Biochemie und Chemie
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Cryo-electron tomography (cryo-ET) is a powerful method to elucidate subcellular architecture and to structurally analyse biomolecules in situ by subtomogram averaging (STA). Specimen thickness is a key factor affecting cryo-ET data quality. Cells that are too thick for transmission imaging can be thinned by cryo-focused-ion-beam (cryo-FIB) milling. However, optimal specimen thickness for cryo-ET on lamellae has not been systematically investigated. Furthermore, the ions used to ablate material can cause damage in the lamellae, thereby reducing STA resolution. Here, we systematically benchmark the resolution depending on lamella thickness and the depth of the particles within the sample. Up to ca. 180 nm, lamella thickness does not negatively impact resolution. This shows that there is no need to generate very thin lamellae and thickness can be chosen such that it captures major cellular features. Furthermore, we show that gallium-ion-induced damage extends to depths of up to 30 nm from either lamella surface.
The trifluoroacetylation of thymidine at room temperature was performed using trifluoroacetic acid phenylester in pyridine. A selective protection of the 5′-position was not possible: Even low molar quantities of the trifluoroacetylating agent gave rise to bis-trifluoroacetylation. The bis-trifluoroacetyl derivatives of thymidine and 5-bromo-deoxyuridine were purified by vacuum sublimation. The completely trifluoroacetylated deoxyribosides of uracil, 5-iodouracil and adenine underwent decomposition during sublimation.
The non-specific inhibition of the poly U directed polymerisation of phenylalanine through polyanions was studied. This inhibition was found to be in order as follows: dextransulfate, polyethylensulfate, heparine, ribosomal RNA and alginate. It was found that poly A, poly AP and poly AG cause a specific inhibition of the poly U directed synthesis of polyphenylalanine. Poly AG and poly AP, but not poly A were found to inhibit the poly C directed polymerisation of proline as well. The mechanism of these two types of inhibition caused by polyanions has been discussed.
HER2 belongs to the ErbB sub-family of receptor tyrosine kinases and regulates cellular proliferation and growth. Different from other ErbB receptors, HER2 has no known ligand. Activation occurs through heterodimerization with other ErbB receptors and their cognate ligands. This suggests several possible activation paths of HER2 with ligand-specific, differential response, which so far remained unexplored. Using single-molecule tracking and the diffusion profile of HER2 as a proxy for activity, we measured the activation strength and temporal profile in live cells. We found that HER2 is strongly activated by EGFR-targeting ligands EGF and TGFα, yet with a distinguishable temporal fingerprint. The HER4-targeting ligands EREG and NRGβ1 showed weaker activation of HER2, a preference for EREG and a delayed response to NRGβ1. Our results indicate a selective ligand response of HER2 that may serve as a regulatory element. Our experimental approach is easily transferable to other membrane receptors targeted by multiple ligands.
Highlights
HER2 exhibits heterogeneous motion in the plasma membrane
The fraction of immobile HER2 correlates with phosphorylation levels
Diffusion properties serve as proxies for HER2 activation
HER2 exhibits ligand-specific activation strength and temporal profiles
HER2 belongs to the ErbB sub-family of receptor tyrosine kinases and regulates cellular proliferation and growth. Different from other ErbB receptors, HER2 has no known ligand. Activation occurs through heterodimerization with other ErbB receptors and their cognate ligands. This suggests several possible activation paths of HER2 with ligand-specific, differential response, which has so far remained unexplored. Using single-molecule tracking and the diffusion profile of HER2 as a proxy for activity, we measured the activation strength and temporal profile in live cells. We found that HER2 is strongly activated by EGFR-targeting ligands EGF and TGFα, yet with a distinguishable temporal fingerprint. The HER4-targeting ligands EREG and NRGβ1 showed weaker activation of HER2, a preference for EREG, and a delayed response to NRGβ1. Our results indicate a selective ligand response of HER2 that may serve as a regulatory element. Our experimental approach is easily transferable to other membrane receptors targeted by multiple ligands.
