Mono- vs. bi-metallic assembly on a bulky bis(imino)terpyridine framework: a combined experimental and theoretical study

The bis(imino)terpyridine ligands, 6,6″-{(2,6-i-Pr[subscript 2]C[subscript 6]H[subscript 3])N=CR}[subscript 2]-2,2′:6′,2″-C[subscript 15]H[subscript 9]N[subscript 3] (R = H L1, Me L2), have been prepared in high yield from the condensation reaction of the corresponding carbonyl compound with two equivalents of 2,6-diisopropylaniline. The molecular structure of L2 reveals a transoid relationship between the imino and pyridyl nitrogen groups throughout the ligand framework. Treatment of aldimine-containing L1 with one equivalent or an excess of MX[subscript 2] in n-BuOH at 110 °C gives the mononuclear five-coordinate complexes, [(L1)MX[subscript 2]] (M = Fe, X = Cl 1a; M = Ni, X = Br 1b; M = Zn, X = Cl 1c), in which the metal centre occupies the terpyridine cavity and the imino groups pendant. Conversely, reaction of ketimine-containing L2 with excess MX[subscript 2] in n-BuOH at 110 °C affords the binuclear complexes, [(L2)M[subscript 2]X[subscript 4]] (M = Fe, X = Cl 3a; M = Ni, X = Br 3b; M = Zn, X = Cl 3c), in which one metal centre occupies a bidentate pyridylimine cavity while the other a tridentate bipyridylimine cavity. [superscript 1]H NMR studies on diamagnetic 3c suggests a fluxional process is operational at ambient temperature in which the central pyridine ring undergoes an exchange between metal coordination. Under less forcing conditions (room temperature in dichloromethane), the monometallic counterpart of 1b [(L2)NiBr[subscript 2]] (2b) has been isolated which can be converted to 3b by addition of one equivalent of (DME)NiBr[subscript 2] (DME = 1,2-dimethoxyethane) in n-BuOH at 110 °C. Quantum mechanical calculations (DFT) have been performed on [(L1)ZnCl[subscript 2]] and [(L2)ZnCl[subscript 2]] for different monometallic conformations and show that 1a is the energetically preferred structure for L1 while there is evidence for dynamic behaviour in L2-containing species leading to bimetallic formation. Single-crystal X-ray diffraction studies have been performed on 1a, 1b, 1c, 2b, 3a, 3b(H[subscript 2]O) and 3c

Comparison of Systemic and Mucosal Immunization with Helper-Dependent Adenoviruses for Vaccination against Mucosal Challenge with SHIV

<div><p>Most HIV-1 infections are thought to occur at mucosal surfaces during sexual contact. It has been hypothesized that vaccines delivered at mucosal surfaces may mediate better protection against HIV-1 than vaccines that are delivered systemically. To test this, rhesus macaques were vaccinated by intramuscular (i.m.) or intravaginal (ivag.) routes with helper-dependent adenoviral (HD-Ad) vectors expressing HIV-1 envelope. Macaques were first immunized intranasally with species C Ad serotype 5 (Ad5) prior to serotype-switching with species C HD-Ad6, Ad1, Ad5, and Ad2 vectors expressing env followed by rectal challenge with CCR5-tropic SHIV-SF162P3. Vaccination by the systemic route generated stronger systemic CD8 T cell responses in PBMC, but weaker mucosal responses. Conversely, mucosal immunization generated stronger CD4 T cell central memory (Tcm) responses in the colon. Intramuscular immunization generated higher levels of env-binding antibodies, but neither produced neutralizing or cytotoxic antibodies. After mucosal SHIV challenge, both groups controlled SHIV better than control animals. However, more animals in the ivag. group had lower viral set points than in in the i.m. group. These data suggest mucosal vaccination may have improve protection against sexually-transmitted HIV. These data also demonstrate that helper-dependent Ad vaccines can mediate robust vaccine responses in the face of prior immunity to Ad5 and during four rounds of adenovirus vaccination.</p></div

IFN-γ Secreting Cells from PBMCs.

<p>PBMCs in ELISPOT plates were stimulated with 3 pools of 50 to 70 peptides spanning the gp140 region of SF162 envelope for 36 h and IFN-γ secreting spots were detected and counted. Responses in terms of IFN-γ spot forming units (SFU) for 10⁵ total input cells were determined for individual monkeys after subtracting background values of cells cultured in the medium. <b>A</b>) IFN-γ secreting cells from individual animals. <b>B</b>) Mean IFN-γ secreting cells from each group.</p

Systemic Cytokines, Peripheral and Mucosal T Cell Responses.

<p><b>A</b>) Cytokine Responses. Heparinized plasma was collected and analyzed for cytokine levels using a human cytometric bead assay (CBA) with standard curves for each cytokine. Statistical comparisons in A are by one way ANOVA. <b>B</b>) T cell responses from PBMCs and colon biopsies. PBMCs and colon biopsies were collected at week 26 before challenge and CD4 and CD8 Tem and Tcm were analyzed for IL-2 and/or IFN-γ production by flow cytometry (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067574#pone-0067574-t001" target="_blank">Table 1</a>). Statistical comparisons in B are T test comparisons of the "stack" of total cytokine-expressing cells for a given cell type (i.e. CD8 or CD4, Tcm or Tem).</p

Antibodies Against HIV-1 Env and Species C Adenoviruses.

<p><b>A</b>) Anti-env antibodies. Plasma was collected from each group and these were analyzed for env-binding antibodies by ELISA against JRFL env (matching the vaccine). <b>B</b>) Anti-adenovirus neutralizing antibodies. Plasma from week 26 was serially diluted and tested for its ability to neutralize HD-Ad vectors expressing luciferase <i>in vitro.</i></p

Schedule of Vaccination and SHIV Challenge.

<p>Schedule of Vaccination and SHIV Challenge.</p