Eliane Wajnberg

Centro Brasileiro de Pesquisas Físicas · Department of Applied Physics (APL)

Luminescent semiconductor nanocrystals or quantum dots (QDs) emerge as important fluorescent probes for in vitro and in vivo Trypanosoma cruzi cells studies. However, to ensure applicability to living organisms, several tests still need to be done. Since several toxic events are caused by QDs, such as loss of mitochondrial membrane potential, ROS g...

Many animals use the geomagnetic field to orient. Among the mechanisms proposed for magnetoreception, the ferromagnetic hypothesis assumes a magnetosensor based on magnetic particles. In this study, magnetic resonance (MR) is applied to 11 Lepidoptera species separated into four body parts: antennae, head, thorax, and abdomen. For the first time, m...

How geomagnetic field information is collected and processed by insects for orientation and navigation remains elusive. In social insects, magnetic particles are well accepted as magnetic sensors. Ants have the ability to home and hunt, and some migratory and nomadic species can migrate or move over long distances for which magnetoreception is an i...

Ferritin has been studied in many animals, plants and bacteria. The main functions of ferritin in mammals are iron concentration and stabilization, protection against oxidants and iron storage for later developmental or iron-dependent activities. Although insect ferritin plays a key role in iron transport, only a few studies to date have examined i...

The most accepted hypothesis of magnetoreception for social insects is the ferromagnetic hypothesis which assumes the presence of magnetic material as a sensor coupled to sensitive structures that transmit the geomagnetic field information to the nervous system. As magnetite is the most common magnetic material observed in living beings, it has bee...

Oriented magnetic nanoparticles have been suggested as a good candidate for a magnetic sensor in ants. Behavioural evidence for a magnetic compass in neotropical leaf-cutter ants, Atta colombica (Formicidae: Attini), motivated a study of the arrangement of magnetic particles in the ants’ four major body parts by measuring the angular dependence of...

Most magnetotactic bacteria (MB) produce stable, single-domain magnetite nanocrystals with species-specific size, shape and chain arrangement. In addition, most crystals are elongated along the [111] direction, which is the easy axis of magnetization in magnetite, chemically pure and structurally perfect. These special characteristics allow magneti...

Insects have been used as models for understanding animal orientation. It is well accepted that social insects such as honeybees and ants use different natural cues in their orientation mechanism. A magnetic sensitivity was suggested for the stingless bee Schwarziana quadripunctata, based on the observation of a surprising effect of a geomagnetic s...

How animals sense, process, and use magnetic information remains elusive. In insects, magnetic particles are candidates for a magnetic sensor. Recent studies suggest that the ant Pachycondyla marginata incorporates iron-containing particles from soil. We used leaf-cutter ants Atta colombica to test whether soil contact is necessary for developing a...

It is known that magnetic fields affect ants behavior. It has been shown that Solenopsis ants are sensitive to magnetic fields but there is no experimental evidence for magnetic orientation. In this paper experiments were done to verify the magnetic orientation of Solenopsis sp. ants. The spontaneous orientation of ants in a circular arena was stud...

Ferromagnetic resonance and SQUID magnetometry have been used to study magnetic material in the head with antennae, thorax, and abdomen of Solenopsis interrupta ants. The temperature dependence of the head with antennae using both techniques was measured. Room-temperature spectra and saturation magnetization were used to compare the magnetic materi...

Behavioural experiments for magnetoreception in eusocial insects in the last decade are reviewed. Ants and bees use the geomagnetic field to orient and navigate in areas around their nests and along migratory paths. Bees show sensitivity to small changes in magnetic fields in conditioning experiments and when exiting the hive. For the first time, t...

In this paper, we quantify the magnetic material amount in Solenopsis ants using ferromagnetic resonance (FMR) at room temperature. We sampled S. interrupta workers from several morphologically indistinguishable castes. Twenty-five oriented samples of each body part of S. interrupta (20 units each) showed that FMR line shapes are reproducible. The...

