Publications by Type: Journal Articles

2000
Magdassi S. Editorial. Colloids Surf., AColloids and Surfaces, A: Physicochemical and Engineering Aspects. 2000;164 (1) :1.
Kamyshny A, Magdassi S. Fluorescence immunoassay based on fluorescer microparticles. Colloids Surf., BColloids and Surfaces, B: Biointerfaces. 2000;18 (1) :13 - 17.Abstract
A novel fluorescence immunoassay based on specific interaction of an antibody with an antigen preadsorbed onto fluorescer (perylene) microparticles (mean diam. 0.8-1.0 μm) is described. The microparticles of perylene are formed by pptn. in IgG soln., and the obtained dispersion is stable in the protein at concns. higher than 1 mg ml-1. Dissolving the particles in a suitable solvent leads to fluorescence when exciting by light of a proper wavelength. The dependencies of the fluorescence intensity on the concns. of antigen, antibody and fluorescer were studied. [on SciFinder(R)]
Kamyshny A, Ermolina I, Magdassi S, Feldman Y. Study of the Dynamic Structure of Native and Hydrophobized Glucose Oxidase by Time-Domain Dielectric Spectroscopy. J. Phys. Chem. BJournal of Physical Chemistry B. 2000;104 (32) :7588 - 7594.Abstract
The dynamic structures of native and hydrophobized (by covalent attachment of palmitoyl chains) glucose oxidase were studied by time-domain dielec. spectroscopy (TDDS). Anal. of the dipole correlation function for both types of the enzyme showed that the decay of the correlation function of the macromol. motion can be presented as a sum of components corresponding to different kinds of protein motion: isotropic rotation of the protein mol. as a whole, anisotropic Brownian tumbling of subunits, and anisotropic intramol. motion of polar groups and substructures. The slowest relaxation time was found to be longer for the modified enzyme than for the native enzyme. The dielec. strengths for all relaxation processes, as well as the dipole moment and the mol. vol., were also larger for the modified glucose oxidase. The obsd. differences between various types of the dipole motion for the native and modified glucose oxidase are discussed. [on SciFinder(R)]
1999
Kamyshny A, Magdassi S, Levashov AV. Novel protein-based colloidal and micellar systems for bioengineering. Sci. Isr.--Technol. AdvantagesScientific Israel--Technological Advantages. 1999;1 (3) :79 - 89.Abstract
New approaches for creation of novel protein-based colloidal and micellar systems are presented. These systems consist of colloidal clusters of chem. modified (hydrophobized) proteins or surfactant aggregates (micelles) contg. incorporated biol. catalysts - enzymes, or mols. capable of specific recognition - antibodies. The principles of formation, functional properties as well as practical applications of the protein-based colloidal and micellar systems in the fields of chem. synthesis, chem. anal., immunodiagnostics, drug targeting and biosensors are discussed. [on SciFinder(R)]
Baszkin A, Boissonnade MM, Rosilio V, Kamyshny A, Magdassi S. Penetration of glucose oxidase and of the hydrophobically modified enzyme into phospholipid and cholesterol monolayers. J. Colloid Interface Sci.Journal of Colloid and Interface Science. 1999;209 (2) :302 - 311.Abstract
The penetrant ability of the native glucose oxidase, GOx, and of the hydrophobically modified enzyme GO(mod) realized by grafting to its lysine residues alkyl C16 chains, into phosphatidylcholine dibehenoyl (DBPC), phosphatidylcholine dipalmitoyl (DPPC), phosphatidyl-ethanolamine dipalmitoyl (DPPE), phosphatidylserine dipalmitoyl (DPPS), and cholesterol (CHOL) monolayers was assessed by surface pressure measurements at const. area by enzyme injection to the aq. phase beneath spread monolayers. As revealed by the magnitude of surface pressure increments (ΔΠ), both the quantities and the rates of penetration of the enzymes into these monolayers were lipid chem. nature and enzyme concn. dependent. When compared with GOx, GO(mod) displayed an enhanced penetrant ability into all the studied monolayers that resulted in rapidly attained ΔΠ plateau values, characteristic of stable systems. The influence of lipid hydrocarbon chain length and of the polar headgroup charge on the efficiency and effectiveness of GOx and GO(mod) penetration into these monolayers is discussed. (c) 1999 Academic Press. [on SciFinder(R)]
