The circular bacteriocins gassericin A and circularin A

Gassericin A, a bacteriocin produced by Lactobacillus gasseri LA39, shows antibacterial activity against a number of Gram-positive food-borne pathogenic bacteria. Circularin A produced by Clostridium beijerinckii ATCC25752 is active against C. tyrobutyricum, a known cheese-spoilage bacterium. Both bacteriocins were purified to homogeneity from culture supernatants by reverse-phase chromatography and the subsequently determined amino acid sequences were used to clone the bacteriocin structural genes. Mature gassericin A and circularin A are class V circular bacteriocins comprised of 58 and 69 amino acid residues, respectively. Both bacteriocins are resistant to several peptidases and proteases, as are other cyclic bacteriocins. Heterologous expression of gassericin A in Escherichia coli was used to produce a non-cyclic mature peptide, which was shown to have a specific activity 173-fold lower than the circular molecule. The minimal region for production and secretion of active circularin A is comprised of five genes, as was deduced by heterologous gene expression in Enterococcus faecalis. Gassericin A and circularin A have limited mutual similarity in their primary sequences. Unlike most bacteriocins, including gassericin A, circularin A has a three-amino-acid-leader sequence.     

Panduratin A inhibits the growth of A549 cells through induction of apoptosis and inhibition of NF-kappaB translocation

In the present study we investigated the effects of panduratin A, isolated from Boesenbergia rotunda, on proliferation and apoptosis in A549 human non-small cell lung cancer cells. Cell proliferation and induction of apoptosis was determined by the real-time cellular analyzer (RTCA), MTT assay and High Content Screening (HCS). The RTCA assay indicated that panduratin A exhibited cytotoxicity, with an IC?? value of 4.4 μg/mL (10.8 μM). Panduratin A arrested cancer cells labeled with bromodeoxyuridine (BrdU) and phospho-Histone H3 in the mitotic phase. The cytotoxic effects of panduratin A were found to be accompanied by a dose-dependent induction of apoptosis, as assessed by DNA condensation, nuclear morphology and intensity, cell permeability, mitochondrial mass/ potential, F-actin and cytochrome c. In addition, treatment with an apoptosis-inducing concentration of panduratin A resulted in significant inhibition of Nuclear Factor-kappa Beta (NF-κB) translocation from cytoplasm to nuclei activated by tumor necrosis factor-alpha (TNF-α), as illustrated by the HCS assay. Our study provides evidence for cell growth inhibition and induction of apoptosis by panduratin A in the A549 cell line, suggesting its therapeutic potential as an NF-κB inhibitor.     

Synthesis of Arcyriarubin A and Arcyriaflavin A via Cross-Coupling of Indolylboronic Acid with Dibromomaleimides

Arcyriarubin A was first isolated by Steglich in 1980; it is also the key intermediate in the synthesis of indolocarbazole compounds. A new synthetic approach to the natural products arcyriaflavin A and arcyriarubin A is described. The key step is a Suzuki cross-coupling reaction using indolylboronic acid as the starting material. The preparation of arcyriaflavin A was accomplished in eight steps from indole for a total yield of 21%.     

Influence of selectivity on the supramolecular polymerization of AB-type polymers capable of Both A x A and A x B interactions

The supramolecular polymerization of two AB-type monomers capable of hydrogen-bond-mediated A x B heterocoupling and A x A homocoupling is discussed. The AB-type supramolecular polymerization is based on the strong interaction between self-dimerizing 2-ureido-pyrimidinone (UPy) and 2,7-diamido-1,8-naphthyridine (NaPy). In an effort to reduce the "self-stoppered" effect that is inherently present in these supramolecular polymerizations we used a novel ureido-pyrimidinone substituted with a dibutylamino group at the pyrimidinone ring. As a result of the substitution, the dimerization constant of the novel UPy unit is lowered compared to the previous UPy unit while the heterodimerization strength is retained. Unexpectedly, the increased selectivity toward heteroassociation not only influences the concentration-dependent degree of polymerization due to reduction of the "self-stoppered" effect but also has a pronounced effect on the ring-chain equilibrium by increasing the tendency to cyclize. In order to quantitatively explain our results, a model was developed that accurately predicts the degree of polymerization by taking into account homo- and heterodimerization as well as cyclization. Finally, molecular weight distributions for noncyclizing AB supramolecular polymerizations with and without a reversible A x A interaction are calculated. It is found that the molecular weight distribution becomes narrower when A x A interactions are present.     

