Molecules
July 2021
The quality of foods has led researchers to use various analytical methods to determine the amounts of principal food constituents; some of them are the NMR techniques with a multivariate statistical analysis (NMR-MSA). The present work introduces a set of NMR-MSA novelties. First, the use of a double pulsed-field-gradient echo (DPFGE) experiment with a refocusing band-selective uniform response pure-phase selective pulse for the selective excitation of a 5-10-ppm range of wine samples reveals novel broad H resonances.
View Article and Find Full Text PDFThe present work describes the development and validation of a first report including several non-invasive NMR schemes to identify parameters as local chemical environments, homo- and heteronuclear site-specific spin correlations, diffusion coefficient-dependent polydispersity indexes and quantification of identified peptide entities that composes a commercial human Dialyzable Leucocyte Extract (DLE), Transferon, an oral liquid formulation of low-molecular-weight peptides. The above parameters were useful indicators to verify reproducibility, consistency and homogeneity among the DLE batches manufactured at Good Manufacturing Practice (GMP) facilities and for batch-releasing purposes in a quality control laboratory. The results showed that peptide identity of the DLE is represented with both high reproducible one-dimensional proton spectra and diffusion coefficient distributions that predicts in turn a weight-average molecular weight of around 6.
View Article and Find Full Text PDFThe oenological industry has benefited from the use of Nuclear Magnetic Resonance (H-NMR) spectroscopy in combination with Multivariate Statistical Analysis (MSA) as a foodomics tool for retrieving discriminant features related to geographical origins, grape varieties, and further quality controls. Said omics methods have gained such attention that Intergovernmental Organizations and Control Agencies are currently recommending their massive use amongst countries as quality compliances for tracking standard and degradation parameters, fermentation products, polyphenols, amino acids, geographical origins, appellations d'origine contrôlée and type of monovarietal strains in wines. This study presents, for the first time, a H-NMR/MSA profiling of industrial Mexican wines, finding excellent statistical features to discriminate between oenological regions and grape varieties with supervised Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA).
View Article and Find Full Text PDFFood Chem
January 2021
Present work comprises the use of different solid-state Nuclear Magnetic Resonance strategies for characterizing structural and motional aspects of the peptide matrix that compose a set of four lyophilized Mexican cheese aqueous soluble extracts, each with a controlled ripening. Heteronuclear dipolar coupling modulation schemes allowed to characterize local mobility and structural homogeneity of cheeses' peptide segments in the solid-state as a function of ripening. Results suggest that ripened samples with certain local flexibility but important structural homogeneity present efficient microbial inhibition against tested bacterial strains, whilst high local rigidity of peptides within ripened cheese soluble fractions could partially explain the observed lack of antimicrobial activity.
View Article and Find Full Text PDFBackground: The deterioration of the skin accentuates over time, affecting its aesthetic appearance. This is characterized by the weakening of the mechanisms involved in the regeneration and repair of the dermal matrix. Consequently, the skin losses elasticity and smoothness resulting in the formation of wrinkles.
View Article and Find Full Text PDFhas been traditionally used by indigenous and socioeconomically disadvantaged people to treat infectious and parasitic diseases, including amoebiasis. The goal of this study was to assess the effect of a crude methanolic extract, an alkaloid extract, and aporphine alkaloids from leaves of on the viability of trophozoite cultures and to identify the mechanism of action. Different concentrations of the extracts and alkaloids purpureine (1: ), 3-hydroxyglaucine (2: ), norpurpureine (3: ) glaziovine (4: ), and oxopurpureine (5: ) were added to the cultures, and dead parasites were counted after 24 h using a tetrazolium dye reduction assay and analyzed by flow cytometry.
View Article and Find Full Text PDFIdentity is a critical quality attribute that must be determined before releasing batches of medicinal and dietary products. However, the identities of peptide-derived products composed of a large number of diverse molecules is challenging since most analytical techniques cannot analyze multiple molecules simultaneously. Here, we proposed the determination of the weight-average molecular weight () and polydispersity index (PDI) by mass spectrometry for control quality for the batch release of complex products, namely, glatiramer acetate (Copaxone), collagen hydrolysate (Colagenart), and a human dialyzable leucocyte extract (Transferon).
View Article and Find Full Text PDFCollagen hydrolysates are dietary supplements used for nutritional and medical purposes. They are complex mixtures of low-molecular-weight peptides obtained from the enzymatic hydrolysis of collagen, which provide intrinsic batch-to-batch heterogeneity. In consequence, the quality of these products, which is related to the reproducibility of their mass distribution pattern, should be addressed.
View Article and Find Full Text PDFThe presence of water has been shown to deeply impact the stability and geometry of Zn complexes in solution. Evidence for tetra- and penta-coordinated species in a pyridylmethylamine-Zn(II) model complex is presented. Novel (1) H NMR tools such as T1 -filtered selective exchange spectroscopy and pure shifted gradient-encoded selective refocusing as well as classical 2D ((1) H-(1) H) exchange spectroscopy, diffusion-ordered spectroscopy and T1 ((1) H) measurements, in combination with density functional theory methods allow the full conformational dynamics of a pyridylmethylamine-Zn(II) complex to be revealed.
View Article and Find Full Text PDFProbing scalar couplings are essential for structural elucidation in molecular (bio)chemistry. While the measurement of JHH couplings is facilitated by SERF experiments, overcrowded signals represent a significant limitation. Here, a new band selective pure shift SERF allows access to δ(1)H and JHH with an ultrahigh spectral resolution.
View Article and Find Full Text PDFInsight into structural and motional features of the C-terminal part of the Human Centrin 2 in complex with the peptide P17-XPC was obtained by using complementary solid-state NMR methods. We demonstrate that the experimental conditions and procedures of sample crystallization determine the quality of solid-state NMR spectra and the internal mobility of the protein. Two-dimensional (2D) (13)C-(13)C and (15)N-(15)N correlation spectra reveal intra- and inter-residue dipolar connectivities and provide partial, site-specific assignments of (13)C and (15)N resonance signals.
View Article and Find Full Text PDFOverlapping (13)C or (15)N solid-state NMR spectra from crystallographically different forms of L-arginine hydrochloride can be separated by exploiting differential proton T(1) relaxation in conjunction with cross-polarization. Dipolar (13)C-(13)C and (15)N-(15)N two-dimensional correlation experiments reveal resonances belonging to crystallographically and magnetically inequivalent molecules.
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