Isometric Group Actions on Banach Spaces and Representations Vanishing at Infinity

Our main result is that the simple Lie group G = Sp(n, 1) acts metrically properly isometrically on L ^p (G) if p > 4n + 2. To prove this, we introduce Property , with V being a Banach space: a locally compact group G has Property if every affine isometric action of G on V, such that the linear part is a C ₀-representation of G, either has a fixed point or is metrically proper. We prove that solvable groups, connected Lie groups, and linear algebraic groups over a local field of characteristic zero, have Property . As a consequence, for unitary representations, we characterize those groups in the latter classes for which the first cohomology with respect to the left regular representation on L ²(G) is nonzero; and we characterize uniform lattices in those groups for which the first L2-Betti number is nonzero.      

Excited-state intramolecular proton transfer distinguishes microenvironments in single- and double-stranded DNA

Herein, the efficient interaction of an environment-sensitive fluorophore that undergoes excited-state intramolecular proton transfer (ESIPT) with DNA has been realized by conjugation of a 3-hydroxychromone (3HC) with polycationic spermine. On binding to a double-stranded DNA (dsDNA), the ratio of the two emission bands of the 3HC conjugates changes up to 16-fold, so that emission of the ESIPT product increases dramatically. This suggests an efficient screening of the 3HC fluorophore from the water molecules in the DNA complex, which is probably realized by its intercalation into dsDNA. In sharp contrast, the 3HC conjugates show only moderate changes in the dual emission on binding to a single-stranded DNA (ssDNA), indicating a much higher fluorophore exposure to water at the binding site. Thus, the 3-hydroxychromone fluorophore being conjugated to spermine discriminates the binding of this polycation to dsDNA from that to ssDNA. Consequently, ESIPT-based dyes are promising for monitoring the interaction of polycationic molecules with DNA and probing the microenvironment of their DNA binding sites.     

Cu-Bound Formates are Main Reaction Intermediates during CO2 Hydrogenation to Methanol over Cu/ZrO2

Cu/ZrO₂ is a promising catalyst for the hydrogenation of CO₂ to methanol. Reaction pathways involving formates or hydroxycarbonyls have been proposed. We show here that three different types of formates can be observed under reaction conditions at 220 °C and 3 bar, one being located on metallic Cu and two others being bound to ZrO₂. The surface concentrations of formates were determined through calibration curves and their reactivity measured during chemical transient experiments. The Cu-bound formate represented only about 7 % of surface formates, but exhibited a higher reactivity and was found to be the only formate that could account for all the production of methanol. Copper is thus not there only to activate H₂, but also bears other crucial intermediates. This work reemphasizes that fully quantitative IR analyses and transient methods are required to unravel the role of surface species.     

AFM for nanoscale microbe analysis

The nanoscale surface analysis of microbial cells represents a significant challenge of current microbiology and is critical for developing new biotechnological and biomedical applications. Using atomic force microscopy (AFM) topographic imaging, researchers can visualize the ultrastructure of live cells under physiological conditions and their subtle modifications upon cell growth or treatment with drugs. Chemical force microscopy, in which AFM tips are modified with specific functional groups, allows investigators to measure molecular forces and chemical properties of cell surfaces on a scale of only 25 functional groups. Molecular recognition imaging using AFM offers a means to localize specific receptors on cells, such as cell adhesion proteins or antibiotic binding sites. With this Highlight on AFM, it is hoped that more and more microbiologists and biophysicists will take advantage of this powerful, multifunctional nanotechnique.     

Imidazole-substituted oxoverdazyl radical as a mediator of intramolecular and intermolecular exchange interaction

The 3-(2'-imidazolyl)-1,5-dimethyl-6-oxoverdazyl radical (imvd(*)) and the corresponding tetrazane H3imvd were prepared and structurally characterized, the former as two different hydrates. Reaction of imvd(*) with [M(hfac)2] led to the formation of monometallic complexes [M(hfac)2(imvd(*))] (M = Ni and Mn). They were characterized by single-crystal X-ray diffraction. In the solid state, all four radical-containing compounds exhibit imidazole-oxoverdazyl pi stacking. Following the structural analysis, imvd(*) behaves as an antiferromagnetic (AF) coupled chain with J = -100 cm(-1) (H = -J summation operator SiS(i+1)). The magnetic behavior of [M(hfac)2(imvd(*))] complexes is interpreted with a four-coupled spin model with a metal ion radical intramolecular interaction (JMn = -62.5 cm(-1) and JNi = 193 cm(-1); H = -JSMSimvd) and an AF intermolecular interaction (JMn' = -12.6 cm(-1) and JNi' = -4.3 cm(-1)) related to imidazole-oxoverdazyl pi stacking.     