Kamyshny A, Toledano O, Magdassi S. Adsorption of hydrophobized IgG and gelatin onto phosphatidyl choline-coated silica. Colloids Surf., BColloids and Surfaces, B: Biointerfaces. 1999;13 (4) :187 - 194.Abstract
Covalent modification of human IgG and gelatin (type A) by fatty acid esters (C8, C12 and C16) of N-hydroxysuccinimide was carried out. Prepns. of hydrophobized IgG contg. 9 and 25 attached caprylic and 25 palmitic chains and prepns. of gelatin with low and high degree of modification were obtained. The adsorption of unmodified and modified proteins at a hydrophobic surface obtained by coating silica with a phosphatidyl choline monolayer was studied. It was found that an increase in the proteins' hydrophobicity leads to an increase in their adsorption detg. by hydrophobic binding which overcomes the electrostatic repulsion between the neg. charged surface and the neg. charged protein mols. An increase in the IgG hydrophobicity also resulted in the formation of a more compact monolayer. An increase in gelatin adsorption after its hydrophobization led to either the formation of a more compact monolayer or the formation of a more condensed mol. configuration after attachment of alkyl chains. For both proteins the adsorption can be accompanied by penetration of these chains into the phospholipid monolayer. [on SciFinder(R)]
Kamyshny A, Feldman A, Baszkin A, Boissonnade MM, Rosilio V, Magdassi S. Chemically Modified Glucose Oxidase with Enhanced Hydrophobicity: Adsorption at Polystyrene, Silica, and Silica Coated by Lipid Monolayers. J. Colloid Interface Sci.Journal of Colloid and Interface Science. 1999;218 (1) :300 - 308.Abstract
Covalent modification of glucose oxidase from Aspergillus niger by the palmitic acid ester of N-hydroxysuccinimide at a molar ratio ester:protein of 56:1 results in the formation of the enzyme deriv. with 11 attached palmitic chains. Surface hydrophobicity measurements by a fluorescent probe, 8-anilino-1-naphthalenesulfonate, indicate a drastic increase in the hydrophobicity index of glucose oxidase after such a modification. The modified glucose oxidase displays a much higher adsorption affinity for hydrophilic (silica) as well as for hydrophobic (silica coated by phosphatidyl choline and cholesterol monolayers and polystyrene latex beads) surfaces, and forms more compact surface layers compared to the native glucose oxidase. Such a difference results from a spontaneous formation of micelle-like aggregates (clusters) of the hydrophobized enzyme mols. (av. size 500 nm), which come into contact with a surface. A possible structure of the glucose oxidase surface layers and the nature of the forces detg. the adsorption of the enzyme on various adsorbents are discussed. (c) 1999 Academic Press. [on SciFinder(R)]
Kamyshny A, Magdassi S, Relkin P. Chemically Modified Human Immunoglobulin G: Hydrophobicity and Surface Activity at Air/Solution Interface. J. Colloid Interface Sci.Journal of Colloid and Interface Science. 1999;212 (1) :74 - 80.Abstract
Covalent modification of human IgG by fatty acid esters (C8 and C16) of N-hydroxysuccinimide was carried out. Surface hydrophobicity measurements, using the fluorescent probe 8-anilino-1-naphthalenesulfonate, indicate an increase in the surface protein hydrophobicity with an increase in the no. and in the length of the attached alkyl chains. The modified IgGs decrease surface tension at the air/soln. interface more effectively than the native protein. The values of the mol. cross-sectional areas (ΔA) estd. from the kinetic data are at 100-300 Å2 and reflect the size of protein segments at the interface during the adsorption process. About 40-50% increase in the ΔA was obsd. upon attachment of the C8 groups to the native IgG. The lengthening of the bound alkyl chain from C8 to C16 results in a further increase in this value. The influence of the overall IgG hydrophobicity and the length of the attached alkyl chain on the dimensions of the mobile protein segment at the surface are discussed. (c) 1999 Academic Press. [on SciFinder(R)]
