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Jack H. Schulman
Columbia University
11Publications
9H-index
900Citations
Publications 11
Newest
#1Dinesh O. ShahH-Index: 53
#2Jack H. SchulmanH-Index: 9
30 CitationsSource
#1Morton RosoffH-Index: 1
#2Karl D. DreherH-Index: 3
Last.Jack H. SchulmanH-Index: 9
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#1Dinesh O. Shah (Columbia University)H-Index: 53
#2Jack H. Schulman (Columbia University)H-Index: 9
Abstract Enzymic hydrolysis of dipalmitoyl, egg, soybean, and dioleoyl lecithin monolayers was studied by measuring the changes in surface pressure (π) and surface potential (Δ V ) upon injection of snake venom ( Naja Naja ) into the subsolution. The presence of Ca ++ , which could not be substituted by Mg ++ , Sr ++ , or Ba ++ , was essential for hydrolysis. Thin layer chromatography of monolayers removed after injection of venom into the subsolution showed that the snake venom indeed hydrolyze...
77 CitationsSource
#1Karl D. Dreher (Columbia University)H-Index: 1
#2Jack H. Schulman (Columbia University)H-Index: 9
Last.Oswald A. Roels (Columbia University)H-Index: 15
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Lipid monolayers have been examined on OsO 4 -containing substrates. The results showed that OsO 4 reacted only when double bonds were present in the hydrocarbon portion of monolayer molecules. No evidence for polar group interaction between saturated lecithins, monoglycerides, fatty acids, nor cholestanol and OsO 4 was obtained. Egg lecithin and oleic acid monolayers were unstable after reaction with OsO 4 and dissolved into the substrate. Cholesterol, monoolein, monolinolein, and d-α -tocopher...
50 CitationsSource
#1O.R. Anderson (Columbia University)H-Index: 1
#2Oswald A. Roels (Columbia University)H-Index: 15
Last.Jack H. Schulman (Columbia University)H-Index: 9
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Myelinics were prepared by dispersing ovolecithin alone, ovolecithin and retinol, ovolecithin and tocopherol, or ovolecithin and cholesterol in water. Electron microscopic observations of the negatively stained myelinics showed that retinol, tocopherol, and cholesterol decreased (in the order given) the thickness of the hydrophobic regions of the lipid bilayers and increased the mean hydrophilic layer thickness, compared to myelinics of ovolecithin alone. When OsO4 was applied to the dried myeli...
33 CitationsSource
5 CitationsSource
Surface potentials of mixed monolayers of dicetyl phosphate and eicosanyl trimethylammonium bromide (1:l) were the same on subsolutions of 0.02 M NaCl or 0.01 M CaC12, which indicated that ionic phosphate does not interact with Ca++ in the presence of a neighboring trimethylammo- nium group. Surface potential-pH plots of dicetyl phosphate, and of dipalmitoyl, egg, and dioleoyl lecithins showed that as the pH of the subsolution is decreased the phosphate groups in the monolayer are neutralized in...
139 Citations
Surface pressures and potentials of mixed monolayers of dicetyl phosphate-cholesterol, dipalmitoyl lecithin-cholesterol, egg lecithin-cholesterol, and phosphatidic acid-cholesterol were measured. The surface potential is shown to be a more reliable parameter for the study of interactions in monolayers than the surface pressure. Monolayers of dicetyl phosphate-cholesterol follow the additivity rule for area/molecule whereas lecithin-cholesterol monolayers deviate from it. The reverse is true for ...
222 Citations
#1Dinesh O. Shah (Columbia University)H-Index: 53
#2Jack H. Schulman (Columbia University)H-Index: 9
44 CitationsSource
Dipalmitoyl lecithin and sphingomyelin monolayers have similar limiting areas, whereas their surface potentials are strikingly different. The double bond at the 4–5 position in sphingomyelin acts as an induced dipole in relation to the surface potentials. This was confirmed by the surface potential of hydrogenated sphingomyelin. The binding of calcium to lecithin and sphingomyelin monllayers resulted in an increase in surface potential. This increase was greater for the dipalmitoyl lecithin mono...
72 CitationsSource
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