[Ion channels of various types induced in lipid membranes by gramicidin A derivatives carrying a cationic sequence at their C-termini].

The channel-forming activity of gramicidin A derivatives carrying positively charged amino acid sequences at their C-termini was studied on planar bilayer lipid membranes and liposomes. We showed previously that, at low concentrations, these peptides form classical cation-selective pores typical of gramicidin A, whereas, at high concentrations, they form large nonselective pores. The ability of the peptides to form nonselective pores, which was determined by the efflux of carboxyfluorescein, an organic dye, from liposomes, decreased substantially as the length of the gramicidin fragment in the series of cationic analogues was truncated. CD spectra showed that large pores are formed by peptides having both beta6.3 single-stranded and beta5.6 double-stranded helical conformations of the gramicidin fragment, with the C-terminal cationic sequence being extended. The dimerization of the peptides by the oxidation of the terminal cysteine promoted the formation of nonselective pores. It was shown that nonselective pores are not formed in membranes of erythrocytes, which may indicate a dependence of the channel-forming ability on the membrane type. The results may be of interest for the directed synthesis of peptides with antibacterial activity.

[Epitope of the catalytic subunit of viscumin, exposed on its interaction with a lipid bilayer]. / Epitop kataliticheskoi sub''edinitsy viskumina, poiavliaiushchiisia pri ee vzaimodeistvii s lipidnym bisloem.

It was previously shown that the catalytic subunit of the plant toxin viscumin induces aggregation of small unilamellar liposomes and this process is inhibited by the mab_TA7 monoclonal antibody produced to the denatured catalytic subunit of viscumin (Agapov, I.I. et al., FEBS Lett., 1999, vol. 464, pp. 63-66). The interaction of the synthetic F101-T105 and A96-T105 fragments of the viscumin catalytic subunit with the mab_TA7 monoclonal antibody was studied by 1H NMR spectroscopy. The results of this study demonstrated that only the A96-T105 fragment is capable of binding to mab_TA7. A nuclear Overhauser effect observed in the antigen-antibody complex and registered on the resonances of the free peptide and exchanging between the free state and the antibody-bound state was analyzed; the mab_TA7 antigen determinant (H99-T105) was identified; and its conformation and orientation within the complex with the antibody were determined. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2003, vol. 29, no. 6; see also http://www.maik.ru.

[Antigenic structure of the foot-and-mouth virus. VI. Functional segments of the immunodominant region of the VP1 protein of foot-and-mouth virus strains O1K and A22]. / Antigennaia struktura virusa iashchura. VI. Funktsional'nye uchastki immunodominantnogo raiona belka VP1 virusa iashchura shtammov O1K i A22.

B- and T-epitopes have been localized within the protective fragments of VP1 protein, viz., 136-152 of the O1K strain and 135-159 of the A22 strain of the foot-and-mouth disease virus (FMDV). Antibodies eliciting after immunization of various animals with the 135-159 A22 peptide are directed to different sites of the peptide. Immunogenicity of fragments of the 135-159 A22 peptide on mice correlates with their activity on T-cells of the same animals and protective activity on guinea pigs. The investigations were carried out using synthetic fragments of the 136-152-O1K and 135-159-A22 peptides.

[Antigenic structure of the foot-and-mouth virus. V. Protection of naturally susceptible animals from foot-and-mouth disease using a synthetic peptide]. / Antigennaia struktura virusa iashchura. V. Zashchita prirodonovospriimchivykh zhivotnykh ot zabolevaniia iashchurom s pomoshch'iu sinteticheskogo peptida.

We have synthesized the peptide representing 135-159 VP1 sequence of A22 strain of the foot-and-mouth disease virus (FMDV). The synthetic peptide induced 100% protection of guinea pigs against the disease. Two-fold immunization of cuttle with the peptide and single immunization of sheep induced full protection of the animals against A22 strain of FMDV.

[Antigenic structure of foot-and-mouth virus. IV. Synthesis and immunogenic properties of new fragments of the VP1 protein of food-and-mouth virus strain A22]. / Antigennaia struktura virusa iashchura. IV. Sintez i immunogennye svoistva novykh fragmentov belka VP1 virusa iashchura shtama A22.

A synthesis of new fragments of VP1 protein with the specificity of A22 strain of foot-and-mouth disease virus is described. Immunization with the free 136-152 peptide and KLH-conjugates of the peptides 136-152 and 197-213 induced 60-80% protection of guinea pigs against challenge with the A22 virus. Synthetic peptides corresponding to the 10-24, 50-69 and 175-189 sequences of VP1 did not show any protective activity. We have found that uncoupled peptides 175-189 and 197-213 are able to induce antipeptide antibodies. However, these antibodies did not possess any neutralizing activity. Immunization of animals with the mixture of (136-152)O1K and (175-189)A22 has led to inhibition of the immune response to the (136-152)O1K fragment.

