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C Anteneodo

Publications and source records attributed to C Anteneodo.

7 recordsLinked to original sources
PubMed1998

Carboxyl groups at the membrane interface as molecular targets for local anesthetics.

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 anesthetic concentrations are spectrophotometrically obtained. They are shown to determine the drug influence on carboxyl groups at the membrane surface, independently of aqueous concentrations. The intramembrane association constants (related to the usual aqueous phase ones through the partition coefficient) of the drugs with fatty acids are determined. The same value (10(2) M-1) is obtained for both drugs, suggesting that it is approximately the same for all tertiary amine local anesthetics. pH titrations of anesthetic-treated spin-labeled membranes are performed. The observed shifts in the fatty acid pK are higher than can be produced assuming uniform distribution of the drug in the membrane surface, implying that there is an increased affinity of local anesthetics for superficial carboxyl. This affinity could account for the resting block of voltage-gated Na+ channels. Under these considerations, local anesthetic binding sites at voltage-gated Na+ channels and at sarcoplasmic reticulum Ca(2+)-ATPase are proposed.

Anesthetics, Local↗
PubMed1997

Nonlinear Dynamics of Lipid Films under Electric Forces

We study the dynamics and rupture of lipid films perturbed in the symmetric mode squeezing through an electrohydrodynamical approach. The lipid phase and the two surrounding aqueous phases are considered as incompressible Newtonian viscous fluids submitted to van der Waals, steric, and electric body forces. A nonlinear evolution equation for the film thickness, at the long-wavelength limit, is obtained for two symmetric cases: a film with equally charged surfaces with no potential drop and a neutral film submitted to an external electric field. At the long-wavelength limit, the electric term only influences the film evolution when the electric field inside the film is nonvanishing. We solve numerically, as an initial value problem with periodic boundary conditions, the nonlinear evolution equation. The rupture time is obtained and compared with analytical estimates. Sufficiently strong steric forces prevent the film from narrowing beyond a minimum thickness leading the film to a steady state different from the planar one consistently with the nonlinear analytical approach. The presence of a transmembrane electric potential destabilizes the perturbed film as predicted by the linear and nonlinear approaches; however, as expected, destabilization is not relevant at physiological values of the potential drop.

Journal Article↗
PubMed1996

Interaction of alkanols and local anesthetics with spin-labeled Ca(2+)-ATPase of sarcoplasmic reticulum vesicles.

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 regions of the protein close to those residues. The EPR measurements showed motional constraints induced by drug-treatment which indicate changes in the enzyme dynamics and structure. n-Alkanols are shown to affect some of the protein-bound labels by restricting their motion. There is, however, no correlation between the functional effects and the observed motional restriction, in the sense that concentrations of the different alcohols leading to the same functional effects do not induce the same degree of restriction. Dibucaine and tetracaine at functional relevant concentrations also restrict the movement of protein bound labels. But, in this case, correlation between spectral changes and functional effects is observed.

1-Butanol↗
PubMed1995

Interaction of chlorpromazine with phospholipid membranes. An EPR study of membrane surface potential effects.

The interaction of chlorpromazine (CPZ) with artificial membranes (egg-yolk phosphatidylcholine liposomes) has been studied. Measurements of the surface electric potential, which is modified in the presence of the ionized form of the drug, were obtained by electron paramagnetic resonance spectroscopy (EPR) using a positively charged amphiphilic spin-probe. This probe partitions between the aqueous and lipidic phases depending on the surface potential and on the structural state of the membrane. The surface potential was measured as a function of drug concentration in the range where the spectral line-shapes are not affected by the incorporation of the drug. From these experimental results and through an appropriate formalism we obtain information on the binding of the drug to the lipid bilayer and on the ionization of the drug in the lipidic phase.

Binding Sites↗
PubMed1995

A model for nucleotide sequences.

We propose a model for generating "artificial" nucleotide sequences and, by the method of mapping those sequences onto a "DNA-walk," we analyze the presence of correlation between nucleotides. Artificial sequences are constructed considering, basically, interactions between first neighbors and between more distant units. We show that long-range correlations may be favored by the occurrence of intrastrand interactions, which give a nonlinear characteristic to the sequence.

Antithrombin III↗
PubMed1994

Interaction of dibucaine with the transmembrane domain of the Ca(2+)-ATPase of sarcoplasmic reticulum.

The site of interaction of dibucaine with the Ca(2+)-ATPase of rabbit sarcoplasmic reticulum, an ion-transporting membrane protein, was investigated by determining the effect of dibucaine on the denaturation of the transmembrane domain and the aqueous domain containing, respectively, the high-affinity Ca2+ binding sites and the site of ATP hydrolysis. In the absence of Ca2+, a single irreversible denaturation transition with Tm approximately equal to 49 degrees C is observed for the Ca(2+)-ATPase by differential scanning calorimetry (DSC). In the presence of Ca2+, but not Mg2+, Sr2+, or Ba2+, a new high-temperature transition is observed that has been shown to be due to stabilization of the transmembrane region [Lepock, J. R., Rodahl, A. M., Zhang, C., Heynen, M. L., Waters, B., & Cheng, K. H. (1990) Biochemistry 29, 681-689]. The maximum stabilization corresponds to a shift in Tm of 13.8 degrees C, and Hill analysis indicates that the Ca2+ binding site yielding stabilization has a Kd = 2.5 x 10(-4) M with a cooperativity (n) of 1. Thus, stabilization is due to Ca2+ binding not to the high-affinity sites but to one of the previously observed sites of low or intermediate affinity, which must be located in the transmembrane or stalk subdomains. Dibucaine has little effect on the Tm of the aqueous domain, but it decreases the Tm of the transmembrane domain with Kd approximately equal to 4.1 x 10(-4) M and a cooperativity of approximately 1.6, implying that destabilization is due to the binding of dibucaine to sites of intermediate or moderately high affinity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