Theoretical study of the three-phase contact line and its tension in adsorbed colloid-polymer mixtures

We perform a theoretical study of the three-phase contact line and the line tension in an adsorbed colloid-polymer mixture near a first-order wetting transition, employing an interface displacement model. We use a simple free-energy functional to describe a colloid-polymer mixture near a hard wall. The bulk phase behavior and the substrate-adsorbate interaction are modeled by the free-volume theory for ideal polymers. The large size of the colloidal particles and the suppression of the van der Waals interaction by optical matching of colloid and solvent justify the planar hard wall model for the substrate. Following the Fisher-Jin scheme, we derive from the free-energy functional an interface potential V(l) for these mixtures. For a particle diameter of 10-100 nm, the calculations indicate a line tension tau approximately 10(-12)-10(-13) N at room temperature. In view of the ultralow interfacial tension in colloid-polymer mixtures, gamma approximately 10(-7) Nm, this leads to a rather large characteristic length scale taugamma in the micrometer range for the three-phase contact zone width. In contrast with molecular fluids, this zone could be studied directly with optical techniques such as confocal scanning laser microscopy.     

Three New Derivatives and Others Constituents from the Roots and Twigs of Trilepisium madagascariense DC

Three new compounds, trilepisflavene ( 1 ), trilepisdepsidone ( 2 ), and daturadiol stearate ( 3 ), together with nine known compounds, 2‐hydroxy‐4‐[(4‐hydroxy‐2‐methoxy‐6‐methylbenzoyl)oxy]‐6‐methylbenzoic acid ( 4 ), lichexanthone ( 5 ), naringenin ( 6 ), 3′,4′,5,7‐tetrahydroxyflavanone ( 7 ), 2‐hydroxybenzoic acid ( 8 ), methyl 2,4‐dihydroxy‐6‐methylbenzoate ( 9 ), β‐amyrin ( 10 ), eurothridiol palmitate ( 11 ), and β‐sitosterol ( 12 ), were isolated from the AcOEt extract of the twigs and the roots of Trilepisium madagascariense. Acetylation of eurothridiol palmitate was carried out and a new acetylated derivative ( 13 ) was obtained. The structures of the isolated and acetylated compounds were elucidated on the basis of spectroscopic analysis. Antimicrobial activity of all these compounds was evaluated using Mueller–Hinton broth (MHB) and Mueller–Hinton agar (MHA) method. Trilepisdepsidone , 2‐hydroxy‐4‐[(4‐hydroxy‐2‐methoxy‐6‐methylbenzoyl)oxy]‐6‐methylbenzoic acid, 3′,4′,5,7‐tetrahydroxyflavanone, and naringenin exhibited moderate to weak antimicrobial activity.     

Route Scouting towards a Methyl Jasmonate Precursor

For the synthesis of methyl jasmonate ( 1 ), via the strategic intermediates 3, 4 , and 6a , we constructed a synthetic network via the diverse intermediates 7 – 10, 13, 14, 17 , and 18 . This allowed us to compare the efficiency of more than 20 novel routes. The most productive pathway with a total yield of 38% is represented by the sequence→ 5a → 5m → 13b → 13a → 6a → 4 and proceeds via sequential bromination, basic elimination, decarbomethoxylation, isomerization, and finally Lindlar hydrogenation. The shortest selective way, 2a →[(E,E)‐ 12b ]→ 3 → 4 , is a two‐pot sequence using a modification of Naef's method, based on an aldol condensation between inexpensive cyclopentanone ( 2a ) and crotonaldehyde, with in situ Corey? Chaykovsky cyclopropanation under phase transfer conditions. The key intermediate 3 was then simply pyrolyzed to afford 4 in 27% total yield. The alternative isomerization method via the six‐step deviation→ 5a → 5c → 8c → 13a → 6a → 4 was longer, although more efficient, with a total yield of 32%. Alternatively, a yield of 34% was obtained via the five‐step sequence→ 5a → 5c → 2h → 2i → 4 . Another favored six‐step pathway,→ 5a → 5c → 2h → 17a → 14a → 4 afforded the target compound in 35% total yield.     

Estimating local bonding/antibonding character of canonical molecular orbitals from their energy derivatives. The case of coordinating lone pair orbitals

According to Koopmans theorem, the derivative of the energy of a canonical molecular orbital (MO) with respect to nuclear coordinates quantifies its bonding/antibonding character. This quantity allows predictions of bond length variation on ionisation in a panel of 19 diatomic species. In polyatomic molecules, the derivative of a MO energy with respect to a given bond length reveals the nature and the degree of the bonding/antibonding contribution of this MO with respect to this bond. Accordingly, the HOMO “lone pairs” of CO and CN^? and the HOMO‐2 of CH₃CN are found to be antibonding with respect to the C? X bond (X = N, O), whereas the HOMO of N₂ is found to be bonding. With the same approach, the variation of the bonding character in the MOs of CO and CH₃CN on interaction with an electron acceptor (modeled through the approach of a proton) or by applying an electric field was studied. © 2016 Wiley Periodicals, Inc.