A new ion source based on dielectric barrier discharge was developed as an alternative ionization source for ambient mass spectrometry. The dielectric barrier discharge ionization source, termed as DBDI herein, was composed of a copper sheet electrode, a discharge electrode, and a piece of glass slide in between as dielectric barrier as well as sample plate. Stable low-temperature plasma was formed between the tip of the discharge electrode and the surface of glass slide when an alternating voltage was applied between the electrodes. Analytes deposited on the surface of the glass slide were desorbed and ionized by the plasma and the ions were introduced to the mass spectrometer for mass analysis. The capability of this new ambient ion source was demonstrated with the analysis of 20 amino acids, which were deposited on the glass slide separately. Protonated molecular ions of [M + H](+) were observed for all the amino acids except for L-arginine. This ion source was also used for a rapid discrimination of L-valine, L-proline, L-serine and L-alanine from their mixture. The limit of detection was 3.5 pmol for L-alanine using single-ion-monitoring (SIM). Relative standard deviation (RSD) was 5.78% for 17.5 nmol of L-alanine (n = 5). With the advantages of small size, simple configuration and ease operation at ambient conditions, the dielectric barrier discharge ion source would potentially be coupled to portable mass spectrometers.

(ii) a trigger that controls autocatalytic growth; and (iii) inhibitory processes that remove activating thiol species produced during the autocatalytic cycle. In contrast to previous studies demonstrating oscillations and bistability using highly evolved biomolecules (i.e., enzymes 15 and DNA 16,17 ) or inorganic molecules of questionable biochemical relevance (e.g. those used in Belousov-Zhabotinsky-type reactions), 18,19 the organic molecules used in our network are relevant to current metabolism and similar to those that might have existed on early Earth. By using small organic molecules to build a network of organic reactions with autocatalytic, bistable, and oscillatory behavior, we identified principles that clarify how dynamic networks relevant to life might possibly have developed. In the future, modifications of this network will clarify the influence of molecular structure on the dynamics of reaction networks, and may enable the design of biomimetic networks, and of synthetic self-regulating and evolving chemical systems.3 Figure 1 summarizes the network of organic reactions that we used to assemble our model system. All of these reactions are nearly quantitative, and the structure of their reactants can be varied by synthesis to control rates of reactions. Thiols and thioesters, which are central to these reactions, are important in many biological processes (e.g., the formation of disulfide bonds in proteins, transformations involving coenzyme-A, the reduction of oxidized molecules by glutathione, 20 the synthesis of polyketides, 21 and the nonribosomal synthesis of peptides 21 ), and thus, might represent reactions that enabled life to emerge on early Earth. 22 To control the dynamics of these processes, we constructed a modular chemical reaction network (CRN) shown schematically in control-theoretic terms 23 in Fig. 1a. A "trigger" produces an initial chemical signal, and an "auto-amplifier" amplifies this signal, which may or may not be suppressed by inhibition. To keep the reactions out of equilibrium-and thus, to enable the self-organization of reactions by communication through concentrations of reactants and products -we used a continuous-stirred tank reactor (CSTR) to mix reactants and products, while allowing a flux of species into and out of the network over time. A biological cell has some conceptual analogies to a micron-scale, diffusively mixed, tank reactor. The dynamic behavior of this system -especially bistability and oscillationsreflects the balances of triggering, auto-amplification, and inhibition.We first constructed a chemical network capable of auto-amplification using thiols and thioesters (Fig. 1b). The starting components of the network are cystamine (CSSC, 3) and L-alanine ethyl thioester (AlaSEt, 2). Trace amounts of cysteamine (CSH, 1) are generated as follows: AlaSEt slowly hydrolyzes, generating alanine (8) and ethanethiol (ESH, 4); EtSH then reacts with CSSC via thiolate-disulfide interchange, 24 yielding disulfide 6 and CSH. With CSH present, self-amplification oc...

Trace amounts of explosives on solid surfaces were detected by mass spectrometry at ambient conditions with a new technique termed dielectric barrier discharge ionization (DBDI). By the needle-plate discharge mode, a plasma discharge with energetic electrons was generated, which could launch the desorption and ionization of the explosives from solid surfaces. Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 2,4,6-trinitrotoluene (TNT), and pentaerythritol tetranitrate (PETN) were desorbed directly from the explosives-contaminated surface by DBDI, forming the typical anions of [TNT](-), [TNT - H](-), [RDX + NO(2)](-), [PETN + ONO(2)](-), and [RDX + ONO(2)](-). The ions were transferred into the MS instrument for analysis in the negative ion mode. The detection limit of present method was 10 pg for TNT (m/z 197, S/N 8 : 1), 0.1 ng for RDX (m/z 284, S/N 10 : 1), and 1 ng for PETN (m/z 260, S/N 12 : 1). The present method allowed the detection of trace explosives on various matrices, including paper, cloth, chemical fiber, glass, paints, and soil. A relative standard deviation of 5.57% was achieved by depositing 100 pg of TNT on these matrices. The analysis of A-5, a mixture of RDX and additives, has been carried out and the results were consistent with the reference values. The DBDI-MS method represents a simple and rapid way for the detection of explosives with high sensitivity and specificity, which is especially useful when they are present in trace amounts on ordinary environmental surfaces.

Biomolecular recognition can be stubborn; changes in the structures of associating molecules, or the environments in which they associate, often yield compensating changes in enthalpies and entropies of binding and no net change in affinities. This phenomenon-termed enthalpy/entropy (H/S) compensation-hinders efforts in biomolecular design, and its incidence-often a surprise to experimentalists-makes interactions between biomolecules difficult to predict. Although characterizing H/S compensation requires experimental care, it is unquestionably a real phenomenon that has, from an engineering perspective, useful physical origins. Studying H/S compensation can help illuminate the still-murky roles of water and dynamics in biomolecular recognition and self-assembly. This review summarizes known sources of H/ S compensation (real and perceived) and lays out a conceptual framework for understanding and dissecting-and, perhaps, avoiding or exploiting-this phenomenon in biophysical systems.

Semiconductor In2O3 nanowires embedded in an alumina template were fabricated using template technology. Scanning electron microscopy and transmission electron microscopy observations show that the In2O3 nanowire single crystal has an average diameter around 80 nm and a length over 10 μm. A strong photoluminescence (PL) emission with a peak at 398 nm (3.12 eV in photon energy) was detected upon excitation of the In2O3 nanowires at 274 nm (4.53 eV in photon energy) and 305 nm (4.08 eV in photon energy) under room temperature. The observed UV PL emission is attributed to the near band edge emission.