Portal Interaction Research Articles

Host-guest complexes of a water soluble cucurbit[6]uril derivative with some dications of 1,ω-alkyldipyridines: 1H NMR and X-ray structures

Interactions between a symmetrical tetramethyl-substituted cucurbit[6]uril (host: TMeQ[6]) and 1,ω-alkylenedipyridine (ω = 2, 4, 6, 8, 10) dicationic guests were investigated using 1H NMR spectroscopy and single crystal X-ray crystallography. In these inclusion complexes, combined cavity and portal binding in TMeQ[6] were observed, and the length of the bridged alkylene was found to play an important role not only in balancing the overall hydrophilic/hydrophobic interaction between the host and the guest, but also in defining the structure of the resulting inclusion complexes. For the guest 1,2-ethylenedipyridine (Edpy), TMeQ[6] includes a positively charged pyridine ring of Edpy to form an unsymmetrical inclusion complex; for the guest 1,4-butylenedipyridine (Bdpy), TMeQ[6] includes a positively charged pyridine ring of Bdpy, but the different competitive interactions in and between the related inclusion complexes could lead to a fast exchange between the hosts and guests. For the guests with longer bridge chains, such as 1,6-hexamethylenedipyridine (Hdpy) or 1,8-octylenedipyridine (Odpy), a stable pseudorotaxane inclusion complex is formed by combining the hydrophobic cavity and the outer portal dipole-ion interactions. However, for 1,10-decatylenedipyridine (Ddpy), the two TMeQ[6] host molecules include the two end pyridine rings of Ddpy and form a dumbbell inclusion complex.

Hidden vector dark matter

We show that dark matter could be made of massive gauge bosons whose stability doesn't require to impose by hand any discrete or global symmetry. Stability of gauge bosons can be guaranteed by the custodial symmetry associated to the gauge symmetry and particle content of the model. The particle content we consider to this end is based on a hidden sector made of a vector multiplet associated to a non-abelian gauge group and of a scalar multiplet charged under this gauge group. The hidden sector interacts with the Standard Model particles through the Higgs portal quartic scalar interaction in such a way that the gauge bosons behave as thermal WIMPS. This can lead easily to the observed dark matter relic density in agreement with the other various constraints, and can be tested experimentally in a large fraction of the parameter space. In this model the dark matter direct detection rate and the annihilation cross section can decouple if the Higgs portal interaction is weak.

Exclusion complexes of the HCl salts of benzidine and bis(4-aminophenyl) methane with two methyl-substituted cucurbiturils

The interaction between two partially methyl-substituted cucurbiturils, a sym-tetramethyl-substituted cucurbit[6]uril (TMeQ[6]) and a meta-hexamethyl-substituted cucurbituril (m-HMeQ[6]), with the hydrochloride salt of benzidine (g1·HCl) and the analogue bis(4-aminophenyl) methane (g2·HCl) was investigated by single crystal X-ray diffraction determination, 1H NMR spectroscopy, electronic absorption spectroscopy and fluorescence spectroscopy. Single crystal X-ray diffraction determination showed the two guest compounds were excluded at the portals of the partial methyl-substituted cucurbiturils in the solid state. The 1H NMR spectroscopic analysis in aqueous solution supported the crystallographic results in which an excluding or portal interaction occurs between the host and guest. Aqueous absorption spectrophotometric and fluorescence spectroscopic analysis defined the stability of the host–guest exclusion complex at pH 5.6 with a host : guest ratio of 1 : 1, which forms quantitatively as ∼105 L mol−1 for the TMeQ[6]–g1 system. The host : guest ratio of 2 : 1 forms quantitatively as ∼1010 L2 mol−2 for the m-HMeQ[6]–g2 system. The experimental results are in good agreement with HF and B3LYP computational approaches with a moderate-sized basis set.