Migration of the Pachycondyla marginata ant is significantly oriented at 13 degrees with respect to the geomagnetic north-south axis. On the basis of previous magnetic measurements of individual parts of the body (antennae, head, thorax and abdomen), the antennae were suggested to host a magnetoreceptor. In order to identify Fe(3+)/Fe(2+) sites in...

Magnetotactic microorganisms use the interaction of internal biomineralized nanoparticles with the geomagnetic field to orientate. The movement of the magnetotactic multicellular prokaryote Candidatus Magnetoglobus multicellularis under an applied magnetic field was observed. A method using digital image processing techniques was used to track the...

Magnetic nanoparticles synthesized in different matrix, films or ferrofluids have been characterized by magnetic techniques as magnetometry, Ferromagnetic Resonance (FMR) and Mossbauer spectroscopy. The first studies were performed on natural magnetic minerals found in soils and sediments, mainly to understand paleogeomagnetic aspects, and more rec...

Ferromagnetic resonance (FMR) has been used to study the magnetic material in the antennae, head, thorax and abdomen of Solenopsis interrupta ants. The measurements were performed at room temperature (RT). The ferrimagnetic broad lines associated to magnetite/maghemite isolated nanoparticles (high field, HF) and to large nanoparticles or aggregates...

Magnetic nanoparticles in the Apis mellifera abdomens are well accepted as involved in their magnetoreception mechanism. The effects of sample preparation on the time evolution of magnetic particles in the honeybee body parts (antennae, head, thorax and abdomen) were investigated by Ferromagnetic Resonance (FMR) at room temperature (RT), for about...

The temperature dependence of Ferromagnetic Resonance spectra, from 5K to 280K, was used to study the magnetic material present in Neocapritermes opacus termite, the only prey of the Pachycondyla marginata ant. The analysis of the resonant field and peak-to-peak linewidth allowed estimating the particle diameters and the effective anisotropy energy...

Microcirculation is the generic name of vessels with internal diameter less than 100 microm of the circulatory system, whose main functions are tissue nutrition and oxygen supply. In microcirculatory studies, it is important to know the amount of oxyhemoglobin present in the blood and how fast it is moving. The present work describes improvements i...

Six behavioural experiments were carried out to investigate the magnetic field effects on the nest-exiting flight directions of the honeybee Schwarziana quadripunctata (Meliponini). No significant differences resulted during six experiment days under varying geomagnetic field and the applied static inhomogeneous field (about ten times the geomagnet...

Magnetic material in the body parts of the stingless bee Schwarziana quadripunctata, heads, pairs of antennae, thorax and abdomens, were investigated by SQUID magnetometry and Ferromagnetic Resonance (FMR). The saturation, J s and remanent, J r, magnetizations and coercive field H c are determined from the hysteresis curves. From H c and J r/J s th...

Ants have the ability of homing and some species can migrate or move over long distances (nomadic). The presence of magnetic particles as geomagnetic sensors is the most accepted hypothesis to explain ant orientation mechanisms. The room temperature Ferromagnetic Resonance (FMR) spectra of migratory, nomadic, arboreal, trap-jaw and fire ants, appli...

Ferromagnetic resonance temperature dependence is used to study the magnetic material in smashed head, thorax, and abdomen of Solenopsis substituta ants. These three body parts present the five lines previously observed in other social insects. The magnetic material content is slightly higher in heads with antennae than in abdomen with petiole. Iso...

This experimental study quantitatively correlates the saturation magnetization obtained from hysteresis curves (SQUID measurements) to the second integral of the magnetic resonance (MR) spectra of Neocapritermes opacus termites. Termites were submitted to an iron private diet, feeding them with pure cellulose for up to four days. This diet cleans t...

Pachycondyla marginata (P.m.), a migratory and termitophageous ant, hunting only the termite species Neocapritermes opacus, migrates significantly oriented 13 degrees with respect to the magnetic North-South axis. Results of hysteresis curves at room temperature of four Pachycondyla marginata heads, thorax, pairs of antennae and abdomens, oriented...