HER2 belongs to the ErbB sub-family of receptor tyrosine kinases and regulates cellular proliferation and growth. Different from other ErbB receptors, HER2 has no known ligand. Activation occurs through heterodimerization with other ErbB receptors and their cognate ligands. This suggests several possible activation paths of HER2 with ligand-specific, differential response, which so far remained unexplored. Using single-molecule tracking and the diffusion profile of HER2 as a proxy for activity, we measured the activation strength and temporal profile in live cells. We found that HER2 is strongly activated by EGFR-targeting ligands EGF and TGFα, yet with a distinguishable temporal fingerprint. The HER4-targeting ligands EREG and NRGβ1 showed weaker activation of HER2, a preference for EREG, and a delayed response to NRGβ1. Our results indicate a selective ligand response of HER2 that may serve as a regulatory element. Our experimental approach is easily transferable to other membrane receptors targeted by multiple ligands.
Cells maintain membrane fluidity by regulating lipid saturation, but the molecular mechanisms of this homeoviscous adaptation remain poorly understood. Here, we have reconstituted the core machinery for sensing and regulating lipid saturation in baker’s yeast to directly characterize its response to defined membrane environments. Using spectroscopic techniques and in vitro ubiquitylation, we uncover a unique sensitivity of the transcriptional regulator Mga2 to the abundance, position, and configuration of double bonds in lipid acyl chains and provide unprecedented insight into the molecular rules of membrane adaptivity. Our data challenge the prevailing hypothesis that membrane viscosity serves as the measured variable for regulating lipid saturation. Rather, we show that the signaling output of Mga2 correlates with the size of a single sensor residue in the transmembrane helix, which senses the lateral pressure and/or compressibility profile in a defined region of the membrane. Our findings suggest that membrane property sensors have evolved remarkable sensitivities to highly specific aspects of membrane structure and dynamics, thus paving the way toward the development of genetically encoded reporters for such membrane properties in the future.
Pyrosulfonyldifluoride reacts with waterfree hydrazine in a molar ratio of 2 : 3 to give hydrazine -1,2-bis(sulfonylfluoride) in a low yield.. The reaction of N-fluorosulfonylamide and SOCl2 yields NH4⊕⊖ N(SO2F)2. This salt is converted to (C6H5)4P⊕⊖N(SO2F)2 in water by (C6H5)4PCl. (CH3)2NNH2 reacts with PSF3, PSF2Br, PSF2CH3 or PSF2C2H5 to yield the following compounds: (CH3)2NNHPSF2, (CH3)2NN (PSF2)2, (CH3)2NNHPSFCH3 and (CH3)2NNHPSFC2H5. The properties and the chemical behaviour of these substances are described. Results of ir-spectra, as well as 31P-, 19F- and 1H-nmr- and mass-spectra and elemental analysis characterize the compounds.
S4N3Cl reacts with sulfonic acids and imido- bissulfonyl derivatives under HCl-evolution to the following compounds: S4N3SO3CF3, S4N3N (SO2F)2, S4NSO3CH3HSO3CH3, S4N3N (SO2CF3) SO2Cl and S4N3N (SO2CF3) SO2F, They are yellow solids which decompose when heated below the melting point. The compounds are formed in nearly quantitative yield and have been characterized by elemental analysis, nmr and electronic spectra.
The reversible one-electron insertion into mono- and 1,4-di-substituted benzene derivatives is favored by dialkoxyboron and especially by dialkylboron groups. The assumption that it should be the symmetric e2u benzene molecular orbital which is occupied in the resulting radical anions can be supported by comparison of ESR coupling constants.
