Results on the edge-connectivity of graphs

It is shown that if G is a graph of order p ≥ 2 such that deg u + deg v ≥ p ? 1 for all pairs u, v of nonadjacent vertices, then the edge-connectivity of G equals the minimum degree of G. Furthermore, if deg u + deg v ≥ p for all pairs u, v of nonadjacent vertices, then either p is even and G is isomorphic to $\text{K}{}_{\mathrm{<mtext>p</mtext><mtext>2</mtext>}}\text{× K}{}_2$ or every minimum cutset of edges of G consists of the collection of edges incident with a vertex of least degree.     

Hydrolysis of amides. Steric effects on kinetics and mechanism of the basic hydrolysis of N-acylcarbazoles

The hydroxide ion catalyzed hydrolysis of a series of N-acylcarbazoles has been studied in water at 25°. Both the rate constants of formation of the tetrahedral intermediate and of its collapse to products are strongly increased by alkyl group branching in the acyl portion.     

Improved resolution with microchip-based enhanced field inversion electrophoresis

We present an improvement of the field inversion electrophoresis (FIE) method in which the passage of sample such as DNA back and forth within a short length of a microchannel can provide a similar resolution to that of a significantly longer microchannel. In constant field FIE the application of an alternating potential (e.g., +/- V) over short periods of time (e.g., several Hz) can provide enhanced separations of DNA fragments. In contrast, the present method consists of a series of separations, each of much longer duration, under high and low fields in such a way that the resolution is enhanced. This method is readily modeled and allows improved resolution to be obtained from extremely short microchannels (e.g., 8 mm) while requiring relatively low applied voltages (e.g., less than 600 V). An additional advantage is that this method can allow for the same equipment to be used in a rapid, low-resolution mode or in a slower, high-resolution mode through what might be referred to as an automated "zoom" capability. We believe that this method may facilitate the integration of microfluidic devices and microelectronic devices by allowing these devices to be of a similar small scale (< 1 cm).     

A chemoenzymatic approach toward the rapid and sensitive detection of O-GlcNAc posttranslational modifications

We report a new chemoenzymatic strategy for the rapid and sensitive detection of O-GlcNAc posttranslational modifications. The approach exploits the ability of an engineered mutant of beta-1,4-galactosyltransferase to selectively transfer an unnatural ketone functionality onto O-GlcNAc glycosylated proteins. Once transferred, the ketone moiety serves as a versatile handle for the attachment of biotin, thereby enabling chemiluminescent detection of the modified protein. Importantly, this approach permits the rapid visualization of proteins that are at the limits of detection using traditional methods. Moreover, it bypasses the need for radioactive precursors and captures the glycosylated species without perturbing metabolic pathways. We anticipate that this general chemoenzymatic strategy will have broad application to the study of posttranslational modifications.     

Transversal Lie group actions on abstract CR manifolds

Supported by NSF Grant DMS 8603176     

Bond ionicity and the strength of carbon-carbon bonds

A simple VB analysis is used to illustrate that the greater stability of geminally disubstituted ethanes and ethylenes compared to their vicinally substituted counterparts is due to the strength of the central C-C bond and not to the stability of the radical and carbene fragments that compose the molecule. The qualitative arguments are supported by MO calculations. The implications to the additivity rules for the estimation of heats of formation are discussed.     

Rate constants for the reactions of OH radicals and Cl atoms with diethyl sulfide,Di-n-propyl sulfide,and Di-n-butyl sulfide

Rate constants for the reactions of OH radicals and Cl atoms with diethyl sulfide (DES), di-n-propyl sulfide (DPS), and di-n-butyl sulfide (DBS) have been determined at 295 ± 3 K and a total pressure of 1 atm. Hydroxyl radical rate data was obtained using the absolute technique of pulse radiolysis combined with kinetic spectroscopy. The chlorine atom rate constants were measured using a conventional photolytic relative rate method. The rate constant for the reaction of Cl atoms with dimethyl sulfide (DMS) was also determined. The following rate constants were obtained:      

Molecular constants for the interacting upper states of the ν1, ν3, 2ν2, ν2 + ν4, and 2ν4 bands in 12CH4

In a previous paper (J.-E. Lolck and A. G. Robiette, J. Mol. Spectrosc.88, 14 (1981)) a theoretical model for the interacting upper states of the ν₁, ν₃, 2ν₂, ν₂ + ν₄, and 2ν₄ bands in methane was described. The present paper summarizes the results obtained, using this model, in a comprehensive analysis of the five bands of ¹²CH₄ through J′ = 12. Values of 80 molecular constants, of which 17 correspond to vibrationally off-diagonal operators, are reported. In addition the computed energy levels of the v₃ = 1 state are compared to the experimental ones and to the result of the previous isolated band approach.