Termites and ants are social insects living organized in nests in castes. Behavioral studies with the migratory ant Pachycondyla marginata have shown that it conducts well-organized predatory raids toward nests of its only prey, the termite Neocapritermes opacus. The magnetic materials in these two insects were studied using a SQUID magnetometer fo...

Temperature dependence of the magnetic resonance is used to study the magnetic material in oriented Neocapritermes opacus (N.o.) termite, the only prey of the migratory ant Pachycondyla marginata (P.m.). A broad line in the g = 2 region, associated to isolated nanoparticles shows that at least 97% of the magnetic material is in the termite's body (...

Biogenic magnetite has been detected in several species of social insects and may well form the basis of a magnetic sensory system in these animals, although other physiological functions are possible, too. We report here on hysteresis measurements on honeybees (Apis mellifera) and the termite Neocapritermes opacus. The ratio of saturation remanenc...

Honeybees are the most studied insects in the magnetic orientation research field. Experiments on the magnetic remanence of honeybees have shown the presence of magnetite nanoparticles, aligned transversely to the body axis on the anterodorsal abdomen horizontal plane. These results support the hypothesis of ferromagnetic sensors for the magnetorec...

In nature, ferritin, an iron-storage molecule, is found in species ranging from bacteria to man. In the past 50 years its chemical, physical, and magnetic properties have been studied, searching to relate function and structure. Horse spleen ferritin has been investigated by EPR at temperatures between 7 and 290 K. These spectra change from an isot...

Protein-lipid interactions are studied in normal and denervated electrocytes from Electrophorus electricus (L.). Structural modifications of the lipid micro-environment encircling integral membrane proteins in membrane fractions presenting Na(+),K(+)-ATPase activity are investigated using ESR spectroscopy of stearic acid spin labeled at the 14th ca...

The induced remanent magnetization (IRM) of honeybees Apis mellifera and ants as Pachycondyla marginata, a migratory species, and Solenopsis sp., a fire ant, was obtained using a SQUID magnetometer from 10 to 300 K. An anomalous sharp change of the remanent magnetization is observed at 67±0.2 K for migratory ants. The IRM at room temperature indica...

Although ferromagnetic material has been detected in Apis mellifera abdomens and identified as suitable for magnetic reception, physical and magnetic properties of these particles are still lacking. Electron paramagnetic resonance is used to study different magnetic materials in these abdomens. At least four iron structures are identified: isolated...

Route directions of migrations by the neotropical termite-hunting ant Pachycondyla marginata at a forest reserve in Southeast Brazil were analysed by circular statistic. Colony movement patterns were compared between the rainy/hot and dry/cold seasons. Migrations during the dry/cold season are significantly oriented 13 with the magnetic North-South...

Electron nuclear double resonance (ENDOR) spectroscopy has been used to study protons in nitrosyl horse heart myoglobin (MbNO). (1)H ENDOR spectra were recorded for different settings of the magnetic field. Detailed analysis of the ENDOR powder spectra, using computer simulation, based on the "orientation-selection" principle, leads to the identifi...

Electron paramagnetic resonance was used to investigate the magnetic material present in abdomens of Pachycondyla marginata ants. A g congruent with 4.3 resonance of high-spin ferric ions and a very narrow g congruent with 2 line are observed. Two principal resonance broad lines, one with g > 4.5 (LF) and the other in the region of g congruent with...

