Dual switchable molecular tweezers incorporating anisotropic MnIII-salphen complexes

An alternative strategy for the synthesis of terpyridine based switchable molecular tweezers has been developed to incorporate anisotropic Mn(iii)-salphen complexes. The free ligand was synthesized using a building block strategy based on Sonogashira coupling reactions and was then selectively metalated with manganese in a last step. The conformation of the tweezers was switched from an open 'W' shaped form to a closed 'U' form by Zn(ii) coordination to the terpyridine unit bringing the two Mn-salphen moieties in close spatial proximity as confirmed by X-ray crystallography. An alternate switching mechanism was observed by the intercalation of a bridging cyanide ligand between the two Mn-salphen moieties that resulted in the closing of the tweezers. These dual stimuli are attractive for achieving multiple controls of the mechanical motion of the tweezers. A crystallographic structure of unexpected partially oxidized closed tweezers was also obtained. One of the two Mn-salphen moieties underwent a ligand-centered oxidation of an imino to an amido group allowing an intramolecular Mn-Oamide-Mn linkage. The magnetic properties of the manganese(iii) dimers were investigated to evaluate the magnetic exchange interaction and analyze the single molecule magnet behavior.

Substrate-dependent allosteric regulation by switchable catalytic molecular tweezers

Allosteric regulation is exploited by biological systems to regulate the activity and/or selectivity of enzymatic reactions but remains a challenge for artificial catalysts. Here we report switchable terpy(Zn-salphen)2 molecular tweezers and their metal-dependent allosteric regulation of the acetylation of pyridinemethanol isomers. Zinc-salphen moieties can both act as a Lewis acid to activate the anhydride reagents and provide a binding site for pyridinemethanol substrates. The tweezers’ conformation can be reversibly switched between an open and a closed form by a metal ion stimulus. Both states offer distinct catalytic profiles, with closed tweezers showing superior catalytic activity towards ortho substrates, while open tweezers presenting higher rate for the acetylation of meta and para substrates. This notable substrate dependent allosteric response is rationalized by a combination of experimental results and calculations supporting a bimetallic reaction in the closed form for ortho substrate and an inhibition of the cavity for meta and para substrates.

Über den Einfluß der antithrombotischen Behandlung auf die Narbenbildung nach experimentellem Myokardinfarkt

Auf Grund histologischer Untersuchungen an Hunden, bei denen durch Unterbindung des linken apikalen Astes des Ramus descendens der linken Koronararterie eine Myomalazie erzeugt worden war, konnte beim Vergleich mit unbehandelten Tieren unter der Behandlung mit Venostasin keine nachteilige Wirkung im Sinne einer Hemmung der Narbenbildung beobachtet werden. Auch wenn Venostasin überdosiert wurde, verlief die Narbenbildung ungestört.

Probleme der Antikoagulantienbehandlung

Die Antikoagulantien beeinflussen neben der Blutgerinnung auch die Zellteilung, das Wachstum von Fibroblastenkulturen und die Bindegewebsbildung. Da diese Vorgänge die Heilung bei Myokardinfarkten ungünstig beeinflussen könnten, wurde das histologische Bild der Abheilungsvorgänge experimenteller Myokardinfarkte bei Hunden mit und ohne Behandlung mit Marcoumar oder Heparin verfolgt. Es zeigte sich, daß bei den Kontrolltieren nach 14 Tagen bereits ein junges, faserreiches Bindegewebe im Bereich des Infarktes nachweisbar ist, während unter Marcoumar noch Nekrosen, reichlich Fibroblasten, aber noch keine Bindegewebsfasern nachgewiesen werden können. Erst nach 4 Wochen ist die Bindegewebsbildung so weit fortgeschritten wie bei den Kontrolltieren nach 14 Tagen. Unter Heparin ist die Proliferation der Fibroblasten besonders ausgeprägt. Die Konsequenzen für die Antikoagulantienbehandlung der Myokardinfarkte werden diskutiert.

Synthesis and Guest Recognition of Switchable Pt-Salphen Based Molecular Tweezers

Molecular tweezers are artificial receptors that have an open cavity generated by two recognition units pre-organized by a spacer. Switchable molecular tweezers, using a stimuli-responsive spacer, are particularly appealing as prototypes of the molecular machines that combine mechanical motion and allosteric recognition properties. In this present study, the synthesis of switchable molecular tweezers composed of a central terpyridine unit substituted in 4,4″ positions by two Pt(II)-salphen complexes is reported. The terpyridine ligand can be reversibly converted upon Zn(II) coordination from a free ‘U’-shaped closed form to a coordinated ‘W’ open form. This new substitution pattern enables a reverse control of the mechanical motion compared to the previously reported 6,6″ substituted terpyridine-based tweezers. Guest binding studies with aromatic guests showed an intercalation of coronene in the cavity created by the Pt-salphen moieties in the closed conformation. The formation of 1:1 host-guest complex was investigated by a combination of NMR studies and DFT calculations.