A Strategy for Specific Fluorescence Imaging of Monoamine Oxidase A in Living Cells

Monoamine oxidase (MAO) has two isoforms, MAO‐A and MAO‐B, which show different functions, and thus selective fluorescence imaging is important for biological studies. Currently, however, specific detection of MAO‐A remains a great challenge. Herein, we report a new strategy for specific imaging of MAO‐A through the design of fluorogenic probes combining the characteristic structure of an inhibitor of the target enzyme along with propylamine as a recognition moiety. The high specificity of our representative probe is demonstrated by imaging MAO‐A in different live cells such as SH‐SY5Y (high levels of MAO‐A) and HepG2 (high levels of MAO‐B), and further validated by western blot analyses. The superior specificity of the probe may enable the accurate detection of MAO‐A in complex biosystems. Importantly, the use of the characteristic structure of an inhibitor, as demonstrated in this work, may serve as a general strategy to design specific recognition moieties for fluorogenic probes for enzymes.     

Synthesis of putative uniflorine A

A diastereoselective synthesis of the putative structure of the natural product uniflorine A has been achieved by using the Petasis borono-Mannich reaction and ring-closing metathesis as key steps. The NMR data of the synthetic material did not match that reported for the natural product. The structure of the final synthetic product was unequivocally determined by single-crystal X-ray study of its pentaacetate derivative. Thus it was concluded that the proposed structure of uniflorine A is incorrect.     

Investigation of the surface structure of zeolite A

The surface structure of zeolite A was investigated by FE-SEM, AFM, and HRTEM. First, it was shown by FE-SEM and AFM that the surface of zeolite A terminated with the same structure. Then, by combining the results with those of HRTEM, the terminal structure of zeolite A was identified as incomplete sodalite cages.     

Molecular modeling of A1 and A2A adenosine receptors: comparison of rhodopsin- and beta2-adrenergic-based homology models through the docking studies

Adenosine receptors (ARs) are members of the superfamily of G protein-coupled receptors. The homology models of adenosine A1 and A2A receptors were constructed. The high-resolution X-ray structure of bovine rhodopsin and crystal structure of beta2-adrenergic receptor were used as templates. The binding sites of the A1 and A2A ARs were constructed by using data obtained from mutagenesis experiments as well as docking simulations of the respective AR antagonsists DPCPX and XAC. To compare rhodopsin- and beta2-adrenergic-based models, the binding mode of A1 (KW-3902, LUF-5437) and A2A (KW-6002, ZM-241385) ARs antagonists were also examined. The differences in the binding ability of both models were noted during the study. The beta2-adrenergic-based A2A AR model was much more capable to stabilize the ligand in the binding site cavity than the corresponding rhodopsin-based A2A AR model, however, such differences were not so clear in case of A1 AR models. It was suggested that for the A1 AR it is possible to use the crystal structure of rhodopsin as a template as well as beta2-adrenergic receptor, but for A2A AR, with the now available beta2-adrenergic receptor X-ray structure, docking studies should be avoided on the rhodopsin-based model. However, taking into account that the beta2AR shares about 31% of the residues with the AR in comparison to 21% in case of bRho, we suggest using beta2-adrenergic-based models for the A1 and A2A ARs for further in silico ligand screening also because of their generally better ability to stabilize ligands inside the binding pocket.     

