(–)‐2‐(1,2,3,4,4a,5,6,7,8,8aα‐Decahydro‐4aβ,8α‐dimethyl‐7‐oxo‐2β‐naphthyl)propionic acid: catemeric hydrogen bonding in a bicyclic sesquiterpenoid ζ‐keto acid

In the title compound, C₁₅H₂₄O₃, derived from a naturally occurring sesquiterpenoid, the asymmetric unit consists of two mol­ecules differing by 167.4 (8)° in the rotational conformation of the carboxyl group. Each molecule aggregates separately with its own type as carboxyl‐to‐ketone hydrogen‐bonding catemers [O⋯O = 2.715 (6) and 2.772 (6) Å, and O—H⋯O = 169 and 168°]. This generates two crystallographically independent single‐strand hydrogen‐bonding helices passing through the cell in the b direction, with opposite end‐to‐end orientations. One intermolecular C—H⋯O=C close contact exists for the carboxyl group of one of the mol­ecules. The structure is isostructural with that of a closely related unsaturated keto acid reported previously.     

NMR investigation of the nature of water in disposable incontinence pads containing superabsorbent polymers and fluffed wood pulp

The use of nuclear magnetic resonance to make quantitative measurements of the absorption processes occurring in the constituent materials of disposable incontinence pads was investigated. Modern incontinence pads often have a layered structure with the absorbent layer principally consisting of superabsorbent polymer (SAP) grains distributed in fluffed wood pulp. T ₂-weighted and magnetisation transfer contrast (MTC) measurements were made using samples of SAP, fluffed wood pulp, and a mixture of 50% SAP and 50% fluffed wood pulp following the addition of water and NaCl solutions. The T ₂-weighted signal always decreased on mixing the liquid and material samples, with SAP showing the smallest magnitude of signal decline. The MTC change was minimal for SAP, but increased for the other samples. The small changes in the T ₂-weighted signals and the MTC observed when adding water to SAP indicate that water is not principally being tightly bound by the polymer. The absorption time-course was further evaluated by acquiring proton-density-weighted 1D profiles after the addition of water to the samples. In SAP, the fitted time constant was comparable to the activation energy measured by other methods. The relaxation times both declined on mixing the liquids with samples of SAP and fluffed wood pulp. The reduction in spin–spin relaxation is sufficient to account for the T ₂-weighted signal changes.     

To Sandwich Technetium: Highly Functionalized Bis-Arene Complexes [99mTc(η6-arene)2]+ Directly from Water and [99mTcO4]−

The labeling of (bio)molecules with metallic radionuclides such as ^99mTc demands conjugated, multidentate chelators. However, this is not always necessary since phenyl rings can directly serve as integrated, organometallic ligands. Bis-arene sandwich complexes are generally prepared by the Fischer–Hafner reaction. In extension of this, we show that [^99mTc(η⁶-C₆R₆)₂]⁺-type complexes are directly accessible from water and [^99mTcO₄]⁻, even using arenes incompatible with Fischer–Hafner conditions. To unambiguously confirm the nature of these unprecedented ^99mTc complexes, their rhenium homologous have been prepared by substituting naphthalene ligands in [Re(η⁶-C₁₀H₈)₂]⁺ with the corresponding phenyl groups. The ease with which highly stable [^99mTc(η⁶-C₆R₆)₂]⁺ complexes are formed under standard labeling conditions enables a multitude of new potential imaging agents based on commercial pharmaceuticals or lead structures.     

Prospect for characterizing interacting soft colloidal structures using spin-echo small angle neutron scattering

Spin-echo small angle neutron scattering (SESANS) provides a new experimental tool for structural investigation. Due to the action of spin-echo encoding, SESANS measures a spatial correlation function in real space, as opposed to the structure factor S(Q), I(Q), in momentum (Q) space measured by conventional small angle neutron scattering. To establish the usefulness of SESANS in structural characterization, particularly for interacting colloidal suspensions, we have previously conducted a theoretical study of the SESANS correlation functions for model systems consisting of particles with uniform density profiles [X. Li, C.-Y. Shew, Y. Liu, R. Pynn, E. Liu, K. W. Herwig, G. S. Smith, J. L. Robertson, and W.-R. Chen J. Chem. Phys. 132, 174509 (2010)]. Within the same framework, we explore in the present paper the prospect of using SESANS to investigate the structural characteristics of colloidal systems consisting of particles with nonuniform intraparticle mass distribution. As an example, a Gaussian model of interacting soft colloids is used to investigate the manifestation of structural softness in a SESANS measurement. The exploration shows a characteristically different SESANS correlation function for interacting soft colloids, in comparison to that of a uniform hard sphere system. The difference arises from the Abel transform imbedded in the mathematical formalism bridging the SESANS spectra and the spatial autocorrelation function.     