1998
Kamyshny A, Magdassi S. Chemiluminescence immunoassay in microemulsions. Colloids Surf., BColloids and Surfaces, B: Biointerfaces. 1998;11 (5) :249 - 254.Abstract
A novel chemiluminescence immunoassay which combines microparticles and microemulsion is described. The method is based on a specific interaction of an antibody with an antigen preadsorbed onto fluorescer (perylene) microparticles (mean diam. 0.8-1.6 μm). Dissolving the particles in a microemulsion-forming mixt. contg. bis(2,4,6-trichlorophenyl) oxalate in toluene (oil phase) and H2O2 in Triton X-100 (surfactant)/2-butanol (cosurfactant)/water leads to chemiluminescence. The dependence of the chemiluminescence intensity on the concns. of antigen, antibody and fluorescer, as well as the kinetics of the chemiluminescence decay, were studied. [on SciFinder(R)]
Toledano O, Magdassi S. Emulsification and foaming properties of hydrophobically modified gelatin. J. Colloid Interface Sci.Journal of Colloid and Interface Science. 1998;200 (2) :235 - 240.Abstract
Surface active gelatins were formed by covalent attachment of hydrophobic groups to gelatin mols. by reacting N-hydroxysuccinimide esters of various fatty acids (C4-C16) with the lysine groups. The surface activity was evaluated by emulsification and foaming properties, and by adsorption at the oil-H2O interface. In general, the modified gelatins are more surface active than the native gelatin. The increase in hydrophobic chain length and the no. of attached alkyl chains per gelatin mol. decreases the emulsion droplet's size and to more stable emulsions. Adsorption isotherms, at the o/w interface, show much higher surface concn., at satn., of the modified gelatin than the native gelatin. The modified gelatins also have high foaming ability and a high foam stability, while the maximal foam activity was obtained by the C8 modified gelatin. The foaming properties of the surface-active gelatins were also compared to that of Na dodecyl sulfate (SDS) and below the CMC of SDS, both foam activity and stability were higher for the modified gelatins. However, above the CMC the foam activity of SDS was higher, but the foam stability was lower than for C8-C16-modified gelatins. [on SciFinder(R)]
Vinetsky Y, Magdassi S. Properties of complexes and particles of gelatin with ionic surfactants. Colloid Polym. Sci.Colloid and Polymer Science. 1998;276 (5) :395 - 401.Abstract
The properties of sol. gelatin-ionic surfactant complexes and insol. particles were evaluated. Colloidal particles of gelatin A-cationic surfactant (dodecyltrimethylammonium bromide, DTAB, and cetyltrimethylammonium bromide, CTAB) were formed. Binding isotherms showed that these particles are obtained above the CMC of each surfactant, while cooperative binding takes place. Surface tension measurements conducted for both gelatin/DTAB and gelatin/anionic surfactant, SDS, a break in the curve describing surface tension vs. no. of bound surfactant mols., (ν) at concns. below the CMC of each surfactant alone. This break, which is attributed to CMC 1, is obsd. at the same no. of bound surfactant mols. (ν = ≈2) for both gelatin/surfactant couples. Contact angle measurements showed that the max. hydrophobicity of the gelatin-surfactant particles is obtained at the same concn. range in which the pptn. occurs. Also the hydrophobicity of gelatin-SDS particles is higher than that of the gelatin-cationic surfactants, due to a different compn. of the resulting particles. The zeta potential of the particles indicated charge neutralization and even charge reversal for gelatin-CTAB at high surfactant concn. [on SciFinder(R)]
1997
Baszkin A, Boissonnade MM, Rosilio V, Kamyshny A, Magdassi S. Adsorption of hydrophobilized glucose oxidase at solution/air interface. J. Colloid Interface Sci.Journal of Colloid and Interface Science. 1997;190 (2) :313 - 317.Abstract
