The Thermodynamic Influence of Trapped Water Molecules on a Protein–Ligand Interaction

Water molecules doing time : Atomic‐resolution crystal structures of the PPIase domain of cyclophilin G, alone and in complex with cyclosporin A, and together with MD simulations and calorimetry, reveal how trapped water molecules influence the thermodynamic profile of a protein–ligand interaction.

     

Comparison of different separation technologies for proteome analyses: isoform resolution as a prerequisite for the definition of protein biomarkers on the level of posttranslational modifications

In this article we evaluate methods used to reveal the molecular complexity, which is generated in biological samples by posttranslational modifications (PTM) of proteins. We show how distinct molecular differences on the level of phosphorylation sites in a single protein (ovalbumin) can be resolved with different success using 1D and 2D gel-electrophoresis and reversed-phase liquid chromatography (LC) with monolithic polystyrol-divinylbenzol (PS-DVB) columns for protein separation, and matrix-assisted laser desorption ionisation-time of flight mass spectrometry (MALDI-TOF MS) for protein identification. Phosphorylation site analysis was performed using enzymatic dephosphorylation in combination with differential peptide mass mapping. Liquid chromatography-MALDI-TOF MS coupling with subsequent on-target tryptic protein digestion turned out to be the fastest method tested but yielded low resolution for the analysis of PTM, whereas 2D gel-electrophoresis, due to its unique capability of resolving highly complex isoform pattern, turned out to be the most suitable method for this purpose. The evaluated methods complement one another and in connection with efficient technologies for differential and quantitative analysis, these approaches have the potential to reveal novel molecular details of protein biomarkers.     

Statistical model for the effects of phase and momentum randomization on electron transport

In this paper, the study of epidemic spreading of mobile individuals on networks focuses on the system in which each node of the network may be occupied by either one individual or a void, and each individual could move to a neighbour void node. It is found that for the susceptible-infected-susceptible (SIS) model, the diffusion increases the epidemic threshold for arbitrary heterogeneous networks having the degree fluctuations, and the diffusion doesn??t affect the epidemic threshold for regular random networks. In the SI model, the diffusion suppresses the epidemic spread at the early outbreak stage, which indicates that the growth time scale of outbreaks is monotonically increasing with diffusion rate d. The heterogeneous mean-field analysis is in good agreement with the numerical simulations on annealed networks.     

Zur Kristallographie von Doppelsalzen aus Calciumsulfat und Natriumsulfat

In the course of investigating a special slurry problem in the Na₂SO₄ production metastable double salts of calcium sulphate and sodium sulphate were detected (Emons, Stegmann). In this paper it is reported on the properties of these compounds and their decomposition products, determined by microscopic, X-ray, thermoanalytic, and IR-spectroscopic methods.     

ESR- und ENDOR-Untersuchungen an Catecholaminen und deren Metaboliten als paramagnetische Thallium-Komplexe

Zusammenfassung Semichinonradikale, die sich von Catecholaminen und ihren Metaboliten ableiten, können leicht durch Autoxidation mit Hilfe der Spinstabilisierungsmethode dargestellt werden. Die Radikale zeigen charakteristische ESR- und ENDOR-Spektren. Die Vorzeichen der Kopplungskonstanten wurden für einige Schlüsselverbindungen durch TRIPLE-Resonanz-Experimente bestimmt. Mit Hilfe der Vorzeichen konnten eindeutige Zuordnungen der Kopplungsparameter vorgenommen werden. Die ESR-Signale zeigen eine starke Abhängigkeit von der Seitenkette, die Beträge der Kopplungen und ihre Temperaturabhängigkeit weisen bei einigen Verbindungen auf gehinderte Rotation hin. Die untersuchten Semichinone können aufgrund ihrer ESR-Daten zur Charakterisierung und zum Nachweis der ihnen zugrundeliegenden Brenzcatechine herangezogen werden. Wegen der großen Empfindlichkeit der ESR-Methode ist der Substanzbedarf gering. Im allgemeinen reicht 1 ml einer 10^–4 molaren Lösung aus, um gut aufgelöste und damit interpretierbare Spektren zu erhalten. Der ESR-spektroskopische Nachweis von Catecholaminen kann auch dann durchgeführt werden, wenn die Wirkstoffe als Arzneimittelzubereitungen vorliegen, ohne daß vorher Trenn- oder Reinigungsoperationen durchgeführt werden müssen. Brenzcatechinmethylether lassen sich ebenfalls mit der ESR-Methode nachweisen, wenn vorher eine Etherspaltung mit Hilfe von Bortribromid durchgeführt wird.

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ESR and ENDOR investigations of catecholamines and their metabolites as paramagnetic thallium complexes

Summary Semiquinone radicals deriving from catecholamines and related catechols generated smoothly by autoxidation in organic solvents have been studied using the spinstabilization technique. The semiquinones have distinctive ESR and ENDOR spectra. The signs of the coupling constants were determined by TRIPLE resonance experiments for several radicals, and, therefore, an unambiguous assignment of the proton couplings could be done. The spectra are strongly influenced by the side chain, reflecting restricted rotation of the methylene protons in some cases. For this reason a characterization and identification of the investigated catechols by electron-spin resonance is possible. According to the pronounced sensitivity of this method, usually 1 ml of a 10^–4 molar solution was used to obtain well resolved ESR spectra. The semiquinones may likely be detected if the catechols are ingredients of complex mixtures, for example drugs, without any separation or purification operations. Catecholmethylethers may be examined by ESR spectroscopy as well if the ether has been cleaved with borontribromide before the radicals were generated.

     

INVESTIGATION OF DAMAGE TO FOREST BY EPR SPECTROSCOPY in vivo

Spruce needles collected from several trees of the Black Forest were investigaled by EPR spectroscopy. These needles show in the g = 2.00 region a signal II_S(Tyr D ₊) and a light-induced signal I(P700₊) and a Mn₂₊ hyperfine structure which superimposes the other absorptions. Difference spectra, light minus dark, partly eliminate the manganese hyperfine structure, and P700₊ can be observed. By comparison of these EPR signals with those of spinach chloroplast or thylakoid membranes described in the literature, significant deviations were observed, whereas several trees grown in the vicinity of Tubingen exhibit the well known D₊ and P700₊ EPR spectra. After treatment of branches of these 'normal' trees with herbicides like Amitrol and Roundup or chemicals like toluene or trichlormethane the EPR signals obtained are comparable with those observed with needles of the Black Forest.