Multivariate curve resolution combined with estimation by cosine similarity mapping of analytical data

We developed a multivariate curve resolution (MCR) calculation combined with the mapping of cosine similarity (cos-s) for estimating multiple mixture spectra of chemicals. The cos-s map was obtained by calculating the similarities of the variation of the signal intensities at each scanning parameter, such as the wavelength. The cos-s map was utilized for the initial estimation of the spectra of pure chemicals and also for the restriction of the iterative least-squares calculation of the MCR. These calculations were performed without arbitrary parameters by introducing soft clustering to the cos-s map. The chemically meaningful initial estimation could prevent the convergence at an incorrect local minimum, which frequently happens for the wrong initial estimation of spectra far away from the real answer. Herein, we demonstrated the robustness of this calculation method by applying it for UV/Vis spectra and XRD patterns of multiple unknown chemical mixtures, whose shapes were totally different (broad overlapped peaks and multiple complicated peaks). Pure spectra/patterns were recovered as >84% consistency with the reference spectra, and <6% accuracy of the concentration ratios was demonstrated.

Sodium cationization can disrupt the intramolecular hydrogen bond that mediates the sunscreen activity of oxybenzone

A key decay pathway by which organic sunscreen molecules dissipate harmful UV energy involves excited-state hydrogen atom transfer between proximal enol and keto functional groups. Structural modifications of this molecular architecture have the potential to block ultrafast decay processes, and hence promote direct excited-state molecular dissociation, profoundly affecting the efficiency of an organic sunscreen. Herein, we investigate the binding of alkali metal cations to a prototype organic sunscreen molecule, oxybenzone, using IR characterization. Mass-selective IR action spectroscopy was conducted at the free electron laser for infrared experiments, FELIX (600-1800 cm-1), on complexes of Na+, K+ and Rb+ bound to oxybenzone. The IR spectra reveal that K+ and Rb+ adopt binding positions away from the key OH intermolecular hydrogen bond, while the smaller Na+ cation binds directly between the keto and enol oxygens, thus breaking the intramolecular hydrogen bond. UV laser photodissociation spectroscopy was also performed on the series of complexes, with the Na+ complex displaying a distinctive electronic spectrum compared to those of K+ and Rb+, in line with the IR spectroscopy results. TD-DFT calculations reveal that the origin of the changes in the electronic spectra can be linked to rupture of the intramolecular bond in the sodium cationized complex. The implications of our results for the performance of sunscreens in mixtures and environments with high concentrations of metal cations are discussed.

Novel insights into wound age estimation: combined with "up, no change, or down" system and cosine similarity in python environment

Wound age estimation is a complex, multifactorial issue. It is considered to have great practical significance that combining multi-biomarkers and multi-methods for injury time estimation. We optimized our earlier "up, no change, or down" model by adding data on the expression levels of mRNAs encoding ABHD2, MAD2L2, and ARID5A, and we converted the relative quantitative expression levels of seven genes into a vector rather than a color model. We used Python to derive the cosine similarity (CS) between a test set and the vector matrix; the highest similarity most accurately reflected the injury time. For the optimized model, the internal and external verifications were approximately 0.71 and 0.66, respectively. The good double-blinded results indicated that the model was stable and reliable. In summary, we used a vector matrix and cosine similarities derived by Python to mine the levels of genes expressed in contused skeletal muscle. We are the first to combine several biomarkers and methods for wound age estimation.

Recent applications of chemometrics in one- and two-dimensional chromatography

The proliferation of increasingly more sophisticated analytical separation systems, often incorporating increasingly more powerful detection techniques, such as high-resolution mass spectrometry, causes an urgent need for highly efficient data-analysis and optimization strategies. This is especially true for comprehensive two-dimensional chromatography applied to the separation of very complex samples. In this contribution, the requirement for chemometric tools is explained and the latest developments in approaches for (pre-)processing and analyzing data arising from one- and two-dimensional chromatography systems are reviewed. The final part of this review focuses on the application of chemometrics for method development and optimization.