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ABSTRACT: Aqueous phase behavior of lipids with isoprenoid type hydrophobic chains (hereafter referred to as "isoprenoid-chained lipids") as functions of the chain length and the hydrophilic headgroup type has been examined over a chain length span from 12 to 16 carbon atoms long and a temperature range from -40 to 65 degrees C by using optical microscopy, DSC (differential scanning calorimetry), and SAXS (small-angle X-ray scattering) techniques. Characteristic phase behavior that arises from the unique "isoprenoid-chain" structure was discussed. This work together with previous studies (Prog. Colloid Polym. Sci. 2004, 123, 56-60 and J. Phys. Chem. B 2008, 112, 12286-12296) has clarified the molecular correlation of the aqueous phase behavior of "isoprenoid-chained lipids" over the chain lengths from 12 to 18 carbon atoms and introduced a new lipid library which can form a range of liquid crystals, such as an HII (an inverted hexagonal phase), a QII (an inverted cubic phase), and an Lalpha (a lamellar phase), that are stable over a wide temperature span from 0 degrees C.
The Journal of Physical Chemistry B 08/2009; 113(30):10196-209. · 3.70 Impact Factor
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ABSTRACT: With a view to discovering a new family of lipids that form inverted cubic phases, the aqueous phase behavior of a series of lipids with isoprenoid-type hydrophobic chains has been examined over a temperature range from -40 to 65 degrees C by using optical microscopy, DSC (differential scanning calorimetry), and SAXS (small-angle X-ray scattering) techniques. The lipids examined are those with 5,9,13,17-tetramethyloctadecyl and 5,9,13,17-tetramethyloctadecanoyl chains linked to a series of headgroups, that is, erythritol, pentaerythritol, xylose, and glucose. All of the lipid/water systems displayed a "water + liquid crystalline phase" two-phase coexistence state when sufficiently diluted. The aqueous phase structures of the most diluted liquid crystalline phases in equilibrium with excess water depend both on the lipid molecular structure and on the temperature. Given an isoprenoid chain, the preferred phase consistently follows a phase sequence of an H II (an inverted hexagonal phase) to a Q II (an inverted bicontinuous cubic phase) to an L alpha (a lamellar phase) as A* (cross-section area of the headgroup) increases. For a given lipid/water system, the phase sequence observed as the temperature increases is L alpha to Q II to H II. The present study allowed us to find four cubic phase-forming lipid species, PEOC 18+4 [mono- O-(5,9,13,17-tetramethyloctadecyl)pentaerythritol], beta-XylOC 18+4 [1- O-(5,9,13,17-tetramethyloctadecyl)-beta- d-xylopyranoside], EROCOC 17+4 [1- O-(5,9,13,17-tetramethyloctadecanoyl)erythritol], and PEOCOC 17+4 [mono- O-(5,9,13,17-tetramethyloctadecanoyl)pentaerythritol]. The values of T K (hydrated solid-liquid crystalline phase transition temperature) of the cubic phase-forming lipids are all below 0 degrees C. Quantitative analyses of the lipid molecular structure-aqueous phase structure relationship in terms of the experimentally evaluated "surfactant parameter" allow us to rationally select an optimum combination of hydrophilic/hydrophobic part of a lipid molecule that will form a desired phase in a desired temperature range.
