A sensitive solid-phase fluoroimmunoassay for detection of opiates in urine

An automated flow fluorometer designed for kinetic binding analysis was adapted to develop a solid-phase competitive fluoroimmunoassay for urinalysis of opiates. The solid phase consisted of polymer beads coated with commercial monoclonal antibodies (MAbs) raised against morphine. Fluorescein-conjugated morphine (FL-MOR) was used as the fluorescein-labeled hapten. The dissociation equilibrium constant (K _D ) for the binding of FL-MOR to the anti-MOR MAb was 0.23 nM. The binding of FL-MOR to the anti-MOR MAb reached steady state within minutes and was displaced effectively by morphine and other opiates. Morphine-3-glucuronide (M3G), the major urinary metabolite of heroin and morphine, competed effectively with FL-MOR in a concentration-dependent manner for binding to the antimorphine MAb and was therefore used to construct the calibration curve. The sensitivity of the assay was 0.2 ng/mL for M3G. The assay was effective at concentrations of M3G from 0.2 to 50 ng/mL, with an IC₅₀ of 2 ng/mL. Other opiates and heroin metabolites that showed >50% crossreactivity when present at 1 μg/mL included codeine, morphine-6-glucuronide, and oxycodone. Methadone showed very low crossreactivity (<5%), which is a benefit for testing in patients being treated for opiate addictions. The high sensitivity of the assay and the relatively high cutoff value for positive opiate tests allows very small sample volumes (e.g., in saliva or sweat) to be analyzed. A double-blind comparison using 205 clinical urine samples showed good agreement between this single-step competitive assay and a commercially performed enzyme multiplied immunoassay technique for the detection of opiates and benzoylecgonine (a metabolite of cocaine).     

Development of a solid‐phase microextraction LC–MS/MS method for determination of oxidative stress biomarkers in biofluids

Recently the connection between oxidative stress and various diseases, including cancer and Alzheimer's, attracts notice as a pathway suitable for diagnostic purposes. 8‐Oxo‐deoxyguanosine and 8‐oxo‐deoxyadenosine produced from the interaction of reactive oxygen species with DNA become prominent as biomarkers. Several methods have been developed for their determination in biofluids, including solid‐phase extraction and enzyme‐linked immunosorbent assays. However, still, there is a need for reliable and fast analytical methods. In this context, solid‐phase microextraction offers many advantages such as flexibility in geometry and applicable sample volume, as well as high adaptability to high‐throughput sampling. In this study, a solid‐phase microextraction method was developed for the determination of 8‐oxo‐deoxyguanosine and 8‐oxo‐deoxyadenosine in biofluids. The extractive phase of solid‐phase microextraction consisted of hydrophilic–lipophilic balanced polymeric particles. In order to develop a solid‐phase microextraction method suitable for the determination of the analytes in saliva and urine, several parameters, including desorption solvent, desorption time, sample pH, and ionic strength, were scrutinized. Analytical figures of merit indicated that the developed method provides reasonable interday and intraday precisions (<15% in both biofluids) with acceptable accuracy. The method provides a limit of quantification for both biomarkers at 5.0 and 10.0 ng/mL levels in saliva and urine matrices, respectively.     

Thet→∞ asymptotic regime of the Cauchy problem solution for the Toda chain with threshold-type Initial data

We obtain formulas allowing us to find solutions of the Toda chain using the inverse scattering transform method and investigate the t→∞ asymptotic behavior of the solutions. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 119, No. 3, pp. 429–440, June, 1999     

Rapidly Decreasing Solution of the Initial Boundary-Value Problem for the Toda Lattice

Using the inverse scattering transform, we investigate an initial boundary-value problem with zero boundary condition for the Toda lattice. We prove the existence and uniqueness of a rapidly decreasing solution and determine a class of initial data that guarantees the existence of a rapidly decreasing solution. __________ Translated from Ukrains'kyi Matematychnyi Zhurnal, Vol. 57, No. 8, pp. 1144 – 1152, August, 2005.     

On the Inverse Scattering Problem for the One-Dimensional Schrödinger Equation with Increasing Potential

Ukrainian Mathematical Journal - We consider a one-dimensional Schrödinger equation on the entire axis whose potential rapidly decreases on the left-hand side and infinitely increases on the...     

Transformation Operators for the Perturbed Hill Difference Equation and One of Their Applications

We construct transformation operators with conditions at infinity for the perturbed Hill equation. We give one application of transformation operators to studying solutions of some nonlinear difference equation.     

Interface sharpness in the Ising model with long-range interaction

For the 3-dimensional Ising model with long-range interaction, Gibbs states are constructed that are small perturbations of non-translation-invariant ground states. These ground states are in one-to-one correspondence with the set of all rational planes.     

Global attractors for the plate equation with a localized damping and a critical exponent in an unbounded domain

In this paper, we study the asymptotic behavior of solutions for the plate equation with a localized damping and a critical exponent. We prove the existence, regularity and finite dimensionality of a global attractor in .