Aggregation Structure Of Monolayers Research Articles

AFM observations of (DMPC/cholesterol) mixed monolayer on aqueous solution of Vibrio cholerae hemolysin

The aggregation structure of monolayer, consisting of phospholipid and cholesterol, on a pure water and an aqueous solution of Vibrio cholerae hemolysin (VCH) was investigated on the basis of surface pressure–area ( π– A) isotherm measurements and atomic force microscopic observations. The behavior of π– A isotherm by addition of VCH revealed changes in the monolayer state due to interaction with VCH. Small dots with a diameter of about 10 nm, assigned to VCH subunits, were observed in the matrix region of the mixed monolayer but not in the domain. This result implies that VCH penetrates into the mixed monolayer, suggesting that a stronger aggregation between cholesterols prevents to its penetration into cholesterol-rich phase (domain region).

Effect of binding state between hydrophilic and hydrophobic portions on aggregation structure of monolayer

The effect of molecular structure of anionic (2C n POH ( n=12, 16)) amphiphiles with dialkyl chains that bind with the hydrophilic group only through ether bond and cationic (2C n N +2C ( n=18, 22)) amphiphiles with dialkyl chains that directly bind with the hydrophilic group without a spacer on aggregation structure of amphiphile monolayers was investigated on the basis of π- A isotherm measurement and electron diffraction (ED) analysis. π- A Isotherms of the 2C 12POH and 2C 18N +2C monolayers exhibited a plateau region, whereas those of the 2C 16POH and 2C 22N +2C monolayers did a sharp rise in surface pressure with decreasing surface area. ED analysis revealed that 2C 12POH, 2C 18N +2C and 2C 22N +2C monolayers were in an amorphous state even at higher surface pressures. On the other hand, the 2C 16POH monolayer was in a crystalline hexagonal state in which the degree of molecular aggregation is low. Noncrystallization of the 2C 12POH, 2C 18N +2C and 2C 22N +2C monolayers and the low degree of molecular aggregation of the 2C 16POH monolayer may be attributed to the molecular aggregation by distantness between dialkyl chains in their parallel alignment due to binding between the hydrophilic and hydrophobic portions without or through only one spacer.

Novel concept for the aggregation structure of fatty acid monolayers on the water surface and direct observation of molecular arrangements in their monolayers

The aggregation structure of fatty acid monolayers on water subphases of different pH’s was investigated by means of transmission electron microscopy. Fatty acid monolayers exhibited the phase transition from an amorphous state to a crystalline one by surface compression in the case of a highly dissociated state of hydrophilic groups, whereas they did not show the phase transition in the case of a slightly dissociated state. The aggregation structure of monolayers on the water surface was systematically classified into “the crystalline monolayer”, “the amorphous monolayer” and “the compressing crystallized monolayer” with respect to thermal and chemical (intermolecular repulsive) factors.Molecular-resolution images of fatty acid molecules in the monolayers on mica substrate were successfully observed with an atomic force microscope (AFM) for the first time. The AFM image of a lignoceric acid monolayer prepared at a surface pressure of 5mNm−1 showed a two-dimensional periodic structure with locally disordered molecular arrangements. Also, the nondestructive AFM image observation was successful for a stearic acid monolayer which was prepared by a multistep creep method, indicating that a high mechanical stability of the monolayer is inevitably required for the nondestructive AFM observation.

Classification for molecular aggregation structure of monolayers on the water surface

The melting temperature, T m , and the crystalline relaxation temperature, Tα c , of palmitic acid and dipalmitoyl phosphatidylcholine monolayers on the water surface were evaluated by combination of two kinds of measurements: first, the subphase temperature, T sp , dependence of the monolayer modulus based on the surface pressure-area (π- A) isotherm and second, the T sp dependence of the electron diffraction, ED patterns of their monolayers. On the basis of their characteristic temperatures of the monolayers, the aggregation structure of the monolayers which were transferred onto a hydrophilic SiO substrate at various surface pressures and T sp s was investigated by means of transmission electron microscopy. The π- A isotherm for the fatty acid monolayer on the pure water surface represented the aggregating process of isolated domains grown right after spreading a solution on the pure water surface. The fatty acid monolayer on the pure water surface was classified into a crystalline monolayer ( T sp < T m ) and an amorphous one ( T sp > T m ). The crystalline monolayer was further classified into two types; crystalline domains were aligned along their crystallographic axes owing to an induced sintering at the interfacial region among monolayer domains by surface compression ( T sp < Tα c ), while not for T sp > Tα c . In the case of the phospholipid monolayer, the monolayer was classified into a compressing crystallized monolayer ( T sp < T m ) and an amorphous one ( T sp > T m ). The compressing crystallized monolayer is a monolayer in which crystallization was gradually induced at plateau region on the π- A isotherm by compression. Electron diffraction studies of arachidic acid monolayers in different dissociated states of hydrophilic groups revealed that formation of the compressing crystallized monolayer was attributed to an electrostatic repulsion among ionic hydrophilic groups. It was concluded that the aggregation structure of monolayers on the water surface was systematically classified into ‘the crystalline monolayer’, ‘the amorphous monolayer’ and ‘the compressing crystallized monolayer’, with respect to thermal and chemical (intermolecular repulsive) factors.

Effect of polycation in subphase on aggregation structure of monolayer and Langmuir-Blodgett film of anionic amphiphile

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of polycation in subphase on aggregation structure of monolayer and Langmuir-Blodgett film of anionic amphiphileTisato Kajiyama, Liangren Zhang, Motoko Uchida, Yushi Oishi, and Atsushi TakaharaCite this: Langmuir 1993, 9, 3, 760–765Publication Date (Print):March 1, 1993Publication History Published online1 May 2002Published inissue 1 March 1993https://doi.org/10.1021/la00027a025RIGHTS & PERMISSIONSArticle Views148Altmetric-Citations30LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (3 MB) Get e-Alerts Get e-Alerts