A Dynamic Chemical Network for Cystinuria Diagnosis

The study of molecular networks represents a conceptual revolution in chemistry. Building on previous knowledge and after understanding the rules of non‐covalent interactions, the design of stimulus‐responsive chemical systems is possible. Herein we report a new strategy, based on the reorganization of a dynamic chemical network that generates new fluorescent associations in the presence of cysteine or cystine. The binding and sensing units are encoded in the components that dynamically assemble and disassemble responding to external stimuli as a successful tool to detect both cysteine and cystine in aqueous media. Moreover, the dynamic sensing system works in human urine, as a prospective application for cystinuria diagnosis.     

Evaluation of the spectral accuracy of mass spectrometers using compounds containing Cl or Br atoms

Current procedures for the evaluation of spectral accuracy of mass spectrometers are limited by the lack of certified isotopic reference materials and the high uncertainty in the isotopic composition of natural abundance molecules. The calculated uncertainties in the ratio M + 1/M for natural abundance molecules containing any number of C, H, N and/or O atoms are close to 5% relative because of the natural variability of the isotopic composition of carbon. So, we have developed two alternative measurement procedures with much lower theoretical uncertainties for a better evaluation of spectral accuracy in both single and triple quadrupole analysers. The first method is based on the measurement of the M + 2/M, M + 4/M + 2, etc. ratios for halogenated organic compounds containing either Cl or Br. The theoretical uncertainties for these ratios because of natural variability are in the order of 0.3 to 1.0% making them suitable for the evaluation of spectral accuracy with the additional advantage that there is no need to take into account other limitations such as cluster purity or poor mass resolution. This procedure was applied to the evaluation of a single quadrupole GC‐MS instruments using natural abundance PCB and PBDE standards with satisfactory results. The second method can be applied to tandem instruments and takes advantage of the loss of two halogen atoms when PCB and PBDE standards are fragmented by Collision Induced Dissociation. Theoretical SRM transition ratios can be calculated as a pure combinatorial probability with theoretical uncertainties lower than 0.1%. By combining PCBs and PBDEs with different number of halogen atoms, a mass range from 100 to 700 u and abundance ratios from 0.1 to 10 can be evaluated. The use of penta‐chlorinated PCBs and/or penta‐brominated PBDEs is finally recommended for the evaluation of spectral accuracy of mass spectrometers with the EI source. Copyright © 2016 John Wiley & Sons, Ltd.     

Molecular Recognition of Zwitterions with Artificial Receptors

Many biomolecules exist as internal ion pairs or zwitterions within a biologically relevant pH range. Despite their importance, the molecular recognition of this type of systems is specially challenging due to their strong solvation in aqueous media, and their trend to form folded or self‐assembled structures by pairing of charges of different sign. In this Minireview, we will discuss the molecular recognition of zwitterions using non‐natural, synthetic receptors. This contribution does not intend to make a full in‐depth revision of the existing research in the field, but a personal overview with selected representative examples from the recent literature.     

Optical control of the singlet-triplet transition in Rb2

By controlling nonresonant dynamic Stark shifts it is possible to effectively decouple the intramolecular couplings of simple molecules. We have illustrated this effect in the 1 (1)Sigma(u)-->1 (3)Pi(u) transition in Rb(2). The laser scheme implies two important control knobs: the laser frequency, which must be chosen to avoid both single and multiphoton resonances and to select different electronic environments for the singlet and triplet states, and the pulse intensity, which must amplify the asymmetry in the dynamic polarizabilities that allows the decoupling, avoiding undesired strong-pulse effects. The mechanism of the scheme implies not only brute-force energy shifts but also light-induced reshaping of the potentials to avoid the undesired crossings. Quantitative aspects of the method are analyzed by using molecular models of increasing complexity for Rb(2).     

Conventional Matrices Loaded Onto a Graphene Layer Enhances MALDI-TOF/TOF Signal: Its Application to Improve Detection of Phosphorylated Peptides

This is the first study where graphene is used as a MALDI adjuvant in combination with the traditional matrix α-cyano-4-hydroxycinnamic acid (CHCA) to improve the signal intensity of peptide samples. Use of this amended matrix not only leads to increased signals but also to a higher number of peaks detected in complex samples. Additionally, the use of graphene has a stabilizing effect that can also be exploited to improve the detection of easily cleavable molecules.

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Computational prediction of the properties of bis(ethynylthienyl)dialcoxynaphthalene-based conjugated polymers for organic solar cell applications

A series of homo- ( P0 ) and copolymers ( P1-P5 ) based on the electron-donor building-block 2,2′-(2,3-bis(2-ethylhexyloxy)naphthalene-1,4-diyl)bis(ethyne-2,1-diyl)dithiophene (1,4-NET) including ethynyl linkers aiming to promote coplanarity were designed, and their properties predicted using theoretical methodologies to evaluate their potential in organic solar cell applications. The geometries, FMO levels, energy bandgaps, and absorption spectra of trimer models were determined using time-dependent density functional theory, while their photovoltaic and charge-transport properties were estimated by the Scharber's model and semiclassical Marcus theory, respectively. Compared to high-performance conjugated polymers (CPs), such as PTB7-Th or PM6, and similar systems based on the 1D-BDT unit, the HOMO and LUMO levels of P0-P5 tend to be higher. In addition, the new CPs have complementary absorptions with narrow-bandgap acceptors, such as ITIC and Y6, and adequate matches between their HOMO and LUMO levels. Although the simulated photovoltaic and charge-transport properties could be overestimated, the best candidate to be synthesized and tested in organic solar cells is P5 due to its suitable and well-balanced properties, demonstrating the positive effect of incorporating ethynyl bridges to improve the optoelectronic properties of CPs.     

Deposition of overlays by electrostatic self-assembly in long-period fiber gratings

It was proved that the deposition of an overlay material onto a long-period fiber grating causes important shifts in the wavelengths of the typical attenuation bands that are caused by coupling between cladding and core modes [Opt. Lett. 27, 682 (2002)]. A theoretical model for analyzing a multilayer cylindrical waveguide is presented that permits the phenomenon to be understood and predicted. An overlay of higher refractive index than the cladding starts to guide a mode if a certain thickness value is exceeded. This causes large shifts in the resonance wavelength induced by the grating. One important application of this phenomenon to sensors is enhancement of the sensitivity of a long-period fiber grating to ambient conditions. Theoretical results are corroborated with experimental ones obtained by electrostatic self-assembly.     

Slurry sampling for the rapid determination of cobalt, nickel and copper in soils and sediments by electrothermal atomic absorption spectrometry

Electrothermal atomic absorption procedures for the rapid determination of cobalt, nickel and copper in soil and sediment samples are presented. The samples are suspended in a hydrofluoric acid solution before being injected into the electrothermal atomizer. Prior mild heating in a microwave oven is recommended for nickel and copper determination. No modifier other than hydrofluoric acid is required. The conventional ashing step is unnecessary since the fast-heating programmes lead to well defined atomization profiles with low background levels that can be corrected using a common deuterium device. Calibration is performed directly using aqueous standards. The results obtained for six certified reference materials confirm the reliability of the procedures.