating group.     

Threshold collision-induced dissociation of diatomic molecules: a case study of the energetics and dynamics of O2- collisions with Ar and Xe

The energetics and dynamics of collision-induced dissociation of O2- with Ar and Xe targets are studied experimentally using guided ion-beam tandem mass spectrometry. The cross sections and the collision dynamics are modeled theoretically by classical trajectory calculations. Experimental apparent threshold energies are 2.1 and 1.1 eV in excess of the thermochemical O2- bond dissociation energy for argon and xenon, respectively. Classical trajectory calculations confirm the observed threshold behavior and the dependence of cross sections on the relative kinetic energy. Representative trajectories reveal that the bond dissociation takes place on a short time scale of about 50 fs in strong direct collisions. Collision-induced dissociation is found to be remarkably restricted to the perpendicular approach of ArXe to the molecular axis of O2-, while collinear collisions do not result in dissociation. The higher collisional energy-transfer efficiency of xenon compared with argon is attributed to both mass and polarizability effects.     

Polymerization of methyl methacrylate initiated by oligoglycine,water, cupric ion,and carbon tetrachloride

The polymerization of methyl methacrylate (MMA) was carried out in the presence of oligoglycines (glycine, its dimer, trimer, tetramer, etc.), water, cupric ions, and carbon tetrachloride. It was found that poly-MMA is formed in the water layer and that the system using triglycine gives the maximum polymer yield. On the effect of pH of water layer, the rate of polymerization is faster in the alkalic condition (pH 8–10) than in normal condition (pH 3.8), while in the acidic media (pH 2–3), the rate is not accelerated. From the results of kinetic studies, the polymerization rate is dependent on the 0.5 power of the amount of diglycine or cupric ion, and it is independent of the amount of MMA. The polymerization mechanism was discussed.     

3R,4R-dihydroxy-L-proline: a potent and specific β-D-glucuronidase inhibitor

The title compound, a naturally-occurring amino acid found in virotoxins, competitively inhibits bovine β-D-glucuronidase but does not affect other glycosidases.     

Advantages of deuterium modification of nitroxide spin labels for biological epr studies

The spin label, perdeuterio-N-(1-oxy 1-2,2,6,6-tetramenthyl-4-piperidinyl)maleimide (DMSL) was synthesized and its EPR and saturation transfer EPR spectra were compared to those of the hydrogen analogue, HMSL- The labels were studied as freely tumbling entities and also bound to bovine serum albumin (BSA). Significant gains in spectral resolution and detectability were observed for DMSL relative to HMSL.     

Electrical properties of diamond surfaces functionalized with molecular monolayers

Recent studies have shown that semiconductor surfaces such as silicon and diamond can be functionalized with organic monolayers, and that these monolayer films can be used to tether biomolecules such as DNA to the surfaces. Electrical measurements of these interfaces show a change in response to DNA hybridization and other biological binding processes, but the fundamental nature of the electrical signal transduction has remained unclear. We have explored the electrical impedance of polycrystalline and single-crystal diamond surfaces modified with an organic monolayer produced by photochemical reaction of diamond with 1-dodecene. Our results show that, by measuring the impedance as a function of frequency and potential, it is possible to dissect the complex interfacial structure into frequency ranges where the total impedance is controlled by the molecular monolayer, by the diamond space-charge region, and by the electrolyte. The results have implications for understanding the ability to use molecularly modified semiconductor surfaces for applications such as chemical and biological sensing.