Hemoproteinoids related to contemporary porphyrin-dependent peroxidases were synthesized under simple conditions. The peroxidative activity of hematin increased by a factor of 50 if the hematin was bound to proteinoids whereas the catalatic activity of hematin decreased rather under the same conditions. The peroxidative activity of hemoproteinoids particularly increased with their lysine content whereas the catalatic activity especially decreased in proteinoids with high phenylalanine content. The isoelectric points of the lysine-rich peroxidic hemoproteinoids were about 8. Their relatively broad pH-activity optimum was about pH 7.0. The molecular weights were a little below 20 000. Hematin content and amino acid composition of the synthetic materials were varied greatly. The substrate specificity appeared as broad as that of biogenous peroxidases, e. g., horseradish peroxidase. Among the many substrates was NADH. The possible importance of the peroxidative oxidation of NADH-type coenzymes by primitive heterotrophic organisms or prebiological systems in an anaerobic environment is discussed.
Li6UO6 has a reversible phase transformation at 680°C and decomposes above about 850°C. At high pressure the low temperature modification becomes unstable because of an invariant point in the system Li2O—Li4UO5 at approximately 13 Kb and 620°C. β-Li6UO6 has a triclinic unit cell with a = 5.203, b= 5.520, c = 5.536 Å, α = 114.7, β = 120.7 and γ = 75.5°. The close relationship between the crystal structures of Li6TeO6 and Li6UO6 is also suggested from similar infrared spectra and from partial solid solution Li6UO6—Li6TeO6.
The interactions between human haptoglobin, Hp II (genetic types 2 - 1 and 2-2), and bovine hemoglobin, Hb, were investigated taking inhibition of complex formation and complex dissociation in various solvent media as criteria.
As shown by relative peroxidase activity and gel chromatography, complex dissociation occurs at high concentrations of guanidine HCl, urea, sodium chloride, dioxane, and formaldehyde, while in case of sodium dodecylsulfate a low molar ratio (SDS/Hb -Hp<5) is sufficient to split the complex. In general the formation of the complex stabilizes the structure of its constituents.
Excluding solvent conditions which lead to denaturation (as measured by optical rotation), ionpairs and H-bonds seem to prevail in the stabilization of the complex, while hydrophobic interactions should be of minor importance. Chemical modification of histidine and tyrosine with diazonium-1-H-tetrazole and N-acetylimidazole, respectively, prove histidyl-groups in Hb and tyrosylgroups in Hp to participate in the Hb-Hp contact, thus confirming earlier results.
Fluorescense spectra of lactate dehydrogenase * (E.C. 1.1.1.27) were investigated in the presence of the coenzyme fragments dihydronicotinamide mononucleotide and dihydronicotinamide-ribose-5'-pyrophospho- (P2) -5“-ribose. The reduced mononucleotide is enzymatically less active as a hydrogen donor. However, formation of a complex with the enzyme was not observed under the conditions used. All the other substances: dihydronicotinamide-ribose-5'-pyrophospho- (P2) -5“-ribose, dihydronicotinamide- benzimidazole-dinucleotide, dihydronicotinamide-3-desazapurine-dinucleotide and dihydronicotinamide-6-mercaptopurine-dinucleotide form more or less stable complexes with lactate dehydrogenase. The complexes do not markedly differ from the complex formed with the natural cofactor. In all cases spectra indicate change in conformation of the coenzyme by forming the coenzyme-enzyme-complex which has been proposed by VELICK 1 too. The cysteine residues of the lactate dehydrogenase are not essential for binding the coenzyme to the active center; this was shown with mercury blocked enzyme.
It is possible to determine the anomeric configuration of nucleosides by a simple, spectrophotometric assay, using the nucleoside phosphorylase activity of cell-free extracts from E. coli. β-nucleo-sides are split, a-anomers remain unchanged. For a single estimation 20-40 µg of nucleoside are required. 6-Azauracil- and 8-azaguanine-β-ᴅ-riboside and some nucleoside phosphates are resistant, a fact, which is of interest in view of the specificity of nucleoside phosphorylases.
