Supramolecular self-assembled arrangements of maltose glyconanoparticles

Our group previously reported the preparation of water-soluble Au-Fe(x)O(y) nanoparticles functionalized with a maltose neoglycoconjugate. A fraction soluble in methanol was also separated and originated a new supramolecular polymeric aggregate. We report here the full characterization of this novel material by transmission electron microscopy (TEM), fluorescence emission, and atomic force microscopy. By means of noncontact dynamic atomic force microscopy, we have been able to obtain information about the organization of the organic components of the polymers, which eluded TEM analysis. We have observed that polymers packed in units about 65 nm in length and 40 nm in width on Au surfaces. The nanoparticles seem to be encapsulated by the organic material. We propose interactions between the sugar residues and the amphiphilic character of the maltose neoglycoconjugate (with a lipophilic undecane spacer) as responsible for the origin of these amazing supramolecular arrangements.     

New Cholesteric and Nematic Lyotropic Mesophases from Di-Sodium N-Lauroyl-Aspartate

Lyotropic liquid crystals are prepared from racemic and optically active di-sodium N-lauroyl aspartate (SNLA). The optically active levo enantiomer is a suitable amphiphile for obtaining cholesteric lyotropic mesophases. In the present work, different types of mesophases, including cholesteric and nematic, were prepared and their type I or II magnetic behavior characterized by deuterium and ²³Na NMR. The polarizing microscope textures were investigated, particularly with regards to magnetic field effects upon the samples. The usual chevron pattern was obtained for particular sample orientations and several characteristic effects were observed for the type I cholesteric lyomesophase in the first few minutes following removal of the sample from the magnetic field. Although the head group of di-sodium N-lauroyl aspartate possesses two negative charges, compositions are not too different from those reported for other amphiphile lyotropic systems.     

Melatonin Reverses the Warburg-Type Metabolism and Reduces Mitochondrial Membrane Potential of Ovarian Cancer Cells Independent of MT1 Receptor Activation

Ovarian cancer (OC) is the most lethal gynecologic malignancy, and melatonin has shown various antitumor properties. Herein, we investigated the influence of melatonin therapy on energy metabolism and mitochondrial integrity in SKOV-3 cells and tested whether its effects depended on MT1 receptor activation. SKOV-3 cells were exposed to different melatonin concentrations, and experimental groups were divided as to the presence of MT1 receptors (melatonin groups) or receptor absence by RNAi silencing (siRNA MT1+melatonin). Intracellular melatonin levels increased after treatment with melatonin independent of the MT1. The mitochondrial membrane potential of SKOV-3 cells decreased in the group treated with the highest melatonin concentration. Melatonin reduced cellular glucose consumption, while MT1 knockdown increased its consumption. Interconversion of lactate to pyruvate increased after treatment with melatonin and was remarkable in siRNA MT1 groups. Moreover, lactate dehydrogenase activity decreased with melatonin and increased after MT1 silencing at all concentrations. The UCSC XenaBrowser tool showed a positive correlation between the human ASMTL gene and the ATP synthase genes, succinate dehydrogenase gene (SDHD), and pyruvate dehydrogenase genes (PDHA and PDHB). We conclude that melatonin changes the glycolytic phenotype and mitochondrial integrity of SKOV-3 cells independent of the MT1 receptor, thus decreasing the survival advantage of OC cells.     

INHIBITION OF DNA REPAIR AND PRODUCTION OF SINGLE-STRAND BREAKS IN ESCHERICHIA COLI BY REDUCTONE

Abstract— Reductone (HOCH₂COCHO), a keto-aldehyde produced by thermal degradation of some sugars, at alkaline pHs, blocks the excision repair of DNA lesions in uv-irradiated wild type Escherichia coli. This probably occurs as a result of inhibition of the exonucleolytic activity of DNA polymerase I. In addition, reductone alone induces DNA single-strand breaks. Repair of this damage is mainly dependent on the polA gene products.     

Determination of Cu,Ni, and Zn in fuel ethanol by FAAS after enrichment in column packed with 2-aminothiazole-modified silica gel

This work describes the synthesis and characterization of 2-aminothiazole-modified silica gel (SiAT), as well as its application for preconcentration (in batch and column technique) of Cu(II), Ni(II) and Zn(II) in ethanol medium. The adsorption capacities of SiAT determined for each metal ion were (mmol g(-1)): Cu(II)=1.20, Ni(II)=1.10 and Zn(II)=0.90. In addition, results obtained in flow experiments, showed a recovery of ca. 100% of the metal ions adsorbed in a column packed with 500 mg of SiAT. The eluent was 2.0 mol L(-1) HCl. The sorption-desorption of the studied metal ions made possible the development of a preconcentration method for metal ions at trace level in fuel ethanol using flame AAS for their quantification.     

