The preparation and characterization of trans-platinum(IV) complexes with unusually high cytotoxicity

The physical and biological properties have been determined for three Pt(IV) complexes with trans amine ligands: trans,trans,trans-[PtCl(2)(OH)(2)(dimethylamine)(isopropylamine)] (1(IV)), trans,trans,trans-[PtCl(2)(OH)(2)(dimethylamine)(methylamine)] (2(IV)) and trans,trans,trans-[PtCl(2)(OH)(2)(isopropylamine)(methylamine)] (3(IV)). The crystal structures of 2(IV) and 3(IV) reveal substantial strain resulting from repulsion between the amine ligands and the chlorido and hydroxido ligands. All three complexes have reduction potentials in the range -666 to -770 mV, values usually associated with high resistance to reduction and low cytotoxicity. However, the complexes all demonstrate surprisingly high cytotoxicity with values and trends that closely follow those seen for the Pt(II) congeners of these complexes. These results are consistent with more rapid reduction of the Pt(IV) complexes than would be expected based on the reduction potentials, perhaps associated with the trans arrangement of the chlorido ligands.     

J-aggregation of a sulfonated amphiphilic porphyrin at the air-water interface as a function of pH

π-A isotherms, ellipsometric measurements, Brewster angle microscopy (BAM) and reflection spectroscopy have been utilized to characterize the films of an amphiphilic porphyrin ((OD)(3)TPPS(3)) at the air-water interface as a function of pH. This porphyrin forms stable mono-molecular layers at such interfaces, and exhibits different J-aggregation as a function of pH. The J-aggregation of (OD)(3)TPPS(3) on neutral pH subphases is notable considering that the nitrogen atoms at the central macrocycle have a pK(a)≈4.9. The type of aggregates at neutral pH is like those detected at pH<4, because the central porphyrin ring is already protonated. However at basic pH the aggregation happens without protonation of the central ring but can be instead controlled by application of the surface pressure. At the air-water interface, (OD)(3)TPPS(3) shows two bands, a red component and a blue component, which have characteristics of non-degenerate linear oscillators being perpendicularly polarized between each other. The spectral behavior observed on subphases at different pHs is qualitatively interpreted by means of exciton coupling theory, assuming that the degenerate transitions attributed to the Soret band are split. Additionally, highly oriented molecular films of these J-aggregates were deposited onto transparent quartz slides.     

PtII Coordination to N1 of 9‐Methylguanine: Why it Facilitates Binding of Additional Metal Ions to the Purine Ring

The preparation and X‐ray crystal structure analysis of {trans‐[Pt(MeNH₂)₂(9‐MeG‐N1)₂]} ? {3 K₂[Pt(CN)₄]} ? 6 H₂O ( 3 a ) (with 9‐MeG being the anion of 9‐methylguanine, 9‐MeGH) are reported. The title compound was obtained by treating [Pt(dien)(9‐MeGH‐N7)]²⁺ ( 1 ; dien=diethylenetriamine) with trans‐[Pt(MeNH₂)₂(H₂O)₂]²⁺ at pH 9.6, 60 °C, and subsequent removal of the [(dien)Pt^II] entities by treatment with an excess amount of KCN, which converts the latter to [Pt(CN)₄]^2?. Cocrystallization of K₂[Pt(CN)₄] with trans‐[Pt(MeNH₂)₂(9‐MeG‐N1)₂] is a consequence of the increase in basicity of the guanine ligand following its deprotonation and Pt coordination at N1. This increase in basicity is reflected in the pK_a values of trans‐[Pt(MeNH₂)₂(9‐MeGH‐N1)₂]²⁺ (4.4±0.1 and 3.3±0.4). The crystal structure of 3 a reveals rare (N7,O6 chelate) and unconventional (N2,C2,N3) binding patterns of K⁺ to the guaninato ligands. DFT calculations confirm that K⁺ binding to the sugar edge of guanine for a N1‐platinated guanine anion is a realistic option, thus ruling against a simple packing effect in the solid‐state structure of 3 a . The linkage isomer of 3 a , trans‐[Pt(MeNH₂)₂(9‐MeG‐N7)₂] ( 6 a ) has likewise been isolated, and its acid–base properties determined. Compound 6 a is more basic than 3 a by more than 4 log units. Binding of metal entities to the N7 positions of 9‐MeG in 3 a has been studied in detail for [(NH₃)₃Pt^II], trans‐[(NH₃)₂Pt^II], and [(en)Pd^II] (en=ethylenediamine) by using ¹H NMR spectroscopy. Without exception, binding of the second metal takes place at N7, but formation of a molecular guanine square with trans‐[(Me₂NH₂)Pt^II] cross‐linking N1 positions and trans‐[(NH₃)₂Pt^II] cross‐linking N7 positions could not be confirmed unambiguously, despite the fact that calculations are fully consistent with its existence.     

C-branched chiral (racemic) macrocyclic amino acids: structure of their Ni(II), Zn(II) and Cu(II) complexes

A new procedure for the synthesis of macrocyclic embedded bis-α-amino acids and their use as cation-ligands is described. These compounds are able to form stable Cu(II), Zn(II) and Ni(II) complexes as long as they have a flexible tether between the two nitrogen atoms. For a given macrocycle, the X-ray diffraction studies revealed diastereomerically pure complexes having different geometries depending on the metal ion.     

