Electrospray mass spectrometric studies of a potential antitumor drug and its analogous platinum(II) and platinum(IV) complexes with the ethylenediamine-N,N′-di-3-propanoato ligand and its dibutyl ester

Abstract  The electrospray mass spectrometric (ESI–MS) behavior of the complexes trans-dichloro(ethylenediamine-N,N′-di-3-propionato)platinum(IV), trans-dibromo(ethylenediamine-N,N′-di-3-propionato)platinum(IV), dichloro(ethylenediamine-N,N′-di-3-propionic acid)platinum(II), tetrachloro(O,O′-di-n-butyl-ethylenediamine-N,N′-di-3-propanoate)platinum(IV), chlorotribromo(O,O′-di-n-butyl-ethylenediamine-N,N′-di-3-propanoate)platinum(IV), and dichloro(O,O′-di-n-butyl-ethylenediamine-N,N′-di-3-propanoate)platinum(II), with the formulae trans-[PtCl₂(eddp)] (1), trans-[PtBr₂(eddp)] (2), [PtCl₂(H₂eddp)] (3), [PtCl₄(Bu₂eddp)] (4), [PtBr₃Cl(Bu₂eddp)] (5), and [PtCl₂(Bu₂eddp)]·H₂O (6), is reported. The deprotonated molecular ions or halide adducts are usually observed. ESI–MS data demonstrate the usefulness of the method for efficient characterization of metal complexes in solution. Graphical Abstract        

Does the DNA Binding Mode of a Molecule Affect its Ability to Interact With Singlet Oxygen?

Singlet oxygen is known to be a potent mutagenic agent and several biologically relevant molecules have been proposed to act as scavengers for this noxious species. However, numerous studies have been conducted in homogenous solution and the reactivity of singlet oxygen scavengers known to bind DNA has never been investigated in double-stranded DNA. In the following paper, we present the results obtained regarding the interaction between 4',6-diamidino-2-phenylindole (DAPI) and singlet oxygen. We show the molecule to be a potent scavenger of singlet oxygen in aqueous solution with an absolute rate constant (chemical and physical quenching of singlet oxygen) of (1.7 ± 0.3) × 10⁷  m ⁻¹ s⁻¹. In addition, we demonstrate that the binding mode of a singlet oxygen scavenger to DNA can strongly influence its reactivity toward singlet oxygen. In the case of DAPI, while the molecule exhibits a chemical reaction with singlet oxygen when the molecule is free in aqueous solution or intercalated in GC sequences of DNA, DAPI becomes chemically unreactive toward singlet oxygen when bound in the minor groove of DNA AT sequences.     

De novo synthesis of pentoses via cyanohydrins as key intermediates

A de novo synthesis of pentoses is described starting from (Z)-2-buten-1,4-diol (1). The key step is the enzyme catalysed enantioselective HCN-addition to O-protected 4-hydroxybut-2-enal using the hydroxynitrile lyase from Hevea brasiliensis, followed by an asymmetric dihydroxylation. For the cyanohydrin reaction the influence of the configuration of the double bond and of the protecting group was investigated. The dihydroxylation step was found to be influenced by the protecting group on position 4.     

Sense and nonsense of high-temperature liquid chromatography

High-temperature liquid chromatography (HTLC) is recognized today as a valuable technique in reversed-phase high-performance liquid chromatography (RP-HPLC). Column temperature can play a role in reducing analysis time, modifying retention, controlling selectivity, changing efficiency or improving detection sensitivity. The different effects of high temperatures on reversed-phase separations, the practical limitations due to the instrumentation, the limits and the main advantages of HTLC, especially for the separation of polar and ionized compounds, are reviewed.     

Columnar Mesophases Controlled by Counterions in Potassium Complexes of Dibenzo[18]crown‐6 Derivatives

Dibenzo[18]crown‐6 derivatives 1 with two lateral tetraalkyloxy o‐terphenyl units were prepared and converted to the corresponding complexes KX ?1 (X=halide, BF₄, PF₆, SCN) and NH₄PF₆ ?1 . Complexation was probed by MALDI‐TOF spectrometry and NMR spectroscopy. Downfield shifts of ¹H NMR signals for complexes with soft anions Br, I, SCN, and PF₆ indicated the presence of tight ion pairs, whereas complexes with hard anions F, Cl, or BF₄ showed no or little shifts. In ¹³C NMR spectra, upfield shifts were detected for soft anions. The character of the anion also influenced the mesomorphic properties of complexes MX ?1 (M=K, NH₄), which were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and XRD in comparison to neat 1 . Hard anions slightly stabilize or even destabilize the mesophase. Soft anions, however, improve the mesomorphic properties yielding mesophases with up to 70 °C phase widths in the case of KI ?1 , KPF₆ ?1 , and NH₄PF₆ ?1 . For complexes KSCN ?1 with a soft and bridging anion, the balance between mesophase stabilization and high order is shifted in favor of the plastic crystal phase.     

The number of Hecke eigenvalues of same signs

We give the best possible lower bounds in order of magnitude for the number of positive and negative Hecke eigenvalues. This improves upon a recent work of Kohnen, Lau and Shparlinski. Also, we study an analogous problem for short intervals.     

Separation conditions for conformal iterated function systems

We extend both the weak separation condition and the finite type condition to include finite iterated function systems (IFSs) of injective C ¹ conformal contractions on compact subsets of \mathbbR^d{{\mathbb{R}}^d} . For conformal IFSs satisfying the bounded distortion property, we prove that the finite type condition implies the weak separation condition. By assuming the weak separation condition, we prove that the Hausdorff and box dimensions of the attractor are equal and, if the dimension of the attractor is α, then its α-dimensional Hausdorff measure is positive and finite. We obtain a necessary and sufficient condition for the associated self-conformal measure μ to be singular. By using these we give a first example of a singular invariant measure μ that is associated with a non-linear IFS with overlaps.     

Feed spacer mesh angle: 3D modeling, simulation and optimization based on unsteady hydrodynamic in spiral wound membrane channel

Basic knowledge on the hydrodynamics in the spacer-filled spiral wound membrane (SWM) channel is vital for the understanding of the formation of concentration polarization at the membrane interface. In the present study, a 3D laminar transient hydrodynamics modeling approach was used to study and optimize the spacer mesh angle for the SWM feed spacer. Based on the simulated results, the optimal spacer mesh angle that yields the minimum effective concentration polarization factor, was found to be α120β30. Under this optimal mesh angles, spacer α120β30 also demonstrated the highest magnitude of unsteady hydrodynamics (which adjacent to the membrane wall) at a moderate degree of pressure loss.     

Band-structure-dependent demagnetization in the Heusler alloy Co₂Mn(1-x)FexSi

We investigate the ultrafast demagnetization for two Heusler alloys (Co?Mn(1-x)FexSi) with a different lineup of the minority band gap and the Fermi level. Even though electronic spin-flip transitions are partially blocked by the band gap in one compound, the respective magnetization dynamics, as measured by the time-resolved Kerr effect, are remarkably similar. Based on a dynamical model that includes momentum and spin-dependent carrier scattering, we show that the magnetization dynamics are dominated by hole spin-flip processes, which are not influenced by the gap.