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Summary Information transmission in biological signaling networks is commonly considered to be a unidirectional flow of information between protein partners. According to this view, many bacterial response regulator proteins utilize input receiver (REC) domains to "switch" functional outputs, using REC phosphorylation to shift pre-existing equilibria between inactive and active conformations. However, recent data indicate that output domains themselves also shift such equilibria, implying a "mutual inhibition" model. Here we use solution nuclear magnetic resonance to provide a mechanistic basis for such control in a PhyR-type response regulator. Our structure of the isolated, non-phosphorylated REC domain surprisingly reveals a fully active conformation, letting us identify structural and dynamic changes imparted by the output domain to inactivate the full-length protein. Additional data reveal transient structural changes within the full-length protein, facilitating activation. Our data provide a basis for understanding the changes that REC and output domains undergo to set a default "inactive" state.

The kinetics of the nopol synthesis by Prins condensation of β-pinene and paraformaldehyde over Sn-MCM-41 synthesized by impregnation was evaluated using the initial reaction rate method. The reaction rate equation obtained from a kinetic model based on the Langmuir–Hinshelwood formalism with the surface reaction of adsorbed reactants on catalytic sites of the same nature as the limiting step, gave a good prediction of the experimental data. The effect of temperature on the kinetics of nopol synthesis over Sn-MCM-41 obtained by impregnation was studied between 75 and 100 °C. The robustness analysis of the kinetic model showed that the surface reaction constant, k sr ′ , should be about 0.185 mol g−1 h−1 at 90 °C, while the ratio between the adsorption equilibrium constant of β-pinene, KA, and formaldehyde species, KB, is approximately 1.2:1 (KA:KB). The obtained apparent activation energy and pre-exponential factor are 78 kJ/mol and 2.3 × 1010 mol g−1 h−1, respectively, but compensation effect analysis using both experimental and simulated data gave strong evidence of the dependency in temperature of the apparent Arrhenius parameters.

Theiler's virus (TMEV) infection of the central nervous system (CNS) induces an immune-mediated demyelinating disease in susceptible mouse strains and serves as a relevant infection model for human multiple sclerosis (MS). The endocannabinoid system represents a novel therapeutic target for autoimmune and chronic inflammatory diseases due to its anti-inflammatory properties by regulating cytokine network. IL-12p70 and IL-23 are functionally related heterodimeric cytokines that play a crucial role in the pathogenesis of MS. In the present study we showed that the endocannabinoid anandamide (AEA) downregulated the gene expression of IL-12p70 and IL-23 forming subunits mRNAs in the spinal cord of TMEV-infected mice and ameliorated motor disturbances. This was accompanied by significant decreases on the serological levels of IL-12p70/IL-23 and more interestingly, of IL-17A. In contrast, serum levels of IL-10 resulted elevated. In addition, we studied the signalling pathways involved in the regulation of IL-12p70/IL-23 and IL-10 expression in TMEV-infected microglia and addressed the possible interactions of AEA with these pathways. AEA acted through the ERK1/2 and JNK pathways to downregulate IL-12p70 and IL-23 while upregulating IL-10. These effects were partially mediated by CB2 receptor activation. We also described an autocrine circuit of cross-talk between IL-12p70/IL-23 and IL-10, since endogenously produced IL-10 negatively regulates IL-12p70 and IL-23 cytokines in TMEV-infected microglia. This suggests that by altering the cytokine network, AEA could indirectly modify the type of immune responses within the CNS. Accordingly, pharmacological modulation of endocannabinoids might be a useful tool for treating neuroinflammatory diseases. © 2011 Elsevier Inc., This work was supported by grants from the Spanish Ministerio de Educación y Ciencia [SAF 2007/60038]; the Comunidad Autónoma de Madrid (CAM) [S/SAL0261/2006] and Red Española de Esclerosis Multiple (RD07/0060; REEM; RETICS; ISCIII). F Correa is a CAM FPI Fellow.

Tropomyosin (Tm) is a dimeric coiled-coil protein, composed of 284 amino acids (410Å), that forms linear homopolymers through head-to-tail interactions at low ionic strength. The head-to-tail complex involves the overlap of approximately nine N-terminal residues of one molecule with nine C-terminal residues of another Tm molecule. In this study, we investigate the influence of 2,2,2-trifluoroethanol (TFE) and glycerol on the stability of recombinant Tm fragments (ASTm1–142, Tm143–284(5OHW269)) and of the dimeric head-to-tail complex formed by the association of these two fragments. The C-terminal fragment (Tm143–284(5OHW269)) contains a 5-hydroxytryptophan (5OHW) probe at position 269 whose fluorescence is sensitive to the head-to-tail interaction and allows us to accompany titrations of Tm143–284(5OHW269) with ASTm1–142 to calculate the dissociation constant (Kd) and the interaction energy at TFE and glycerol concentrations between 0% and 15%. We observe that TFE, but not glycerol, reduces the stability of the head-to-tail complex. Thermal denaturation experiments also showed that the head-to-tail complex increases the overall conformational stability of the Tm fragments. Urea and thermal denaturation assays demonstrated that both TFE and glycerol increase the stability of the isolated N- and C-terminal fragments; however, only TFE caused a significant reduction in the cooperativity of unfolding these fragments. Our results show that these two cosolvents stabilize the structures of individual Tm fragments in different manners and that these differences may be related to their opposing effects on head-to-tail complex formation.

Inflammation, autoimmune response, demyelination and axonal damage are thought to participate in the pathogenesis of multiple sclerosis (MS). Understanding whether axonal damage causes or originates from demyelination is a crucial issue. Excitotoxic processes may be responsible for white matter and axonal damage. Experimental and clinical studies indicate that cannabinoids could prove efficient in the treatment of MS. Using a chronic model of MS in mice, we show here that clinical signs and axonal damage in the spinal cord were reduced by the AMPA antagonist, NBQX. Amelioration of symptomatology by the synthetic cannabinoid HU210 was also accompanied by a reduction of axonal damage in this model. Moreover, HU210 reduced AMPA-induced excitotoxicity both in vivo and in vitro through the obligatory activation of both CB1 and CB2 cannabinoid receptors. Together, these data underline the implication of excitotoxic processes in demyelinating pathologies such as MS and the potential therapeutic properties of cannabinoids. © 2006 Elsevier Inc. All rights reserved., FD is an I3P postdoctoral fellow (CSIC, Spain). This work was supported by the CICYT (Grant #002004/416, Ministerio de Educación y Ciencia, Spain).

From the ESR spectra of anion radicals of bis(4-biphenylyl)dimethylsilane and 4,4′-bis(4-biphenylyldimethylsilyl)biphenyl, the delocalization of spin density is inferred. The bridging SiMe2-groups separate practically independent π-systems. The rate of electron transfer between biphenyl sub-units is less than ∼ 106 sec−1 at 223 K.

For the compounds C 6 H 5 C 6 H 4 YC 6 H 4 C 6 H 5 and C 6 H 5 C 6 H 4 YC 6 H 4 C 6 H 4 YC 6 H 4 C 6 H 5 where Y is either Si(CH 3 ) 2  or CH 2 , reduction potentials and p -band positions are reported. These data as well as the UV data for several phenyl derivatives are consistent with silicon blocking, to a large extent, conjugation (little or no through conjugation) of biphenyl moieties separated by Si(CH 3 ) 2 groups.