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F Reig

Publications and source records attributed to F Reig.

At least 37 records · Page 2Linked to original sources
PubMed1996

A fluorescence and CD study on the interaction of synthetic lipophilic hepatitis B virus preS(120-145) peptide analogues with phospholipid vesicles.

The interaction of the immunogenic peptide of human hepatitis B virus (HBV) preS(120-145), including B and T epitopes, with phospholipid vesicles has been studied by fluorescence techniques and CD. In addition, interaction of three lipopeptides derived from preS(120-145) containing stearoyl, cholanoyl, and tripalmitoyl-S-glyceryl-cysteine (Pam3C) SS moieties with dipalmitoylphosphatidylcholine (DPPC) has been investigated by polarization fluorescence spectroscopy. Fluorescence experiments showed an increase in fluorescence intensity and a blue shift of the maximum emission wavelength upon interaction of preS(120-145) with DPPC vesicles below the transition temperature (Tc), indicating that the tryptophan moiety enters a more hydrophobic environment. Moreover, fluorescence polarization experiments showed that the peptide decreased the membrane fluidity at the hydrophobic core, increasing the Tc of the lipid and decreasing the amplitude of the change of fluorescence polarization associated with the cooperative melting of 1,6-diphenyl-1,3,5-hexatriene labeled vesicles. The absence of leakage of vesicle-entrapped carboxyfluorescein indicates that the peptide did not promote vesicle lysis. Besides, the three lipopeptides derived from preS(120-145) showed a more pronounced rigidifying effect at the hydrophobic core of the bilayer, with a significative increase in the Tc. Stearoyl- and cholanoyl-preS(120-145) restricted the motion of lipids also at the polar surface, whereas Pam3CSS-preS(120-145) did not alter the polar head group order. Finally, CD studies in 2,2,2-trifluoroethanol or in presence of vesicles suggested that the bound peptide adopted amphiphilic alpha-helical and beta-sheet structures, with an important contribution of the beta-turn. It is concluded that preS(120-145) can interact with the lipid membrane through the formation of an amphipathic structure combination of beta-sheet and alpha-helix aligned parallel to the membrane surface, involving the N-terminal residues, and penetrating only a short distance into the hydrophobic core. The C-terminal part, with a combination of beta-turn and beta-sheet structure, remains at the outer part of the bilayer, being potentially accessible to immunocompetent cells. Furthermore, coupling of an hydrophobic moiety to the N-terminal part of the peptide favors anchoring to the membrane, probably facilitating interaction of the peptide with the immunoglobulin receptor. These results are in agreement with the induction of immune response by preS(120-145) and with the enhanced immunogenicity found in general for lipid-conjugated immunopeptides.

Amino Acid Sequence↗
PubMed1996

Synthesis, lipophilic derivatization and interaction with liposomes of HAV-VP3 (102-121) sequence by using spectroscopic techniques.

Hepatitis A virus (HAV) is composed mainly of three structural capsid proteins: VP1, VP2 and VP3. Our group has reported the synthesis and the immunogenic evaluation of VP3 (110-121) peptide sequence. In the present work, in order to stimulate a T-cell immune response, we have selected the HAV-VP3 (102-121) peptide which has maximum amphipathicity. Its synthesis was carried out manually in the solid phase and semipreparative HPLC was used for purification of the crude peptide. Finally the purified peptide was characterized by analytical HPLC, amino acid analysis and MS. A palmitoyl derivative of VP3 (102-121) was synthesized to modify the hydrophobicity of the peptide. Both free and lipophilically derivatized peptides were incorporated into multilamelar liposomes. Physicochemical studies of the HAV-related peptides described above were carried out using monolayers as membrane models. Compression isotherms, surface activity and penetration kinetics into dipalmitoylphosphatidylcholine monolayers were determined. Moreover, changes in the fluidity of bilayers induced by these peptides were determined by means of polarizable probes such as 8-anilino-1-naphthalenesulfonic acid and 1,6-diphenyl-1,3,5-hexatriene. The integrity of the membranes has also been ascertained with the carboxyfluorescein.

Amino Acid Sequence↗
PubMed1995

Anti-hepatitis A virus antibody response elicited in mice by different forms of a synthetic VP1 peptide.

