scholarly journals Characterization of Microbial Degradation Products of Steviol Glycosides

Molecules ◽  
2021 ◽  
Vol 26 (22) ◽  
pp. 6916
Author(s):  
Gert Steurs ◽  
Nico Moons ◽  
Luc Van Meervelt ◽  
Boudewijn Meesschaert ◽  
Wim Michel De Borggraeve
Keyword(s):  
Chemical Synthesis ◽  
Microbial Degradation ◽  
Degradation Products ◽  
Reduced Form ◽  
Steviol Glycosides ◽  
X Ray ◽  
Incubation Experiments ◽  
Tricyclic Ketone ◽  
Nmr Methods

Steviol glycosides were subjected to bacteria present in a soil sample collected from a Stevia plantation in Paraguay. During the incubation experiments, next to the aglycon steviol, steviol degradation products were also formed. X-ray analysis and NMR methods in combination with chemical synthesis and GIAO NMR calculations were used to fully characterize the structure of these compounds as a tricyclic ketone and the corresponding reduced form. They were nicknamed monicanone and monicanol. The latter has the (S)-configuration at the alcohol site.

Darstellung und Charakterisierung von Spezies der Zusammensetzung η5-C5H5Cr(NO)2SR (R = C6H5, C6F5, t–C4H9) und [η5-C5H5CrNO]2(ER)2 (E = O, S, Se, Te, R = Alkyl, Aryl); Röntgenstrukturanalysen von [η5-C5H5(NO)Cr(μ-SeC6H5)2Cr(NO)-η5-C5H5] und [η5-C5H5(NO)Cr(μ-Se-n-C4H9)(μ-OH)Cr(NO)-η5-C5H5] / Synthesis and Characterization of Species of Composition η5-C5H5Cr(NO)2SR (R = C6H5, C6F5, t-C4H9) and [η5-C5H5CrNO]2(ER)2 (E = O, S, Se, Te, R = Alkyl, Aryl); Röntgenstrukturanalysen von [η5-C5H5(NO)Cr(μ-SeC6H5)2Cr(NO)-η5-C5H5] and [η5-C5H5(NO)Cr(μ-Se-n-C4H9)(μ-OH)Cr(NO)-η5-C5H5]

1982 ◽  
Vol 37 (1) ◽  
pp. 13-23 ◽  
Author(s):  
Johannes Rott ◽  
Ernst Guggolz ◽  
Albert Rettenmeier ◽  
Manfred L. Ziegler
Keyword(s):  
Mass Spectra ◽  
Membered Ring ◽  
Molecular Structures ◽  
Binuclear Complexes ◽  
Alkyl Aryl ◽  
X Ray ◽  
H Nmr ◽  
Crystal And Molecular Structures ◽  
Nmr Methods

The title compounds have been synthesized and characterized by elemental analysis, IR and 1H NMR methods and mass spectra. The crystal and molecular structures of the binuclear complexes [η-C5H5(NO)Cr(μ-SeC6H5)2Cr(NO)-η5-C5H5] and [η5-C5H5(NO)Crμ-Se-n-C4H9)(μ-OH)Cr(NO)-μ5-C5H5] have been determined by X-ray structure analysis. The latter is shown to have a four-membered ring consisting of two chromium atoms, one selenium, and one oxygen atom.

Micro-analytical Evidence of Copper-Based Pigment and Fungal Contamination of Medieval Mural Paintings in Beram, Croatia

2019 ◽  
Vol 25 (6) ◽  
pp. 1471-1481
Author(s):  
Tea Zubin Ferri ◽  
Emina Pustijanac ◽  
Ines Kovačić ◽  
Josipa Bilić
Keyword(s):  
Degradation Products ◽  
Fungal Species ◽  
X Ray Diffraction ◽  
Fungal Contamination ◽  
X Ray ◽  
Painting Materials ◽  
Mural Paintings ◽  
The Church ◽  
Sem Analyses

