X-ray diffraction study on interdigitated structure of phosphatidylcholines in glycerol

X-ray diffraction was used to study the interdigitated structure of phosphatidylcholines in glycerol. In this study, we investigated five different saturated diacyl phosphatidylcholines with carbon number from 14 to 18 in their acyl chains. It was found that lamellar spacings increase linearly as increasing the carbon number in the chains and that the increment is 0.10 ± 0.01 nm per one carbon atom. The lamellar diffraction intensity data were analyzed, by applying a method proposed by Adachi [Chem. Phys. Lipids 107 (2000) 93-97]. The results indicate that the moiety around polar headgroup regions is almost unchanged, being independent of the carbon number

Cooperativity or phase transition? Unfolding transition of DNA cationic surfactant complex

We recently reported that single duplex DNA, with the size above the order of several tens kilobase pairs, undergoes a large discrete transition from an elongated coil into a collapsed globule with the addition of a cationic surfactant. In the present article, we describe the manner of the unfolding transition of compact long DNA, or globule DNA, complexed with cationic surfactants, cetyltrimethylammonium bromide ͑CTAB͒ and distearyldimethylammonium bromide (D 18 DAB), as is induced by the addition of sodium bromide. The conformational dynamics of individual single duplex T4DNA molecules was directly observed with the use of fluorescence microscopy. We found that on the level of individual DNAs, the salt-induced unfolding transition of the globules is largely discrete, or first-order phase transition for the both complexes with CTAB and D 18 DAB. On the other hand, for the ensemble average of the DNAs, the transition is discrete with CTAB but is continuous ͑sigmoidal͒ with D 18 DAB. The discreteness for the coil-globule transition in the ensemble of DNAs complexed with CTAB is attributed to the existence of the phase transition in whole over the bulk solution: the sphere-rod transition in surfactant micelles. On the other hand, for D 18 DAB such phase transition on the micelle structure in the bulk solution seems to be absent. In correspondence to such a large difference on the manner of the transition, x-ray diffraction analysis indicates marked difference on the structure of DNA complexes with CTAB and with D 18 DAB

Stratum Corneum Structure and Function Studied by X-ray Diffraction

X-ray diffraction is one of the powerful tools in the study of a variety of structures in the stratum corneum at the molecular level. Resolving structural modifications during functioning is an important subject for clarifying the mechanism of operating principles in the function. Here, the X-ray diffraction experimental techniques used in the structural study on the stratum corneum are widely and deeply reviewed from a perspective fundamental to the application. Three typical topics obtained from the X-ray diffraction experiments are introduced. The first subject is concerned with the disruption and the recovery of the intercellular lipid structure in the stratum corneum. The second subject is to solve the moisturizing mechanism at the molecular level and the maintenance of normal condition with moisturizer, being studied with special attention to the structure of soft keratin in the corneocytes in the stratum corneum. The third subject is the so-called 500 Da rule in the penetration of drugs or cosmetics into skin, with attention paid to the disordered intercellular lipid structure in the stratum corneum

A Possible Percutaneous Penetration Pathway That Should Be Considered

The intercellular lipids in the stratum corneum form structures composed of ordered phases with orthorhombic and hexagonal hydrocarbon-chain packing structures and, in addition, a structure composed of a disordered fluid phase. Although the fluid phase plays an important role in percutaneous penetration, little attention has been paid to it in the literature thus far. Recently, a method to estimate the proportion of the fluid phase within the lipids of the stratum corneum was proposed and it was shown to reach about 80%. However, since that study assumed uniform extraction of the intercellular lipids from the stratum corneum, the analysis might give rise to an overestimation of the proportion of the lipids in the fluid phase. We developed a way to investigate the proportion of the lipids in the fluid phase by treating with ethanol, into which the lipids in the fluid phase might be dominantly dissolved. From the experiment we pointed out the possibility that the proportion of the lipids in the fluid phase reached more than 50% of the whole intercellular lipids. Therefore, the fluid-phase region in the intercellular lipid matrix should be taken into account when considering the percutaneous penetration mechanism

マクセイジンショウニオケルシキュウタイキテイマクノデンシケンビキョウテキカイセキ

京都大学0048新制・論文博士医学博士乙第2248号論医博第533号新制||医||177(附属図書館)3300UT51-48-E598(主査)教授 花岡 正男, 教授 加藤 篤二, 教授 髙安 正夫学位規則第5条第2項該当Kyoto UniversityDA

Growth of Molecular Superlattice in Fully Hydrated Dipalmitoylphosphatidylcholine during Subgel Phase Formation Process

Recently, it has been reported that the structure of the subgel phase of dipalmitoylphosphatidylcholine (DPPC) is characterized by two lattices, i.e., a hydrocarbon lattice and a molecular superlattice [1]. On the basis of the results, the domain growth of the molecular superlattice in fully hydrated DPPC multilamellar vesicles at $2.5~^\circ$C was studied by means of X-ray diffraction. The change of the intensities of the (11) diffraction peak originated from the molecular superlattice was analyzed by the Kolmogorov-Avrami theory. We found that the effective dimensionality of the growing domains is $2.3 \pm 0.4$. This result indicates that the domains of the molecular superlattice grow two-dimensionally during the subgel phase formation process, i.e., the domain grows in a single bilayer and is independent between the domains in adjacent bilayers

A Possible Percutaneous Penetration Pathway That Should Be Considered

The intercellular lipids in the stratum corneum form structures composed of ordered phases with orthorhombic and hexagonal hydrocarbon-chain packing structures and, in addition, a structure composed of a disordered fluid phase. Although the fluid phase plays an important role in percutaneous penetration, little attention has been paid to it in the literature thus far. Recently, a method to estimate the proportion of the fluid phase within the lipids of the stratum corneum was proposed and it was shown to reach about 80%. However, since that study assumed uniform extraction of the intercellular lipids from the stratum corneum, the analysis might give rise to an overestimation of the proportion of the lipids in the fluid phase. We developed a way to investigate the proportion of the lipids in the fluid phase by treating with ethanol, into which the lipids in the fluid phase might be dominantly dissolved. From the experiment we pointed out the possibility that the proportion of the lipids in the fluid phase reached more than 50% of the whole intercellular lipids. Therefore, the fluid-phase region in the intercellular lipid matrix should be taken into account when considering the percutaneous penetration mechanism