Showing papers by "Technical University of Berlin published in 1976"

Regulation of degradation of thyrotropin releasing hormone by thyroid hormones

Abstract: WHEN thyrotropin releasing hormone (TRH, pyroGlu–His–Pro–NH2) was isolated and its structure determined1,2 the concept of neurohumoral regulation of hormone secretion by the anterior pituitary3 was confirmed, but the mechanisms involved are not well understood Enzymatic inactivation of TRH by blood and serum may regulate the hormone's activity by determining the number of molecules available to the thyrotroph4 With this physiological function, degradative enzyme(s) would itself need to be regulated and I report here that the activity of the TRH-degrading enzyme(s) is controlled by the thyroid hormones

Quenching experiments on high-purity nickel

Abstract: High-purity Ni is used for quenching experiments in a He cryostat, the electrical resistivity being used as a defect indicator. The quenched-in resistivity recovers in two stages: a steep one, A, around 120°C with a decrease of 50% and a rather broad one, B, around 560°C with a decrease of 45%. The formation energy of monovacancies is determined to be (1.58 to 1.63) ± 0.05 eV. From the Meechan-Brinkman analysis H ≈ 1.27 eV can be estimated, whereas it can be calculated to HmIV = (1.32 to 1.27) eV using self diffusion data. Stage A is attributed to the recovery of monovacancies and of multivacancies built during migration of single vacancies, stage B is discussed as annealing of voids and perfect dislocation loops. An hochreinem Ni werden Abschreckexperimente im He-Kryostaten durchgefuhrt. Der elektrische Widerstand wird als Leerstellenindikator benutzt. Der eingeschreckte Wider-stand heilt in zwei Stufen aus: einer steilen, A, bei 120°C mit einem Abfall um 50% und einer breiten, B, um 560°C mit einem Abfall von 45%. Die Bildungsenergie der Einzelleer-stellen wird zu Hf = (1,58 bis 1,63) ± 0,05 eV bestimmt. Aus der Meechan-Brinkman-Auftragung kann HIVm ≈ 1,27 eV abgeschatzt werden. Unter Benutzung von Selbstdiffusionsdaten ergibt sich HmIV = (1,32 bis 1,27) eV. Stufe A wird der Erholung von Einzelleer-stellen und von Vielfachleerstellen, die sich wahrend der Wanderung der Einzelleerstellen bilden, zugeordnet. Stufe B wird als Erholung von Lochern und vollstandigen Versetzungs-ringen gedeutet.

Natürlich vorkommende Terpen-Derivate, 71. Über die Inhaltsstoffe aus Stevia-Arten

Abstract: Die Untersuchung von zwei Stevia-Arten liefert vier neue Sesquiterpene (1, 2, 6 und 7), deren Konstitution durch spektroskopische Methoden sowie durch einige chemische Reaktionen geklart wird. Die chemotaxonomische Bedeutung der Isolierung von 6 und 7 wird diskutiert. Naturally Occurring Terpene Derivatives, 71 On the Constituents of Stevia Species The investigation of two Stevia species yields four new sesquiterpenes (1, 2, 6, und 7) their structures being elucidated by spectroscopic methods and some chemical reactions. The chemotaxonomic importance of the isolation of 6 and 7 is discussed.

Concerning the Conformation of Isolated Benzylideneaniline

Abstract: From PE.-spectroscopical studies the torsional angle φ of the N-phenyl ring in isolated benzylideneaniline 1 has been found to be definitely smaller than φ= 90°. An approximate valueφ= 36°has been estimated which is even smaller than the one observed in the crystal (φ= 55°) and suggested to prevail also in solutions of 1. A reevaluation of the gas phase optical spectrum of isolated 1 supports a torsional angle similar to that found in the other phases. Calculations of the most stable conformation of 1 as well as of stilbene and azobenzene by the MINDO/3-technique lead to torsional angles φ= 90° for both phenyl rings in all cases. These results are at variance with the experimental results and suggest that MINDO/3-like its less advanced precursor MINDO/2 or like CNDO/2–is unreliable for low energy processes involving rotation of π-systems connected by essential single bonds. It is concluded that the π-energy of benzylideneaniline, like that of stilbene or azobenzene, would favor a planar conformation. The increased torsional angle in 1 as compared to the other two iso-conjugate systems arises from a larger steric interaction between phenyl- and bridgeprotons.