Six States Switching of Redox-Active Molecular Tweezers by Three Orthogonal Stimuli

A six level molecular switch based on terpyridine(Ni-salphen)₂ tweezers and addressable by three orthogonal stimuli (metal coordination, redox reaction, and guest binding) is reported. By a metal coordination stimulus, the tweezers can be mechanically switched from an open "W"-shaped conformation to a closed "U"-shaped form. Theses two states can each be reversibly oxidized by the redox stimulus and bind to a pyrazine guest resulting in four additional states. All six states are stable and accessible by the right combination of stimuli and were studied by NMR, XRD, EPR spectroscopy, and DFT calculations. The combination of the supramolecular concepts of mechanical motion and guest binding with the redox noninnocent and valence tautomerism properties of Ni-salphen complexes added two new dimensions to a mechanical switch.

Randomized controlled trial of silymarin treatment in patients with cirrhosis of the liver

Silymarin, the active principle of the milk thistle Silybum marianum, protects experimental animals against various hepatotoxic substances. To determine the effect of silymarin on the outcome of patients with cirrhosis, a double blind, prospective, randomized study was performed in 170 patients with cirrhosis. 87 patients (alcoholic 46, non-alcoholic 41; 61 male, 26 female; Child A, 47; B, 37; C, 3; mean age 57) received 140 mg silymarin three times daily. 83 patients (alcoholic 45, non-alcoholic 38; 62 male, 21 female; Child A, 42; B, 32; C, 9: mean age 58) received a placebo. Non-compliant patients and patients who failed to come to a control were considered as 'drop outs' and were withdrawn from the study. All patients received the same treatment until the last patient entered had finished 2-years of treatment. The mean observation period was 41 months. There were 10 drop outs in the placebo group and 14 in the treatment group. In the placebo group, 37 (+2 drop outs) patients had died, and in 31 of these, death was related to liver disease. In the treatment group, 24 (+4 drop outs) had died, and in 18 of these, death was related to liver disease. The 4-year survival rate was 58 +/- 9% (S.E.) in silymarin-treated patients and 39 +/- 9% in the placebo group (P = 0.036). Analysis of subgroups indicated that treatment was effective in patients with alcoholic cirrhosis (P = 0.01) and in patients initially rated 'Child A' (P = 0.03). No side effects of drug treatment were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

[The influence of therapy with silymarin on the survival rate of patients with liver cirrhosis (author's transl)]

A randomized double-blind study about the therapy of the cirrhosis of the liver shows a significant higher surviving rate of the alcoholic cirrhosis in the group treated with Silymarin. This result can be well explained by the protective influence of this substance against toxic injuries. The etiology of many chronic liver diseases is uncertain and therefore it is advisable to try the therapy also in other cases. The conditions of the study are exactly reported. The influence on the clinic of the disease and on the laboratory data obtained in many controls will be published later, because the statistical analysis needs some more time.

[Clinical experience with the cardiac glycoside Gitoformat (author's transl)]

Gitoformat, a new derivate of Gitoxin, was tested with 50, mainly geriatic patients with a manifested cardiac insufficiency. The initial treatment as well as a changeover from the usual glycosid-treatment after a renewed decompensation was without any problems. With a rate of success of 95 per cent the efficiency of this new glycosid can be classified as excellent. Side effects or incompatibility were consequences of overdosage. It is remarkable that also patients with a reduced renal function did not need a reduction in dose. At 10 patients the recompensation with Gitoformat continued after discharge over an observation period of 6 months. The maintenance dose had not to be changed, incompatibility or overdosage reactions didn't appear.

[Results of the Austrian myocardial infarction study on the effects of streptokinase (author's transl)]

A multicentre study of cases of acute myocardial infarction was undertaken at 27 departments at teaching and non-teaching hospitals throughout Austria over a period of three years. Altogether 3397 patients were investigated. On classification of the patients according to the number of shock indicators, two comparable groups (B and C) of "mild" infarction with 0, 1 or 2 signs of shock were obtained. These low-risk groups comprised 728 patients. The mortality in group C ("mild" infarction, no streptokinase) was 17.3%, significantly higher (p less than 0.01) than the corresponding figure of 10.5% in group B ("mild" infarct, streptokinase therapy). The decrease in mortality by streptokinase therapy applied both to monitored patients as well as to those who were not monitored. Haemorrhage was a very rare complication, but somewhat more frequent in the streptokinase-treated cases, as expected. The incidence of complications such as stereocardia, asystole, and cardiac insufficiency, as well as the conversion of "mild" cases into a "severe" symptomatology was markedly reduced in the streptokinase-treated group.

[Experimental investigations on the effect of various doses of streptokinase on blood viscosity (author's transl)]

The decrease in blood viscosity induced by streptokinase (SK) in the present investigation in proportional to the streptokinase concentration up to a concentration of 2000 IE/ml blood. A maximum decrease in viscosity is attained with a dosage of between 200 and 300 IE/ml blood. The decrease in viscosity is already clearly detectable at 10 minutes at all investigated doses and is completed after 20 to 30 minutes. An increase in SK resistance delays the decrease in viscosity. Prevention of the decrease, however, only seems to occur with a very high SK resistance and a very low SK dosage (50 IE/ml blood). The optimum dosage of SK to achieve a maximum decrease in viscosity is 200 IE/ml blood.