Spectrin-phospholipid interaction. A monolayer study

1.(1) The interaction of synthetic and natural phospholipids with spectrin, purified from human erythrocyte membranes, was studied using the monolayer technique at constant surface pressure. Spectrin penetration into the lipid monolayer was recorded as the rate of surface area increase on a two-compartment trough. 2. (2) High spectrin penetration rates were observed with negatively charged phospholipids while zwitterionic or neutral lipids showed only poor spectrin affinity. This penetration rate was strongly affected by the subphase pH. At pH 5.5, maximal pentration rates were observed for phosphatidylglycerol and phosphatidylserine but not for phosphatidylcholine. 3. (3) In comparing the penetration rates for phospholipids with a natural fatty acid composition and the dimyristoyl species of phosphatidic acid, phosphatidylglycerol, phosphatidylserine and phosphatidylcholine, the lipid fatty acid composition proved to be an important parameter. The differences are correlated with the area per lipid molecule. 4. (4) Other parameters affecting the area per lipid molecule such as surface pressure, pH and salt concentration also strongly influenced spectrin penetration rates for negatively charged phospholipids. Spectrin penetration into phosphatidylcholine monolayers is only slightly affected by variation of these conditions. 5. (5) The effect of Ca2+ on spectrin-lipid interactions was studied for several phosphatidylglycerol and phosphatidylserine species. Both lipids condensed upon the addition of Ca2+, but only in the case of the phosphatidylserine was this accompanied by extrusion of the spectrin from the interface, which is in agreement with earlier calorimetric experiments with bilayer systems of analogous composition (Mombers, C., Verkleij, A.J., de Gier, J. and van Deenen, L.L.M. (1979) Biochim. Biophys. Acta 551, 271–281). For this phenomenon a model is presented

Fusion of phospholipid vesicles in association with the appearance of lipidic particles as visualized by freeze fracturing

The addition of Ca2+ to small unilamellar vesicles of an equimolar mixture of egg phosphatidylcholine and cardiolipin induces fusion of these vesicles in association with the appearance of lipidic particles on the fusion sites

The suitability of quality-of-life questionnaires for psoriasis research - A systematic literature review

Objective: To critically appraise the suitability of current quality-of-life (QOL) questionnaires for psoriasis research. Data Sources: Computerized searches of 5 bibliographic databases. Questionnaire Selection: Predefined criteria were used to identify QOL questionnaires in dermatologic studies. Two investigators independently assessed and agreed on multidimensional generic, dermatology-specific, and psoriasis-specific QOL questionnaires for inclusion. Data Extraction: Data were extracted on the internal structure, reliability, and validity of the included questionnaires. Data Synthesis: Three generic, 3 dermatology-specific, and none of the psoriasis-specific questionnaires met the inclusion criteria: the Nottingham Health Profile (NHP), the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36), the Sickness Impact Profile (SIP), the Dermatology Quality of Life Scales (DQOLS), the Dermatology-Specific Quality of Life Instrument (DSQL), and the Skindex-29. The generic NHP, SF-36 and SIP are well established, reliable, and valid. Although the data are not conclusive, the SF-36 was useful to assess effects of psoriasis on its component scales. The dermatology-specific DQOLS, DSQL, and Skindex-29 are relatively new and, therefore, less widely tested. Available psychometric data demonstrated the reliability and validity, of all 3 dermatology-specific questionnaires. The Skindex-29 was also useful to assess change. Conclusions: None of the identified psoriasis-specific questionnaires met the inclusion criteria. Data on. the suitability of the included questionnaires for psoriasis research were relatively sparse. The included generic questionnaires allow comparisons with nondermatologic diseases but do not allow assessment of relevant dermatology-specific aspects and are not sensitive to subtle effects of psoriasis on QOL. On the basis of the psychometric data of the present review, we find the Skindex-29 to be the most valuable dermatology-specific questionnaire for psoriasis research. Combination of the Skindex-29 with the generic SF-36 combines the merits of both types of questionnaires and we therefore recommend this combinatio

The occurrence of lipidic particles in lipid bilayers as seen by 31P NMR and freeze-fracture electron-microscopy

A new type of lipid organization is observed in mixtures of phosphatidylcholine with cardiolipin (in the presence of Ca2+), monoglucosyldiglyceride and phosphatidylethanolamine (in the presence of cholesterol). This phase is characterised by an isotropic 31P NMR signal and is visualised by freeze-fracturing as particles and pits on the fracture faces of the lipid bilayer. As the most favourable model for this phase we propose the inverted micelle sandwiched in between the two monolayers of the lipid bilayer