Juan S. Gómez-Jeria

A Neurobiological Model for Near-Death Experiences

Article presenting a neurobiological model for near-death experiences (NDEs) in an attempt to correlate the biological and psychological domains. This model is based on temporal lobe dysfunction, hypoxia/ischemia, stress, and neuropeptide/neurotransmitter imbalance.

SERS and theoretical studies of arginine.

Arginine amino acid (Arg) has been vibrationally studied through its infrared, Raman and surface-enhanced Raman scattering (SERS) spectra, and theoretical calculations. Net charge is used to predict the possibility to obtain the SERS spectrum of Arg in colloidal solution. The interpretation of the SERS spectral data suggests that the Arg-Ag nanoparticles interaction in a colloidal solution and in the case of the Arg coated by Ag is mainly verified through the guanidinium moiety. Theoretical calculations performed by using extended Hückel theory method for a model of Arg interacting with an Ag cluster support the observed SERS experimental result.

Surface-enhanced Raman scattering and theoretical studies of the C-terminal peptide of the β-subunit human chorionic gonadotropin without linked carbohydrates.

Raman and surface-enhanced Raman scattering (SERS) spectra of the synthetic carboxy terminal peptide of human chorionic gonadatropin β-subunit free of carbohydrate moieties(P37) are reported. The spectral analysis is performed on the basis of our reported Raman spectrum and SERS data of oligopeptides displaying selected amino acids sequences MRKDV, ADEDRDA, and LGRGISL. SERS samples of P37 were prepared by coating the solid peptide with metal colloids on a quartz slide. This treatment makes possible to obtain high spectral batch to batch reproducibility. Amino acids components of P37 display net charges and hydrophobic characteristics, which are related to particular structural aspects of the adsorbate-substrate interaction. The spectroscopic results are supported by quantum chemical calculations performed by using extended Hückel theory method for a model of P37 interacting with an Ag surface. The P37-metal interaction is drove by positively charged fragments of selected amino acids,mainly threonine 109, lysine 122, and arginine in positions 114 and 133. Data here reported intend to contribute to the knowledge about the antigen-antibody interaction and to the drugs delivery research area

A near-death experience among the Mapuche people

This paper describes a possible near-death experience (NDE) among the Mapuche people of Chile. The individual reporting the experience was in a cataleptic-like state for two days, the experience itself occurring at the end of this period. Some common features of NDEs, such as encounters with deceased people and being sent back, are present, together with clear evidence that past and present cultural environment shape in part the content of mental experiences.

Quantum chemical study of electronic structure and receptor binding in opiates.

Abstract A Quantitative Structure-Activity Relationship study for a group of opiates interacting with the mu receptor was carried out. The study consisted in searching a relationship between the drug-receptor equilibrium constant and steric/ electronic structure factors. Several equations were obtained and analyzed. It is possible to conclude from this study that if all the experimental values correspond only to the interaction with the mu receptor, then the hypothesis of a common skeleton interacting with the mu receptor cannot be supported.

Quantum-chemical Structure-Activity Relationships in carbamate insecticides

A non-empirical Quantitative Structure-Activity Relationship (QSAR) method is employed to analyze the reversible complex formation during the reaction of phenyl-N-methylcarbamates with the enzyme acetylcholinesterase. No common equation for theortho, meta andpara-substituted molecules could be obtained. A good description of the reversible complex formation is achieved by separating the molecules according to the position of the aromatic substituent. The introduction of a substituent orientation parameter helps account for the percentage of molecules attaining the proper orientation to interact with their partner. This parameter is useful in describing physical effects depending on the rotational partition function. A model for the carbamate-acetylcholinesterase reversible complex is proposed.

Influence of aluminum oxide on the prebiotic thermal synthesis of Gly-Glu-(Gly-Glu)n polymer

The effect of the aluminum oxide on the thermal synthesis of the glycine-glutamic acid (Gly-Glu-(Gly-Glu)(n) polymer is described. The thermal synthesis in the molten state was carried out in the absence and presence of the oxide. In both cases, the vibrational spectra showed characteristic group frequencies corresponding predominantly to a Gly-Glu-(Gly-Glu)(n) sequence in the polymeric structure. The theoretical spectral data support the experimental proposed Gly-Glu-(Gly-Glu)(n) sequence for the polymer. The SEM-EDX characterization of the solid phase involved in the thermal synthesis showed that the aluminum oxide participates as a site for nucleation and growth of the polymer, explaining the increase of 25% efficiency in the presence of aluminum oxide. Electrophoresis data show shorter polypeptide chains in the presence of aluminum oxide.

Quantum-Chemical Structure-Affinity Studies on Kynurenic Acid Derivatives as Gly / NMDA Receptor Ligands

A quantum-chemical structure)affinity relationship for kynurenic acid . derivatives KA acting at the GlyrNMDA site is presented. The results of this study . strongly suggest that these molecules bind to this site through three mechanisms: 1 a H . bond between the N atom and an OH group of the receptor; 2 a p)p orbital interaction between the empty MOs of the aromatic ring of KA derivatives and occupied MOs of the . receptor; and 3 an orbital interaction between the carboxylate group and an electron- accepting site of the receptor. Q 1999 John Wiley & Sons, Inc. Int J Quant Chem 71: 505)511, 1999

Interaction of the CLPFFD peptide with gold nanospheres. A Raman, surface enhanced Raman scattering and theoretical study

In a previous work we demonstrated that toxic aggregates of the protein β-amyloid (ATAβ) involved in the Alzheimers disease (AD) can be destabilized upon electromagnetic irradiation of the peptide Cys-Leu-Pro-Phe-Phe-Asp (CLPFFD) adsorbed on gold nanospheres (AuNSs). For a selective recognition of the therapeutic target (i.e. ATAβ) of AD by the conjugates peptide-nanoparticle it is relevant to understand how the interaction between attached ligands and nanoparticles occurs. In this work a surface enhanced Raman scattering spectroscopy (SERS) study of the interactions of CLPFFD with AuNSs of 10nm average diameter was carried out. The SERS data suggest that phenylalanine displays its aromatic ring coplanar to the surface which is supported by theoretical data obtained from molecular mechanics (MM) and Extended Hückel Theory (EHT) calculations.

A THEORETICAL STUDY OF THE INHIBITION OF WILD-TYPE AND DRUG-RESISTANT HTV-1 REVERSE TRANSCRIPTASE BY SOME THIAZOLIDENEBENZENESULFONAMIDE DERIVATIVES

ABSTRACT We present the results of a quantum chemical study of the relationship between the electronic-conformational structure of a group of thiazolidenebenzenesulfonamide derivatives (TBS) and their Immunodeficiency Type 1 Virus (HIV-1) Reverse Transcriptase (RT, the wild one and two mutated types) inhibitory capacity. Our results show that the variation of the inhibitory capacity of TBS against the three types of HIV-1 RTs is regulated by different mechanisms. Also, as expected in a highly specific interaction, molecular orbitals other than the frontier molecular orbitals seem to regulate the inhibition of RT by TBS. The increase of the inhibitory capacity with increasing size of some substituents is not attributable to their interaction with a hydrophobic site but to their effect on the distribution of the rotational velocities. Specific π-π stacking interactions are the main components of the TBS-RT coupling. For each type of RT, the results provide a list of sites in the common skeleton that can be modulated through substitution to improve the inhibitory capacity.Keywords: ZINDO/1, HIV-1 Reverse Transcriptase, Thiazolidenebenzenesulfonamide, KPG method, structure-activity relationships.