Liquid chromatography-mass spectrometry method to determine alcohol ethoxylates and alkylamine ethoxylates in soil interstitial water,ground water and surface water samples

Alcohol ethoxylates (AEs) and alkylamine ethoxylates (AMEs) are used as adjuvants in pesticide formulations. Analytical procedures for these compounds in environmental aqueous samples using LC-MS are presented. Sample preparation uses solid-phase extraction with Porapak Rdx cartridges. Detection limits and recoveries in ground water and surface water are, respectively, AEs: 16-60 ng/l, 35-93% and AMEs: 0.3-6 microg/l, 28-96%. The lower recoveries are obtained for the apolar surfactants. The procedure was employed on samples of ground water and soil interstitial water collected from farming areas. The individual AEs were detected at concentration levels ranging from 33 to 189 ng/l water.     

Formation of a silicon‐containing macrocycle with a pyridoxalimine Schiff base ligand

The reaction of dichlorodiphenylsilane with a polydentate Schiff base ligand derived from pyridoxal and 2‐hydroxyaniline yields the macrocyclic centrosymmetric silicon compound 9,27‐dimethyl‐3,3,21,21‐tetraphenyl‐2,4,20,22‐tetraoxa‐8,13,26,31‐tetraaza‐3,21‐disilapentacyclo[30.4.0.0^6,11.0^14,19.0^24,29]hexatrideca‐1(32),6,8,10,12,14,16,18,24,26,28,30,33,35‐tetradecaene‐10,28‐diol chloroform tetrasolvate, C₅₂H₄₄N₄O₆Si₂·4CHCl₃. The asymmetric unit contains half of the macrocycle and two molecules of chloroform, with C—H...O and C—H...N contacts binding the two guests to the host in the crystal structure. This macrocyclic silicon compound represents a promising host for molecular‐recognition processes and for the construction of nanostructures.     

Kalirin12 interacts with dynamin

Background  

Guanine nucleotide exchange factors (GEFs) and their target Rho GTPases regulate cytoskeletal changes and membrane trafficking. Dynamin, a large force-generating GTPase, plays an essential role in membrane tubulation and fission in cells. Kalirin12, a neuronal RhoGEF, is found in growth cones early in development and in dendritic spines later in development.     

Self‐Assembly Behaviors of a Penta‐Phenylene Maltoside and Its Application for Membrane Protein Study

We prepared an amphiphile with a penta‐phenylene lipophilic group and a branched trimaltoside head group. This new agent, designated penta‐phenylene maltoside (PPM), showed a marked tendency to self‐assembly into micelles via strong aromatic–aromatic interactions in aqueous media, as evidenced by ¹H NMR spectroscopy and fluorescence studies. When utilized for membrane protein studies, this new agent was superior to DDM, a gold standard conventional detergent, in stabilizing multiple proteins long term. The ability of this agent to form aromatic–aromatic interactions is likely responsible for enhanced protein stabilization when associated with a target membrane protein.     

Diffraction-based assay for detecting multiple analytes

The principles of diffraction are utilized to enable the simultaneous detection of multiple analytes in solution, forming the basis of a multi-analyte sensor. Probe molecules are immobilized on a substrate such that each type of molecule defines a specific pattern within the same region of substrate. The binding of a target molecule to its complementary probe is heralded by a characteristic diffraction image. This principle is demonstrated using antibody conjugates.     

Characterisation of a gas-diffusion membrane-based optical flow-through sensor exemplified by the determination of nitrite

A membrane-based optical flow-through sensor is described which can be alternatively used for absorbance and reflectance detection within the receiver channel of a sandwich-type gas-diffusion separation cell. Using the common spectrophotometric detection scheme for nitrite based on azo-dye formation, the principle features of the flow-through sensor are investigated and the performance is characterised particularly with regard to selectivity and sensitivity aspects. The determination of nitrite in waste waters and meat extracts was used to demonstrate the applicability to real sample analysis. The main advantage of the proposed flow-through sensor is the absence of interferences due to sample colour and turbidity enabling direct sample admission of complex samples without tedious sample pretreatment.     

Ear-canal acoustic admittance and reflectance effects in human neonates. I. Predictions of otoacoustic emission and auditory brainstem responses

This report describes the extent to which ear-canal acoustic admittance and energy reflectance (YR) in human neonates (1) predict otoacoustic emission (OAE) levels and auditory brainstem response (ABR) latencies, and (2) classify OAE and ABR responses as present or absent. Analyses are reported on a subset of ears in which hearing screening measurements were obtained previously [Norton et al., Ear. Hear. 21, 348-356 (2000a)]. Tests on 1405 ears included YR, distortion-product OAEs, transient-evoked OAEs, and ABR. Principal components analysis reduced the 33 YR variables to 5-7 factors. OAE levels decreased and ABR latencies increased with increasing high-frequency energy reflectance. Up to 28% of the variance in OAE levels and 12% of the variance in ABR wave-V latencies were explained by these factors. Thus, the YR response indirectly encodes information on inter-ear variations in forward and reverse middle-ear transmission. The YR factors classify OAEs with an area under the relative operating characteristic (ROC) curve as high as 0.79, suggesting that middle-ear dysfunction is partly responsible for the inability to record OAEs in some ears. The YR factors classified ABR responses less well, with ROC areas of 0.64 for predicting wave-V latency and 0.56 for predicting Fsp.     

Reactions of 2-aminopyridine with picryl halides

2-Aminopyridine reacts with picryl halides to give mixtures of 1-picryl-2-(N-picrylimino)-1,2-dihydropyridine and 2-(N-picrylamino)pyridine. When picryl fluoride is treated with an excess of 2-aminopyridine, the 1-picryl-2-(N-picrylimino)-1,2-dihydropyridine reacts further with 2-aminopyridine to yield two molecules of 2-(N-picrylamino)pyridine in a reaction catalyzed by the by-product, hydrogen fluoride. In contrast, the compositions of the mixtures obtained from the reactions of picryl chloride and picryl bromide with excess 2-aminopyridine are stable in their reaction media.