Peptide VP1 (11-25) of the capsid of hepatitis A virus was synthesized by the Fmoc-polyamide solid phase method, and administered to mice in different forms: (1) free, (2) encapsulated in multilamellar liposomes, (3) coupled to keyhole limpet hemocyanin (KHL), and (4) incorporated into a tetrameric branched lysine core. The highest anti-VP1 peptide responses were generated by synthetic peptides entrapped into liposomes and coupled to KLH. No anti-HAV response was generated with the free peptide, while all the other forms induced both anti-HAV and HAV-neutralizing antibodies. Maximum neutralization indices were observed in ascites from mice treated with liposome-entrapped and KLH peptides.

Adjuvants, Immunologic↗
PubMed1995

Sustained release of liposome-encapsulated enrofloxacin after intramuscular administration in rabbits.

Enrofloxacin was encapsulated in multilamellar liposomes composed of phosphatidylcholine and cholesterol (molar ratio, 1:1), and its potential use as sustained release formulation was evaluated. The encapsulated drug was administered IM to rabbits (n = 6). Results indicated that absorption rate was slow, compared with previous studies; additionally, peak concentration was lower (0.5 +/- 0.1 microgram/ml), and the time to peak concentration was considerably longer for liposome-encapsulated enrofloxacin (1.5 +/- 1.08 hours) than for unencapsulated drug. Apparent elimination half-life of drug in the body was significantly (P < 0.05) increased (4.05 +/- 1.08 hours) when it was administered encapsulated in liposomes. Large-size liposomes containing enrofloxacin administered IM to rabbits gave sustained drug release from the injection site, providing therapeutic and prolonged plasma concentrations of drug in the body.

Animals↗
PubMed1995

Solid phase synthesis and immunogenicity of a VP3 peptide from hepatitis A virus.

The synthesis of a peptide belonging to the VP3 capsid protein of Hepatitis A virus has been accomplished by the continuous flow Fmoc-polyamide solid phase method. The use of methoxytrimethylbenzenesulphonyl (Mtr) and pentamethylchromansulphonyl (Pmc) as arginine side-chain protecting groups in the presence of tryptophan without lateral protection or protected with t-Boc is discussed. The synthetic VP3 peptide has been administered to mice in different forms: (i) free, (ii) coupled to keyhole limpet hemocyanin, (iii) encapsulated in multilamellar (MLV) liposomes, and (iv) incorporated to a tetrameric branched lysine core. The immune response induced by these preparation is reported.

Animals↗
PubMed1994

Effect of succinylation on the membrane activity and conformation of a short cecropin A-melittin hybrid peptide.

A 15-residue hybrid peptide (KWKLFKKIGAVLKVL-amide) incorporating partial sequences of cecropin A and melittin causes the release of carboxyfluoresceine encapsulated in phosphatidylcholine liposomes. Succinylation of the amino groups in the N-terminus and lysine side chains inhibits the effect of this peptide on liposome permeability. Conformational analysis of the parent peptide and its succinyl derivative by CD and nmr indicates that both peptides form amphipathic alpha-helices in the presence of hexafluoro-2-propanol, but only the unmodified peptide acquires a relevant level of alpha-helical conformation in the presence of liposomes.

Amino Acid Sequence↗
PubMed1994

Coating of liposomes with transferrin: physicochemical study of the transferrin-lipid system.

Transferrin was incorporated into the external surface of liposomes that were previously derivatized with ceramides. This new hydrophobic derivative of transferrin was incubated with liposomes at different protein-to-lipid ratios. The surface activity of both native and derivatized transferrin was determined with monomolecular layers as a membrane model. The maximal interaction was found with dipalmitoylphosphatidylcholine in all the experiences.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

Interaction of opiate molecules with lipid monolayers and liposomes.