氟烷基取代的双酚A类衍生物的合成

利用相转移催化剂十六烷基三甲基溴化铵(CTMAB)催化的连二亚硫酸钠引发的苯酚衍生物与含氟碘代烷的氟烷基化反应, 合成了含氟烷基取代的酚类化合物. 研究了双酚A与含氟碘代烷的氟烷基化反应, 得到了一类重要的含氟单体, 即含氟烷基取代的双酚A衍生物. 通过改变含氟碘代烷与双酚A的摩尔比, 可以得到单取代、二取代和四取代的含氟烷基双酚A衍生物.     

Il17A Autoantibody Induced by Recombinant Protein Ag85A-Il17A

IL17A is a widely studied cytokine which plays an important role in autoimmune diseases as well as asthma. In this study, murine IL17a gene fragment was inserted into pET28a-Ag85A and it was expressed as a fusion protein named Ag85A-IL17A. Recombinant protein Ag85A-IL17A was expressed as an open reading frame of 1,287 bp, encoding a polypeptide of 429 amino acid residues with a predicted molecular mass of 50 kDa. It was expressed in Escherichia coli. BL21 and purified by metal affinity chromatography using a nickel–nitrilotriacetic acid column. Bioinformatics revealed that Ag85A-IL17A contained B cell epitopes of IL17A. Purified proteins Ag85A-IL17A and Ag85A were injected with adjuvants into mice then antibody responses in sera were measured by enzyme-linked immunosorbent assay and western blot assay. Experiments showed that purified protein Ag85-IL17A could bind to a standard IL17A antibody and could induce IL17A autoantibody in mice.     

Facile Synthesis of Isoamericanol and Isoamericanin A

A number of benzodioxane compounds were synthesized using the palladium-catalyzed etherification of aryl halides by employing triphenylphosphane ligands. This method was used as key step in the synthesis of isoamericanol A and isoamericanin A.     

A total synthesis of mycalisine A

In this paper, we report a total synthesis of a naturally occurring pyrrolo[2,3-d]pyrimidine nucleoside, mycalisine A. Our synthetic strategy uses D-xylose as the startingmaterial and Vorbrüggen glycosylation as the key step. Mycalisine A was synthesized in 11 steps with a 15% overall yield.     

A structural analysis of lead hydroxyvanadinite

Hydroxyvanadinite, Pb(10)(VO(4))(6)(OH)(2), was prepared by the co-precipitation method and analyzed by X-ray absorption spectroscopy (XANES, EXAFS), infrared spectroscopy, Raman scattering and X-ray diffraction (XRD). The results showed that the structure is very similar to that of vanadinite, Pb(10)(VO(4))(6)Cl(2), with space group P6(3)/m (176) and cell parameters a = 10.2242(3) A and c = 7.4537(2) A. A Rietveld refinement of the structure was performed using vanadinite as the starting model and fixing the geometry of the vanadate ion as a rigid body. First-principles Density Functional embedded cluster models are developed to analyze electronic structures, bonding, and densities of states. Interaction of Pb with the OH channel anion is examined in detail, as an important structural feature. A periodic band structure approach was used to obtain a further estimate of relaxed atomic coordinates.     

A trans diacyloxylation of indoles

A trans diacyloxylation of indoles is accomplished by employing PhI(OAc)(2) as the oxidant. A broad range of functional groups are well tolerated. Both the electronic properties of the N-protecting groups of indoles and the acidity of the reaction media play important roles in the selectivity of indole acyloxylation reactions.     

A Vicinal Diol Approach for the Total Synthesis of Molestin E,ent-Sinulacembranolide A and ent-Sinumaximol A

In this work an approach for the synthesis of furanocembranoid natural products containing the C-7,8-diol moiety is disclosed. This culminated in the first total synthesis of the natural product molestin E, together with ent-sinulacembranolide A and ent-sinumaximol A as well as a thorough exploration of their chemistry. Late-stage ring-closure of the C-7,8-diols to the corresponding epoxides was also demonstrated. Key features of this synthetic strategy include a stereoselective Baylis-Hillman reaction, ring-closing metathesis and Shiina macrolactonisation. Chiral-pool materials were deployed to ensure the desired absolute stereochemistry which was confirmed by late-stage single crystal X-ray diffraction.     

