Polarographic kinetics of reactions which proceed via carbonium ion intermediates

Zusammenfassung Mit Hilfe der Polarographie wird die Kinetik der Solvolyse vonp-Methoxy-isopropalakohol bestimmt.

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We wish to thank the National Research Council of Canada for a grant in support of this study and the University of New Brunswick for a post doctoral fellowship for one of us (D.B.).     

Polarographic activity of the antitumor drug cis-dichlorodiammineplatinum (II). The effect of hydrolysis and trans-isomerization of the drug

Electrochemical activities of cis-dichlorodiammineplatinum (II) (cis-DDP) and its trans isomer were studied by classical and differential pulse polarography (d.p.p.). It was shown that both isomers yielded a polarographic step or peak at about -1.6 V (vs. Ag/AgCl), which corresponded to electroreduction of the complex and to catalytic hydrogen evolution. This signal was easily measurable with the aid of d.p.p. and was suitable for investigation of the extent of hydrolysis and trans-isomerization of cis-DDP leading to the formation of toxic products. The detection limit for determination of cis-DDP and its trans isomer by d.p.p. was 1 X 10(-6) mol/l.     

Polarographic activity of the antitumor drug cis-dichlorodiammineplatinum (II). The effect of hydrolysis and trans-isomerization of the drug

Summary Electrochemical activities of cis-dichlorodiammineplatinum(II) (cis-DDP) and its trans isomer were studied by classical and differential pulse polarography (d.p.p.). It was shown that both isomers yielded a polarographic step or peak at about –1.6V (vs. Ag/AgCl), which corresponded to electroreduction of the complex and to catalytic hydrogen evolution. This signal was easily measurable with the aid of d.p.p. and was suitable for investigation of the extent of hydrolysis and trans-isomerization of cis-DDP leading to the formation of toxic products. The detection limit for determination of cis-DDP and its trans isomer by d.p.p. was 1×10^–6 mol/l.Acknowledgment. This work was supported in part by Lachema n.e., Brno (Czechoslovakia).     

Autoantibodies in canine neoplasms. II. Tumor tissue specificity and lack of cross-reactivity with embryonic antigens

Zusammenfassung Durch Immunofluoreszenz wird eine Kreuzreaktion zwischen Tumoren des gleichen histologischen Typs, jedoch keine solche zwischen verschiedenartigen Tumoren des Hundes festgestellt.

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Supported, in part, by a National Science Foundation fellowship.     

The use of dipeptide-p-nitranilides for the study of aminopeptidase specificity.

The use of dipeptide-p-nitranilides for the study of 2 placental aminopeptidases separated on Sephadex G200 helped in establishing some regular features of their specifities. The high-molecular (320,000 daltons) one prefers Phe in position P'1 to Leu, whereas the lower-molecular aminopeptidase (145,000 daltons) prefers Leu. The high-molecular aminopeptidase splits very slowly the N-terminal Leu when Gly is in adjacent position. Leu-Gly-p-NA is therefore an inhibitor of this AP.     

The specificity of histones in nucleated erythrocytes

Riassunto Dagli eritrociti del pollo, dellaRana cateasbeiana e del pesceCaranx hippos sono stati isolati gli istoni nella ipotesi che gli eritrociti forniti di nucleo contengano una frazione di istone funzionante come repressore permanente della sintesi degli acidi nucleici. Detti istoni sono stati frazionati ed analizzati nella loro composizione in amino-acidi. In tutte e tre le speci su menzionate è stata trovata una frazione relativamente ricca in lisina, arginina, alanina, e serina che è stata denominata F2c. L'assenza di detta frazione negli altri tessuti incluso il midollo osseo indica che la frazione F2c può costituire un repressore genetico permanente.

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This investigation was supported by the U.S. Public HEalth Service Grant No. CA-07746, American Cancer Society Grants E-388 and IN-43-F2, and by the Robert A. Welch Foundation Grant G-138.     

The specificity of histones in chicken erythrocytes

Zusammenfassung Isolierung, qualitative und quantitative Charakterisierung der Histone von Hühnererythrocyten wird beschrieben. Mittels Gelfiltration an Sephadex G 75 wurde eine Fraktion des Histons, charakteristisch für die Hühnererythrocytenzellkerne isoliert und analysiert. Diese Fraktion, als F2c bezeichnet, ist ein Teil des lysinreichen Histons F2, reich an Lysin, Alanin, Serin und Arginin (z.B. 21,0, 15,1, 11,9 und 10,6% respektive). Threonin konnte als N-terminale Aminosäure in dieser Fraktion festgestellt werden.     

Structure specificity of some immunoadjuvant synthetic glycopeptides.

The immunoadjuvant activity of muramyl dipeptide seems to be critically dependent on the type of substitution of the gamma-carboxyl group of the D-isoglutamine residue. Moreover the nonapeptide L-Ala-D-isoGlu-L-lys-D-Ala-(Gly)5-OME also shows a definite effect.     

Chromatographic conditions in the expression of corticosteroid receptor specificity.

