Fluorescent Dimers of Merocyanine 540 (MC540) in the Gel Phase of Phosphatidylcholine Liposomes

SummaryPlatelet membrane glycoproteins IIb and IIIa and platelet thrombospondin were incorporated onto phosphatidylcholine liposomes, by freeze thawing and sonication. Protein orientation on the liposomes was confirmed by susceptibility to neuraminidase cleavage and binding to lentil lectin-Sepharose (GPIIb-IIIa liposomes) and to heparin-Sepharose (thrombospondin liposomes). Glycoproteins Ilb-IIIa bound 125I-fibrinogen with Kd of 7.5 × 10™7M. Binding was reversible and calcium-dependent. Ilb-IIIa liposomes underwent fibrinogen-dependent aggregation in the presence of 10 mM CaCl2. Maximal aggregate formation was observed with a combination of IIb-IIIa liposomes and thrombospondin liposomes. This aggregation was partially inhibited by preincubation with monoclonal antibodies to the IIb-IIIa complex. Addition of EDTA caused complete reversal of aggregates. Thrombospondin liposomes also underwent fibrinogen and calcium dependent aggregation, however, this aggregation was less than that observed with the GPIIb-IIIa liposomes. Maximal aggregate formation was observed with a mixture of IIb-IIIa liposomes and thrombospondin liposomes. These studies demonstrate that GPIIb-IIIa and thrombospondin can be incorporated into phospholipid vesicles with preservation of function. Direct evidence is provided to demonstrate that glycoprotein lib and Ilia and fibrinogen are sufficient for platelet aggregation and to demonstrate that thrombospondin may also contribute to platelet aggregation.

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Porous Gel Coatings Obtained by Phase Separation in ORMOSIL System

MRS Proceedings ◽

10.1557/proc-628-cc7.6 ◽

2000 ◽

Vol 628 ◽

Cited By ~ 1

Author(s):

Kazuki Nakanishi ◽

Souichi Kumon ◽

Kazuyuki Hirao ◽

Hiroshi Jinnai

Keyword(s):

Phase Separation ◽

Reaction Time ◽

Volume Fraction ◽

Sol Gel ◽

Reaction Times ◽

Dip Coating ◽

Coating Solution ◽

Coating Method ◽

Gel Phase ◽

Dip Coating Method

ABSTRACTMacroporous silicate thick films were prepared by a sol-gel dip-coating method accompanied by the phase separation using methyl-trimethoxysilane (MTMS), nitric acid and dimethylformamide (DMF) as starting components. The morphology of the film varied to a large extent depending on the time elapsed after the hydrolysis until the dipping of the coating solution. On a glass substrate, the films prepared by early dipping had inhomogeneous submicrometer-sized pores on the surface of the film. At increased reaction times, relatively narrow sized isolated macropores were observed and their size gradually decreased with the increase of reaction time. On a polyester substrate, in contrast, micrometer-sized isolated spherical gel domains were homogeneously deposited by earlier dippings. With an increase of reaction time, the volume fraction of the gel phase increased, then the morphology of the coating transformed into co-continuous gel domains and macropores, and finally inverted into the continuous gel domains with isolated macropores. The overall morphological variation with the reaction time was explained in terms of the phase separation and the structure freezing by the forced gelation, both of which were induced by the evaporation of methanol during the dipping operation.

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