Gegenstand der vorliegenden Untersuchung ist das hydrolytische Verhalten von Glycyl-seryl-alanin beim Erhitzen in einer rein wäßrigen Lösung bei einem pH-Wert in der Nähe des isoelektrischen Punktes. Die Reaktionsmöglichkeiten des Tripeptids und aller Folgeprodukte, die Alanin enthalten, wurden qualitativ aufgeklärt und die kinetischen Daten der einzelnen Reaktionen durch quantitative Hydrolyseversuche an den mit dem Kohlenstoffisotop 14C geeignet radioaktiv markierten Verbindungen Glycyl-seryl-alanin, Seryl-alanin, Alanyl-serin und Seryl-alanyl-diketopiperazin bei mehreren Temperaturen zwischen 55 und 95 °C bestimmt. Die Trennung der Hydrolysatproben erfolgte mit Hilfe der Papierchromatographie bzw. der Papierelektrophorese; für die Konzentrationsbestimmung der radioaktiven Substanzen wurde ein Verfahren ausgearbeitet, das eine Radioaktivitätsmessung mit hoher reproduzierbarer Ausbeute direkt auf den zur Trennung benutzten Filterpapieren nach der Flüssigkeitsszintillations-Methode ermöglicht.
Alle beobachteten Reaktionen verlaufen unter den Versuchsbedingungen nach einem Zeitgesetz 1. Ordnung. Die Konzentrations-Zeit-Funktionen der einzelnen Reaktionsteilnehmer wurden durch Auflösung der simultanen linearen Differentialgleichungen 1. Ordnung bestimmt und zur Berechnung der Reaktionsgeschwindigkeits-Konstanten nach einem iterativen Ausgleichsverfahren herangezogen.
In der Diskussion wird versucht, die beobachteten thermodynamischen Daten in ihrer Größenordnung aus anderen Eigenschaften und aus der Molekularstruktur der einzelnen Verbindungen abzuleiten und durch bestimmte Reaktionsmechanismen zu interpretieren.
Zur Klärung der Frage nach der Beteiligung von Protein-Actinomycin (AMC) -Wechselwirkungen am antibiotischen Wirkungsmechanismus von AMC wurden mit Hilfe von Absorptions-, Fluoreszenz- und Rotationsdispersions-Spektroskopie, sowie Gelfiltration, Gleichgewichts-Dialyse, Ultrazentrifugation und enzymatischen Tests physikalisch-chemische Wechselwirkungen von AMC und Actinocinanalogen mit Ribonuclease, Serumalbumin und einigen SH-Enzymen (ADH, LDH, GAPDH) untersucht. Photochemische Reaktionen wurden ausgeschlossen.
Eine Bildung starker Komplexe wird nur bei pH < 2 beobachtet. Unter quasi-physiologischen Bedingungen des Mediums ergibt sich aus einer Differenzbande im Bereich der Phenoxazin-Absorption schwache Komplexbildung, die bei hohen Proteinkonzentrationen auch durch die gemeinsame Sedimentation von AMC und Protein bestätigt wird. Die Peptid-Lacton-Ringe des AMC und die aromatischen Aminosäuren der Proteine scheinen an der Wechselwirkung nicht beteiligt zu sein (Reaktion mit AMC-Dimeren, Null-Differenzspektrum bei λ ~ 280 mμ). Die Ähnlichkeit im Verhalten von Cystein, Glutathion und SH-Enzymen und der kompetitive Effekt von Cystein bei der AMC-Enzym-Wechselwirkung weisen auf eine Beteiligung von Cystein am Komplex hin.
Eine durch AMC bewirkte Desaktivierung oder Stimulierung von Ribonuclease wird nicht beobachtet. Dagegen tritt im Fall von SH-Enzymen im pH-Optimum eine dem molaren Verhältnis AMC/Enzym proportionale Desaktivierung auf, die durch DNA bzw. RNA nur z. T. aufgehoben wird. Konformationsänderungen sind dabei nicht nachweisbar; die optische Drehung erweist sich als additiv. „Extrinsic“ Cotton-Effekte treten nicht auf.