The Journal of Physical Chemistry B 10/2008; 112(39):12286-96. · 3.70 Impact Factor
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ABSTRACT: Surfactant self-diffusion coefficients have been measured on a binary system of 1-O-beta-3,7-dimethyloctyl-D-maltopyranoside (beta-Mal(2)(Ger))/water and a mixed surfactant system of beta-Mal(2)(Ger)/1-O-beta-3,7-dimethyloctyl-D-glucopyranoside (beta-Glc(Ger))/water at 25 degrees C. For comparison, measurements have also been made on 1-O-beta-decyl-D-maltopyranoside (beta-Mal(2)C(10))/water and beta-Mal(2)C(10)/1-O-beta-decyl-D-glucopyranoside (beta-GlcC(10))/water. The hydrodynamic radius of beta-Mal(2)(Ger) micelles obtained from the micellar diffusion coefficient is around 3 nm and nearly equal to that of beta-GlcC(10) micelles within experimental error. In the mixed surfactant systems, the hydrodynamic radii for both systems increase with increasing X(G) (the mole fraction of beta-Glc(Ger) or beta-GlcC(10) in the total mixed solute) above X(G) congruent with 0.4 when the total surfactant concentration is kept constant at 2 wt%. The R(H) of beta-Glc(Ger)/Mal(2)(Ger) micelles increases more rapidly than beta-GlcC(10)/beta-Mal(2)C(10) micelles, and then phase separation occurs at X(G) congruent with 0.65. On the other hand, the R(H) of beta-GlcC(10)/beta-Mal(2)C(10) micelles continues to increase until the phase separation occurs at X(G) congruent with 0.92. Measurements have also been performed as a function of total surfactant concentration at constant X(G) (=0.6). The CMC of the beta-Glc(Ger)/Mal(2)(Ger) system is larger than that of the beta-GlcC(10)/beta-Mal(2)C(10) system as expected from the results of the pure surfactant systems published previously. The R(H) increases with increasing total surfactant concentration for both systems. At higher concentrations, the R(H) of beta-Glc(Ger)/Mal(2)(Ger) micelles increases more rapidly than beta-GlcC(10)/beta-Mal(2)C(10) micelles. These results can be explained by the fact that the geranyl and decyl chains have the same volume but different chain lengths.
Journal of Colloid and Interface Science 09/2007; 312(1):122-9. · 3.07 Impact Factor
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ABSTRACT: Mixtures of amphiphilic cholesteryl phosphate (CP), sitosteryl phosphate (SP), or cholesteryl phosphocholine (CPC) with the nonphosphoryl diacyl lipid dimyristoylglycerol (DMG) or with cholesterol give self-organized systems (giant vesicles) in a wide range of pH, as demonstrated by fluorescence microscopy, differential scanning calorimetry, and small-angle X-ray scattering. The water permeability of a 1 : 1 molar mixture of CPC and DMG was also measured by a stopped-flow/light-scattering method. The novel self-organized systems are akin to natural eukaryotic ones, the only difference being the site of the phosphate-containing head-group, located on cholesterol instead of DMG. They might be present in some organisms not yet studied for the composition of their membranes.
Chemistry & Biodiversity 03/2006; 3(2):198-209. · 1.80 Impact Factor
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ABSTRACT: The aqueous phase behavior and the interfacial properties of alkylglycosides, AGs, with a 3,7-dimethyloctyl (geranyl) chain have been investigated as a function of the number of glucose units, N, in the maltooligosaccharide headgroup. The results can be interpreted in terms of a "helical conformation" of the maltooligosaccharide, where the cross section area increases as N increases.
Chemistry and Physics of Lipids 05/2005; 134(2):151-60. · 2.57 Impact Factor
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ABSTRACT: Two alkyl glycosides with the same type of disaccharide headgroups (melibiose) and different methyl-branched alkyl chains, short chiral [(2R,4R,6R,8R)-2,4,6,8-tetramethyldecyl, extracted from an animal source] and long nonchiral (3,7,11,15-tetramethylhexadecyl, from a plant source), were synthesized. The supramolecular aggregate structure formed in dilute solutions was investigated by small-angle neutron scattering and surface tension measurements. The lyotropic phase diagram was studied by differential scanning calorimetry and water penetration scans. The thermotropic phase behavior was investigated by polarizing microscopy. The compounds showed unusual phase behavior: (i) The liquid-crystalline polymorphism is reduced to only form smectic A phases in the pure state; the formation of lyotropic phases such as hexagonal or lamellar phases was not observed. (ii) The compound with the longer nonchiral alkyl chain is more soluble in water than the one with the shorter chiral chain, most likely because of the different flexibilities of the chains. (iii) For the long-chain compound, the formation of micelles is observed, whereas the short-chain compound forms large disklike/bilayer aggregates. The method of methylation of the chain controls the self-assembly and can explain different biological functions for either plants (variable temperature) or animals (constant temperature).