AbstractThe aim of the present study was to map the painting materials, degradation processes, and biological features present on the mural painting in the church of St. Mary in Beram (Croatia) to study their possible interaction and produce information helping the preservation of this valuable painting. The research was conducted on micro samples of painting materials taken from different sites along the painting and the characterization of the present fungal species was carried out. The painting samples, together with observable patinas and degradation products, were studied by optical microscopy (OM), scanning electron microscopy, energy-dispersive spectroscopy (SEM/EDS), Fourier-Transform Infrared spectroscopy, and powder X-ray diffraction. Fungal diversity was studied using cultivation methods followed by OM and SEM analyses in addition to molecular analysis. The results contribute to the characterization of the original painting materials, successively added materials and occurred interventions, to the understanding of degradation progressions and fungal biotransformation processes. A mineral, cumengite, a copper-based pigment extremely rarely used in art, was found. Its occurrence together with barium sulfate, gypsum, and calcium oxalate possibly produced by microbiological activity was studied and information was added regarding the composition of painting materials in St. Mary church mural cycle.

scholarly journals bHLH–PAS Proteins: Their Structure and Intrinsic Disorder

2019 ◽  
Vol 20 (15) ◽  
pp. 3653 ◽  
Author(s):  
Marta Kolonko ◽  
Beata Greb-Markiewicz
Keyword(s):  
X Ray ◽  
Intrinsically Disordered ◽  
Helix Loop Helix ◽  
Knowledge Based ◽  
Current State ◽  
Conserved Domain ◽  
Living Organisms ◽  
Nmr Methods ◽  
And Function

The basic helix–loop–helix/Per-ARNT-SIM (bHLH–PAS) proteins are a class of transcriptional regulators, commonly occurring in living organisms and highly conserved among vertebrates and invertebrates. These proteins exhibit a relatively well-conserved domain structure: the bHLH domain located at the N-terminus, followed by PAS-A and PAS-B domains. In contrast, their C-terminal fragments present significant variability in their primary structure and are unique for individual proteins. C-termini were shown to be responsible for the specific modulation of protein action. In this review, we present the current state of knowledge, based on NMR and X-ray analysis, concerning the structural properties of bHLH–PAS proteins. It is worth noting that all determined structures comprise only selected domains (bHLH and/or PAS). At the same time, substantial parts of proteins, comprising their long C-termini, have not been structurally characterized to date. Interestingly, these regions appear to be intrinsically disordered (IDRs) and are still a challenge to research. We aim to emphasize the significance of IDRs for the flexibility and function of bHLH–PAS proteins. Finally, we propose modern NMR methods for the structural characterization of the IDRs of bHLH–PAS proteins.

scholarly journals Calibration and Characterization of a Reduced Form-Factor High Accuracy Three-Axis Teslameter

Electronics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 151
Author(s):  
Johann Cassar ◽  
Andrew Sammut ◽  
Nicholas Sammut ◽  
Marco Calvi ◽  
Zarko Mitrovic ◽  
...  
Keyword(s):  
Form Factor ◽  
Measurement Techniques ◽  
Calibration Procedure ◽  
Reduced Form ◽  
Hall Probe ◽  
X Ray ◽  
Temperature Offset ◽  
Paul Scherrer ◽  
Reference Fields

A new reduced form-factor three axes digital teslameter, based on the spinning current technique, has been developed. This instrument will be used to characterize the SwissFEL insertion devices at the Paul Scherrer Institute (PSI) for the ATHOS soft X-ray beamline. A detailed and standardized calibration procedure is critical to optimize the performance of this precision instrument. This paper presents the measurement techniques used for the corrective improvements implemented through non-linearity, temperature offset, temperature sensitivity compensation of the Hall probe and electronics temperature compensation. A detailed quantitative analysis of the reduction in errors on the application of each step of the calibration is presented. The percentage peak error reduction attained through calibration of the instrument for reference fields in the range of ±2 T is registered to drop from 1.94% down to 0.02%.

scholarly journals Characterization of two new degradation products of atorvastatin calcium formed upon treatment with strong acids

2019 ◽  
Vol 15 ◽  
pp. 2085-2091
Author(s):  
Jürgen Krauß ◽  
Monika Klimt ◽  
Markus Luber ◽  
Peter Mayer ◽  
Franz Bracher
Keyword(s):  
Degradation Products ◽  
Crystal Structure Analysis ◽  
Side Chain ◽  
The Novel ◽  
Isopropyl Group ◽  
X Ray ◽  
Atorvastatin Calcium ◽  
Acidic Conditions ◽  
Strong Acids