The modification of glucose oxidase by palmitic acid ester of N-hydroxysuccinimide leads to the formation of a new hydrophobized enzyme with five covalently bound C16 groups. Such a modification was shown not to alter noticeably the native structure of the enzyme. The modified glucose oxidase displays enhanced surface activity at the water/air interface in comparison with the native enzyme. The max. redn. of surface tension at all concns. studied was higher for the modified glucose oxidase than for the native one. The modified enzyme also displayed a much steeper rise of the surface potential with time and a much more rapid attainment of the satn. plateau than the unmodified enzyme. [on SciFinder(R)]
Magdassi S. Delivery Systems in Cosmetics. Colloids Surf., AColloids and Surfaces, A: Physicochemical and Engineering Aspects. 1997;123-124 :671 - 679.Abstract
A review with 29 refs. Cosmetic delivery systems such as different types of emulsions, liposomes, niosomes, and microcapsules are discussed. [on SciFinder(R)]
Vinetsky Y, Magdassi S. Formation and surface properties of microcapsules based on gelatin-sodium dodecyl sulfate interactions. Colloids Surf., AColloids and Surfaces, A: Physicochemical and Engineering Aspects. 1997;122 (1-3) :227 - 235.Abstract
Formation and surface properties of microcapsules, which are based on interaction of gelatin and sodium dodecyl sulfate (SDS) were investigated. It was found that microcapsules of oil droplets can be obtained at a specific range of SDS/gelatin concn. ratios. Both the amt. of gelatin and SDS which were bound to the oil/water interface were maximal in this range, in agreement with Zeta-potential measurements and fluorescence microscopy performed for FITC labeled gelatin. [on SciFinder(R)]
Magdassi S, Bach U, Mumcuoglu KY. Formation of positively charged microcapsules based on chitosan-lecithin interactions. J. MicroencapsulationJournal of Microencapsulation. 1997;14 (2) :189 - 195.Abstract
The formation of microcapsules which contain rosemary oil, is described. The process is based on two steps; (a) formation of oil-in-water emulsions, by using lecithin as emulsifier, thus imparting neg. charges on the oil droplets; (b) addn. of a cationic biopolymer, chitosan, in conditions that favor the formation of an insol. chitosan-lecithin complex. Zeta potential measurements revealed that addn. of very low concns. of chitosan to lecithin stabilized emulsions, led to reversal of charge. At a suitable pH range the chitosan pptd. around the oil droplets forming pos. charged microcapsules. The chitosan-lecithin insol. complex is composed of a 1:1 molar ratio of the chitosan monomeric unit and lecithin, as evaluated by elementary anal. and turbidity measurements. [on SciFinder(R)]
Toledano O, Magdassi S. Formation of surface active gelatin by covalent attachment of hydrophobic chains. J. Colloid Interface Sci.Journal of Colloid and Interface Science. 1997;193 (2) :172 - 177.Abstract
Surface active gelatin was formed by covalent attachment of hydrophobic groups to gelatin mols. The modification was carried out at various degrees of attachment and with various chain lengths. These modified gelatins (MGs) were synthesized in dry DMSO by a simple and rapid method. The new method leads to high yields and allows high degrees of modification. The MGs, which have various hydrophobicities, have better surface activity than the native gelatin, as detd. by surface tension redn. The surface tension redn. is correlated to the hydrophobicity of the modified mol., which was detd. by a fluorescent probe. It appears that both the increase in the no. of the hydrophobic groups and the increase in the chain lengths lead to decreased surface tension. [on SciFinder(R)]
Kamyshny A, Magdassi S. Hydrophobically modified human IgG: surface and biological activities. Colloids Surf., BColloids and Surfaces, B: Biointerfaces. 1997;9 (3/4) :147 - 155.Abstract
