Biomedical subjects

Masakatsu Hato

Publications and source records attributed to Masakatsu Hato.

7 recordsLinked to original sources

PubMed2006

A novel type of membrane based on cholesteryl phosphocholine, cholesteryl phosphate, or sitosteryl phosphate, and dimyristoylglycerol.

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.

Cholesterol Esters↗

PubMed2005

Comparison of the supramolecular structures of two glyco lipids with chiral and nonchiral methyl-branched alkyl chains from natural sources.

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).

Animals↗

PubMed2005

Headgroup effects on phase behavior and interfacial properties of beta-3,7-dimethyloctylglycoside/water systems.

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.

Carbohydrate Conformation↗

PubMed2004

Aqueous phase behavior of a 1-O-phytanyl-beta-D-xyloside/water system. Glycolipid-based bicontinuous cubic phases of crystallographic space groups Pn3m and Ia3d.

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.

Alkanes↗

PubMed2004

Glycolipid based cubic nanoparticles: preparation and structural aspects.

Kinetically stable cubic colloidal particle dispersion was produced from a glycolipid using a novel preparation strategy based on the dialysis principle. The use of synchrotron small-angle X-ray diffraction (SSAXD) permitted the identification of exact structure of these dispersed particles in the colloidal state. Dynamic light scattering methods were used to obtain size and size distributions. A glycoside, 1-O-phytanyl-beta-D-xyloside (beta-XP), that exhibits Pn3m cubic phase in an excess aqueous medium, was used as the lipid material. The dialysis technique includes controlled stirring action both inside and outside of the dialysis membrane tube. Initially, a mixed micellar system composed of beta-XP, n-octyl-beta-D-glucopyranoside (beta-OG) and a triblock copolymer, Pluronic F127 (PL) was prepared in the aqueous medium. About 10 wt.% of PL to lipid weight was found to be sufficient to produce stable colloidal dispersions. The mean volume diameter of these colloidal particles was found to be in the range of 0.85 +/-0.05 microm. The cubic phase structure of these colloidal particles is greatly depended on the final beta-OG concentration level in the system. Coexistence of Im3m and Pn3m cubic structures has been identified in these colloidal particles. This coexistence has the characteristics of Bonnet relation, which forms a compelling case for the infinite periodic minimal surface (IPMS) descriptions. These colloidal particles could restore pure Pn3m phase structure, but a longer dialysis time was needed. This work, in general, will open up new possibilities for membrane protein reconstitution and other relevant biological applications using colloidal cubic lipid particles.

Dialysis↗

PubMed2004

Alkylglucosides with isoprenoid-type hydrophobic chains-effects of hydrophobic chain size on the aqueous phase behavior.

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.

Calorimetry, Differential Scanning↗

PubMedDate not supplied

Polymer-dispersed bicontinuous cubic glycolipid nanoparticles.

We found that certain amphiphilic polymers such as PEO-PPO-PEO triblock copolymer (PL) can directly disperse a cubic glycolipid, 1-O-phytanyl-beta-D-xyloside (beta-XP), into bicontinuous cubic nanoparticles in water medium. The use of synchrotron small-angle X-ray diffraction (SSAXD) permitted the identification of the exact structure of these dispersed particles in the colloidal state. Dynamic light scattering method was used to obtain particle size distributions. The dispersion quality and the dispersion time can be improved by co-dissolving the lipid and the polymer in a common solvent. The mean volume diameter of these dispersed colloidal particles depends on the mixing time and polymer concentration. About 5 wt % (0.18 mol %) of polymer to lipid weight was found to be sufficient to produce stable colloidal dispersions. At this polymer content and at 3 h of stirring time, the mean volume diameter of cubic colloidal particles was found to be 1.0 microm. Increase of dispersion time to 6 h reduced the colloidal particle size from 1.0 microm to 660 nm. At 3 h of mixing time, the increase of polymer content, from approximately 5 to approximately 10 wt %, reduced the particle mean diameter from 1.0 microm to 675 nm. Irrespective of these dispersion times and polymer contents, the dispersed colloidal particles exhibit predominately the Pn3m cubic phase structure, the same as that of a beta-XP-water binary mixture, although a weak coexistence of Im3m cubic phase is identified in these colloidal particles. This coexistence is found to have the characteristics of a Bonnet relation, which forms convincing evidence for the infinite periodic minimal surface descriptions (IPMS). Considering the biotechnological significance, the preparation of these colloidal dispersions was carried out in a phosphate-buffered saline (PBS) system. These cubic colloidal dispersions exhibited good stability and the cubic phase structure remained intact in the PBS system.

Biotechnology↗