[Antigenic structure of the foot-and-mouth disease virus. III. Immunogenic properties of synthetic peptides of the sequence of the immunodominant region of VP1 proteins of the O1K and A22 strains of foot-and-mouth virus]. / Anigennaia struktura virusa iashchura. III. Immunogennye svoistva sinteticheskikh peptidov posledovatel'nosti immunodominantnogo raiona belkov VP1 shtammov O1K i A22 virusa iashchura.

Immunogenic and protective properties of uncoupled and KLH-conjugated peptides covering the sequence of the immunodominant region of VP1 proteins of the O1K and A22 strains of foot-and-mouth disease virus have been studied. The uncoupled peptides 136-148 O1K, 136-152 O1K, 131-149 A22 and 140-149 A22 were shown to be immunogenic in guinea pigs and induced 50-100% protection against homologous virus. On the other hand, the A22 specific peptides, in contrast to the O1K peptides, were not immunogenic in rabbits. Immunization of nonresponders with the A22 specific peptides containing the O1K peptide can bypass nonresponsiveness to the A22 peptide in terms of the antibody production. The induced antibodies showed virus-neutralizing activity in vitro.

[Antigenic structure of the foot-and-mouth-disease virus. I. Synthesis of protective peptides from the major immunogenic region of VP1 protein of foot-and-mouth virus type O1K]. / Antigennaia struktura virusa iashchura. Sintez protektivnykh peptidov posledovatel'nosti osnovnogo immunogennogo raiona belka VP1 virusa iashchura shtamma O1K.

A series of overlapping peptides with the sequence of the immunodominant region of VP1 protein of FMDV strain O1K have been synthesized by the classical solution method. Peptides were purified by standard methods and used for immunization of guinea pigs. It is shown that the 136-152 and 136-148 segments provide antiviral protection in guinea pigs, both in the free state and conjugated with an immunogenic carrier. Results with uncoupled peptides indicated that these segments may form not only B-, but also T-cell affecting sites.

[Antigenic structure of the foot-and-mouth disease virus. II. Synthesis of protective peptides from the major immunogenic region of VP1 protein of foot-and-mouth disease virus type A22]. / Antigennaia struktura virusa iashchura. II. Sintez protektivnykh peptidov posledovatel'nosti osnovnogo immunogennogo raiona belka VP1 virusa iashchura shtamma A22.

Earlier we found that the immune response and antiviral protection from FMDV can be achieved by immunization with uncoupled FMDV peptides. In a search of approaches to animal protection from FMDV A22 strain we prepared a series of peptides corresponding to the putative antigenic determinants. Synthetic 131-149 and 140-149 sequences afforded 50 to 80% protection, both in the free state and conjugated with keyhole limpet hemocyanin. We believe that the 140-149 segment is so far the smallest peptide capable of eliciting specific antiviral protection without conjugation with a high molecular carrier.

[Is the Arg-Gly-Asp sequence the site for foot-and-mouth disease virus binding with cell receptor?]. / Iavliaetsia li posledovatel'nost' Arg-Gly-Asp uchastkom sviazyvaniia virusa iashchura s kletochnym retseptorom?

The Arg-Gly-Asp sequence is being found in an increasing wide range of proteins with "adhesive" function. Studying a series of synthetic peptide fragments of VP1 protein of FMDV, we showed that peptides containing the Arg-Gly-Asp sequence, but not control peptides, inhibited FMDV binding to pig kidney cells in vitro, thus indicating participation of that sequence in FMDV binding to host cells.

[Synthetic peptides simulating the protective epitopes of VP1 protein of foot-and-mouth disease virus type O and A]. / Modelirovanie s pomoshch'iu sinteticheskikh peptidov protektivnykh épitopov belka VP1 virusa iashchura serotipov O i A.

In a search of novel approaches to cattle protection from foot-and-mouth disease we have prepared a series of peptides from the major antigenic region 130-160 of the VP1 protein. The 144-159 peptide as well as 141-152, 141-148, 148-159 segments (strain O1K) were inactive in all in vitro and in vivo experiments on virus inhibiting. On the other band, synthetic 136-152, 136-148 O1K sequences as well as 131-149, 140-149 A22 sequences afforded 50 to 100% protection, both in the free state and conjugated with keyhole limpet hemocyanin. Therefore the 136-145 region should be considered as an essential part of the major sequential epitope, necessary for full-scale antiviral immune response. We also believe that the 136-152 segment is so far the smallest peptide capable of eliciting virus neutralizing antibodies and antiviral protection without conjugation with a high-molecular carrier.