Hydrophobic modification of human IgG by fatty acid esters (C8, C12 and C16) of N-hydroxysuccinimide was carried out. Such a modification leads to a spontaneous formation of micelle-like colloidal clusters with a mean diam. of 19.9-22.7 nm for C8-modified IgG. C12- and C16-modified IgGs form larger clusters in spite of a lower no. of attached alkyl chains. The adsorption of the modified IgGs onto latex particles was studied. It was found that the affinity of modified IgGs to the neg. charged hydrophobic polystyrene surfaces is higher than that of the native protein, although an increase in hydrophobicity is also followed by an increase in the net charge of the protein mol. In all cases, the highest equil. concns. correspond to the nearly satd. layer of adsorbed protein mols., this layer being more compact for hydrophobized IgG. The mol. areas of IgGs on the surface are close to those calcd. from the known structural data for the "leg-on" disposition of the "T"- or "Y"-shaped mols. The modified IgG retains recognition ability in ELISA tests, the activity decreases only at a high degree of modification. [on SciFinder(R)]
Vinetsky Y, Magdassi S. Microencapsulation by surfactant-gelatin insoluble complex: effect of pH and surfactant concentration. J. Colloid Interface Sci.Journal of Colloid and Interface Science. 1997;189 (1) :83 - 91.Abstract
The interactions between gelatin and sodium dodecyl sulfate (SDS) were studied, and the conditions which favor formation of insol. complex of gelatin-SDS were applied to form microcapsules of oil droplets. It was found that the insol. complex is formed only while the protein has a net pos. charge, at pH 4.0 and only at a narrow range of surfactant concns., below the crit. micellar concn. The compn. of the coating layer around the oil droplets was evaluated as a function of SDS/gelatin ratio. The maximal adsorbed amt. of gelatin and SDS on the oil droplets corresponds to the SDS concn. in which the zeta potential was minimal and in which insol. gelatin-SDS particles were obtained in absence of the oil phase. [on SciFinder(R)]
1996
Mumcuoglu KY, Galun R, Bach U, Miller J, Magdassi S. Repellency of essential oils and their components to the human body louse, Pediculus humanus humanus. Entomol. Exp. Appl.Entomologia Experimentalis et Applicata. 1996;78 (3) :309 - 314.Abstract
Five essential oils and nine of their components were compared to di-Et toluamide (DEET) for their repellent activity against the human body louse, Pediculus humanus humanus. The abs. or intrinsic repellency of the compds. was tested by applying the repellent to corduroy patches and comparing them with untreated patches. The most effective repellents were DEET and citronella, whose activity lasted at least 29 days. The activity of rosemary lasted at least 18 days and that of eucalyptus more than 8 days. The repellent activity of the oil components such as citronellal and geraniol lasted more than 15 and 8 days, resp. DEET remained effective at a diln. of 1:32, geraniol at 1:8, citronella at 1:4 and rosemary and citronellal at 1:1. The comparative or std. repellency of the candidate repellents was examd. with the aid of a new screening technique using hairs treated with ammonium bicarbonate which is attractive to lice. Using this technique it could be shown that the repellent activity of citronella and geraniol lasted 2 days and that of rosemary and citronellal for only one day. DEET was active for less than one day. Serial dilns. of these substances also revealed that citronella was the most potent repellent for lice, followed by citronellal, rosemary, geraniol and DEET. The differences however, were not significant. [on SciFinder(R)]
Magdassi S, Toledano O, Zakay-Rones Z. Solubilization in colloidal immunoclusters. J. Colloid Interface Sci.Journal of Colloid and Interface Science. 1996;184 (2) :360 - 364.Abstract
Micelle-like clusters of antibody mols. were prepd. by covalent attachment of various hydrophobic groups to the protein mols. These colloidal clusters were capable of solubilizing two hydrophobic probes, while the solubilizate:solubilizer molar ratio was dependent on the chain length of the hydrophobic groups, the degree of modification, and have, on the size of the colloidal clusters. By using a fluorescent solubilizate, it was demonstrated that the immunoclusters may have a specific recognition ability. [on SciFinder(R)]

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