The Journal of Physical Chemistry B 03/2005; 109(4):1599-608. · 3.70 Impact Factor
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ABSTRACT: Temperature- and concentration-dependent aqueous phase diagram of a novel alkylglycoside, 1-O-phytanyl-beta-D-xyloside (beta-Xyl(Phyt)), was studied using small-angle X-ray scattering, polarizing optical microscopy, and differential scanning calorimetry. The phases found in this system include an Lc phase, an Lalpha phase, an HII phase, two inverted cubic phases of crystallographic space groups Pn3m and Ia3d, and a fluid isotropic phase, FI. The phase diagram of the beta-Xyl(Phyt)/water system is similar to that for the 1-monooleylglycerol (MO)/water system, suggesting that the phase behavior is largely determined by the overall molecular shape rather than the details of surfactant molecular structure. Moreover, the structural parameters of the beta-Xyl(Phyt) liquid crystals are also similar to those of the MO/water, due primarily to the similar molecular dimensions of two molecules. As compared to the MO/water system, however, the beta-Xyl(Phyt)/water system displays a lower value of TK ( approximately 8.(5) degrees C) and a wider temperature window for the mesophases (8.(5)-120 degrees C). Moreover, beta-Xyl(Phyt) is chemically more robust than MO, as the ether linkage is more stable against hydrolysis than the ester linkage and the phytanyl chain is fully saturated.
Langmuir 01/2005; 20(26):11366-73. · 4.19 Impact Factor
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ABSTRACT: The aqueous phase behavior of novel alkylglycosides, AGs, that have a 3,7,11,15-tetramethylhexadecyl (phytanyl) group as their
hydrophobic part was examined as a function of the headgroup type, i.e., glycerol, xylose, glucose, and maltose in order of
the increasing number of hydroxy groups of the headgroup. The aqueous phase structures at full hydration are well correlated
with the headgroup size; an H
I
I phase for the glycerol-headgroup, a cubic phase of crystallographic space group Pn3m / Pn3 at lower temperatures and an H
I
I phase at higher temperatures for the xylose-headgroup, and an Lα phase for the glucose- and the maltose-headgroup. Krafft eutectic temperatures, T
K
, of the phytanyl-chained AGs are significantly lower than those of conventional AGs, although the total number of carbon
atoms in the hydrophobic group is as large as 20. Their low T
K
values afford greater control of the aqueous phase structures at low temperatures.
KeywordsPhytanyl-chained akylglycoside–Akylglycoside–Phase diagram–Cubic phase–Krafft eutectic temperature
05/2004: pages 56-60;
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ABSTRACT: Aqueous phase diagrams were constructed for two new alkylglucosides with isoprenoid-type hydrophobic chains, viz. 1-O-beta-(3,7-dimethyloctyl)-D-glucopyranoside, beta-Glc(Ger), and 1-O-beta-(3,7,11,15-tetramethylhexadecyl)-D-glucopyranoside, beta-Glc(Phyt). In a low concentration regime, from 0.17 to 34 wt.% beta-Glc(Ger), the beta-Glc(Ger)/water system exhibits two phase, a dilute (L1dil) and a concentrated isotropic phase (L1con), coexistence region. Above about 62 wt.% beta-Glc(Ger), an Lalpha phase is formed. The extent of the L1dil + L1conc two-phase region decreases as temperature increases and totally disappears above 130 degrees C, exhibiting an upper critical temperature. The beta-Glc(Phyt)/water system exhibits an Lalpha phase above 78 wt.% surfactant below which, an Lalpha + water two-phase region appears. One notable feature of these compounds is their low values of Krafft-eutectic temperature, TK, e.g. the value of TK for beta-Glc(Phyt) is below 0 degrees C although the total number of carbon atoms in the hydrophobic chain is as large as 20.
