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Biomedical subjects

M Pawlak

Publications and source records attributed to M Pawlak.

9 recordsLinked to original sources
PubMed1991

A combined study of aggregation, membrane affinity and pore activity of natural and modified melittin.

The pore activity of melittin and several chemically modified derivatives has been investigated using conductance measurements on planar lipid bilayers and marker release from small unilamellar vesicles. The modifications included N-terminal formylation, acetylation, succinylation and modification of the tryptophan residue. All of the compounds showed bilayer permeabilizing properties, though quantitative differences were evident. These comprised changes in the voltage dependence of the conductance, in the single-pore kinetics, in the concentration of aqueous peptide required to induce a given pore activity and in the apparent 'molecularity' reflected by the power law of its concentration dependence. A strong tendency for disrupting bilayers was not always correlated with strong pore activity. For a better understanding of these results, measurements of pore activity were complemented by studying the aggregation behavior in solution and the water-membrane partition equilibrium. Modifications of charged residues gave rise to significant changes in the aggregation properties, had virtually no influence on the partition coefficient. The latter decreased strongly, however, as a result of tryptophan modification. Analysis of the isotherms was consistent with the assumption that the arginine residues in melittin do not contribute very much to charge accumulation at the immediate membrane/water interface.

Acetylation↗
PubMed1991

Melittin induced voltage-dependent conductance in DOPC lipid bilayers.

Melittin-induced conductance was measured on planar bilayers made from dioleoylphosphatidylcholine. Upon application of a fixed voltage, the current response was monophasic and remained so even after prolonged observation times. The conductance of melittin-doped bilayers increased exponentially with voltage. In addition, an ohmic contribution appeared after some current had passed. The voltage-dependent conductance increased e-fold every 22 mV and was proportional to the fourth power of the aqueous monomeric peptide concentration, for all salt concentrations investigated (0.4-1.8 M NaCl). Discrete conductance steps could be resolved at all these salt concentrations. The amplitudes of these steps were highly variable. In each experiment, conductance was initially only observed for potentials which were positive on the side of peptide addition. As more and more current passed across the bilayer, the current-voltage curves became symmetric. The system needed some time to reach stationary current-voltage characteristics: about 50 min at pH 7 but only about 15 min at pH 8, suggesting involvement of the N-terminus (pK around 7.5) of melittin in the slow formation of a 'prepore'.

Amino Acid Sequence↗
PubMedDate not supplied

[Common-sense knowledge of epilepsy].

The purpose of this study was to find an answer to the question what is the knowledge on epilepsy in the population and what is the attitude towards epileptics. The study was carried out in a randomly selected sample of 150 people living in a province capital and it was a continuation of similar studies conducted abroad and in Poland (Bagley, 1972; Zieliński, 1974). The analysis of the knowledge level on various aspects of epilepsy showed that 41.3% of the responders had a quite good information on this disease. Sex-related differences were observed in favour of women. The knowledge possessed by subjects with high and medium education was better than that of subjects with elementary education. A decidedly non-accepting attitude towards epileptics was manifested by 36.6% of the studied subjects, and decidedly accepting attitude by 19.3%. The accepting attitude was more frequent among women with elementary education. The non-accepting attitude was expressed most frequently by responders with elementary vocational education and those with incomplete high education. The comparison of certain results of these investigations with those carried out in Warsaw (1974) demonstrated an essential difference in the level of acceptance of epileptics. Generally speaking, the Warsaw responders had an accepting attitude, and the presently studied ones has a non-accepting attitude. The Warsaw study demonstrated a rising social acceptance level with higher educational levels, this relationship was not observed in the present study.

Adolescent↗