Biomedical subjects

J M de la Fuente

Publications and source records attributed to J M de la Fuente.

9 recordsLinked to original sources

PubMed2006

Fe impurities weaken the ferromagnetic behavior in Au nanoparticles.

In this Letter, we report on a crucial experiment showing that magnetic impurities reduce the ferromagnetic order temperature in thiol-capped Au glyconanoparticles (GNPs). The spontaneous magnetization of AuFe GNPs exhibits a fast decrease with temperature that contrasts with the almost constant value of the magnetization observed in Au NPs. Moreover, hysteresis disappears below 300 K. Both features indicate that Fe impurities reduce the high local anisotropy field responsible for the ferromagnetic behavior in Au GNPs. As a consequence, the amazing ferromagnetism in Au NPs should not be associated with the presence of magnetic impurities.

Journal Article↗

PubMed2005

Gold nanoparticles with different capping systems: an electronic and structural XAS analysis.

Gold nanoparticles (NPs) have been prepared with three different capping systems: a tetralkylammonium salt, an alkanethiol, and a thiol-derivatized neoglycoconjugate. Also gold NPs supported on a porous TiO(2) substrate have been investigated. X-ray absorption spectroscopy (XAS) has been used to determine the electronic behavior of the different capped/supported systems regarding the electron/hole density of d states. Surface and size effects, as well as the role of the microstructure, have been also studied through an exhaustive analysis of the EXAFS (extended X-ray absorption fine structure) data. Very small gold NPs functionalized with thiol-derivatized molecules show an increase in d-hole density at the gold site due to Au-S charge transfer. This effect is overcoming size effects (which lead to a slightly increase of the d-electron density) for high S:Au atomic ratios and core-shell microstructures where an atomically abrupt Au-S interface likely does not exist. It has been also shown that thiol functionalization of very small gold NPs is introducing a strong distortion as compared to fcc order. To the contrary, electron transfer from reduced support oxides to gold NPs can produce a higher increase in d-electron density at the gold site, as compared to naked gold clusters.

Journal Article↗

PubMed2004

Permanent magnetism, magnetic anisotropy, and hysteresis of thiol-capped gold nanoparticles.

We report on the experimental observation of magnetic hysteresis up to room temperature in thiol-capped Au nanoparticles with 1.4 nm size. The coercive field ranges from 860 Oe at 5 K to 250 Oe at 300 K. It is estimated that the Au atoms exhibit a magnetic moment of mu=0.036mu(B). However, Au nanoparticles with similar size but stabilized by means of a surfactant, i.e., weak interaction between protective molecules and Au surface atoms, are diamagnetic, as bulk Au samples are. The apparent ferromagnetism is consequently associated with 5d localized holes generated through Au-S bonds. These holes give rise to localized magnetic moments that are frozen in due to the combination of the high spin-orbit coupling (1.5 eV) of gold and the symmetry reduction associated with two types of bonding: Au-Au and Au-S.

Journal Article↗

PubMed2001

Adhesion Forces between Lewis(X) Determinant Antigens as Measured by Atomic Force Microscopy.

The adhesion forces between individual molecules of Lewis(X) trisaccharide antigen (Le(X) ) have been measured in water and in calcium solution by using atomic force microscopy (AFM, see graph). These results demonstrate the self-recognition capability of this antigen, and reinforce the hypothesis that carbohydrate-carbohydrate interaction could be considered as the first step in the cell-adhesion process in nature.

antigens↗

PubMed1997

Aluminum tolerance in transgenic plants by alteration of citrate synthesis.

Aluminum when in soluble form, as found in acidic soils that comprise about 40 percent of the world's arable land, is toxic to many crops. Organic acid excretion has been correlated with aluminum tolerance in higher plants. Overproduction of citrate was shown to result in aluminum tolerance in transgenic tobacco (Nicotiana tabacum) and papaya (Carica papaya) plants.

Aluminum↗

PubMed1994

A trial of carbamazepine in borderline personality disorder.

Borderline personality disorder does not have a first choice pharmacological treatment. We studied 20 borderline inpatients in a double-blind parallel placebo-controlled trial with carbamazepine for a mean of 30.9 days. No significant positive effects of the drug were found.

Adult↗

PubMed1994

Temporal glucose metabolism in borderline personality disorder.

The pathophysiology of borderline personality disorder (BPD) is obscure. Underlying organic factors such as epilepsy are suspected because clinical characteristics of the syndrome are similar to some manifestations of patients with complex partial seizures (CPS). Positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) reveals hypometabolism in the area surrounding epileptic foci. To test the epilepsy hypothesis in BPD, we have explored 10 patients with BPD and compared them with 15 control subjects using PET with FDG. We conclude that PET provides no metabolic indication of temporal lobe epilepsy in BPD.

Adult↗

PubMed1992

Flow cytometric analysis of Saccharomyces cerevisiae autolytic mutants and protoplasts.

Simple methods, based on the technique of flow cytometry, have been developed for the phenotypic characterization of yeast autolytic mutants and for the analysis of the formation and regeneration of the yeast protoplasts. The expression of lytic mutations determined uptake of the fluorescent dye propidium iodide, which could be carefully monitored by flow cytometry. Mixed populations of lysed and viable cells were precisely quantified and sorted, and the technique was also applied to demonstrate protection from lysis of mutant cells with cell wall defects, in the presence of osmotic stabilizers. Protoplast formation and regeneration was monitored by analysing relative cell size; this was facilitated by the preparation of homogeneous protoplast preparations. The technique of flow cytometry proved superior to other conventional methods for these types of study.

Autolysis↗

PubMedDate not supplied

[An electromagnetic problem].

Induced psychotic disorder in infrequent. We report a case in which four members of the same family were affected. The bibliography is reviewed and certain etiological factors implicated in our case are discussed.

Adult↗