Electrospraying: an in-situ polymerisation route for fabricating high macroporous scaffolds

This paper reports a direct jet-based polymerisation by polycondensation approach to forming a self-supporting scaffold structure. The processing technique is electrospraying, which is also known as electrohydrodynamic atomization. A specially formulated ethanolic siloxane sol derived from alkoxysilanes was synthesised and electrosprayed using a ring-shaped ground electrode configuration. The medium was seen to electrospray in the stable cone-jet mode, which later gave rise to the growing or forming of “fir-tree” like structures. The materials were characterised using microscopy, solid state NMR, FTIR, XRD and DSC. Hence this paper explains the direct controlled polycondensation from the siloxane sol and further presents the basis by which these scaffolds take shape.     

L-functions of second-order cusp forms

We discuss equivalent definitions of holomorphic second-order cusp forms and prove bounds on their Fourier coefficients. We also introduce their associated L-functions, prove functional equations for twisted versions of these L-functions and establish a criterion for a Dirichlet series to originate from a second order form. In the last section we investigate the effect of adding an assumption of periodicity to this criterion. 2000 Mathematics Subject Classification Primary—11F12, 11F66 G. Mason: Research supported in part by NSF Grant DMS 0245225. C. O’Sullivan: Research supported in part by PSC CUNY Research Award No. 65453-00 34.     

Cisplatin-DNA cross-link retro models with a chirality-neutral carrier ligand: evidence for the importance of "second-sphere communication"

We employ retro models, cis-PtA2G2 (A2 = a diamine, G = guanine derivative), to assess the cross-linked head-to-head (HH) form of the cisplatin-DNA d(GpG) adduct widely postulated to be responsible for the anticancer activity. Retro models are designed to have minimal dynamic motion to overcome problems recognized in models derived from cisplatin [A2 = (NH3)2]; the latter models are difficult to understand due to rapid rotation of G bases about the Pt-N7 bond in solution and the dominance of the head-to-tail (HT) form in the solid. Observation of an HH form is unusual for cis-PtA2G2 models. Recently, we found the first HH forms for a cis-PtA2G2 model with A2 lacking NH groups in a study of new Me2ppzPtG2 models. (Me2ppz, N,N'-dimethylpiperazine, has inplane bulk which reduces dynamic motion by clashing with the G O6 as the base rotates into the coordination plane from the ground state position approximately perpendicular to this plane G = 5'-GMP and 3'-GMP.) The finding of an HH form (albeit in a mixture with HT forms) with both G H8 signals unusually downfield encouraged us to study additional Me2ppzPtG2 analogues in order to explain the unusual spectral features and to identify factors that influence the relative stability of HT and HH forms. Molecular modeling techniques suggest HH structures with the H8's close to the deshielding region of the z axis of the magnetically anisotropic Pt atom, explaining the atypical shift pattern. When G = 1-Me-5'-GMP, we obtained NMR evidence that the HH rotamer has a high abundance (34%) and that the three rotamers have nearly equal abundance. These findings and the observation that the relative HT distributions varied little or not at all as a function of pH when G = Guo, 1-MeGuo, or 1-Me-5'-GMP are consistent with two of our earlier proposals concerning phosphate groups in HT forms of cis-PtA2(GMP)2 complexes. We proposed that a G phosphate group can form hydrogen bonds with the cis G N1H ("second-sphere" communication) and (for 5'-phosphate) A2 NH groups. The new results with 1-Me-5'-GMP led us to propose a new role for a 5'-phosphate group; it can also favor the HH form by counteracting the natural preference for the G bases to adopt an HT orientation. Finally, the HH form was also sufficiently abundant to allow observation of a distinct 195Pt NMR signal (downfield of the resonance observed for the HT forms) for several complexes. This is the first report of an HH 195Pt NMR signal for cis-PtA2G2 complexes.     

Nature et stabilité des complexes métalliques de cryptands dinucléants en solution II. Polythiamacrotricycles et monocycles apparentés

Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution II. Polythiamacrotricycles and Related Monocyclic Subunits The stability constants of the Cu²⁺ and Ag⁺ complexes of the cylindrical macrotricycle 1a (1,7,13,19-tetraaza 4,16-dioxa 10,22,27,32-tetrathiatricyclo[17.5.5.5]tetratriacontane) have been determined by pH-metry, as well as those of the Cu²⁺, Co²⁺, Zn²⁺, Cd²⁺, Pb²⁺, and Ag⁺ complexes of the monocyclic subunit 2a (1,7-dimethyl-1,7-diaza 4,10-dithiacyclododecane), in aqueous solutions (NaClO₄) at 25°. In the Cu(II) systems, equilibria were reached slowly, and the results established by pH-metry were confirmed by UV/VIS spectrophotometric studies. The tricycle 1a forms dinuclear cryptates with copper and silver, with overall stability constants log β₂₁₀ (Cu₂- 1a )⁴⁺ = 18.5, log β_21-2 (Cu₂- 1a (OH)₂)²⁺ = 4.8, log β₂₁₀(Ag₂- 1a )²⁺ = 23.0. Ag⁺ also forms a mononuclear (Ag- 1a )⁺ complex, with log β₁₁₀ = 13.1, but no mononuclear species were detected in the Cu- 1a system. The absorption spectra of the bis-Cu(II) complexes of 1a and 2a in aqueous medium, MeOH and propylene carbonate (PC) are given, as well as those, in MeOH and PC, of the bis-copper complexes of the related monocycles 3 and 4 (1,7-diaza-4,10,13-trithiacyclopentadecane and 1.10-diaza 4,7,13,16-tetrathiacyclooctadecane, respectively), and tricycle 5 with two benzyl groups in the lateral chains. The complexing properties of the polyoxa- and polythia macrotricycles (Parts I and II of this series) are compared to those of other bis-chelating ligands, the bicyclic bis-tren and the monocyclic bis-dien.     

Defect formation on surfaces bombarded by energetic multiply charged proteins: Implications for the conformation of gas-phase electrosprayed ions

Indirect information on the conformation of highly charged molecular ions may be obtained by monitoring their collisional cross sections and the course of simple gas-phase reactions such as hydrogen-deuterium exchange. In this work, another indirect but more visually oriented approach is explored: electrosprayed protein ions are accelerated toward a highly oriented pyrolytic graphite surface and the resulting single-ion defects are imaged by scanning force and tunneling microscopy. All protein impacts generated shallow hillocks: the shapes depended on the identity and charge state of the incident protein. Lysozyme and myoglobin, both compact, globular proteins in the native state, produced compact, almost circular hillocks. However, hillocks generated by myoglobin that had been denatured in the solution phase were elongated, and the elongation was positively correlated with the charge state of the ion. It appears that structural information about gas-phase multiply charged proteins can be derived from imprints generated by energetic protein impacts on surfaces.