Chemistry and Physics of Lipids 02/2004; 127(1):65-75. · 2.57 Impact Factor
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ABSTRACT: We have proposed novel alkylglycosides, AGs, that consist of an isoprenoid-type hydrophobic chain, the 3,7,11,15-tetramethylhexadecyl (phytanyl) group. One notable feature of the proposed AGs lies in the fact that their Krafft eutectic temperatures, TK, are well below room temperature although the total number of carbon atoms in the hydrophobic chain is as large as 20. As compared to the conventional AGs with straight and saturated alkyl chains, their low TK values significantly expand our freedom to control their aqueous phase structures at low temperatures. The aqueous phase structures are controlled by modification of the headgroup: an HII phase for the glycerol headgroup, a cubic phase with crystallographic space group Pn3m/Pn3 at low temperatures and an HII phase at higher temperatures for a xylose headgroup, and an Lα phase for a glucose and a maltose headgroup.
04/2002;
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ABSTRACT: We have investigated the temperature−concentration dependent phase diagram of an aqueous maltoheptaose-containing lipid, 1,3-di-O-dodecyl-2-(β-maltoheptaosyl)glycerol, Mal7(C12)2. In the region examined (25−90 °C and 0−65 wt % lipid), two liquid crystalline phases form: a normal hexagonal phase (HI) above 40−45 wt % lipid and a second phase (most probably a lamellar phase Lα) at higher temperatures (>55 °C) and higher concentrations (>60 wt % lipid). From the dilute solution to about 30 wt % lipid, an optically isotropic solution region is found where normal micelles exist. The present results together with the phase behavior of MalN(C12)2/water systems with N = 1−5 (Hato, M.; Minamikawa, H. Langmuir 1996, 12, 1658) indicate that a preferred phase of the MalN(C12)2 where the headgroup is composed of N glucose residues linked via α-1,4-O-glycosidic bonds shifts from an HII to an HI via an Lα phase as N increases. The observed phase sequence makes a marked contrast to the CelN(C12)2/water systems where the headgroup is composed of N glucose residues linked via β-1,4-O-glycosidic bonds (Hato, M.; Minamikawa, H. Langmuir 1996, 12, 1658). The stereochemistry-dependent phase behavior can be interpreted in terms of different conformations of the headgroups, i.e., a “helical” conformation of the maltooligosaccharide headgroups, and an “extended” conformation of the cellooligosaccharide headgroups.
12/1998;
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ABSTRACT: A synthetic glucolipid, 1,3-di-O-phytanyl-2-O-(β-glucosyl)glycerol in water was examined by small-angle X-ray scattering, differential scanning calorimetry, and polarizing microscopy. These measurements showed that the aqueous lipid forms an Fd3m reverse micellar cubic phase (lattice constant = 148 Å) over a wide temperature range (at least from −20 to 80 °C). The X-ray scattering revealed that the phase structure is stable at 0 and 25 °C for months without any detectable chemical change. For the fully hydrated cubic phase, its hydration amount was determined to be 4.4 mol/mol (water/lipid) by calorimetry at 0 °C. From these experimental values, the structural parameters of the cubic phase were evaluated on the basis of the proposed structure model. The evaluation is compared with the molecular dimensions of the glucolipid.
07/1998;
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ABSTRACT: We have synthesized 1,3-di-O-phytanyl-2-O-(glycosyl)glycerols possessing maltooligosaccharide headgroups, MalN(Phyt)2, as model archaebacterial glycolipids (the number of glucose units N = 1, 2, 3, and 5) and investigated the phase behavior of the lipid/water systems using small-angle X-ray scattering and differential scanning calorimetry. The hydrated-solid to liquid-crystalline phase transition temperatures of MalN(Phyt)2 are well below 0 °C, so that MalN(Phyt)2 are in a liquid crystalline state above 0 °C. The structures of the aqueous MalN(Phyt)2 are largely determined by N; a weakly birefringent mesophase for a glucolipid, Glc(Phyt)2, an HII phase for Mal2(Phyt)2, and an Lα phase for Mal3(Phyt)2 and Mal5(Phyt)2. This indicates an increasing tendency for the MalN(Phyt)2 monolayers to curve toward apolar regions with increasing N. The salient feature of the phytanyl chain lies in significantly larger cross section areas of the lipids at the hydrophobic part−headgroup interface (e.g., 1.0 nm2/lipid for an Lα phase) compared with those of the straight-chained counterparts (0.65−0.75 nm2/lipid). A state of alkyl chain disorder appears similar in both phytanyl- and straight-chained lipids. The phase behavior of MalN(Phyt)2 is compared with that of straight-chained glycolipids.