Natürlich vorkommende Terpen‐Derivate, 58: Über Inhaltsstoffe der Gattung Brickellia

Abstract: Neben einem Dehydronerolidol-Derivat (2) und eine, Benzofuran-Derivat (14) werden mehrere neue Diterpene (3, 9, 17, 18, 27 und 28) isoliert. Ihre Strukturen werden durch spektroskopische Methoden und einige chemische Reaktionen geklart. 9 ist ein neuer Typ eines abgebauten Diterpens, der jedoch in enger Beziehung zu 3 steht. Naturally Occurring Terpene Derivatives, 58: Constituents of the Genus Brickellia Besides a dehydronerolidol derivative (2) and a benzofuran derivative (14) several new diterpenes (3, 9, 17, 18, 27, and 28) have been isolated. Their structures are elucidated by spectroscopic methods and some chemical reactions. 9 is an new type of degraded diterpene which, however, is closely related to 3.

Indirect evidence for a very fast recovery kinetics of chlorophyll-aII in spinach chloroplasts.

Abstract: The 690 nm absorption change reflecting the turnover of the system-II-reaction center chlorophyll, Chl-aII (often referred to as P 680), has been investigated under different experimental conditions in spinach chloroplasts. A comparison was made with oxygen evolution and with absorption changes of Chl-aI measured at 703 nm, both indicating the number of electrons produced by system II. It was found: 1. The dependency on actinic flash intensity of the initial amplitudes of the measured 690 nm absorption change, deltaalpha0(Chl-aII) in Tris-washed chloroplasts is similar to that for the total amplutude of the 703 nm absorption change, deltaalpha0(Chl-aI) in normal chloroplasts, and can be described by an exponential function. On the other hand, deltaalphao(chl-aII) in normal chloroplasts exhibits a more complex biphasic dependency and much higher flash intensities are required for saturation. 3. Unver repetitive flash group excitation and in the presence of an ADRY(= acceleration of the deactivation reactions of the water-splitting enzyme system Y)-reagent the initial amplitude of the 690 nm absorption change oscillates in the same characteristic pattern as the oxygen evolution. 4. The initial amplitude of the 690 nm absorption change, deltaalpha0(Chl-aII), IN Tris-washed chloroplasts becomes significantly smaller (more than 50%) by the addition of system-II-electron donors (benzidine, p-phenylendiamine, tetraphenylboron), whereas the total amplitude of the 703 nm absorption change, detalalpha0)Chl-aI) increases 3-4-fold. In order to explain these results, the existance of a very fast reduction kinetics of Chl-aII+ is postulated, which is not detectable by our measuring equipment. The half time of this reaction is less than or equal to mus. Reaction centers with the very gast "undetected" Chl-aII+-reduction are photochemically transformed into slower one by double hit processes with a comparatively low quantum yield. Furthermore, it is inferred, that the dark recovery kinetics of Chl-aII is dependent on be charge accumulation state of the watersplitting enzyme system Y. This phenomenon is shown to explain also the oscillation pattern of delayed fluorescence. On the basis of the present results two alternative reaction schemes for the functional organization of the electron transport on the donor side of system II are discussed.

Optical activity of oriented molecules. II. Theoretical description of the optical activity

Abstract: The theory of the optical activity of oriented molecules is developed starting from an expression given by Gō In order to describe the experiments, a tensioral rotational strength RT = gkl33KNKkl is introduced The orientational distribution coefficients gkl33 determine the influence of the type and magnitude of the orientation to RT The tensor of rotation RNKkl is a function of magnetic dipole, electric dipole and electric quadrupole transition moments Not all the coordinates of the tensor can be determined experimentally at present It is shown however, that for molecules of a sufficiently high symmetry eg D2-symmetry the tensor will have a very simple form For two unsaturated keto steroids the magnitude of the coordinates RNK11, RNK 22 and RNK33 is estimated from experimental results

Natürlich vorkommende Terpen‐Derivate, LVI: Neue Furanoeremophilane aus mexikanischen Senecio‐Arten

Abstract: Die untersuchung von zwei mexikanischen Senecio-Arten ergibt neben bekannten Sesquiterpenen mehrere neue, deren Konstitutionen hauptsachlich durch spektroskopische methoden geklart werden (2,3,6–9, 14–16, 21, 22). Naturally Occuring Terpene Derivatives, LVI: New Furanoeremophilanes from Mexican Senecio Species The investigation of two Mexican Senecio species yields, besides known sesquiterpenes, several new ones, their constitutions being elucidated mainly by spectroscopic methods (2, 3, 6–9, 14–16, 21, 22).