Z2-singlino dark matter in a portal-like extension of the minimal supersymmetric standardmodel

We propose a Z2-stabilized singlino () as a dark matter candidate in extended andR-parity violating versions of the supersymmetric standard model. interacts with visible matter via a heavy messenger fieldS, which results in a supersymmetric version of the Higgs portal interaction. The relicabundance of can account for cold dark matter if the messenger mass satisfies GeV. Our model can be implemented in many realistic supersymmetric models such as thenext-to-minimal supersymmetric (SUSY) standard model and nearly minimal SUSYstandard model.

Cucurbit[ n]urils-induced room temperature phosphorescence of quinoline derivatives

The cucurbit[7,8]urils (Q[7] and Q[8])-induced room temperature phosphorescence (RTP) of quinoline and its derivatives were firstly found in the cucurbit[ n]urils chemistry. The luminophores (quinolines) and their RTP are affected by the concentration of different Q[ n]s, heavy metal ions and amounts, and pH. The RTP lifetime of the luminophore has been investigated. In presence of Na 2SO 3, the cation Tl + led to stronger Q[ n]-induced RTP, while the RTP lifetimes of luminophore/Q[7 or 8]/KI were generally longer than that of luminophore/Q[7 or 8]/TlNO 3, the RTP lifetimes of these systems were between 0.18 and 47.4 ms. Contrary to the stable 1:2 Q[8]:guest ternary inclusion complexes at lower pHs, as suggested by 1H NMR, electronic absorption and fluorescence spectroscopy, low Q[8]-induced room temperature phosphorescence was observed. However, at higher pHs, high intensity of cucurbit[ n]urils-induced room temperature phosphorescence of these quinoline derivatives were observed, and a 1:1 Q[8]:guest inclusion complex was formed. Investigations of dependence of RTP intensity on concentration of Q[ n] revealed that the highest intensity of the Q[ n]-induced RTP was observed at a low mole ratio of host:guest, which is closed to 1:1. It was presumably resulted from the strong interaction of Q[ n] and these guests due to the combined hydrophobic cavity interaction and the hydrophilic portal interaction of the cucurbit[ n]urils with the nitrogen heterocycles guest.

NMR study on self-assembled cage complex of hexamethylenetetramine and cucurbit[n]urils

Self-assembled complexes between cage compounds cucurbit[n = 5–8]urils and hexamethylenetetramine were studied by using NMR techniques. Experimental results reveal that hexamethylenetetramine can lid cucurbit [5] uril to forming self-assembled capsules in which nothing is encapsulated yet; the cavity of the cucurbit[7]uril can accommodate a hexamethylenetetramine molecule to form a selfassembled host-guest inclusion. Moreover, both the cavity interaction of the cucurbit[7]uril with hexamethylenetetramine·HCl and the portal interaction of the dipole carbonyl of the cucurbit[7]uril with hexamethylenetetramine·HCl lead to form self-assembled capsules in which the hexamethylenetetramine·HCl are encapsulated in the hexamethylenetetramine·HCl “lidded” cucurbit[7]uril. Although the structures of the portal and cavity to cucurbit[5]uril are similar, there is no obvious interaction between decamethylcucurbit[5]uril and hexamethylenetetramine, and also between cucurbit [6]uril or cucurbit[8]uril and hexamethylenetetramine.

Analysis of capsid portal protein and terminase functional domains: interaction sites required for DNA packaging in bacteriophage T4

