The phase diagram of the ternary system potassium laurate-1-decanol-020 was studied over concentration ranges where nematic phases are likely to occur. Two uniaxial nematic phases which are separated by a biaxial nematic phase are found. In limited concentration range the following phase sequence may be observed reversibly on heating and on cooling: isotropic-uniaxial nematic (positive optical anisotropy) -biaxial nematicuniaxial nematic (negative optical anisotropy)biaxial nematicuniaxial nematic (positive optical anisotropy) -isotropic.PACS numbers: 64.70.Ew, 61.30. Gd, 76.60.Gv, 78.20.Fm The existence of a uniaxial nematic phase with negative diamagnetic anisotropy in aqueous solutions of potassium laurate (KL) containing some 1-decanol and potassium chloride was first reported by Long and Goldstein. ' ' The properties indicate that the phase has micelles of a bilayer structure. We denote this phase as N~( see Refs. 3 and 4 for a discussion of structures and relations to Type-I and Type-II phases'). In studying the phase diagram of the ternary system KL-1decanol-D, O, we found that besides N~t wo additional nematic phases occur. One of the additional phases is also uniaxial but of negative optical and positive diamagnetic anisotropy. It corresponds probably to a phase with cylindrical micelles and we denote it as N~. ' The third nematic phase occurs in concentration and temperature ranges that separate N~a nd N~. It is a biaxial nematic phase that we will denote as N, ". To our knowledge this is the first time that the existence of a biaxial nematic phase has been clearly established. The phases were classified by microscopic studies and by deuteron resonances as described in the following sections. Figure 1 shows part of the phase diagram of the KL-1-decanol-D, O system. The 1-decanol concentration is constant at 6.24 wt. % while the weight concentration ratio of D,O to KL varies from 2.67 to 2.56. For D,O concentrations higher than 68 wt. % only one nematic phase N~i s formed. Upon cooling it transforms to a viscous isotropic phase and upon heating to an isotropic phase of a relatively low viscosity. The biaxial nematic phase N, " is formed at 68 wt. % D,O concentration. It transforms on cooling and on heating to N~(N~-N~"-N~). The N~p hase forms when the D,O concentration is lowered to 67.8 wt. %. All three nematic phases occur near this concentration and the sequency by which they transform into each other is N-N~-N~-N»-N~. The range of N~w idens with decreasing water concentration whereas those of N~a nd N, "arenarrowed. The N~p hase of the mixture with 67.4 wt. % D,O transforms on heating directly to the isotropic micellar solution. Upon further heating a formation of batonnets takes place which may belong to a lamellar smectic phase.Microscopic observations were made on the films sealed in flat capillaries. In general some

We have synthesized a novel molecule, 3,6-bis(1-methyl-4-vinylpyridium)carbazole diiodide (BMVC), for recognizing specific quadruplex structures, particularly the quadruplex of human telomeric sequence d(T(2)AG(3))(4). The fluorescence intensity of the BMVC molecule increases from 1 to almost 2 orders of magnitude upon interacting with various DNAs. At a concentration of BMVC of 10 microM, fluorescence bands with different colors of BMVC in electrophoresis gels of various DNAs can be observed. The fluorescence of BMVC can be used to discriminate between duplex and quadruplex DNAs. At the low concentration of 0.1 microM BMVC in prestained gels, the fluorescence is observed in the presence of quadruplexes with anti-anti-anti-anti and anti-anti-syn-syn arrangements. However, no fluorescence band is detected upon interacting with duplexes and quadruplexes with anti-syn-anti-syn arrangement. Moreover, the sensitivity assays show that as little as 0.2 pmol of quadruplex of d(T(2)AG(3))(4) can be revealed by BMVC.

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A systematic structural modification is carried out to change the molecular shapes of stilbene derivatives from rodlike through hockey stick then to bananalike by tuning the length of the functional group attached to the lateral direction of the rodlike skeletons. The mesophases and the corresponding properties are monitored by optical polarizing microscopy, differential scanning calorimetry, electric field effect, and X-ray diffraction. The existence of mesophase is strongly affected by the molecular conformation and intermolecular forces inherited in the moiety employed. Nematic, smectic C (SmC), and anticlinic smectic C (SmCa) phases are formed by the hockey stick molecules. Defects of 2- and 4-brushes are observed for the SmC and SmCa phases and indicate the existence of anticlinic arrangements of neighboring layers. Anticlinic layer structures constitute the intermediate phases between the calamitic and banana mesophases. Electric-field-switched texture changes are evident for the nematic and SmC phases and are different from those of known calamitic mesogens. These behaviors are ascribed to the bent conformation of these hockey stick molecules. Antiferroelectric B2 banana phases are formed by hockey stick molecules with two arms carrying moieties of large enough polarizability.