Tandem α-aminoxylation-allylation reaction based approach for the synthesis of goniothalesdiol A, leiocarpin A and (+)-goniodiol

A short and efficient syntheses of goniothalesdiol A, leiocarpin A, and (+)-goniodiol are reported by a convergent strategy using tandem aminoxylation-allylation reaction as a key step starting from benzaldehyde.     

A Unique Oscillatory Phenomenon Revealed by A Microweighing Method

An earlier study of the interaction between solid urea and n-octane vapour in the presence of noncomplex-forming hydrocarbons by means of a vacuum microbalance technique revealed the oscillatory nature of urea-octane inclusion compound (complex) formation: process damping, occurrence in the reverse direction and repeated renewal without attainment of the complete saturation of the urea with octane. The phenomenon is interpreted on the basis of the recently discovered oscillatory adsorption, regarded as the surface competition between the spottily adsorbed A and B components, which results alternatively in spontaneous transitions from a state ‘A in B’ to a state ‘B in A’ and vice versa, with simultaneous dramatic change in the spot configurations under A and B, as well as changes in the chemical potentials of adsorbed A and B at the inversion points, certain minimal parts of the surface under A and B being permanently occupied by each of the components. This latter signifies that the non-complex-forming hydrocarbon hinders the complete transition of the urea to its inclusion compound phase. This revised version was published online in August 2006 with corrections to the Cover Date.     

A comparative laser Raman study on TB4A, TB7A and TB10A

The basic structural differences between three thermotropic liquid crystals TB4A, TB7A and TB10A have been interpreted by analysing their Raman spectra. Three spectral regions, 925-1025, 1275-1475 and 1525-1650 cm-1, have been chosen in this context to incorporate their structural dissimilarity. The induced planarity of the backbone, as an effect of increasing chain length, has been studied by observing the changes in the respective Raman spectra of the three compounds. A tentative assignment of all the modes observed in the region 400-1700cm-1 is made in this context. The molecular conformations of the three compounds have been predicted in their solution states, and are compared with the molecular environment that exists in their liquid crystalline states. Structural disorder at the solid-SmG transition is discussed and the changes are incorporated systematically.     

Apoptolidinone A: synthesis of the apoptolidin A aglycone

An efficient stereocontrolled synthesis of apoptolidinone A, the aglycone of apoptolidin A is described. The synthetic strategy relies on a cross coupling between C11/C12 of a northern half (C1-C11) and a southern part (C12-C28) followed by a ring-size selective macrolactonization. Key steps for the introduction of the southern half stereocenters are a stereoselective aldol reaction, a substrate controlled dihydroxylation and a chelation-controlled Grignard/aldehyde addition. The conjugated triene of the northern half was built up successively by E-selective Wittig reactions. L-Malic acid was chosen as the chiral pool source for the C8/C9 stereocenters. The final cleavage of the silyl ethers and the conversion of the C21 methyl ketal into the hemiketal was achieved by HF.pyridine.     

Synthesis of two osteoclast-forming suppressors,demethylincisterol A3 and chaxine A

The synthesis of two potent osteoclast-forming suppressing agents isolated from the Chinese mushroom Agrocybe chaxingu, demethylincisterol A₃ and chaxine A, was accomplished using ergocalciferol as the starting material. Our methodology for the synthesis of demethylincisterol A₃ and chaxine A featured the construction of a butenolide moiety by the intramolecular Horner–Wadsworth–Emmons reaction under Masamune–Roush conditions. This is the first reported synthesis of chaxine A.