Bacteriophage DNA packaging results from an ATP-driven translocation of concatemeric DNA into the prohead by the phage terminase complexed with the portal vertex dodecamer of the prohead. Functional domains of the bacteriophage T4 terminase and portal gene 20 product (gp20) were determined by mutant analysis and sequence localization within the structural genes. Interaction regions of the portal vertex and large terminase subunit (gp17) were determined by genetic (terminase-portal intergenic suppressor mutations), biochemical (column retention of gp17 and inhibition of in vitro DNA packaging by gp20 peptides), and immunological (co-immunoprecipitation of polymerized gp20 peptide and gp17) studies. The specificity of the interaction was tested by means of a phage T4 HOC ( h ighly antigenic o uter c apsid protein) display system in which wild-type, cs20, and scrambled portal peptide sequences were displayed on the HOC protein of phage T4. Binding affinities of these recombinant phages as determined by the retention of these phages by a His-tag immobilized gp17 column, and by co-immunoprecipitation with purified terminase supported the specific nature of the portal protein and terminase interaction sites. In further support of specificity, a gp20 peptide corresponding to a portion of the identified site inhibited packaging whereas the scrambled sequence peptide did not block DNA packaging in vitro. The portal interaction site is localized to 28 residues in the central portion of the linear sequence of gp20 (524 residues). As judged by two pairs of intergenic portal-terminase suppressor mutations, two separate regions of the terminase large subunit gp17 (central and COOH-terminal) interact through hydrophobic contacts at the portal site. Although the terminase apparently interacts with this gp20 portal peptide, polyclonal antibody against the portal peptide appears unable to access it in the native structure, suggesting intimate association of gp20 and gp17 possibly internalizes terminase regions within the portal in the packasome complex. Both similarities and differences are seen in comparison to analogous sites which have been identified in phages T3 and λ.

Dynamics of arterial and portal venous flow interactions in perfused rat liver: an intravital microscopic study.

Intravital epifluorescent microscopy was used to quantitate microvascular parameters in the single-pass, dually perfused rat liver preparation. Livers perfused via the hepatic artery (HA) and portal vein (PV) at physiological pressures and perfusion rates responded to vasoactive agents and exhibited the HA buffer response. The distribution of arterial blood was found to be highly heterogeneous, whereas PV flow was distributed uniformly. The intrasinusoidal velocity of fluorescein isothiocyanate (FITC)-labeled red blood cells (RBCs) arriving from the HA was higher than that for RBCs arriving from the PV, indicating a shorter transit time for the arterially delivered FITC-RBCs. Experiments on livers perfused simultaneously via the HA and retrogradely via the hepatic vein revealed the presence of arteriovenous shunts, with some of the arterially delivered FITC-RBCs reaching the terminal hepatic venules via direct channels without traversing the sinusoidal bed. In livers perfused portally only, changes in PV flow rate (from 8 to 20 ml/min) produced small changes in perfusion pressure but large changes in vascular diameters, while portal pressure and transit time of portal blood remained relatively constant. In experiments designed to identify the location of hepatic vascular resistance, it was observed that hepatic venular diameters measured in the preparation under identical pressure and flow conditions were greater during retrograde than during prograde perfusion, suggesting that the site of hepatic vascular resistance is presinusoidal or sinusoidal.

Hemodynamic changes in blood flow through the denervated liver in pigs.

We investigated the effects of liver denervation on hemodynamic circulation in seven anesthetized pigs. Simultaneous measurements of the hepatic artery and portal vein were performed with an ultrasound Doppler flow meter before and after liver denervation. Neither resting systemic nor hepatic hemodynamics changed following liver denervation. However, temporary occlusion of the portal vein resulted in a significant increase in hepatic artery flow in the innervated liver (from 123 +/- 15 ml/min to 177 +/- 17 ml/min, p < .01), whereas, in the denervated liver, a significant decrease was observed (from 128 +/- 11 ml/min to 106 +/- 19 ml/min, p < .05). Thus, the reciprocity between the hepatic artery and portal vein in the hepatic artery flow during portal vein occlusion might intensify symptoms of portal vein thrombosis in liver transplantation. In the denervated liver, a significant decrease also occurred in systolic blood pressure and central venous pressure from 1 to 3 min after portal vein occlusion. Since the liver plays a crucial role in the maintenance of cardiovascular homeostasis during blood loss, it is likely that denervation at the porta hepatis induced a lack of vasoconstriction in the portal territory. Liver denervation might further exacerbate this response to hypotension. The current study confirms that the hepatic nerves play an important role in hepatic arterial and portal venous interactions aimed at maintaining a constant blood flow through the liver. We also suggest that the hepatic nerves are important for cardiovascular homeostasis.

Portal Vein and Hepatic Artery Interactions: Studies in the Isolated, Perfused Liver

Portal Vein and Hepatic Artery Interactions: Studies in the Isolated, Perfused Liver