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Biophysical studies of membranes and proteins using the molecular dynamics simulation method

100%

Pasenkiewicz-Gierula M. , Jezierski G. , Murzyn K. , Rog T. , Czaplewski C. , Ciarkowski J.

Biotechnologia

2000

nr 2

83-97

The main structural element of biological membranes is a liquid-crystalline lipid bilayer. Other constituents i.e. proteins, sterols and carbohydrates, either intercalate into or loosely attach to the bilayer. Many properties common to the membranes can be explored by studying lipid bilayers. In this paper, the molecular dynamics simulation method was applied to study membranes at various levels of compositional complexity. Whenever it was possible, results of the simulations were compared with published experimental data. The reactive site loop of a1-antitrypsin is held in a tightly constrained conformation by a salt bridge between Glu342 and Lys290. Guanidinium ions induce a1-antitrypsin polymerisation by disrupting this salt bridge. The mechanism of this process, proposed on the basis of experimental studies, was confirmed and further explained by molecular modelling methods.

Thiol?activated hemolysins as virulence markers of bacteria

100%

Szramka B. , Kurlenda K. J. , Kurlenda J. , Podhajska P. A. J. , Podhajska A. J.

Biotechnologia

2001

nr 3

152-168

The article contains information regarding the similarities and differences between proteins of the thiol-activated cytolysins family (TACY). Members of this group of haemolysins are produced by several species of Gram-positive bacteria (Listeria spp., Streptococcus spp., Bacillus spp., Clostridium spp.,) and also by Gram-negative Klebsiella spp.. Their cytolytic activity is sensitive to oxygen and can be restored by adding reducing compounds. TACY bind to cholesterol-containing membranes to form pores. Preincubation of the toxin with small amounts of cholesterol inhibits hemolytic activity as well as cytolysis of eucaryotic cells. Members of the group show 40-70% similarity in amino acid sequence, and contain an almost invariant Trp-rich undecapeptide sequence (ECTGLAWEWWR). The TACY are important virulence factors. Recently increased use has been made of molecular methods (PCR, hybridization) in the detection and identification of the TACY producing bacteria.

The assimilation of cholesterol by starter cultures of mesophilic lactococci

100%

Ziarno M. , Sekul E. , Makowska M.

Biotechnologia

2006

nr 2

234-246

The aim of this work was the determination of the ability of four commercial starter cultures of mesophilic lactococci to cholesterol assimilation during 24-hours-long culture in MRS broth medium at 30oC. The tested starter cultures showed various ability to assimilate cholesterol from culture medium varying from 10,4 ? 1,56% to 29,8 ? 5,22%. The results of this study proved the existence of significant differences in cholesterol assimilation ability between commercial starter cultures of mesophilic lactococci, and also even between individual repetitions for the same culture. The best cholesterol-assimilating starter culture of mesophilic lactococci was used for the production of sour cream, that was stored at 5-6oC for 14 days and tested in respect of microbiological (number of lactococci) and physicochemical properties (pH, titrable acidity, fat acidity, cholesterol content). During the 14-day refrigerating storage, the number of lactococci and pH did not change. Titrable acidity and fat acidity increased negligible. After the 14-day refrigerating storage, the decrease of the cholesterol content was observed. The decrease of cholesterol content in sour cream was over 35% in comparison with cholesterol content in sweet cream used for sour cream production and stored for 14 days at the same conditions as sour cream.

Distribution of major lipids and fatty acids of the estuarine gastropod mollusc Telescopium telescopium

75%

Rakshit S. , Bhattacharyya D. K. , Misra K. K.

Folia Biologica

1997

tom 45

83-87

Lipid fractions and fatty acid composition of different organs, viz., digestive gland, mantle, and foot of the gastropod Telescopium telescopium inhabiting estuarine waters of West Bengal, India were studied. Thin layer chromatography and subsequent colorimetric analyses revealed the presence of phospholipid, cholesterol, and, to a lesser extent, triglycerides. Considerable variation in the three classes of lipids was observed in the organs studied so far. Gas liquid chromatography analyses showed the presence of saturated fatty acids (16: 0, 18: 0, 14:0), monoenoics (18:1, 16:1, 20:1), and polyenoic fatty acids (22:5 w6, 20:5 w3, 18:2) in varying amounts in the three organs. This may be related with a specific function of the organ. Polyunsaturated fatty acids are present in fair amounts in T. telescopium. The occurrence of arachidonic acid (20:4) in this gastropod may be related to salinity, as was pointed out by other workers.