Temperature jump induction of isomerization dynamics of alkali halide clusters

The time resolved dynamics of diffusionless cube → ring isomerization of the Na₄Cl₄ cluster was interrogated by constant energy molecular dynamics simulations, utilizing the first passage time method. The nonreactive isomerization induced by nonselective vibrational excitation is well accounted for in terms of the statistical RRK theory, opening avenues for experimental exploration of time-resolved cluster isomerization dynamics.     

Soliton chaos and lengthscale competition in nonlinear dynamics

Perturbing soliton-bearing completely integrable dynamics can give rise to rich and fascinating behaviour. If the perturbation introduces a lengthscale which is large compared to the spatial extent of the solitons present in the system, the solitons move like particles in an effective potential. Taking into account two-soliton interaction can result in chaotic behaviour called ‘soliton chaos’. In the opposite limit of a small-lengthscale perturbation the solitons acquire a dressing which effectively shields them from the perturbation. If the resulting ‘dressed solitons’ are subject to an additional long-wavelength perturbation they move like renormalised particles. Furthermore they can scatter nearly elastically. If the perturbation contains lengthscales which are comparable to one of the soliton's typical lengthscales then lengthscale competition can occur. Neither the particle approximation nor the dressed-particle approximation for the soliton is valid and complicated spatio-temporal behaviour is observed. We illustrate this scenario by means of the perturbed nonlinear Schrödinger equation. The perturbed sine-Gordon equation and the Ablowitz-Ladik equation are also discussed.     

The Photochemical Synthesis of Fine Chemicals with Sunlight

The light of the sun can be used directly for changing chemical structures photochemically. Any industrial application must conform to the limitations imposed by the spectral distribution of the photons from the sun, the interruptions to the radiation due to the day/night rhythm, and the weather. In this review, we describe the photochemical potential of the sun, give a fundamental treatment of the concept of photoreactors driven by sunlight (abbreviated to solar photoreactors), and give an account of the realization of this concept in the first pilot plant on the “Plataforma Solar de Almeria” in southern Spain and in other activities in this field. Based on experimental data from photochemical investigations on the pilot plant scale, possibilities, limitations, and the potential growth of solar photochemistry are described. Solar photochemistry, in our opinion, is a technique which could make a contribution to the chemistry of the future because of its photochemical synthesis potential, the avoidance of waste products, and the direct utilization of the sun, not only as a primary energy source, but also as a reaction partner.     

The Nature of the vibronic intensity borrowing mechanism in the 1B3u(n)1Ag(X) transition of pyrazine

The transition intensities of the S₀S₁ gas phase absorption spectra of pyrazine-d₀ and -d₄ were carefully measured. A discussion of the various aspects of vibronic intensity borrowing for this unique case is presented using our new experimental results.     

Substituenteneffekte auf die C–C-Bindungsstärke, 8. Standardbildungsenthalpien und Spannungsenthalpien von 1,1,2,2-Tetraethylethylenglykol-dimethylether und D,L-1,2-Dimethyl-1,2-diphenylethylenglykol-dimethylether

Effects of Substituents on the Strength of C - C Bonds, 8¹. - Heats of Formation and Strain of 1,1,2,2-Tetraethylethylene Glycol Dimethyl Ether and D,L .-1,2-Dimethyl-l,2-diphenylethylene Glycol Dimethyl Ether The heats of combustion of the title compounds 1 and 2 were measured calorimetrically with the result (kcal mol ^-1, s. d. in parentheses) ΔH°_c = − 1880.1 (± 0.6) and − 2373.3 (± 1.4). The heat of vaporisation of 1 ΔH^v = 14.3 (± 0.3) and the heat of sublimation of 2 ΔH^sub = 27.2 (± 0.5) were derived from their temperature dependance of the vapor pressure. The latter were determined between 30 and 80°C using a flow method. The resulting standard heats of formation ΔH°_t(g) = −122.4 (± 0.7) and −43.8 (±1.5) for 1 and 2 correspond to a strain enthalpy (_s) of 15.9 and 8.0 kcal mol^-1, respectively. The steric strain of the dimethoxyethanes 1 and 2 is about one fourth lower than the strain of the corresponding dimethylethanes 3 and 4 bearing the same substituents. Thus, a methoxy group causes less steric stress than a methyl group.     