04/1997;
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ABSTRACT: Effects of the stereochemistry of oligosaccharide head groups on the physical properties of aqueous synthetic glycolipids, 1,3-di-O-dodecyl-2-(β-glycosyl)glycerols bearing cellooligosaccharides (β-1,4-O-glycosidic bonds) and maltooligosaccharides (α-1,4-O-glycosidic bonds) as hydrophilic groups have been studied. The increase in the number of glucose residues, N, in the two different headgroups exhibited opposite effects on the physical properties of the aqueous glycolipids. For the maltooligosaccharide-containing lipid, MalN(C12)2, increasing N in the head groups decreases the hydrated solid/liquid crystalline phase transition temperature Tm and increases the “hydrophilicity” of the lipids. However, the Tm of the cellooligosaccharide-containing lipids CelN(C12)2 increases with increasing N of the cellooligosaccharide head groups. It is noteworthy that Tm jumps from 59 °C (for N = 4) to above 160 °C (N = 5), so that the Cel5(C12)2 cannot form a liquid crystalline phase and was totally insoluble in water. The results can be explained in terms of different conformations of the head groups, i.e., a “helical” conformation of the maltooligosaccharides and an “extended” conformation of the cellooligosaccharides.
03/1996;
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ABSTRACT: The surface property of two kinds of synthetic glyceroglycolipids was investigated to confirm the stereoeffect of sugar residues on the phase behavior in monolayers: one is the maltooligosaccharide-containing lipids [MalN(C12)2] and the other is cellooligosaccharide-containing lipids [CelN(C12)2]. The two kinds of glycolipids exhibit the opposite dependence of the surface pressure−area (Π−A) isotherm on the number of glucose residues (N), in that MalN(C12)2 tends to be more expanded as N increases, while CelN(C12)2 tends to be more condensed. The liquid-expanded/liquid-condensed phase transition in Cel4(C12)2 was evaluated by the Brewster angle microscopy and the latent heat analysis with the Clausius−Clapeyron equation, as a model of film condensation induced by the attraction between oligosaccharide head groups. The film morphology of Cel4(C12)2 was unique in that it exhibits the optically isotropic and flexible fluid type of the LC phase, while Glc(C16)2 forms a two-dimensional tilted crystalline phase in the same way as fatty acids and phospholipids. The heat of transition (ΔH) of Cel4(C12)2 does not converge toward zero even at high temperature. In other words, the main transition of Cel4(C12)2 does not become second order in contrast to the behavior usually encountered in monolayers. The refractive index of the oligosaccharide head groups in water as well as the alkyl chains in air must be properly taken into account to interpret the reflectivity.
03/1996;
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Tetrahedron Letters 35(5):745-748. · 2.68 Impact Factor
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ABSTRACT: Small angle X-ray scattering (SAXS) is measured for the lamellar phase in aqueous systems of 1-o-β-3,7-dimethyoctyl-d-glucopyranoside (β-Glc(Ger)), which has recently been prepared by us, 1-o-β-decyl-d-glucopyranoside (β-GlcC10), and 1-o-β-octyl-d-glucopyranoside (β-GlcC8). The repeat distance d obtained from the position of the diffraction peak does not follow the swelling law d = 2δhc/ϕhc, where δhc and ϕhc are the thickness and the volume fraction of the hydrophobic layer, respectively. This may result from the fact that δhc increases and, equivalently, the surface area per surfactant molecule (as) decreases with increasing concentration. So we calculate δhc and as from the observed d value at each concentration using the above swelling law. The half-thickness δhc increases in the order β-GlcC8 < β-Glc(Ger) < β-GlcC10 at a fixed concentration. On the other hand, the data on as for β-GlcC10 and β-GlcC8 lie on the same line and the data for β-Glc(Ger) lies above this line. These results suggest that the cross-sectional area of the geranyl chain is larger than that of the glucose headgroup. Existence of water filled defects in bilayer sheets is also discussed based on the SAXS pattern and the concentration dependence of d.
Colloids and Surfaces A Physicochemical and Engineering Aspects 250:485-490. · 2.24 Impact Factor