Development of naturally selected and molecularly engineered intrachain and competitive FRET-aptamers and aptamer beacons

Several different approaches have been taken to development of homogeneous fluorescent aptamer assays including end-labeled beacons and signaling aptamers which are intrinsically quenched by nucleotides. Two new strategies dubbed "intrachain" and "competitive" FRET-aptamer assays are summarized in this review. Intrachain and competitive FRET-aptamers can be engineered on the molecular level through a series exploratory experiments involving prior knowledge of aptamer secondary or tertiary structures and hypotheses about aptamer conformational changes. However, there is an intrinsic risk of altering aptamer affinity or specificity associated with chemical modifications of an aptamer. Natural selection methods for FRET-aptamers have also been devised to potentially obviate the chemical modification problem. The naturally selected aptamers are subjected to fluorophore (F)- and or quencher (Q)-conjugated nucleotide triphosphate (NTP) incorporation by polymerase chain reaction (PCR) with permissive polymerases such as Deep Vent exo-, but still demonstrate sensitive and specific assay performance despite modified bases, because they are ultimately selected after decoration with F and Q. This paper summarizes work in this area and presents some new examples of the engineered and naturally selected FRET-aptamers for detection of vitamin D.     

Highly stable cooperative distortion in a weak Jahn-Teller d2 cation: perovskite-type ScVO3 obtained by high-pressure and high-temperature transformation from bixbyite

A novel ScVO(3) perovskite phase has been synthesized at 8 GPa and 1073 K from the cation-disordered bixbyite-type ScVO(3). The new perovskite has orthorhombic symmetry at room temperature, space group Pnma, and lattice parameters a = 5.4006(2) ?, b = 7.5011(2) ?, and c = 5.0706(1) ? with Sc(3+) and V(3+) ions fully ordered on the A and B sites of the perovskite cell. The vanadium oxygen octahedra [V-O(6)] display cooperative Jahn-Teller (JT) type distortions, with predominance of the tetragonal Q(3) over the orthorhombic Q(2) JT modes. The orthorhombic perovskite shows Arrhenius-type electrical conductivity and undergoes a transition to triclinic symmetry space group P-1 close to 90 K. Below 60 K, the magnetic moments of the 4 nonequivalent vanadium ions undergo magnetic long-range ordering, resulting in a magnetic superstructure of the perovskite cell with propagation vector (0.5, 0, 0.5). The magnetic moments are confined to the xz plane and establish a close to zigzag antiferromagnetic mode.     

Detection of nanocellulose in commercial products and its size characterization using asymmetric flow field-flow fractionation

The paper reports on a method for the detection of nanocellulose (NC) in consumer products by making use of a combination of (a) liquid-liquid extraction with an ionic liquid, and (b) size characterization by asymmetric flow field-flow fractionation (AF4) coupled to multi-angle light scattering (MALS) and refractive index (RI) detection. Both AF4 and MALS are viable tools for characterizing the size of the nanofibers. Sample preparation is easy, and the extraction efficiency of the method is 80.9 ± 1.8% (n = 5). It was applied to the detection of NC in toothpaste and coconut foodstuff to verify the practicability of the method.

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Graphical abstract Nanocellulose (NC) monitoring from coconut products and toothpaste and its size characterization by liquid-liquid extraction and asymmetric flow field-flow fractionation equipped with multi-angle light scattering and refractive index detection (AF4-MALS-RI).

     

Stereoselective allylation and reduction of N-tert-butanesulfinyl-α-keto aldimines

A simple methodology for the synthesis of N-tert-butanesulfinyl-α-keto aldimines from both α-keto aldehydes and carboxylic esters has been developed. The addition of an in situ formed allyl indium reagent to these chiral imines was also studied. The addition took place in a sequential manner, first to the imine group with excellent diastereoselectivity and then to the carbonyl group with lower diastereoselectivity. Ruthenium-catalyzed ring closing metathesis of the resulting 5-aminoocta-1,7-dien-4-ol derivatives provided access to 6-aminocyclohex-3-enols. Reduction of the α-keto aldimines led to N-tert-butanesulfinyl-1,2-aminoalcohols as a 1:1 diastereomeric mixture.     

Toward inorganic electrides

Electrides are materials in which alkali metals (Li through Cs) ionize to form bound alkali cations and "excess" electrons. The electrons reside in large cavities or channels or both in the host lattice. We report here the first synthesis of thermally stable inorganic electrides with cation-to-electron ratios of 1:1 as in organic electrides. Although alkali metal adducts to alumino-silicate zeolites are well known, the cation-to-electron ratio is generally 3:1 or greater because these zeolites contain alkali cations prior to incorporation of the alkali metal. In this work, two pure silica zeolites, ITQ-4and ITQ-7, with pore diameters of approximately 7 A, absorb up to 40 wt % cesium from the vapor phase (even at room temperature). The other alkali metals (except Li) can also be introduced at elevated temperatures. The optical and magnetic properties of the cesium-loaded samples suggest ionization to form Cs+ and e- with substantial electron-spin pairing. The metal-loaded samples are stable to at least 100 degrees C and are able to reduce small aromatic molecules such as benzene and naphthalene to the radical anions within the pores of the zeolite.