Computer analysis of proteins separated by polyacrylamide gradient pore gel electrophoresis

A method for measuring lymph-to-plasma (L/P) protein concentration ratios obtained from protein fractions separated by polyacrylamide gradient gel electrophoresis is presented. A curve-fitting technique is used to decompose lymph and plasma electropherograms containing multiple components into individual components, eliminating protein-protein overlap regions. This allows the concentration of each component in the mixture to be measured accurately, yielding more precise estimates of L/P ratios. This technique consists of three phases. Individual electropherograms are constructed for proteins of various sizes by taking a weighted average of measured electropherograms obtained from the two protein standards closest in size to the protein of interest. Using these generated standard curves, the multicomponent lymph and plasma curves are decomposed into the least number of equally spaced components that yield a good fit. A linear least-squares method is used to do this. Each protein fraction is multiplied by the total measured protein concentration to provide a concentration for each component. Finally, L/P concentration ratios of protein fractions with visible peaks were computed by applying an averaging technique to the equally spaced protein fractions. Plots of sheep lung L/P ratio versus protein size obtained in this manner were compared to L/P ratios obtained using a method of analysis which does not correct for protein overlap. The corrected L/P ratios showed less scatter than the uncorrected curves. Lung lymph data analyzed with the correction method indicated an increased lung microvascular permeability for large proteins following endotoxin infusion, whereas the uncorrected curves were too noisy to support this concept.     

On multicyclic operators and the Vasjunin-Nikol'ski206-1206-1206-1discotheca

If A is a bounded linear multicyclic operator acting on a complex Banach spaceX, then thedisc of A is defined by: disc A = sup(R ∈ Cyc A) min{dimR′: R′ ? R, R′ ∈ Cyc A}, where Cyc A denotes the family of all finite dimensional subspacesR ofX such that X = (R+AR+A ² R+?)^?. It is shown that if the set {λ ∈ ?: dim ker (λ-A)^* ≥ n} has nonempty interior (in particular, if A is a Fredholm operator of index -n), then disc A ≥ n+1. This result affirmatively answers a question of V.I. Vasjunin and N.K. Nikol'skiï. In the case whenX is a Hilbert space, it is shown that the set of all operators A such that A is n-multicyclic, but disc A =∞, is dense in the set of all n-multicyclic operators. If M_λ = "multiplication by λ" acting on the disk algebra (and many other spaces of continuous and/or analytic functions), then M_λ is cyclic, but disc M_λ = ∞. However, the analogous result is false if the disk algebra is replaced by the algebra of functions analytic on the disk and smooth on the boundary, or algebras of Lipschitz functions. If T is a multicyclic unicellular operator, then T is cyclic and disc T=1.     

Analysis of native carotenoid composition in orange juice using C30 columns in tandem

In the present contribution, a novel analytical approach based on using serial coupled conventional LC columns is proposed to the study of the native carotenoid composition of orange juice. The great difficulties that are found when analyzing complex carotenoid samples, due to the high natural variability of these compounds as well as to the presence of carotenoid esters are well documented. To overcome some of these limitations, we have developed a methodology including the study of both the saponified and the intact sample by means of two different LC-DAD/APCI-MS methods. The increase in the resolution and separation power obtained when using two serial coupled C(30) columns is demonstrated, and significant increases in peak capacity have been achieved. By using this new methodology, 44 different carotenoids have been tentatively identified. Among them, several violaxanthin diesters have been directly identified in orange juice for the first time. The main carotenoids in orange juice were violaxanthin, lutein, luteoxanthin, 9-cis-antheraxanthin, and beta-cryptoxanthin. Some of them were found in both their free and esterified forms. To the best of our knowledge, this is the first application of serial couplings of C(30) columns for the identification of the native carotenoid composition of natural matrices.     

On the mechanism and kinetics of radical reactions of epoxyketones and epoxynitriles induced by titanocene chloride

The reactions of a series of epoxynitriles and epoxyketones induced by titanocene chloride have been studied. The kinetics of the decyanogenation of beta,gamma-epoxynitriles with Ti(III) corresponds to a radical reaction (k25 approximately 106 s-1), as demonstrated by competition experiments with H-transfer from 1,4-cyclohexadiene (1,4-CHD) or PhSH or conjugate addition to acrylonitrile. The 5-exo cyclization onto nitrile induced by Ti(III) is a radical reaction (k25 approximately 107 s-1) as seen in competition experiments with H-transfer from PhSH or the titanocene-water complex. The iminyl or alkoxyl radicals generated by 5-exo cyclization onto nitriles or ketones only undergo a reduction with Ti(III). This reaction overwhelms any alternative process, such as tandem cyclization onto alkenes or beta-scission. Iminyl radicals generated by 4-exo cyclizations onto nitriles undergo reduction with Ti(III) and beta-scission reaction in a ratio of 96:4 when the alpha-substituent is CN. Alkoxyl radicals from 4-exo cyclizations onto ketone carbonyls undergo reduction with Ti(III) and beta-scission in a ratio of 60:40 when the alpha-substituent is COOR. In nearly all the reactions studied, the role of Ti(III) is triple: a radical initiator (homolytic cleavage of oxirane), a Lewis acid (coordination to CN or C=O), and a terminator (reduction of iminyl or alkoxyl radicals).     

Solvent-free thermal and microwave-assisted [3 + 2] cycloadditions between stabilized azomethine ylides and nitrostyrenes. An experimental and theoretical study

The stereochemical outcomes observed in the thermal and microwave-assisted [3 + 2] cycloaddition between stabilized azomethine ylides and nitrostyrenes have been analyzed using experimental and computational approaches. It has been observed that, in the absence of solvent, three stereoisomers are formed, both under classical heating conditions and under microwave irradiation. This result contrasts with that observed in solution under classical thermal conditions. The 4-nitropyrrolidines obtained in this way can be aromatized under further microwave irradiation to yield mixtures of pyrroles and 4-nitropyrroles. It is found that ground state cycloadditions between imines and nitrostyrenes take place by three-step mechanisms. The first step involves enolization of the starting imine, and this is followed by a pseudopericyclic 10-electron [1.4]-hydrogen shift. Finally, the cycloaddition takes place by a relatively asynchronous aromatic six-electron supra-supra thermal mechanism.     

Ion chemistry in cold plasmas of H2 with CH4 and N2

The distributions of ions and neutrals in low-pressure (approximately 10(-2) mbar) DC discharges of pure hydrogen and hydrogen with small admixtures (5%) of CH(4) and N(2) have been determined by mass spectrometry. Besides the mentioned plasma precursors, appreciable amounts of NH(3) and C(2)H(x) hydrocarbons, probably mostly from wall reactions, are detected in the gas phase. Primary ions, formed by electron impact in the glow region, undergo a series of charge transfer and reactive collisions that determine the ultimate ion distribution in the various plasmas. A comparison of the ion mass spectra for the different mixtures, taking into account the mass spectra of neutrals, provides interesting information on the key reactions among ions. The prevalent ion is H3+ in all cases, and the ion chemistry is dominated by protonation reactions of this ion and some of its derivatives. Besides the purely hydrogenic ions, N(2)H+, NH(4)+, and CH(5)+ are found in significant amounts. The only mixed C/N ion clearly identified is protonated acetonitrile C(2)H(4)N+. The results suggest that very little HCN is formed in the plasmas under study.