Einfluß exogener und endogener Faktoren auf den Calciumgehalt von Paprika‐ und Bohnenfrüchten

Abstract: Effect of external and internal factors on the calcium content of paprika and bean fruits In water culture experiments with paprika and bean plants the effect of Ca supply, transpiration and growth rate on the Ca content of the fruits has been studied. A 10-fold increase in Ca supply only slightly increased the Ca content. The Ca content of the paprika fruits was increased considerably at high transpiration rates of either the whole shoot or the single fruit. High transpiration also increased the Mg content but had no effect on the K content. In bean high transpiration rates only increased the Ca content in the early stages of fruit development. The ratio of Ca translocation versus water loss by transpiration sharply declined during fruit growth in both species. In paprika the highest ratio (μg Ca/ml) in the fruits corresponded with the ratio in the leaves. In bean fruits, however, this ratio distinctly exceeded that of fully developed leaves. At high transpiration rates of the shoot 20% of the Ca (45Ca) injected into the fruit were translocated out of the fruit. At low transpiration rates of the shoot the corresponding value was below 1%. Most of all the growth rate of the fruits affected the Ca content. With increasing growth rate the Ca transport into the fruits was hardly altered which in turn led to a sharp decrease of the Ca content per unit dry weight. The results support the idea of the Ca transport into the fruit via the xylem. This Ca transport — i.e. also the Ca content of the fruit — is regulated and is also to be influenced by direct or indirect alterations of the water transport in the xylem.

Natürlich vorkommende Terpen‐Derivate, 62. Über die Inhaltsstoffe von Senecio abrotanifolius L.

Abstract: Es werden zwei neue Sesquiterpene isoliert, ein Bisabolen-Derivat (1) sowie ein Triester mit anomalem Kohlenstoffgerust (3). Die Konstitutionen und Konfigurationen werden durch NMR-spektroskopische Untersuchungen sowie durch einige Reaktionen geklart. Weiterhin werden zwei Chinolderivate (7 und 8) isoliert. Naturally Occurring Terpene Derivatives,62. On the Constituents of Senecio abrotanifolius L. Two new sesquiterpenes have been isolated, a bisabolen derivative (1) as well as a triester with an anomalous carbon skeleton (3). The structures and configurations have been elucidated by n. m. r. spectroscopic investigations as well as by some reactions. Furtheron two quinol derivatives (7 and 8) have been isolated.

Calciumgehalte in Früchten von Paprika, Bohne, Quitte und Hagebutte im Verlauf des Fruchtwachstums

Abstract: Calcium content in fruits of paprika, bean, quince and hip during fruit growth The Ca content and the Ca translocation into the fruits during their growth was determined in paprika and bean under controlled conditions (nutrient solution, growth room) and in quince and hip (Rosa rugosa Thumb.) under field conditions. Compared to leaves the Ca content in the fruits is very low in all 4 species and declines further during their growth. The K content, however, is similar in the leaves and in the fruits of all 4 species and remains nearly constant during fruit growth. The low Ca content of the fruits cannot directly be related to the cation exchange capacity (CEC) as there are no differences in the CEC between leaves and fruits. The generally low Ca content of the fruits and its decline during fruit growth is causally related in all 4 plant species to the low rate of Ca translocation compared to the rate of dry matter translocation into the fruits. There are, however, distinct differences between the 4 plant species in the course of the ratio Ca/dry matter translocation into the fruits: In paprika the Ca translocation into the fruits strongly declines during fruit growth and in bean the Ca translocation practically ceases with the onset of seed growth. In quince under field conditions the Ca translocation into the fruits rapidly declines at later stages and finally a translocation of Ca out of the fruit takes place (decrease in the amount of Ca/fruit). Only in hip the Ca translocation into the fruits remains constant during fruit growth. There is, however, a distinctly different distribution of Ca to the various parts within the hip fruits. The decline in Ca translocation during fruit growth can be explained in paprika and bean with a shift in water influx from the xylem (rich in Ca) to the phloem at the stage of high rates of dry matter influx into the fruit. In quince and hip, however, additional mechanisms (alternating water flux in the xylem, CEC) seem to be involved in the regulation of the Ca content of these fruits.