In this work we investigated phase diagrams of CTAB and different polar solvents such as water, formamide, and glycerol in order to compare the effects of a nonaqueous solvent on the existence of intermediate phases. A small-angle X-ray scattering setup was used to observe the diffraction peak corresponding to the high values of the phase parameters and their transformations. We developed a method for rapid and continuous observation of the surfactant-solvent system over their transitions from the micellar to the lamellar phase. The following sequence of intermediate phases was identified in the CTAB/water system: hexagonal-monoclinic (close to a centered rectangular phase)-cubic-lamellar. Comparison with the results from CTAB/formamide and CTAB/glycerol systems showed the same sequence (except that the monoclinic phase existence was only found with water), but the existence regions of these phases are different and the parameters are smaller.

Structures formed by self-assembly of α- and β-1-n-dodecyl d-maltosides in water depend on the configuration at the anomeric center. The α-anomer forms quasi-spherical aggregates, while the β-maltoside forms larger oblate ellipsoidal micelles. This difference in behavior suggests that the configuration of the head group influences the orientation of the polar residue and hence the packing of monomers during self-assembly.

Galactosylceramide (GalCer) is an alternative receptor allowing human immunodeficiency virus (HIV)-1 entry into CD4-negative cells of neural and colonic origin.Several lines of evidence suggest that this glycosphingolipid recognizes the V3 region of HIV-1 surface envelope glycoprotein gp120. Since the V3 loop plays a key role in the fusion process driven by HIV-1, we decided to synthesize soluble analogs of GalCer with the aim to develop a new class of anti-HIV-1 agents that could neutralize HIV-1 infection through masking of the V3 loop. We describe a short route, in three steps, for the synthesis of soluble analogs of GalCer, using unprotected lactose as the starting sugar. The analogs were prescreened in an assay based on the interaction between a V3 loopderived synthetic peptide and [ 3 H]suramin, a polysulfonyl compound displaying high affinity for the V3 loop. One of the soluble analogs, i.e. CA52(n15), strongly inhibited the binding of [ 3 H]suramin to the V3 peptide, with an IC 50 of 1.2 M. This molecule was also able to inhibit [ 3 H]suramin binding to recombinant gp120 with similar activity. Using a competition enzyme-linked immunosorbent assay with highly specific anti-gp120 monoclonal antibodies, the region recognized by CA52(n15) could be mapped to amino acids 318 -323, which corresponds to the highly conserved consensus motif GPGRAF. Interestingly, the region recognized by suramin, i.e. IQRGP-R-F, was partially overlapping this motif. CA52(n15) was able to inhibit HIV-1-induced cell fusion as well as HIV-1 entry into both CD4 ؉ and CD4 ؊ / GalCer ؉ cells. A structure-activity relationship study showed that: (i) the antiviral activity of soluble analogs of GalCer correlates with V3 loop binding, and (ii) the hydrophobic moiety of the molecule plays an important role in this activity. Taken together, these data show that synthetic analogs of GalCer can inhibit HIV-1 entry into both CD4 ؊ and CD4 ؉ cells through masking of the V3 loop.

New double-chain and gemini catanionic analogues of the glycolipid galβ1ceridentified as a cell receptor of the HIV-1 viruswere easily prepared in two steps from unprotected lactose. Due to their sugar moiety, these new catanionic surfactants were able to be cationized by sodium ions and therefore to be characterized in their monomeric forms by electrospray mass spectrometry. To our knowledge, this is the first time that catanionic surfactants have been directly observed, proving undoubtedly their existence as monomeric species. These new catanionic glycolipids showed interesting anti-HIV-1 activities, acting as monomeric analogues of galβ1cer. Finally, these new catanionic glycolipids were characterized by their surface active properties, by lamellar mesophases, and by their aptitude to spontaneously form vesicles.

eV for an indirect transition, and 1.24 eV for a direct transition are close to the reported single value of 1.21 eV (again, the mode was not assigned).The occurrence of both an indirect and direct transition is common for the CdIn2VI4 family of materials, and the difference between £ind and £d has been reported to be 0.1 eV for CdIn2Te4.12 Our value of 0.08 eV is close to the 0.1 eV value. We also obtained a value of 0.16 eV for the difference between £ind and £d for p-Hg!n2Te4. It seems that the difference between £ind and £d decreases from 0.22 eV for CdIn2Se4 to 0.08 eV for CdIn2Te412 and increases from 0.08 eV for CdIn2Te4 to 0.16 eV for HgIn2Te4.The Mott-Schottky plot intercept value of -0.48 V was close to that of the onset of photocurrent (-0.53 V, see Table I); therefore, the open circuit photovoltage is expected to be ~0.6 V (£redox = -1.09 V). Considering a band gap value of 1.20 eV (0.9 eV for HgIn2Te4) and an analysis parallel to that given for p-HgIn2Te4 above, the valence band would be located at -0.4 V (-0.6 V for HgIn2Te4) and the conduction band near -1.6 V (-1.5 V for HgIn2Te4).The photocurrent onset and the maximum power efficiency in[Cr(III)EDTA]' with monochromatic light irradiation were close to that in Fe(III)TEA complex solution, but the maximum power efficiency in [Cr(III)EDTA]' with polychromatic light irradiation was less than that in Fe(III)TEA complex solution (the reason for this is given above). Therefore, the Fe(III)TEA complex solution is a preferred one for both p-HgIn2Te4 and p-CdIn2Te4 electrodes.

No abstract

In this work we investigate lyotropic phases in different sugar-based surfactantlwater systems. Studies are carried out with the (N-alky1amino)-1-deoxylactitols (CS, C10, CIZ) and P-dodecyl maltoside. Liquid crystal phases are detected and lattice parameters determined by X-ray diffraction. The phases observed are the normal phases found in binary ionic or nonionic surfactantlwater systems. Schematic diagrams show the sequences of the lyotropic phases formed by these disaccharide surfactants. The difference in behavior is accounted for by the difference in chain length, hydrophilic ability, and steric hindrance of the polar head. IntroductionSurfactants derived from sugars form a large class of amphiphiles, which are currently receiving attention in view of their excellent biocompatibility and biodegradabi1ity.l Among the numerous applications of these compounds mention can be made of extraction and crystallization of membrane proteins2 and emulsification of substrates for enzymatic reaction^.^The first studies on the associative properties of these compounds were devoted to the solid-solid phase transitions and the liquid crystal properties of alkyl derivatives of carbohydrates in which the alkyl chain contained generally a t least eight carbon a t o m~.~-l~ Micellization of compounds of this family has been the subject of a few studies.13-15 More recently the surface properties of monolayers and the forces between bilayers of gangliosides

Two series of water-soluble dendritic catanionic assemblies, acting as multisite analogues of galactosylceramide (Galbeta1cer), have been prepared with the goal of blocking HIV infection prior to the entry of the virus into human cells. Trifunctional and hexafunctional cinnamic acid-terminated dendrimers have been synthesized from phosphorus-containing dendrimers bearing aldehyde end groups. A classical acid-base reaction performed in water between acid-terminated dendrimers and stoichiometric amounts of N-hexadecylamino-1-deoxylactitol provided the expected catanionic assemblies. Antiviral assays on these supramolecular entities confirmed the crucial roles both of multivalency effects and of lipophilicity on the biological activity of Galbeta1cer analogues. Moreover, correlation between in vitro tests and molecular modeling highlights the specific influence of the assembly shape on the anti-HIV efficiency, with the tri- and hexafunctional cored dendrimers, both decorated with 12 sugar moieties, exhibiting IC50 values of 1.1 and 0.12 microM, respectively.