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The current prostate cancer (PCa) diagnosis, based on the blood prostate-specific antigen (PSA) level measurement, is not a precise science. The widely used PSA biomarker for PCa has poor sensitivity and specificity and often leads to false-negative and false-positive test results. Recently, sarcosine, proline, kynurenine, uracil, and glycerol 3-phosphate were found in higher concentrations in metastatic prostate cancer urine samples. By measuring all five of these metabolites, doctors may be better able to diagnose prostate cancer with high accuracy. However, there is no method reported for simultaneous detection of these compounds in urine samples. In this study, a novel method was developed to separate and quantify six urinary metabolites including creatinine in urine samples by using liquid chromatography/tandem mass spectrometry. Chromatographic separations of the analytes were carried out using a phenyl-hexyl column with 0.1% formic acid in water and acetonitrile, respectively, under a gradient program. The six metabolites were detected in the multiple reaction monitoring modes with the ES1positive mode. The linear range of the analytes was from 0.003 to 40 [micro]mol/L. The limit of detection was from 0.05 to 4 nmol/L, and the limit of quantification ranged from 3 to 20 nmol/L The factors affecting the separation and quantification of the six metabolites, such as mobile-phase and MS conditions, were also investigated. The technique developed in this study is simple, fast, sensitive, and selective. It can be used for quantifying these six metabolites in urine samples for potential early cancer screening. 10.1021/ac1019914

The study of dynamics and thermodynamics of single biological molecules at confined liquid-solid interfaces is crucially important, especially in the case of low-copy number molecules in a single cell. Using a high-throughput single molecule imaging system and Lagrangian coordinates of single molecule images, we discovered that the local equilibrium isotherms of single [lambda]DNA molecules at a confined liquid-solid interface varied from a stair type for the regions of single or double molecular DNA to a mild 'S' type for the regions of triple molecular DNA spots, which does not agree with the conventional equilibrium isotherms in the literature. Single molecule images in time sequence for different [lambda]DNA concentrations were statistically analyzed by measuring preferential partitioning from shearing effects, which were used to measure the local velocity of DNA molecules by directly observing the migration of DNA fluorescence spots for the 12 continuous images. The local linear velocity of hydrodynamic flow was calculated by the Hagen-Poiseuille equation in different microregions with a local Lagrangian approach. The local single molecule isotherms for the tracked molecules in the regions of single, double, or triple molecular DNA layers within the laminar flows were obtained according to the average local velocities of both the stochastic molecule events and the corresponding local Poiseuille flows. A millisecond and microvolume approach to directly determine local single molecule isotherms at confined liquid-solid interfaces was established, and the microspace scale effects on the types of isotherms were discovered. This study may have significant impact on preparations of low-copy number proteins in a single cell, membrane separations, and other bioseparation studies.