Magnetic orientation in social insects such as ants, bees, wasps and termites has aroused great interest in the last years. However, the mechanisms that transduce the magnetic information into useful sensory signals are still poorly understood. The most popular hypothesis, named the ferromagnetic hypothesis, considers that tiny magnetic particles,

We report on the presence of magnetic iron oxides in the migratory ant Pachycondyla marginata. Magnetic particles were extracted from different parts of the ant (head, thorax and abdomen) using magnetic precipitation methods. Electron spectroscopic images for iron and oxygen were obtained from the extracted particles, and, by using the correspondin...

sp. The spectra are interpretedas a sum of different lines with differ-ent relative intensities. Results sug-gest the presence of magnetite par-ticles of various sizes, reopening thediscussion of the magnetic responsein fire ants.Adaptability of living beings to theenvironment includes complex navi-gation or orientation systems (Wehn-er 1996). In p...

Photolysis of denatured HbNO were carried out at temperatures below 26 K. The normalized kinetic curves were fitted using either two exponentials or a conformational substate energy distribution or a fractal model. The parameters are related to the protein structure. The two exponentials model assumes the existence of two fractions of photolysed mo...

The interaction of the tertiary amine drugs chlorpromazine and dibucaine in their cationic form with carboxyl groups at the membrane surface is studied at concentrations relevant to anesthesia. Spin-labeled stearic acid is used both to provide the carboxyl groups and to monitor binding and ionization behavior in egg lecithin liposomes. Membrane ane...

The Q-band (35 GHz) electron paramagnetic resonance (EPR) spectra of nitrosyl hemoglobin (HbNO) and nitrosyl myoglobin (MbNO) were studied as a function of temperature between 19 K and 200 K. The spectra of both heme proteins show two classes of variations as a function of temperature. The first one has previously been associated with the existence...

The temperature dependence of the spin-lattice relaxation of denatured nitrosyl hemoglobin (HbNO), nitrosyl myoglobin, powdered HbNO, and hematin-NO was studied between 4 and 70 K. The results were fitted with both Tn and e-delta/tau models. In the first model, the relaxation is mediated by tunneling modes of a two-level system. A correlation betwe...

Alkanols and tertiary amine derivative local anesthetics modify the activity of Ca(2+)-ATPase. In order to investigate the primary binding sites, associated to the functional changes, sarcoplasmic reticulum (SR) Ca(2+)-ATPase was labeled with maleimide derivative spin labels which bind covalently to SH groups of cysteine residues and allow to probe...

The EPR spectra of nitrosyl hemoglobin and myoglobin in different conditions (native, denatured and lyophilized), as well as of hematin-NO were obtained in the temperature range of 80-280 K. There is a substantial and reversible decrease of the areas of the EPR spectra of all the hemoglobin samples above 150 K. The interpretation of the results imp...

The hyperfine coupling constant,A0, of peroxylamine disulfonate in aqueous solutions depends upon the temperature and the concentration of added K2CO3buffer. Near room temperature,A0varies from 13.036 to 13.201 G for K2CO3concentrations varying from zero to near saturation. For samples prepared in 50.0 mMK2CO3, the results are independent of Fremy'...

Nitrosyl hemoglobin was prepared by bubbling fresh57Fe-enriched rat hemoglobin with NO. S- and X-band EPR spectra at 77 K are typical for anS=1/2 system with an anisotropicg-tensor and exhibit hyperfine interactions of14N with the electronic spin. Mssbauer spectra at 4.2 and 100 K consist of a superposition of spectra from high- and low-spin Fe(III...

Electron paramagnetic resonance was used to follow the time dependence of heat denaturation of met- and nitrosyl-haemoglobin (metHb and HbNO) at 60 degrees C, 70 degrees C and 80 degrees C. The spectral changes of both complexes indicate that conformational changes in the protein manifest themselves in changes of the equilibrium of hemichromes in m...

Photolysis of nitrosyl haemoglobin (HbNO) has been studied from 5.9 K to 20 K for R, T and RT conformations. It was observed that the experimental curves have two different behaviours at a given temperature in a particular conformation. At shorter time scales the data are well reproduced by a model based on fractal concepts, where the relevant para...

