From the SmA to the hexatic, including the SmC*, SmC*(A) and SmC*(re) phases: a 2H NMR relaxation study.

The molecular dynamics of a ferroelectric liquid crystal, denoted ZLL 7/*, is investigated by means of (2)H NMR relaxation. The spin-lattice (T(1Q) and T(1Z)) and spin-spin (T(2)) relaxation times of two isotopomers of ZLL 7/*, labeled on the phenyl and biphenyl fragments, are measured and their behavior upon passing from the SmA to the hexatic phase, through the ferroelectric SmC*, antiferroelectric SmC*(A), and re-entrant ferroelectric SmC*(re) phases, is discussed. A comparison between the measured T(2) and T(2)*, directly related to the experimental linewidth, provides information on the heterogeneity of the system, thus allowing confirmation of previous hypotheses concerning the structural and ordering properties of the SmC*(A) and SmC*(re) phases. The possibility to look at different sites of the core of the ZLL 7/* smectogen reveals a peculiar sensitivity of the phenyl moiety with respect to the biphenyl fragment, which may be justified by its vicinity to the chiral centers. Interestingly, the trend of the longitudinal relaxation times is characterized by a minimum that corresponds to the SmC*(A) and SmC*(re) phases, which is reproducible for the two isotopomers and at several Larmor frequencies. A quantitative analysis of T(1Q) and T(1Z) is performed in the SmA and SmC* phases, for which the narrowing regime approximation is valid. A multifrequency approach is applied to self-consistently determine the diffusion coefficients for the overall molecular motions, namely spinning and tumbling, and the internal rotations around the para axes of the phenyl and biphenyl fragments. The effect of the magnetic field in unwinding the helical structure of the SmC* phase (for H>9 T) allows observation of a sensitive change in the rotational diffusion coefficients in the frustrated unwound SmC* phase with respect to the SmC* phase.

Evaluation of in-vitro anti-inflammatory activity of some 2-alkyl-4,6-dimethoxy-1,3,5-triazines.

The ability of some 2-alkyl(aryl)-4,6-dimethoxy-1,3,5-triazine derivatives to interfere with production of reactive oxygen species (ROS) by human phagocytes was evaluated in an in-vitro cell model. Superoxide anion (O(2)(-*)) production by human polymorphonuclear cells (PMNs), challenged by the chemotactic agent N-formylmethionyl-leucyl-phenylalanine (FMLP), was inhibited in a dose-dependent manner by all the compounds tested, compounds 3, 4 and 5 being statistically the most active. Adhesion of PMNs to vascular endothelial cells (ECs) is a critical step in recruitment and infiltration of leucocytes into tissues during inflammation, and the effects of 1,3,5-triazine derivatives on PMN adhesion to ECs from the human umbilical vein (HUVEC) were also investigated. Triazines were incubated with PMNs and HUVEC; adhesion was quantitated by computerized micro-imaging fluorescence analysis. The 1,3,5-triazines tested inhibited the adhesion evoked by pro-inflammatory stimuli, such as platelet activating factor (PAF), FMLP, phorbol myristate acetate (PMA), tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta(IL-1beta) in a dose-response manner over the concentration range 10(-9) to 10(-4)M, compounds 5 and 6 being the most active. Both of these compounds inhibited PMN adhesion to HUVEC, even when endothelial or PMN stimuli were used. Indeed, when both cell populations were activated contemporarily, the anti-adhesive effect was enhanced. The study suggests that 2-aryl-4,6-dimethoxy-1,3,5-triazines deserve further evaluation as anti-inflammatory agents.

In vitro cytotoxic activities of 2-alkyl-4,6-diheteroalkyl-1,3,5-triazines: new molecules in anticancer research.

The cytotoxic activities of new 2-alkyl-4,6-dihetero(N,O)alkyl-1,3,5-triazines toward selected tumor cell lines have been evaluated, and for the first time, the potential of 2-alkyl-4,6-dialkoxy-1,3,5-triazines has been shown.