The interaction of opiate molecules (buprenorphine, codeine, dextromethorphan, diprenorphine, etorphine, meperidine, methadone, morphine, and naloxone) with lipids (phosphatidylcholine, phosphatidylinositol, phatidylinositol, phosphatidylserine, and cholesterol) by using liposomes and monomolecular layers as membrane models is described. The ability of opiates to induce leakage of carboxyfluorescin from liposomes is highly dependent on the hydrophobicity of the opiate molecules. Buprenorphine and etorphine increased the membrane permeability in all the experiments. On the contrary, naloxone, morphine, and codeine only caused a slight release of the entrapped dye in the presence of acidic phospholipids. Moreover, the leakage of carboxyfluorescein is directly related to the concentration of drug in the incubation media. Studies of the kinetics of the surface penetration of these molecules into monolayers of phospholipids were performed. Again, in this system, buprenorphine and etorphine exhibited stronger interactions than the most hydrophilic opiates. Nevertheless, in these experiments, differences among the opiate molecules are not so high as in the liposomes. The time course of the penetration of all of these molecules in the monolayers fits the Lineweaver-Burk equation. This fact suggests a lack of specific interactions and the predominance of hydrophobic factors. Moreover, the high percentage of release of entrapped dye caused by some opiate molecules suggests a possible toxic side-effect for these agents.

Chemical Phenomena↗
PubMed1992

Pharmacokinetics of enrofloxacin after intravenous and intramuscular injection in rabbits.

The pharmacokinetics and bioavailability of enrofloxacin were determined after IV and IM administration of 5 mg/kg of body weight to 6 healthy adult rabbits. Using nonlinear least-squares regression methods, data obtained were best described by a 2-compartment open model. After IV administration, a rapid distribution phase was followed by a slower elimination phase, with a half-life of 131.5 +/- 17.6 minutes. The mean body clearance rate was 22.8 +/- 6.8 ml/min/kg, and the mean volume of distribution was 3.4 +/- 0.9 L/kg. This large volume of distribution and the K12/K21 ratio close to 1, indicated that enrofloxacin was widely distributed in the body, but not retained in tissues. After a brief lag period (6.2 +/- 2.86 min), IM absorption was rapid (4.1 +/- 1.3 min) and almost complete. The mean extent of IM absorption was 92 +/- 11%, and maximal plasma concentration of 3.04 +/- 0.34 micrograms/ml was detected approximately 10 minutes after administration.

Animals↗
PubMed1990

A synthetic glycopeptide of substance P analogue (SP6-11) with enhanced NK-1 receptor specificity.

A new glycopeptide analogue of substance P (6-11) (SP6-11), namely, N1,6 (beta-D-glucopyranosyl) [Glu6, Pro9]SP6-11, has been synthesized and found to be water soluble. The in vitro biological activity of this glycopeptide was determined for spasmogenic activity in the guinea pig ileum and for potentiation of electrically evoked contractions in the rat vas deferens. Thus, activities on NK-1, NK-2, and NK-3 receptor types have been differentiated by two assays and, in the case of NK-1 and NK-3, receptors in guinea pig ileum (GPI) were assayed using specific pharmacological procedures. The ED50 values for the analogue and reference peptides substance P (SP), neurokinin A(NKA), and neurokinin B (NKB) were determined and potencies relative to SP were calculated. The analogue is three times more potent than the potent NK-1 agonist SP on NK-1 receptors. Moreover, this glycopeptide proved to be as selective for the NK-1 receptor as the specific agonist SPOMe (the methyl ester of substance P).

Animals↗
PubMed1990

Antinociceptive activity of glycosidic enkephalin analogues.

The antinociceptive activity of two new enkephalin analogues: N1.5-(beta-D-glucopyranosyl)[D-Met2, Pro5]enkephalinamide and N1.5-(beta-D-galactopyranosyl)[D-Met2, Pro5]enkephalinamide was assessed using the tail immersion and paw pressure behavioural tests. Both enkephalin analogues appear to be more active than morphine when injected either into the fourth ventricle or intrathecally; the galactose analogue is more than 5000 times more active than morphine when injected into the fourth ventricle. The analgesic effects produced by the analogues are partially reversed by SC naloxone (0.1 mg/kg) and totally reversed when the dose of naloxone used was 1 mg/kg, suggesting that the analogues act upon more than one type of opiate receptor (mu/delta).

Analgesics↗
PubMed1990

Continuous-flow solid-phase synthesis of potential antigenic peptides of hepatitis B virus.