It is shown that cytosol preparations bound with various concentrations of a steroid are necessary to reveal physicochemically distinct, heterogeneous and polymorphic receptors present in the hormone specific target organ, that these cannot be fully appreciated in one-shot experiments at suboptimal steroids levels, and that they escape detection by equilibrium binding and Scatchard analysis alone.     

The use of dipeptide-p-nitranilides for the study of aminopeptidase specificity

Summary The use of dipeptide-p-nitranilides for the study of 2 placental aminopeptidases separated on Sephadex G200 helped in establishing some regular features of their specifities. The high-molecular (320,000 daltons) one prefers Phe in position P'₁ to Leu, whereas the lower-molecular aminopeptidase (145,000 daltons) prefers Leu. The high-molecular aminopeptidase splits very slowly the N-terminal Leu when Gly is in adjacent position. Leu-Gly-p-NA is therefore an inhibitor of this AP.     

The specificity of binding of glycoprotein hormones to their receptors

The glycoprotein hormone receptor family is peculiar because, in contrast to other G protein-coupled receptors, a large N-terminal extracellular ectodomain is responsible for hormone recognition. Hormone-receptor pairs have evolved in such a manner that a limited number of positions both at the 'seat-belt' domain of the hormone and the leucine-rich repeats of the receptor, play attractive and repulsive interactions for binding and specificity, respectively. Surprisingly, the constitutive activity of the receptor, mostly modulated by highly conserved amino acids within the heptahelical domain of the receptor (i.e., outside the hormone binding region), also regulates effectiveness of hormone recognition by the extracellular part. In this review we analyze, at the molecular level, these important discriminating determinants for selective binding of glycoprotein hormones to their receptors, as well as natural mutations, observed in patients with gestational hyperthyroidism or ovarian hyperstimulation syndrome, that modify the selectivity of binding.     

Direct fluorination of carcinogenic polycyclic aromatic hydrocarbons. 6-Fluorobenzo[a]pyrene

Summary Xenon difluoride reacts with benzo[a]pyrene (BaP) in dichloromethane solution in an open system to give 6-fluorobenzo[a]pyrene. This method constitutes a direct route to fluorine substituted carcinogenic polycyclic aromatic hydrocarbons.Acknowledgment. This work was financed in part by a grant from The Israel Commission for Basic Research.     

The Newton letters (Vols. I and II)

The metaphysical commitment to the circle as the essential element in the analysis of celestial motion has long been recognized as the hallmark of classical astronomy. What has not always been clear, however, is that the circle continued to serve Kepler as a central element in his astronomy after the discovery of the elliptical orbit of Mars. Moreover, the circle also functioned for Kepler in geometry to select the basic polygons, in music to select the basic harmonies, and in astrology to select the basic aspects. His basic set of polygons consisted of those figures that could be constructed using only a compass and a rule; the set of fundamental harmonies consisted of the consonances of the just intonation; and the traditional set of astrological aspects were enlarged by Kepler to include three new aspects in order to make the astrological set consistent with geometry and music. And as the circle served to unify these three areas, so also did it serve to supply the fundamental answers to astronomical problems well after the discovery of his new astronomy—a topic to be discussed in Part II of this paper.     

The role of oxygen diffusivity in biochemical reactions

Summary It has been shown that increasing protein concentrations can decrease oxygen diffusion in 3 in vitro systems. We postulate that it is possible, and in some circumstances probable, that diffusion might be a rate limiting step in both in vitro and in vivo biological systems.     

The role of oxygen diffusivity in biochemical reactions

It has been shown that increasing protein concentrations can decrease oxygen diffusion in 3 in vitro systems. We postulate that it is possible, and in some circumstances probable, that diffusion might be a rate limiting step in both in vitro and in vivo biological systems.     

The mechanism of reactions catalyzed by thiamine pyrophosphate

Zusammenfassung Es wird ein Mechanismus für verschiedene enzymatische Reaktionen, bei denen Thiaminpyrophosphat als Coferment wirkt, vorgeschlagen.     

Studies on lysosomes in rat heart cell cultures. II. The effect of exogenous lysosomes

Zusammenfassung Isolierte Lysosomen wie auch intakte Monozyten hatten keinen zytopathischen Einfluss auf Herzmuskelzellen von Ratten, gezüchtet im Medium mit pH 7,2. Ein erniedrigtes Medium wie auch Nachbehandlungen der Kulturen mit Vitamin A nach Chlorpromazin 10^–4 konnten keinen synergistisch zerstörenden Einfluss auf die Herzkulturen hervorrufen.

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Supported by Grant No. HE-05739 from the National Institutes of Health, U.S. Public Health Service.     

The investigation of the action of ultrasound on some proteid substances. Part II. The action of ultrasound on diastase

Zusammenfassung Die Ultraschallwirkung auf Diastase wurde an deren Aktivitäts- und pH-Änderung untersucht. Verschieden lang beschallte, 0.5% ige wässerige Diastaselösungen ergaben stufenweises und regelmässiges Absinken der Aktivitäten und pH-Werte.

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Part I: Bull. Soc. chim. Belgrade (in press).