No abstract

Iron oxide nanoparticles modified with oleate have been employed for the extraction of peptides and proteins from aqueous solution before matrix-assisted laser desorption/ionization (MALDI) mass spectrometric (MS) analysis. Adsorption of peptides and proteins onto the nanoparticles were mainly through electrostatic attraction and hydrophobic interaction. The analyte-adsorbed iron oxide nanoparticles could be efficiently collected from solution using a magnet. No elution step was needed. With this preconcentration strategy, the lowest detectable concentration of angiotensin I, insulin, and myoglobin in 500 L of aqueous solution were 0.1 nM, 0.1 nM, and 10.0 nM, respectively. In addition, the nanoparticles could extract the analytes from solution with a high content of salt and surfactant, thus eliminating suppression effect during MALDI MS analysis. This method was successfully applied to concentrate the tryptic digest products of cytochrome c. In addition, the tryptic digestion of cytochrome c can be directly conducted on the iron oxide nanoparticles. atrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) has become a routine analytical tool to determine the molecular mass of biomolecules [1][2][3]. However, samples containing excessive amounts of salts, surfactants, or other contaminations suffer from ionization suppression and adduct formation [4,5]. This limits the application of MALDI technique. Therefore, a simple and selective procedure for extraction and concentration of analyte from complex samples before MALDI MS is required.Various methods have been developed to isolate the analyte from complex sample matrix. In surface-enhanced laser desorption/ionization (SELDI), the sample target played an active role in the extraction, purification, or concentration of the analyte of interest [6 -9]. The target surface was derivatized for the selective retention of analyte while removing interferences through on-target washing. Several surface derivatizations have been designed to extract and concentrate the analyte through hydrophobic interaction [10,11], ionic interaction [12,13], or immunoaffinity [14,15]. However, the sensitivity improvement was limited by the number of binding sites on the target. In another approach, the so-called surface-enhanced affinity capture (SEAC), micrometer-sized beads made for chromatography column were used to capture peptides and proteins from sample solution [16]. Various types of beads have been used, which include reverse-phase chromatographic beads [17,18] and immobilized metal ion beads [19 -21]. To speed up the collection of analyteadsorbed beads from sample solution, magnetic particles, which can be simply collected using a magnet, were developed [22][23][24]. After collection, the microbeads were washed and placed on sample target, followed by analyzing with MALDI MS. Unfortunately, the presence of those particles on the sample target was reported to cause decrease in mass accuracy and resolution [25,26].Recently, nanoparticles have become interesting p...

Organic fluorescent nanoparticles, excitation-dependent photoluminescence, hydrogen-bonded clusters and lysobisphosphatidic acid are four interesting individual topics in materials and biological sciences. They have attracted much attention not only because of their unique properties and important applications, but also because the nature of their intriguing phenomena remained unclear. Here we report a new type of organic fluorescent nanoparticles with intense blue and excitation-dependent visible fluorescence in the range of 410–620 nm. The nanoparticles are composed of ten bis(monoacylglycerol)bisphenol-A molecules and the self-assembly occurs only in elevated concentrations of 2-monoacylglycerol via radical-catalysed 3,2-acyl migration from 3-monoacylglycerol in neat conditions. The excitation-dependent fluorescence behaviour is caused by chromophores composed of hydrogen-bonded monoacylglycerol clusters, which are linked by an extensive hydrogen-bonding network between the ester carbonyl groups and the protons of the alcohols with collective proton motion and HO···C=O (n→π*) interactions.

Mass spectrometry (MS) is usually coupled on-line with capillary electrophoresis (CE) to analyze biomolecules by using electrospray ionization or continuous-flow fast-atom bombardment. We present a new design for laser vaporization/ionization time-of-flight mass spectrometry. CE, with its low flow rate (<1 μL/min), is highly compatible with MS, even if the total column effluent is introduced directly. A UV laser is used to vaporize and ionize the solution eluting from the column. There is no need to have a makeup solvent. Using this system, we have analyzed a group of amines and peptides. The concentration detection limit of serotonin is in the 10(-)(7) M level. The separation and identification of an amine mixture by CE/MS demonstrates the complementary nature of the information.