The Simple Synthesis of Chiral Polyazaoxacoronands Derived from α-Amino Acids

Abstract

Bisamidation of oxaloyl chloride using L-amino acid methyl ester hydrochlorides afforded chiral diesters. The following reactions of diesters with 2,2-(ethylene-dioxy)diethylamine, afforded tetramides possessing C₂ symmetry. Coupling of N-hydroxysuccinimide ester of N-benzyloxycarbonyl-L-alanine with 1,5-diamino-3-oxapentane, followed by cleavage of protecting groups, afforded an optically active diamine, which was transformed consequently into tetramide via the reaction with diglycolic acid dimethyl ester under high pressure conditions.     

A Study of the Activity of Recombinant Mn-Superoxide Dismutase in the Presence of Gold and Silver Nanoparticles

Applied Biochemistry and Biotechnology - Superoxide dismutase (SOD) is one of the best characterized enzyme maintaining the redox state in the cell. A bacterial expression system was used to...     

Phenol adsorption on closed carbon nanotubes

We present the results of systematic studies of phenol adsorption on closed commercially available, unmodified carbon nanotubes. Phenol adsorption is determined by the value of tube-specific surface area, the presence of small amount of surface groups influence adsorption only in very small amount. Phenol can be applied as a probe molecule for comparative analysis of tube surface areas. Tube curvature influences adsorption from solution, i.e., we observe increasing adsorption energy (and slower desorption process) with the decrease in tube curvature. This is in full accordance with molecular simulation results.     

Application of thermovision for estimation of the optimal and safe parameters of the whole body cryotherapy

Exposure to the extreme low temperatures, ranging between ?60 and ?140 °C, has many beneficial effects on the human body what is exploited for example in sport medicine, for treatment of locomotory system diseases or even some psychiatric disorders. To insure the safe treatment in a cryochamber, careful planning of the procedure and proper qualification of patients, is required. Cardiovascular system, especially skin vasculature plays the major role of the body response to the extreme cold. The changes in skin blood flow are reflected in changes of the temperature distribution. Therefore, the thermal imaging, which allows to analyze the temperature distribution on the human body, may be successfully exploited to examine the influence of extremely low temperatures on the skin vascular system. The aim of this work was to examine the temperature, blood pressure, and heart rate changes after the whole body cryotherapy in healthy subjects to determine the safety conditions of the treatment. 480 healthy students of the Wroc?aw University School of Physical Education were divided into two groups (each 240 persons). All subjects were exposed for 1–3 min to the extremely low temperatures: ?60, ?100, ?120, and ?140 °C. In one group, the thermograms were recorded before and 5 and 30 min after the cryotherapy by means of ThermoVision A20 M thermal camera. In the other one, heart rate and blood pressure were measured before and 5 min after the cryotherapy. It was demonstrated that 3-min exposure in the cryochamber and the temperature ?120 °C are the optimal and safe cryotherapy parameters.     

Structural studies of new chiral nickel (II) complexes of cyclams: The influence of a systematically varied number of amide groups

The synthesis and structures of nickel (II) complexes of chiral cyclams originating from l-proline are presented. Upon addition of nickel acteate, oxocyclams having amide groups underwent deprotonation forming distorted square-planar complexes. In the case of the all-amine analogue a six-coordinate octahedral complex is formed.     

The alpha-helix folds more rapidly at the C-terminus than at the N-terminus

The helix-coil dynamics of different sections of an alpha-helical model peptide were observed separately by nanosecond temperature jump experiments with IR detection on a series of isotopically labeled peptides. The results show that the helix-coil dynamics of the alpha-helical C-terminus are faster than those of the N-terminus.     

The synthesis of 8‐hydroxyquinazoline derivatives and their acid‐base interactions

The reaction of N‐(2‐R¹‐oxyphenyl)benzimidoyl chlorides with cyanamide derivatives in the presence of titanium tetrachloride as a catalyst has yielded some new 4‐amino‐8‐R¹‐oxy‐2‐phenylquinazolines. pK_a values have been determined for these compounds and the influence of substituents at the basicity of the parent system has been discussed. Some investigations on the methyl‐quinazolinyl ether cleavage in different medium have been done yielding the appropriate hydroxyquinazoline derivatives. In those cases when the deprotection of 4‐amino‐8‐methoxy‐2‐phenylquinazoline was carried in aqueous acidic solutions, the formation of the hydrolysis products 3,4‐dihydro‐2‐phenyl‐4‐quinazolone derivatives was observed as well.     

Strategy of Cr detoxification by Callitriche cophocarpa

The present work focused on the qualitative and quantitative analysis of Cr detoxification strategy of aquatic cosmopolitan plant Callitriche cophocarpa. This plant species has just been described in the context of its unusual accumulation potential of Cr. The emphasis of the work was placed on the redox reaction Cr(VI)→Cr(III) which is considered to be remediation mechanism of highly reactive and mobile Cr(VI) ions. Plants were immersed for 5 days in 1 mM of Cr(VI) (potassium dichromate) or 1 mM of Cr(III) (chromium sulphate) solutions in semi-natural conditions. Cr was effectively removed from the solution up to the extent of ca.58% or 35% of the starting amount, in the case of Cr(III) and Cr(VI), respectively. No plant-induced Cr(VI) reduction accompanying Cr accumulation was observed in Cr(VI) solutions except from the apparent one, noticed at the fourth day of incubation. On the contrary to these results, according to the method of electron paramagnetic resonance spectroscopy (L-band EPR), biphasic signal of Cr(V) attending Cr(VI) to Cr(III) reduction was detected inside the plant tissue every day of investigations. Our results show that phytoextraction but not phytostabilization is the main strategy of Cr detoxification by C. cophocarpa in aquatic systems.