Die SH-Spezifität des Ribonuclease-Inhibitors legt in Analogie zu den untersuchten SH-Enzymen die Annahme nahe, daß eine AMC-Protein-Wechselwirkung (Blockierung des RNase-Inhibitors) am biologischen Wirkungs-Mechanismus des AMC beteiligt sein könnte.
The ribonucleic acid of reovirus was extracted with 2 M sodium perchlorate solution and spread by the protein monolayer technique. Areas of the monolayer were transferred to support films, rotary shadowed, and observed in the electron microscope. Filaments of RNA obtained by extraction prior to spreading were similar in appearance and in distribution of contour lengths (0.2 to 1.2 μ) to those obtained by phenol extraction of the virus. Most of the filaments resulting from extraction of the virus suspension during spreading on a sodium perchlorate solution, however, were longer than 1 μ. The lengths of the longest filaments exceeded the 5 μ length predicted from chemical data for one single piece of complementary-stranded RNA in the reovirus particle.
The short filaments, 1.2 μ and less in length, fell into a tri-modal pattern of length distribution with peaks at 0.35 μ, 0.60 μ and 1.10 μ. These shorter lengths probably resulted from breakage of the intact RNA during the extraction procedures. The consistently observed pattern of length distribution suggests that they represent relatively stable subunits of the molecule.
Sodium perchlorate extracted reovirus RNA was thermally denatured in formaldehyde prior to spreading by the protein monolayer technique. Length distributions and relative numbers of filaments in the peaks of the tri-modal distribution pattern were similar to those found for unheated material when extracted prior to spreading. This similarity indicates that heating subsequent to extraction produced no further filament breakage. The thin, kinky appearance of the heated filaments, and the appearance of congruent pairs, indicated that heating had separated the strands of the complementary-stranded RNA subunits.
The formation of aliphatic α-amino acids by X-ray induced carboxylation of simple amines or amination of simple carboxylic acids is not favored over the formation of other amino acids. The new carboxylic and amino groups are more or less distributed statistically over the carbon atoms of the starting material. On radiationchemical formation of aliphatic hydrocarbons over C3, therefore, an increasing amount of unusual amino acids is produced. The results are influenced by various parameters such as temperature, pH, concentration, linear energy transfer and total dosis of radiation applied. Also peptides can be formed radiationchemically. However, the formation of greater molecules by radiationchemical processes under the conditions of a primitive earth seems to have only a low probability. The reaction mechanisms of radiationchemical carboxylation and amination are discussed.
Lumineszenz von Hefe
(1968)
Mit äußerst fein dispergiertem 3.4-Benzpyren (=BP**) wurde seine Löslichkeit in Wasser und wäßrigen Nucleotidlösungen fluoreszenz-spektroskopisch neu bestimmt. Wir fanden, daß ATP deutlich größere lösungsvermittelnde Eigenschaften für BP besitzt als ADP oder AMP. Die gesättigte Lösung von BP in ATP-Lösung verliert bei Zugabe von ATP-ase ihre zusätzliche Lösungsvermittlung. Zwischen DNS und BP, jedoch nicht zwischen RNS und BP wird eine Energieübertragung nachgewiesen.
Wir versuchen, aus den Löslichkeitsunterschieden für BP in Nucleotidlösungen den gerichteten Transport des BP von den Mitochondrien zu den kernnahen Bereichen der Zelle über das ATP-Konzentrationsgefälle zwischen diesen Strukturen zu erklären. Die gelbgrüne Fluoreszenz, die sich nach Inkubation mit BP im endoplasmatischen Retikulum zeigt, wird auf kristallines oder dimerisiertes BP bzw. Reaktionsprodukte des Benzpyrenyl-Radikalkations mit nucleophilen Zellstrukturelementen zurückgeführt. Hieraus werden Blockierungs- und Störmodelle der DNS abgeleitet. Auf die Ähnlichkeit dieser Prozesse mit der carcinogenen Wirksamkeit indifferenter Phasengrenzflächen und alkylierender Agenzien wird hingewiesen und die Bedeutung der Symmetrieelemente der Carcinogene bei diesem Prozeß diskutiert.
