Multivariate curve resolution combined with gas chromatography to enhance analytical separation in complex samples: A review

This review describes the major advantages and pitfalls of iterative and non-iterative multivariate curve resolution (MCR) methods combined with gas chromatography (GC) data using literature published since 2000 and highlighting the most important combinations of GC coupled to mass spectrometry (GC–MS) and comprehensive two-dimensional gas chromatography with flame ionization detection (GC × GC-FID) and coupled to mass spectrometry (GC × GC–MS). In addition, a brief summary of some pre-processing strategies will be discussed to correct common issues in GC, such as retention time shifts and baseline/background contributions. Additionally, algorithms such as evolving factor analysis (EFA), heuristic evolving latent projection (HELP), subwindow factor analysis (SFA), multivariate curve resolution-alternating least squares (MCR-ALS), positive matrix factorization (PMF), iterative target transformation factor analysis (ITTFA) and orthogonal projection resolution (OPR) will be described in this paper. Even more, examples of applications to food chemistry, lipidomics and medicinal chemistry, as well as in essential oil research, will be shown. Lastly, a brief illustration of the MCR method hierarchy will also be presented.     

Evaluation of Mechanical Properties and Water Vapor Permeability in Chitosan Biofilms Using Sorbitol and Glycerol

Summary: Chitosan biofilms were prepared with and without plasticizer (glycerol and sorbitol). The physical and mechanical properties of chitosan biofilms with and without plasticizer were evaluated. Chitosan was obtained from shrimp wastes and characterized. The film forming solution (FFS) was obtained through chitosan dissolution and drying. The solution had its pH adjusted to 6.0 and oven dried (40 °C, 24 h) with forced air circulation. Chitosan biofilms without plasticizer showed a tensile strength about 36% higher than biofilms produced with plasticizer. On the other hand, biofilms with plasticizer presented superior values of elongation. The permeability of the water vapor and color presented significant difference (p < 0.05) between all biofilms. Chitosan/plasticizer biofilms showed higher values of water vapor permeability in relation to chitosan biofilms without plasticizer.     

Chemical and mineralogical characterization on glazes of ceramics from Coimbra (Portugal) from the sixteenth to nineteenth centuries

Chemical, mineralogical and textural characterizations were performed on glazed pieces prepared in laboratory as well as on faiences fragments collected from the existing remains in “Santa Clara-a-Velha” monastery (Coimbra, Portugal). The chemical investigation was carried out using micro X-ray fluorescence (μ-EDXRF) and wavelength dispersive X-ray fluorescence (WDXRF); the mineralogical results using X-ray diffraction (XRD) and the textural profile was obtained by scanning electron microscopy coupled with an energy dispersive spectroscopy system (SEM-EDS). Attention has been drawn to the glaze mineralogical changes during the firing temperature process, where three different types of glazes were submitted to three different firing temperatures (800 °C, 900 °C and 1,000 °C). Under these conditions, it is possible to relate the mineralogical content of the fragments to their firing temperature. Furthermore, we focused our purposes on identifying the technological aspects of the ceramic production in Coimbra, such as the raw materials, manufacture techniques and firing temperature adopted for the glaze. The latter aspect is highly dependent on the ceramic materials. In the framework of a more general project, this survey has as premise the recognition of a pattern, which is thought to be exclusively typical from the region of Coimbra. The perspective developed in the present work is towards reliable archaeometric criteria, which can be used to characterise scientifically the ceramics from Coimbra.     

The interaction of the antitoxin DM43 with a snake venom metalloproteinase analyzed by mass spectrometry and surface plasmon resonance

DM43 is a circulating dimeric antitoxin isolated from Didelphis aurita, a South American marsupial naturally immune to snake envenomation. This endogenous inhibitor binds non-covalently to jararhagin, the main hemorrhagic metalloproteinase from Bothrops jararaca snake venom, and efficiently neutralizes its toxicity. The aim of this study was to apply mass spectrometry (MS) and surface plasmon resonance (SPR) to improve the molecular characterization of this heterocomplex. The stoichiometry of the interaction was confirmed by nanoelectrospray ionization-quadrupole-time-of-flight MS; from native solution conditions, the complex showed a molecular mass of ~94 kDa, indicating that one molecule of jararhagin (50 kDa) interacts with one monomer of DM43 (43 kDa). Although readily observed in solution, the dimeric structure of the inhibitor was barely preserved in the gas phase. This result suggests that, in contrast to the toxin-antitoxin complex, hydrophobic interactions are the primary driving force for the inhibitor dimerization. For the real-time interaction analysis, the toxin was captured on a sensor chip derivatized with the anti-jararhagin monoclonal antibody MAJar 2. The sensorgrams obtained after successive injections of DM43 in a concentration series were globally fitted to a simple bimolecular interaction, yielding the following kinetic rates for the DM43/jararhagin interaction: k(a) = 3.54 ± 0.03 × 10(4) M(-1) s(-1) and k(d) = 1.16 ± 0.07 × 10(-5) s(-1), resulting in an equilibrium dissociation constant (K(D) ) of 0.33 ± 0.06 nM. Taken together, MS and SPR results show that DM43 binds to its target toxin with high affinity and constitute the first accurate quantitative study on the extent of the interaction between a natural inhibitor and a metalloproteinase toxin, with unequivocal implications for the use of this kind of molecule as template for the rational development of novel antivenom therapies.