Atorvastatin calcium (Lipitor®, Sortis®) is a well-established cholesterol synthesis enzyme (CSE) inhibitor commonly used in the therapy of hypercholesterolemia. This drug is known to be sensitive to acid treatment, but only little data has been published on the structures of the degradation products. Here we report the identification of two novel degradation products of atorvastatin, which are formed only under drastic acidic conditions. While treatment with conc. sulfuric acid led to a loss of the carboxanilide residue (accompanied by an expectable lactonization/dehydration process in the side chain), treatment with conc. aqueous hydrochloric acid gave a complex, bridged molecule under C–C-bond formation of the lactone moiety with the pyrrole, migration of the isopropyl group and loss of the carboxanilide residue. The novel degradation products were characterized by NMR spectroscopy, HRMS data and X-ray crystal structure analysis.

scholarly journals Novel Non-Metal Cation (NMC) Pentaborate Salts of Some Amino Acids

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2790 ◽  
Author(s):  
Ümit Sızır ◽  
Ömer Yurdakul ◽  
Dursun Ali Köse ◽  
Fatih Akkurt
Keyword(s):  
Thermal Analysis ◽  
Amino Acids ◽  
Hydrogen Storage ◽  
Metal Cation ◽  
Degradation Products ◽  
Analysis Data ◽  
X Ray ◽  
Ft Ir ◽  
11B Nmr

Non-metal cation (NMC) pentaborate structures, in which some amino acids (valine, leucine, isoleucine, and threonine) were used as cations, were synthesized. The structural characterization of molecules was carried out by elemental analysis, FT-IR, mass, 11B-NMR, and thermal analysis (TGA/DTA) methods. The hydrogen storage capacity of molecules was also calculated by taking experimental results into consideration. The FT-IR spectra support the similarity of structures. The characteristic peaks attributable to pentaborate rings and amino acids were observed. When thermal analysis data were examined, it was observed that pentaborate salts gave similar degradation steps and degradation products. As a final degradation product of all thermal analysis experiments, a glassy form of B2O3 was observed. The valine pentaborate is the most thermally stable. Also, the amounts of hydrate water outside the coordination sphere of the compounds were determined by thermal analysis curves. The peaks of boric acid, triborate, and pentaborate structures were obtained in ppm with the 11B-NMR results of synthesized pentaborate compounds. With powder X-ray spectroscopy, all structures were found to be crystalline but not suitable for single-crystal X-ray analysis. The molecular cavities of the compounds detected by BET were found to be 3.286, 1.873, 2.309, and 1.860 g/cm3, respectively. A low number of molecular cavities can be interpreted in several existing hydrogen bonds in structures. The hydrogen storage capacities of the molecules were found to be in the range of 0.04 to 0.07% by mass.

Characterization of copper-based pigment preparation and alteration products

MRS Advances ◽  
2017 ◽  
Vol 2 (63) ◽  
pp. 3973-3981 ◽  
Author(s):  
Marcie B. Wiggins ◽  
Jocelyn Alcántara-García ◽  
Karl S. Booksh
Keyword(s):  
Photoelectron Spectroscopy ◽  
Degradation Products ◽  
Copper Acetate ◽  
Accelerated Aging ◽  
Organic Substrates ◽  
X Ray Diffraction ◽  
X Ray ◽  
Complex Interactions ◽  
Historical Methods

ABSTRACTCopper-based pigments are common in works of art that show signs of decay on green and blue areas and are frequently associated with the degradation of organic substrates and/or media (drying oils, cellulose, etc.). The exact causes of degradation remain unknown. This prompted us to study possible starting and degradation products of one especially reactive copper pigment, verdigris (copper acetate), as well as pigments of the same family (salt and soap greens). Preparation of pigments using historical methods was followed by spectroscopic and crystallographic characterization using Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Synthesis of verdigris and verdigris-like pigments resulted in a mixture of starting polymorphs of verdigris, including neutral and basic verdigris. With accelerated aging, pigments degraded to a polymorph of basic verdigris when not affected by organic media, whereas pigments on cellulosic substrates showed oxidized copper species. With this study, we are beginning to understand verdigris starting materials and highlight the complex interactions between pigments and substrates that influence pigment degradation pathways.

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