Wäßrige Sephadex-Gele nehmen Vielfache der in Wasser gelösten Anteile polycyclischer, aromatischer Kohlenwasserstoffe auf, wenn diese als Suspension vorliegen. Beobachtbar ist dieser Effekt an der Erhöhung der Fluoreszenzintensität des gelösten Anteils der Aromaten bei Zugabe von Sephadex-Körnern und anschließender kräftiger Rührung. Verwertbar ist dieses Phänomen zumindest für die Ermittlung der Lage der Emissionsbanden der Kohlenwasserstoffe in Wasser, denn es bestehen nur geringe Unterschiede zwischen den Fluoreszenzsprektren in Sephadex und Wasser. Weiterhin ist beachtlich, daß die carcinogenen Kohlenwasserstoffe nach diesen ersten orientierenden Versuchen, zu einer Gruppe gehören, die eine geringe Diffusionsgeschwindigkeit in das Sephadex-Gel, bei gleichzeitigem Erreichen relativ hoher Endkonzentrationen, besitzen. Der Quotient aus beiden Größen wird daher für die Carcinogene maximal. Nach Desoxycholsäure, Detergentien, Purinen, Desoxynucleinsäuren, Adenosintriphosphat 24 und Proteinen wurde damit gefunden, daß auch Polysaccharid-artige Systeme in der Lage sind, Lösungs-vermittelnd auf Kohlenwasserstoffe in wäßriger Phase zu wirken.
Es verspricht daher, interessant zu werden, an Sephadex, als primitivem Modell von Zellbestandteilen, in der Zukunft standartisierte Kohlenwasserstoff-Suspensionen in dieser Weise zu untersuchen und gleiche Experimente mit stärker hydrophobiertem Gel durchzuführen.
Über den Einfluß der Kationen auf die Kraftkonstanten der WO-Bindung in den Hexaoxowolframaten (VI)
(1970)
The autoxidation of NaSH and Cysteine in the presence of heavy metal ions is accompanied by chemiluminescence due to the formation of O2⊖ or adequate compounds as intermediates. The observation of the luminescence intensity and its time dependence has been used as analytical indication of the occurrence of electron transfer reactions from - SH to O2.
This enabled the study of the influence of different catalytic promoters. The efficiency of different metal ions could easily be demonstrated by their enhancement of light production during the reaction of NaSH with molecular oxygen. Cu (II) as one of the most efficient catalysts was also applied in the form of different complexes. Because it would catalyse the oxidation of cysteine, glutathione and other electron donors of biological interest, the influence of the nature of the ligands of the complexes was investigated. In the case of cysteine only complexes with stability constants of medium strength and planar configuration acted as effective catalysts. Therefore it has to be assumed that for an effective electron transport to the loosely bound oxygen the cysteine molecule has to enter the inner sphere of the complex. The much longer time of luminescence of this reaction (4 -10 min) compared to the short time luminescence caused by free O2H. OH and H2O2 indicates that these intermediates are stabilized by binding to the Cu (II) -complex as in compounds (I), (II) and (III) of oxidizing enzymes.
