Sequence dependence of secondary-structure formation part IV Helix-forming potential of amphiphilic oligopeptides containing aib residues

The conformational properties of Aib-containing oligopeptides having the propensity to adopt amphiphilic helical conformations were investigated by CD spectroscopy in solution. The peptides CF₃COOH.H-Pro-Glu-[Ala-Aib-Glu-Aib-]₄Gly-OH ( I ), HCl.H-Pro-Ala-Aib-[Gul-Ala-Ala-Aib-]₂Glu-Ala-Aib-Gly-PEGM ( II ), and CF₃COOH.H-Ala-Aib-[Glu-Glu-Ala-Aib-]₃PEGM ( III ) were synthesized according to the general principles of the liquid-phase method for peptide synthesis. Peptides I-III exhibit helical conformations in CF₃CH₂OH, MeOH, and in H₂O at acidic pH; however, at pH 7, only II forms a stable helix, whereas I and III are predominantly in an unordered conformation. Some general features for the construction of amphiphilic helices are discussed in the light of the experimental data.     

Prediction of humic acid content and respiration activity of biogenic waste by means of Fourier transform infrared (FTIR) spectra and partial least squares regression (PLS-R) models

Fourier transform infrared (FTIR) spectroscopy has been proven to be an appropriate analytical method for the qualitative assessment of compost stability. This study focuses on quantitative determination of two time-consuming parameters: humic acid (HA) contents and respiration activity. Reactivity/stability and humification were quantified by respiration activities (oxygen uptake) and humic acid contents. These features are also reflected by a specific infrared spectroscopic pattern. Based on this relationship partial least squares regression (PLS-R) models for the prediction of respiration activities and humic acid contents were calculated. Characteristic wavenumber regions that are assigned to the biological/chemical parameter were selected for multivariate data analysis. The coefficient of determination (R²) obtained for the humic acid prediction model from infrared spectra was 87% with a root mean square error of cross-validation (RMSECV) of 2.6% organic dry matter (ODM). The prediction model for respiration activity resulted in a R² of 94% and a RMSECV for oxygen uptake of 2.9 mg g⁻¹ dry matter (DM).     

Synthesis of ‘Pear Ester’. A novel synthesis of 2,4-diolefinic aldehydes and esters

Vinylogous epoxyaldehydes undergo stereospecific Wittig condensations in high yields. The resulting diolefinic epoxides are cleaved at the C(1)–C(2) single bond, when treated with periodic acid, to give the corresponding aldehydes. Direct transformation into the corresponding ethyl-ester leads to an efficient synthesis of the ‘pear ester’.     

4a,6-Bis-(N-methlanilino)-7-hydroxy-2,3,8-trimethyl-4a,9a-dihydro-xanthen-1,4-dion: Ein thermolyseprodukt von 6-(N-methylanilino)-7a-methyl-3a,7a-dihydroindazol-4,7-dion

Summary 4a,6-Bis-(N-methylanilino)-7-hydroxy-2,3,8-trimethyl-4a,9a-dihydro-xanthene-dione (4) was obtained by thermolysis of 6-(N-methylanilino)-7a-methyl-3a,7a-dihydroindazol-4,7-dione (1) The structure was determined on basis of 1D- and 2D-NMR techniques.Herrn Prof. Dr. G. Zigeuner zum 70. Geburtstag gewidmet     

Fluordiazadiphosphetidine, 5. Mitt.

Reaction of (CH₃NPF₃)₂ with equimolar amounts of N-methylhexamethyldisilazane yields a reaction product, which can be separated in a polymer and a crystalline fraction. High-vacuum sublimation of the crystalline part yields the already known compound (CH₃N)₄P₃F₇, the new spiro-isomer F₃P(CH₃N)₂PF(CH₃N)₂PF₃ and the spiro-compound F₃P(CH₃N)₂PF(CH₃N)₂PF(CH₃N)₂PF₃, an isomer of the known compound (CH₃N)₆P₄F₈.     

Analysis of highly polar compounds in groundwater samples from ammunition waste sites. Part I-Characterization of the pollutant spectrum

Five groundwater samples from the former ammunition production site at Elsnig, Germany, were analyzed for highly polar components by LC-NMR and LC-MS. A variety of unknown pollutants could be identified. Possibilities and limitations of the combined use of LC-NMR and LC-MS techniques for on-line identification are discussed. Further unknown components were identified through isolation by HPLC cuts and off-line NMR and MS investigations. Most of the polar compounds in the investigated samples could also be quantified.     

Finite size effects at thermally-driven first order phase transitions: A phenomenological theory of the order parameter distribution

We consider the rounding and shifting of a firstorder transition in a finited-dimensional hypercubicL ^d geometry,L being the linear dimension of the system, and surface effects are avoided by periodic boundary conditions. We assume that upon lowering the temperature the system discontinuously goes to one ofq ordered states, such as it e.g. happens for the Potts model ind=3 forq3, with the correlation length of order parameter fluctuation staying finite at the transition. We then describe each of theseq ordered phases and the disordered phase forL by a properly weighted Gaussian. From this phenomenological ansatz for the total distribution of the order parameter, all moments of interest are calculated straight-forwardly. In particular, it is shown that forL exceeding a characteristic minimum sizeL _min the forthorder cumulantg _L (T) exhibits a minimum atT _min>T _c, withT _min–T _cL ^–d and the value of the cumulant and the minimum (g(T _min)) behaving asg(T _min)L ^–d. All cumulantsg _L (T) forL approximately intersect at a common crossing pointT _crossL ^–2d, with a universal valueg(T _cross)=1–n/2q, wheren is the order parameter dimensionality. By searching for such a behavior in numerical simulation data, the first order character of a phase transition can be asserted. The usefulness of this approach is shown using data for theq=3,d=3 Potts ferromagnet.     

Production of large sodium clusters (Nax,.x⩽65) by seeded beam expansions

Seeded beam expansions of high-temperature sodium vapour in helium, neon, argon, krypton and nitrogen carrier gases are examined. Photoionization coupled with mass spectroscopic detection is used to determine beam constituents. Contrary to non-seeded supersonic expansions, in which the abundance of sodium clusters observed decreases exponentially with increasing cluster size, large abundances of higher clusters (Na_x, x ?65) are observed. Maxima centered at m/z = 161, m/z = 437 and m/z = 874 occur under certain conditions.     

Kolorimetrische Schnellbestimmung der Kristallviolettbase (KVB)

Zusammenfassung Es wird eine Methode zur kolorimetrischen Bestimmung der Kristallviolettbase in benzolischen Lösungen beschrieben. Das Prinzip gründet sich auf der Salzbildung der farblosen Base mit der ebenfalls in Benzol löslichen Pikrinsäure. Dabei resultiert das tief blauviolett gefärbte KV-Pikrat, dessen Konzentration mit dem Spektralphotometer ermittelt wird.Mit 4 Abbildungen     

Structure d'alcaloïdes indoliques doubles d'un type nouveau

The Structure of bis-indoline alkaloids of a novel type The structure of folicangine 4 , a bis-indoline alkaloid from the leaves of Voacanga africana, is obtained by correlation with voafolidine 3a and isovoafolidine 3b . It requires an ether bridge between the two parts of the molecule, as in subsessiline (amataine 5a ). Subsessiline-lactone, from the leaves of Voacanga thouarsii has structure 5b proved by correlation with 5a . The CD. curves of double-indole alkaloids of vobtusine type are given (Table 3).