Thermal Analysis of Membranes

Keough, K. M. W.; Davis, Philip J.

doi:10.1007/978-1-4684-4667-8_2

Cited by 9 publications

(7 citation statements)

References 160 publications

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“…In addition, C. cucumerinum contains a high quantity of cardiolipin in its lipids. This phospholipid has the highest transition temperature of all lipids at neutral pH (32). However, it cannot be directly involved in the alteration of plasma membrane function as this lipid is characteristically located in the inner membrane of mitochondria.…”

Section: Discussionmentioning

confidence: 99%

Influence of a subinhibitory dose of antifungal atty acids fromSporothrix flocculosa on cellular lipid composition in fungi

Benyagoub

Willemot

Bélanger

1996

Lipids

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Antifungal fatty acids produced by the biocontrol fungus Sporothrix flocculosa were studied on the basis of their effect on growth and cellular lipid composition of three fungi, Cladosporium cucumerinum, Fusarium oxysporum, and S. flocculosa, whose growth was decreased by 51, 33, and 5%, respectively, when exposed to 0.4 mg fatty acid per ml. The sensitivity to fatty acid antibiotics from S. flocculosa was related to a high degree of unsaturation of phospholipid fatty acids and a low proportion of sterols. The major responses of sensitive fungi to sublethal doses of antifungal fatty acids from liquid culture of S. flocculosa were: (i) a decrease in total lipid; (ii) an increase in the degree of fatty acid unsaturation (18:1 > 18:2 > 18:3); (iii) an increase in free fatty acids and phosphatidic acid and a decrease in total phospholipids; and (iv) an increase in sterol/phospholipid ratio. These modifications in lipid composition led to an increase in membrane fluidity in sensitive fungi as demonstrated by assessment of fluoresence anisotropy using liposomes and 1,6-diphenyl-1,3,5-hexatriene probe. This alteration in the physical state of lipids appears to be responsible for the previously demonstrated alteration of membrane structure and function in fungi confronted to S. flocculosa.

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Section: Discussionmentioning

confidence: 99%

Influence of a subinhibitory dose of antifungal atty acids fromSporothrix flocculosa on cellular lipid composition in fungi

Benyagoub

Willemot

Bélanger

1996

Lipids

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“…pores were formed because of the absence of toxin in solution. The slight haemolysis observed for this sample (Figure 4) was probably caused by a few pores that had already formed at 4 • C. It is possible that the toxin specifically interacted with a lipid microdomain that was 'frozen' at 4 • C. However, the bulk lipid of RBCs is known not to undergo any thermal phase transitions at 4 • C [17]. It is also unlikely that the toxin oligomer itself has a temperaturedependent conformational change that is inhibited at 4 • C. If this was the cause, haemolysis of toxin-treated cells at 4 • C should have been markedly increased when the cells were moved to toxin-free solution at 37 • C. The same observation argues against the possibility that the pore is closed at 4 • C. One alternative explanation for our findings is that the conformational change in the toxin that accompanies membrane binding could be different at 4 • C and 37 • C, with the latter favouring the oligomerization and the former not.…”

Section: Effect Of Temperature On Pore Formation By Cyt2aa1mentioning

confidence: 92%

Investigation of the pore-forming mechanism of a cytolytic δ-endotoxin from Bacillus thuringiensis

Promdonkoy

Ellar

2003

Biochemical Journal

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Cyt2Aa1 is a cytolytic protein produced by Bacillus thuringiensis subsp. kyushuensis. Penetration of the toxin into membranes has been studied to learn more about membrane-insertion mechanisms and transmembrane-pore formation. The haemolysis assay of Cyt2Aa1 showed a steep and sigmoidal dose-response curve, indicating that toxin aggregation or oligomerization is required for pore formation. Studies of the effect of temperature on pore formation and fluorimetric studies of acrylodan-labelled toxin suggest that toxin inserts into the membrane before oligomerizing to form a pore. Low temperature neither inhibited membrane binding nor closed pores that have been formed, but markedly inhibited oligomerization of the toxin molecules. When toxin-treated red blood cells at 4 degrees C were transferred to a toxin-free solution at 37 degrees C, no significant increase in haemolysis was observed. This result suggests that membrane-bound toxin could not diffuse laterally and interact with other molecules to form a pore. From these results, we propose that Cyt2Aa1 binds and inserts into the membrane as a monomer. Oligomerization occurs when toxin molecules have bound in close proximity to each other and pores are formed from large oligomers.

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“…The application of DSC to membrane research has been reviewed by Keough and Davis, but, as pointed out by these authors and also previously in this review (Section n.D.l), difficulties are attendant to this procedure. 55 A recent research advance has made it possible to obtain more useful calorimetric data from whole membranes. Quick-freeze differential scanning calorimetry (QF-DSC) was first used by Melchior to separate transitions in a model system.…”

Section: A X-ray Diffractionmentioning

confidence: 99%

Biological membrane deterioration and associated quality losses in food tissues

Stanley

Parkin

1991

Critical Reviews in Food Science and Nutrition

183

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Biological membranes are rarely considered by food scientists when the deteriorative reactions that take place during the processing or storage of food tissues are studied. Yet, membranes and their deterioration play a major but underestimated role in food losses, and recent biochemical information indicates that at least some of these reactions can be controlled by procedures suited to food materials. Much of the present information available on membrane degradation in food systems is incomplete and speculative. It is known, however, that in order to accomplish their many indispensable functions in cells, membranes are constituted mainly of phospholipids, protein, and some carbohydrates arranged in thin, bimolecular sheet-like structures that serve to compartmentalize cells and their organelles. Membranes have embedded in their asymmetric surfaces complements of catalytic and cytoskeletal proteins that serve permeability and structural functions. Membrane surfaces exhibit fluidity, due partially to the continuous lateral diffusion of lipids and some proteins. Two important consequences of fluidity are the ability of membrane phospholipids to exist in different interconvertible conformational phase structures and the formation of heterogenous lipid domains on the membrane surface. Cellular death leads unavoidably to the initiation of membrane deterioration. While the time course of this series of reactions differs in animal and plant tissue, they are damaged by generally similar mechanisms. These include an initial peroxidative attack on polyunsaturated fatty acids, with the concomitant production of free radicals. Many biological agents can act as accelerating agents in these reactions, including transition metal ions, heme compounds, radiation, illuminated chlorophyll, calcium, and ethylene. Once formed, free radicals catalyze further reactions that can affect all aspects of membrane function and cellular metabolism, and lead ultimately to significant losses in food quality through defects such as chilling injury and cold shortening. These are aggravated by many food-processing steps, especially those that involve tissue disruption. Control of membrane breakdown by exogenous chemical intervention has been practiced, but, at best, this only slows the rate of these reactions. Newer approaches to this problem include dietary treatment of meat animals, modified storage and packaging conditions, and genetic interventions. This review advances the proposition that membrane deterioration can be considered a "universal mechanism" that leads to significant quality losses in food. Perhaps because the study of biological membranes and the biochemical and physiological properties has only begun recently, not much progress has been made in finding practical control mechanisms for these reactions in food systems.(ABSTRACT TRUNCATED AT 400 WORDS)

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Thermal Analysis of Membranes

Cited by 9 publications

References 160 publications

Influence of a subinhibitory dose of antifungal atty acids fromSporothrix flocculosa on cellular lipid composition in fungi

Influence of a subinhibitory dose of antifungal atty acids fromSporothrix flocculosa on cellular lipid composition in fungi

Investigation of the pore-forming mechanism of a cytolytic δ-endotoxin from Bacillus thuringiensis

Biological membrane deterioration and associated quality losses in food tissues

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