Spin—lattice relaxation time, T1 of tanol (protonated and deuterated), in crystal matrix of 4-hydroxy-2,2,6,6-tetramethylpiperidine has been studied in the range 10–300 K. Continuous saturation technique was applied to inhomogeneous broadened ESR signals. For tanol-p a transition was observed at 133 K due to the freezing of methyl rotations: line b...

The EPR spectrum of nitrosyl hemoglobin has been studied from 7.5 K to 104 K. It is composed of at least three components (A, B and C) which have a different dependence on temperature and power level. The A component decreases with increasing temperature. The B component disappears at around 30 K and is replaced by C. Relaxation of A follows the Or...

Photolysis of nitrosyl haemoglobin (HbNO) has been studied from 6.5 K to 20 K for different NO saturation conditions. The kinetic curves are fitted equally well by a biphasic exponential and a distribution of activation energies. The parameters are straightforwardly related to the quaternary structure of the protein. The biphasic model indicates th...

The temperature (T) dependence of the spin lattice relaxation time of nitrosyl myoglobin (MbNO) was measured in the range from 9 to 310 K. Both powdered and solution samples exhibit an unexpected dependence. Experimental data is well fitted by a Tn function with n=2.2±0.3 in this large temperature range. This result is interpreted within the tunnel...

Photolysis of HbNO has been studied from 6.2 K to 15.5 K by electron spin resonance during and after continuous illumination. Non-exponential kinetics of both dissociation and reassociation of NO was observed. The prolonged illumination separates the fast and slow ligands. This picture is consistent with NO tunnelling from two sites at different di...

The effects of pH and drug concentration on aggregation properties of chlorpromazine-HCl (CPZ) are examined. The critical micelle concentration (cmc) changes from 0.2 mM at pH 7.3 to 2 mM at pH 5.6 as estimated from the stearic acid spin label solubility measurements. For concentrations above the cmc CPZ micelles undergo a concentration-, temperatu...

Spin-lattice relaxation of Fe3+ has been measured as a function of temperature in azide methemoglobin in natural and heat denaturated condition. Of the two spin states present (S= 1 2, and S= 5 2) the high spin state always follows on Orbach mechanism of relaxation with a characteristic energy dependent on the protein conformation. In the absence o...

A comparison among three models for reassociation of carbon monoxide with carp haemoglobin, in relaxed state, is made for temperatures below 200 K. The experimental data utilized are from Cobau et al. who analysed them according to one of these models. The differences among the models lead to distinct shapes of their energy distributions. Neverthel...

The first direct measurements of magnetic properties of magnetotactic bacteria from natural samples are presented. Measurements were made at 4.2 K, using a Superconducting Quantum Interfering Device (SQUID) magnetometer. From the magnetization results an anisotropy is obtained that is typical of magnetized ferro- or ferri-magnetic materials. The av...

In hemoproteins the relaxation mechanism of iron is Orbach for high spin (HS) and Raman for low spin (LS). We found that in met-hemoglobin and met-myoglobin, under conditions in which the two spin states coexist, both the HS and the LS states relax to the lattice through Orbach-like processes. Alos, very short (approximately 1 ns) and temperature i...

The mixture of low and high iron spin states is studied by electron spin resonance in methemoglobin and in metmyoglobin between 6K and 100K. The crystals contain iron (Fe3) exclusively in the high spin state, while powdered samples show a mixture of high and low spin iron. We detected, for the first time, the low spin state in metmyoglobin at low t...

While experiments involving measurements of magnetic susceptibility in undergraduate laboratories are quite common, it is perhaps not fully appreciated that the anisotropy of magnetic susceptibility can be measured with the use of a small magnet, a microscope, and a stopwatch. This problem is discussed in relation to an illustrative example which i...

Deoxygenated sickle cells (HbS) have been shown to orient in homogeneous magnetic fields because of magnetic anisotropy of the hemes. The time of rotation is proportional to 1/H2 and is in agreement with theory. Structural information concerning the orientation of HbS molecules in the fibers is obtained from these experiments and is shown to agree...