Formal structures,the concepts of covariance,invariance, equivalent reference frames,and the principle Relativity

In this paper a given spacetime theoryT is characterized as the theory of a certainspecies of structure in the sense of Bourbaki [1]. It is then possible to clarify in a rigorous way the concepts ofpassive andactive covariance ofT under the action of the manifold mapping groupG _M . For eachT, we define also aninvariance groupG _I T and, in general,G _I T ≠G _M . This group is defined once we realize that, for eachτ ∈ModT, each explicit geometrical object defining the structure can be classified as absolute or dynamical [2]. All spacetime theories possess alsoimplicit geometrical objects that do not appear explicitly in the structure. These implicit objects are not absolute nor dynamical. Among them there are thereference frame fields, i.e., “timelike” vector fieldsX ∈TU, \(U \subseteq M\) M, whereM is a manifold which is part ofST, a substructure for eachτ ∈ModT, called spacetime. We give a physically motivated definition of equivalent reference frames and introduce the concept of theequivalence group of a class of reference frames of kind X according to T, G _X T. We define thatT admits aweak principle of relativity (WPR) only ifG _X T ≠ identity for someX. IfG _X T =G _I T for someX, we say thatT admits a strong principle of relativity (PR). The results of this paper generalize and clarify several results obtained by Anderson [2], Scheibe [3], Hiskes [4], Recami and Rodrigues [5], Friedman [6], Fock [7], and Scanavini [8]. Among the novelties here, there is the realization that the definitions ofG _I T andG _X T can be given only when certain boundary conditions for the equations of motion ofT can be physically realizable in the domainU \(U \subseteq M\) M, where a given reference frame is defined. The existence ofphysically realizable boundary conditions for eachτ ∈ModT (in ?U), in contrast with the mathematically possible boundary condition, is then seen to be essential for the validity of a principle of relativity forT. The methodology of the present paper has been applied to several topics of spacetime physics with very interesting results. Here we mention:

1. The Newtonian concepts of absolute space and absolute time can be presented in a very elegant way as “species of structure”. One of the surprising results is that we succeeded in finding a Lorentzian structure [9] in Newtonian spacetime without introducing any new explict geometrical object in the original structure. The Newtonian spacetime structure and its relation to the relativistic spacetime structure and to the structure of the spacetime of the so-called Lorentz aether theories [11,12] is fully discussed in [13].
2. It is possible to present in a novel and unified way the question concerning experiments designed to detect a possible breakdown of Lorentz invariance, a subject we already dedicated attention to in Rodrigues and Tiomno [11,12] and Rodrigues [14,15]. A full account of this subject will be published elsewhere.
3. In Rodrigues and Scanavini [16], we proved that there are models of General Relativity that contain a canonical privileged locally inertial reference frame that can be physically distinguished from any other frame by experiments doneinside the frame.

Although the formalism of this paper may at first sight look very abstract, actually it is easy to aplly it to specific theories. We present an example at the end of the paper which is sufficiently general to show “in action” almost all concepts introduced in this paper.     

Phase Characterization,Enthalpies and Entropies of Transition,of Five Substituted N-(1-Biphenylethylidene) Benzylamines

Five N-(1-biphenylethylidene) benzylamines expressed by the general formula C₆H₅C₆H₄C(CH₃) = N-CH₂-C₆4HX (X = H, m-F, m-Cl, M-Br and p-OCH₃) were synthesized and their thermal behavior studied within the temperature range of -75 to 250°C.

The solid-liquid, liquid-solid transition temperatures were recorded with a DSC analyzer and the thermodynamic parameters ΔH_m and ΔS_m were estimated. A relationship between these parameters and the molecular weigth was found. The compound m-fluoro N- (1-biphenylethylidene) benzylamine showed an l_i → l_n transition at 341.5°K, which was better observed by cooling the sample at 10°C/min. The liquid crystal behavior was confirmed by cross polarized microscopy.     

Perception of amplitude envelope variations of pulsatile electrotactile stimuli

Gross variations of the speech amplitude envelope, such as the duration of different segments and the gaps between them, carry information about prosody and some segmental features of vowels and consonants. The amplitude envelope is one parameter encoded by the Tickle Talker, an electrotactile speech processor for the hearing impaired which stimulates the digital nerve bundles with a pulsatile electric current. Psychophysical experiments measuring the duration discrimination and identification, gap detection, and integration times for pulsatile electrical stimulation are described and compared with similar auditory measures for normal and impaired hearing and electrical stimulation via a cochlear implant. The tactile duration limen of 15% for a 300-ms standard was similar to auditory measures. Tactile gap detection thresholds of 9 to 20 ms were larger than for normal-hearing but shorter than for some hearing-impaired listeners and cochlear implant users. The electrotactile integration time of about 250 ms was shorter than previously measured tactile values but longer than auditory integration times. The results indicate that the gross amplitude envelope variations should be conveyed well by the Tickle Talker. Short bursts of low amplitude are the features most likely to be poorly perceived.     

Optical Sign Determinations on Cholesteric Lyotropic Mesophases

Optical signs of type I and II micellar cholesteric lyotropic mesophases were for the first time determined. Lyomesophases were prepared from the following amphiphiles: potassium l-N-lauroyl-serinate, potassium laurate, sodium decylsulfate, cesium decylsulfate and decyl-ammonium chloride. Cholesterol was added to all mesophases in order to obtain the chevron pattern for magnetically oriented samples. The method involves the direct observation of the textures at the polarizing microscope. Using a quartz-wedge retardation plate the directions of the slow and fast light vibration components are determined. This method is simpler than the usual observation, under conoscopic illumination, of the basal interference figure which is hardly obtained in micellar lyotropic cholesteric mesophases. All type I cholesteric lyotropic mesophases here investigated exhibited a positive optical sign, whereas all type II cholesteric lyomesophases showed a negative birefringence.