Quantitative polymerase chain reaction using capillary electrophoresis with laser-induced fluorescence detection: Analysis of duck hepatitis B

We report an accurate and reproducible DNA quantitation method using the polymerase chain reaction (PCR). The amount of PCR product is monitored after each PCR cycle by capillary electrophoresis. To ensure accurate quantitation, a non-amplified internal standard is added to each PCR-amplified electrophoresis sample to correct for variations in injection volume. Quantitation of the sample is based on the number of cycles necessary to generate a predetermined amount of PCR product. Duck hepatitis B virus genome was used as a model in this study. The genome was quantified with a linear relationship between cycle number and logarithm of sample DNA for amounts of sample DNA between 30 and 3.1 x 10(8) copies ( r(2)>0.999). The relative standard deviation for the corrected capillary electrophoresis signal was 2.7%, while the relative standard deviation for the overall assay was 3.0%. Results from a single-blind study generated a relative error of 1.3%.     

Cobalt(II) halide complexes ofN-2-(4-picolyl)-,N-2-(6-picolyl)-andN-2-(4,6-lutidyl)-N′-phenylthioureas

Summary Co^II complexes of various stoichiometries have been isolated from reactions of the metal chlorides and bromides withN-2-(4-picolyl)-,N-2-(6-picolyl)- andN-2-(4,6-lutidyl)-N-phenylthioureas.     

Simple method for the assay of linezolid in Brain Heart Infusion broth by high-performance liquid chromatography

A simple HPLC method was developed and validated for quantification of linezolid in Brain Heart Infusion (BHI) broth. Eperezolid was employed as internal standard and the sample pre-treatment procedure was simple. Calibration standards ranged from 0.05 to 16 mg/L. Accuracy was within 7.8% and reproducibility (RSD) was less than 8.3%. Recovery was approximately 100% at all concentrations examined. Linezolid was stable in the autosampler insert for at least 24 h at ambient temperature and in BHI for 72 h at 37 degrees C. This assay is rapid and ideal for analysis of a large number of samples.     

()‐3‐Ethyl‐2‐methyl‐4‐oxo­cyclo­hexane­carboxyl­ic acid: catemeric hydrogen bonding in a cyclic δ‐keto acid

In the title compound, C₁₀H₁₆O₃, the two mol­ecules of the asymmetric unit form acid‐to‐ketone hydrogen‐bonded chains. The two species differ only very slightly and are related by a pseudo‐center, so that the apparent translational relationship among the units of the hydrogen‐bonded chain is actually a pseudo‐translation, with the mol­ecules alternating in type. Two counterdirectional pairs of chains proceed through each cell [O⋯O = 2.743 (2) and 2.683 (2) Å, and O—H⋯O = 171 (3) and 157 (3)°]. Three intermolecular C—H⋯O close contacts were found, involving all three O atoms of one of the mol­ecules.     

Trifunctional 99mTc based radiopharmaceuticals: metal-mediated conjugation of a peptide with a nucleus targeting intercalator

The development of molecular imaging agents with multiple functions has become a major trend in radiopharmaceutical chemistry. We present herein the syntheses of trifunctional compounds, combining an acridine orange (AO) based intercalator with a GRP receptor specific bombesin like peptide (BBN). Metal-mediated conjugation of these two functions via the [2 + 1] approach to the third function, the [M(CO)(3)](+) (M = (99m)Tc, Re) moiety, yielded the final trifunctional molecules. The strongly fluorescent acridine orange, a nuclear targeting agent, has been derivatised with 4-imidazolecarboxylate as a bidentate ligand and bombesin with an isonitrile group as a monodentate ligand. For cell and nuclear uptake studies, [Re(L(1)-BBN)(L(2)-Ical)(CO)(3)] type complexes were synthesized and characterized. For radiopharmaceutical purposes, the (99m)Tc analogues have been prepared in a stepwise synthesis. Fluorescence microscopy studies on PC-3 cells, bearing the BBN receptor, showed high and rapid uptake into the cytoplasm. For the bifunctional molecule, lacking the BBN peptide, no internalization was observed.