The synthesis of three hepatitis B surface antigens derived from S and pre-S proteins (adw S(140-147), [Tyr148] adw S(139-148), and adw pre-S(120-145)) has been accomplished by the continuous flow Fmoc-polyamide solid phase method. The use of different scavengers and trimethylsilyl bromide (TMSBr) in trifluoroacetic acid as deprotecting procedures is discussed.

Amino Acid Sequence↗
PubMed1990

Synthesis and purification of two SP (6-11) analogues with enhanced selectivity for the NK-1 receptor.

Two hexapeptide analogues of Substance P (6-11) have been synthesized. Replacement of Gly9 by proline provides a peptide with tenfold enhanced selectivity for the NK-1 receptor. The corresponding proline-containing glycopeptide incorporating a beta-D-glucopyranosyl residue linked to the side-chain of Glu6 was 100 times more selective than Substance P for the same receptor.

Chemical Phenomena↗
PubMed1989

Synthesis and conformational analysis of a series of galactosyl enkephalin analogues showing high analgesic activity.

Two galactosyl derivatives of [DMet2,Pro5] enkephalin-amide (compound 1), namely [DMet2,Pro5] enkephalin [N1.5-beta-D-galactopyranosyl] amide (compound 2) and O1.5-(beta-D-galactopyranosyl) [DMet2,Hyp5] enkephalin-amide (compound 3) have been synthesized. Such glycosylpeptides have been shown to be extremely potent analgesic agonists. The conformational analysis of these three compounds in DMSO-d6 solution has been carried out using two-dimensional NMR methods. Both the parent compound (1) and the beta N-galactosyl derivative (2) show similar NMR parameters which are consistent with fairly rigid beta-strands at both the N-terminus and C-terminus, connected by a glycine residue that displays a mixture between multiple conformational states. Thus, although the beta N-galactosyl derivative (2) has been shown to be significantly more potent than the parent compound (1) in the tail immersion and paw pressure tests of analgesia, no correlation can be established between the conformation of (1) and (2) in DMSO and the difference in analgesic activity. In contrast, important conformational differences with respect to (1) and (2) have been detected in the beta O-galactosyl derivative (3). In this case, only one of the likely conformations for (1) and (2) are consistent with the experimental data. These data show that the position of the galactose residue in compound (3) causes Gly3 to loose flexibility leading to a more rigid folded conformation. Such a change in conformation could be related to the difference in analgesic activity between (2) and (3).

Amino Acid Sequence↗
PubMed1989

In vitro activity and selectivity of glucosidic SP(6-11) analogues.

The relative potencies of a series of substance P (6-11) analogues have been determined for spasmogenic activity in the guinea pig ileum in vitro and for potentiation of electrically evoked contractions in the rat vas deferens in vitro. ED50 values were determined for the new analogues. Substance P and its methyl ester were used as standard agonists. Substitution of Gly9 by Pro on [Glu6]SP(6-11) increased four times the activity on the NK-1 receptor. The glycosilation of [Glu6]SP(6-11) by the incorporation of a beta-D-glucopyranosyl amide residue on the gamma-carboxyl group of Glu6 reduced both the activity and selectivity. The simultaneous substitution of Gly9 by Pro and the incorporation of a monosaccharide moiety on the gamma-carboxyl of Glu6 on [Glu6]SP(6-11) yielded an analogue with 60-fold enhanced selectivity relative to substance P for the NK-1 receptor. These results may indicate that the critical factor providing potency to SP(6-11) analogues is mostly related to conformational rather than hydrophilicity aspects of the molecular structure.

Animals↗
PubMed1989

Synthesis and biological activity of substance P analogues.

The synthesis of the hexapeptide [Glu6]SP6-11 and its glycosylated analogue at the Glu6 gamma-carboxyl position by solution procedures according to several strategies is discussed. The biological activity of SP, [Glu6]SP6-11 (VI) and [Glu(beta-D-Glcp)6]SP6-11 (VIII) have been determined and compared to SP by the GPI and RVD assays. The introduction of a beta-D-glucopyranosyl moiety at the sixth position of the [Glu6]SP6-11 did not affect to a great extent the in vitro activity pattern of the parent hexapeptide.

Animals↗