Um den Mechanismus der Reaktion des Cysteins mit molekularem Sauerstoff in Gegenwart von Komplexen des zweiwertigen Kupfers als Katalysatoren zu ermitteln, wurden Messungen der Chemilumineszenz, der Sauerstoff- und der Cysteinkonzentration in Abhängigkeit von der Zeit vorgenommen. Variation der Konzentration der Reaktionsteilnehmer führte zu Meßergebnissen, die die Aufstellung eines Reaktionsschemas gestattete. Das hieraus abzuleitende System nichtlinearer Differentialgleichungen für die Reaktionsgeschwindigkeiten wurde in einem Analogrechner gelöst, wobei Übereinstimmung zwischen Rechnung und Meßergebnissen sowohl für die Zeitabhängigkeit als auch für die Konzentrationsabhängigkeit gefunden wurde.
Über Natriumhexaoxometallate
(1969)
Über Lithiumhexaoxometallate
(1969)
Thermal denaturation of RNA free coat proteins of tobacco mosaic virus (TMV) was studied for wildtype TMV (vulgare) and the temperature-sensitive mutant, Ni 118. The ability to form soluble aggregates as well as the optical properties (ORD, UV-difference spectra), and the sedimentation behavior were used as criteria for the native state.
At pH 7.5, I= 0.02 denaturation is reversible for both proteins. The ORD data indicate that the denatured proteins contain residual secondary structure. The “melting temperatures”, as defined by ORD measurements (cp = 0.02 mM), are 39.5 ± 1°C for vulgare and 27 ± 1°C for Ni 118 at pH 7.5, I= 0.02. By means of the aggregation test (cp = 0.05 mM) somewhat lower melting temperatures were found under the same solvent conditions. The difference between the primary structures of vulgare and Ni 118 proteins being a proline → leucine (pos. 20) replacement, the results suggest the cyclic structure of proline (20) to have a specific stabilizing function in the three dimensional protein structure. This conclusion is supported by preliminary experiments on a temperature-sensitive mutant with a threonine residue in pos. 20.
Über Li6ReO6
(1969)
Die Ergebnisse einer Selendehydrierung des Cholesterins bei 350°C werden mit Produkten verglichen, die sich aus dem Steroid im aktiviert absorbierten Zustand auf Kieselgel durch Oxydation mit Joddampf bei Raumtemperatur bilden. Alkylsubstituierte Cyclopentenophenanthrene konnten hierbei mit Sicherheit gefaßt werden. Da die äußeren Versuchsbedingungen, im Gegensatz zu allen bisherigen Dehydrierungsversuchen an Steroiden, am ehesten mit physiologischen verglichen werden können (20°C, ein dem freien Sauerstoff entsprechendes Oxydationspotential von ca. +0,4 V und eine aktivierende Grenzfläche), werfen die Ergebnisse ein neues Licht auf die alte Hypothese der endogenen Bildung carcinogener Kohlenwasserstoffe im Organismus.
Der erleichterte Reaktionsverlauf im Adsorpt wird durch Erhöhung der Adsorptionswärme im Zuge der Aromatisierung erklärt.
DNA points accumulation for imaging in nanoscale topography (DNA-PAINT) is a super-resolution technique with relatively easy-to-implement multi-target imaging. However, image acquisition is slow as sufficient statistical data has to be generated from spatio-temporally isolated single emitters. Here, we trained the neural network (NN) DeepSTORM to predict fluorophore positions from high emitter density DNA-PAINT data. This achieves image acquisition in one minute. We demonstrate multi-color super-resolution imaging of structure-conserved semi-thin neuronal tissue and imaging of large samples. This improvement can be integrated into any single-molecule microscope and enables fast single-molecule super-resolution microscopy.
Steroid initiated enzyme induction (Δ5-Ketosteroid-Isomerase, 3α-Hydroxysteroid-Dehydrogenase, and 3β.17β-Hydroxysteroid-Dehydrogenase) in Pseudomonas testosteroni was investigated with respect to the kinetics of induction, operon control of the induced enzymes, and the relative strengths of various inducers. The induction process was followed indirectly by selective inhibition of different stages in the protein synthetic pathway. Comparisons between bacterial and mammalian steroid induction are discussed.