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Solution structure of conformationally restricted vasopressin analogues.

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Trzepałka E., Oleszczuk M., Maciejczyk M., Lammek B.

Acta Biochimica Polonica

2004

vol. 51

issue 1

33-49

In recent years, a massive effort has been directed towards designing potent and selective antagonists of neurohypophyseal hormones substituted at position 3. Modification of vasopressin at position 3 with 4,4'-biphenylalanine results in pharmacologically inactive analogues. Chemically, this substitution appears to vary only slightly from those previously made by us (1-Nal or 2-Nal), which afforded potent agonists of V2 receptors. In this situation, it seemed worthwhile to study the structure of the analogues with 4,4'-biphenylalanine (BPhe) at position 3 in aqueous solution using NMR spectroscopy and total conformational analysis. This contribution is part of extensive studies aimed at understanding spatial structures of 3-substituted [Arg8]vasopressin analogues of different pharmacological properties. NMR data were used to calculate 3D structures for all the analogues using two methods, EDMC with the ECEPP/3 force field, and molecular dynamic with the simulated annealing (SA) algorithm. The structures obtained by the first method show a better fit between the NMR spectral evidence and the calculation for all the peptides.

Free energy of helix propagation in short polyalanine chains determined from peptide growth simulations of La3+-binding model peptides. Comparison with experimental data

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Maciejczyk M., Hermans J., Bierzyński A.

Acta Biochimica Polonica

2006

vol. 53

issue 1

121-130

Molecular dynamics (MD) is, at present, a unique tool making it possible to study, at the atomic level, conformational transitions in peptides and proteins. Nevertheless, because MD calculations are always based on a more or less approximate physical model, using a set of approximate parameters, their reliability must be tested by comparison with experimental data. Unfortunately, it is very difficult to find a peptide system in which conformational transitions can be studied both experimentally and using MD simulations so that a direct comparison of the results obtained in both ways could be made. Such a system, containing a rigid α-helix nucleus stabilized by La3+ coordination to a 12-residue sequence taken from an EF-hand protein has recently been used to determine experimentally the helix propagation parameters in very short polyalanine segments (Goch et al. (2003) Biochemistry 42: 6840-6847). The same parameters were calculated here for the same peptide system using the peptide growth simulation method with, alternatively, charmm 22 and cedar potential energy functions. The calculated free energies of the helix-coil transition are about two times too large for cedar and even three times too large for charmm 22, as compared with the experimental values. We suggest that these discrepancies have their origin in the incorrect representation of unfolded peptide backbone in solution by the molecular mechanics force fields.

Oxidative stress assessment in lung of lead-exposed rats

76%

Machoń-Grecka A., Kaletka Z., Pryzwan T., Szczęsny P., Maciejczyk M., Kasperczyk A., Dobrakowski M.

Medycyna Środowiskowa - Environmental Medicine

2018

vol. 21

issue 1

21-24

Objective. Little is known about lead toxic effects on lung tissue. Therefore, the present study was undertaken to estimate the values of selected parameters related to oxidative stress in the lung of rats exposed to lead acetate. Material and methods. Twenty male Wistar rats were randomly divided into two groups: control (n=10) and lead-treated (n=10). The lead-treated group was fed with regular rat chow and distilled water supplemented with lead acetate (1200 ppm) for 7 days. In lung homogenates, the level of malondialdehyde (MDA) and the activities of superoxide dismutase (SOD, CuZn-SOD, Mn-SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione-S-transferase (GST) were determined. Results. The activity of catalase was significantly higher in the lung of lead-treated rats than in controls by 98%. Similarly, the activities of GPx and GR were higher by 57% and 45%, respectively. The level of MDA was also higher in lead-exposed rats than in the control group by 52%. The remaining parameters did not differ between the studied groups. Conclusions. Lead exposure stimulates antioxidant defense mechanisms in rat lung; however, these mechanisms are insufficient to prevent lead-induced oxidative stress development

Wstęp. Toksyczny wpływ ołowiu na tkankę płucną jest słabo poznany. W związku z tym, prezentowany eksperyment miał na celu ocenę zmian w wybranych parametrach związanych ze stresem oksydacyjnym w tkance płucnej u szczurów narażonych na octan ołowiu. Materiał i metody. Dwadzieścia szczurów szczepu Wistar, podzielono na dwie grupy: kontrolną (n=10) i badaną z podawanym ołowiem (n=10). Szczury z grupy badanej były regularnie karmione granulatem dla szczurów i pojone wodą destylowaną z octanem ołowiu (1200 ppm) przez 7 dni. W homogenatach z tanki płucnej oznaczany był poziom malonylodialdehydu (MDA) i aktywność dysmutazy ponadtlenkowej (SOD, CuZn-SOD, Mn-SOD), katalazy (CAT), peroksydazy glutationowej (GPx), reduktazy glutationowej (GR), oraz transferazy glutationowej (GST). Wyniki. Aktywność katalazy była o 98% wyższa w grupie badanej aniżeli w grupie kontrolnej. Podobnie, aktywności GPx i GR były wyższe odpowiednio o 57% i 45%. Poziom MDA był również wyższy w grupie badanej, o 52% w porównaniu do grupy kontrolnej. Pozostałe parametry nie różniły się pomiędzy grupami. Wnioski. Ekspozycja na ołów stymuluje mechanizmy obrony antyoksydacyjnej, jednakże mechanizmy te są niewystarczające by zapobiec stresowi oksydacyjnemu wywołanemu działaniem ołowiu.

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2 Acta Biochimica Polonica

1 Medycyna Środowiskowa - Environmental Medicine

1 2018

1 2006

1 2004

3 Maciejczyk M.

1 Bierzyński A.

1 Dobrakowski M.

1 Hermans J.

1 Kaletka Z.

1 Kasperczyk A.

1 Lammek B.

1 Machoń-Grecka A.

1 Oleszczuk M.

1 Pryzwan T.

1 Szczęsny P.

1 Trzepałka E.

Search results

Solution structure of conformationally restricted vasopressin analogues.

Free energy of helix propagation in short polyalanine chains determined from peptide growth simulations of La3+-binding model peptides. Comparison with experimental data

Oxidative stress assessment in lung of lead-exposed rats