Zur Kenntnis der Reaktionen von Carbonsäurechloriden in Lösungsmitteln mit Wolle

Zusammenfassung Wolle und-Keratose wurden mit Carbonsäure-chloriden in Dimethylsulfoxid mit Pyridinzusatz oder ohne Base bei 20–60 °C bis zu 4 Stunden umgesetzt. Die dabei eintretende Vernetzungsreaktion beruht auf der Bildung von Formaldehyd aus den Säurechloriden und Dimethylsulfoxid. Damit werden auch die Anafysendaten verständlich: geringe Gewichtsänderungen, Beteiligung des Lysins, keine Beteiligung der Carboxylgruppen, Verschwinden des Tyrosins erst nach saurer Totalhydrolyse. Läßt man Acylchloride in Dimethylformamid, Dimethylacetamid, Hexamethyl-phosphorsäuretriamid,-Butyrolacton und Methyl-pyrrolidon auf Wolle einwirken, so erfolgt N,O-Acylierung unter Gewichtszunahme.

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Summary Wool and -Keratose were reacted at 20–60° for 4 hours with acylchlorides in dimethylsulfoxide with addition of pyridine or without a base. The ensuing crosslinking reaction. was due to formation of formaldehyde by reaction of the acid chlorides with the solvent dimethylsulfoxide. This explains the analytical data found: small weight changes participation of lysine, no participation of the carboxylic groups, disappearance of tyrosine during the acid hydrolysis.If the acyl chlorides are reacted with wool in the solvents dimethylformamide, dimethylacetamide, hexamethyl-phosphortriamide,-butyrolacton and methyl-pyrrolidone, normal acylation and corresponding weight increases were found.

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Teil der DissertationH.-D. Scharf, RWTH Aachen, 1972; 21. Mitteilung über ,Reaktivität von Aminosäureseitenketten. 20. Mitteilung vgl.W. Wellner, D. Nissen und H. Zahn, Colloid u. Polymer Sci.255, 444 (1977).

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Jetzt Dynamit-Nobel AG., Troisdorf.

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Jetzt Wella AG, Darmstadt.

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Mit 4 Abbildungen und 8 Tabellen     

Prerequisites for peptidomic analysis of blood samples: II. Analysis of human plasma after oral glucose challenge -- a proof of concept

Mass spectrometric plasma analysis for biomarker discovery has become an exploratory focus in proteomic research: the challenges of analyzing plasma samples by mass spectrometry have become apparent not only since the human proteome organization (HUPO) has put much emphasis on the human plasma proteome. This work demonstrates fundamental proteomic research to reveal sensitivity and quantification capabilities of our Peptidomics technologies by detecting distinct changes in plasma peptide composition in samples after challenging healthy volunteers with orally administered glucose. Differential Peptide Display (DPD) is a technique for peptidomics studies to compare peptides from distinct biological samples. Mass spectrometry (MS) is used as a qualitative and quantitative analysis tool without previous trypsin digestion or labeling of the samples. Circulating peptides (< 15 kDa) were extracted from 1.3 mL plasma samples and the extracts separated by liquid chromatography into 96 fractions. Each fraction was subjected to MALDI MS, and mass spectra of all fractions were combined resulting in a 2D-display of > 2,000 peptides from each sample. Endogenous peptides that responded to oral glucose challenge were detected by DPD of pre-and post-challenge plasma samples from 16 healthy volunteers and subsequently identified by nESI-qTOF MS. Two of the 15 MS peaks that were significantly modulated by glucose challenge were subsequently identified as insulin and C-peptide. These results were validated by using immunoassays for insulin and C-peptide. This paper serves as a proof of principle for proteomic biomarker discovery down to the pM concentration range by using small amounts of human plasma.