Protein hydrolysates are of great interest in the food industry due to their nutritional and functional properties, but their use often implies solubilization in water and therefore hamper the use of ...plant proteins with inherent low water solubility. Protein solubility in water can be modified by enzymatic hydrolysis, but during this process several collateral properties of the protein hydrolysates changes. It is therefore important to determine the end-point of the process and to monitor its development. In this feasibility study, we demonstrated the potential of different spectroscopic techniques (1H NMR and IR) coupled with chemometrics analysis in monitoring the hydrolysis of five different industrial grade plant proteins by the enzyme Alcalase. Logarithmic modeling of the PCA (Principal Component Analysis) scores confirmed that they can represent a measurement of the solubilized protein material released and resulted in kinetic parameters describing the suitability of protein sources as substrates for the hydrolysis. This way, we showed that a qualitative evaluation of the degree of hydrolysis is possible using fast at-line technologies and PCA.
Display omitted
•Rapid methods for evaluating solubilization of proteins during enzymatic hydrolysis•Demonstration of NMR and IR coupled with chemometrics as tools to monitor hydrolysis•Modeling of the PCA scores enabled determination of hydrolysis kinetics.•Qualitative as well as quantitative information were obtained during the hydrolysis.
Abstract
The complexation of Mg
II
with adenosine 5′‐triphosphate (ATP) is omnipresent in biochemical energy conversion, but is difficult to interrogate directly. Here we use the spin‐
β‐emitter
31
...Mg to study Mg
II
‐ATP complexation in 1‐ethyl‐3‐methylimidazolium acetate (EMIM‐Ac) solutions using β‐radiation‐detected nuclear magnetic resonance (β‐NMR). We demonstrate that (nuclear) spin‐polarized
31
Mg, following ion‐implantation from an accelerator beamline into EMIM‐Ac, binds to ATP within its radioactive lifetime before depolarizing. The evolution of the spectra with solute concentration indicates that the implanted
31
Mg initially bind to the solvent acetate anions, whereafter they undergo dynamic exchange and form either a mono‐ (
31
Mg‐ATP) or di‐nuclear (
31
MgMg‐ATP) complex. The chemical shift of
31
Mg‐ATP is observed up‐field of
31
MgMg‐ATP, in accord with quantum chemical calculations. These observations constitute a crucial advance towards using β‐NMR to probe chemistry and biochemistry in solution.
The general-purpose PreAmplifier-DIscriminator application-specific integrated circuit (ASIC) chip, PADI, was originally designed to be used as front-end electronics (FEE) for reading out the timing ...resistive plate chambers in the time-of-flight (TOF) wall of the compressed baryonic matter (CBM) experiment of the future Facility for Antiproton and Ion Research (FAIR) facility in Darmstadt, Germany. Here, we present the last models of this 0.18-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> CMOS technology-PADI-X, PADI-XI, and PADI-XII-as well as their key features and test results. While the PADI series was originally developed for high-energy physics experiments carried out at ground facilities, it turned out that PADI is also suitable for space experiments and PADI-X was selected for one sensor of the European Space Agency, JUpiter ICy moons Explore (JUICE) mission. Currently, the most recent model of the series, PADI-XII, has been tuned for space applications and the prototype batch is currently under production.
In this work we present a systematic, theoretical investigation of the sup.13 C NMR chemical shifts for several mono-, di- and trisaccharides in the solid state. The chemical shifts have been ...calculated using density functional theory (DFT) together with the gauge including the projector augmented wave (GIPAW) method as implemented in the CASTEP program. We studied the changes in the sup.13 C NMR chemical shifts in particular due to the formation of one or two glycosidic linkages and due to crystal water. The largest changes, up to 14 ppm, are observed between the mono- and disaccharides and typically for the glycosidic linkage atoms, but not in all cases. An analysis of the bond angles at the glycosidic linkage and the observed changes in chemical shifts displays no direct correlation between them. Somewhat smaller changes in the range of 2 to 5 ppm are observed when single crystal water molecules are close to some of the atoms. Relating the changes in the chemical shifts of the carbon atoms closest to the crystal water to the distance between them does, however, not lead to a simple relation between them.
Designed metal ion binding peptides offer a variety of applications in both basic science as model systems of more complex metalloproteins, and in biotechnology, e.g. in bioremediation of toxic metal ...ions, biomining or as artificial enzymes. In this work a peptide (HS: Ac-SCHGDQGSDCSI-NH2) has been specifically designed for binding of both Zn(II) and Hg(II), i.e. metal ions with different preferences in terms of coordination number, coordination geometry, and to some extent ligand composition. It is demonstrated that HS accommodates both metal ions, and the first coordination sphere, metal ion exchange between peptides, and speciation are characterized as a function of pH using UV-absorption-, synchrotron radiation CD-, (1)H-NMR-, and PAC-spectroscopy as well as potentiometry. Hg(II) binds to the peptide with very high affinity in a {HgS2} coordination geometry, bringing together the two cysteinates close to each end of the peptide in a loop structure. Despite the high affinity, Hg(II) is kinetically labile, exchanging between peptides on the subsecond timescale, as indicated by line broadening in (1)H-NMR. The Zn(II)-HS system displays more complex speciation, involving monomeric species with coordinating cysteinates, histidine, and a solvent water molecule, as well as HS-Zn(II)-HS complexes. In summary, the HS peptide displays conformational flexibility, contains many typical metal ion binding groups, and is able to accommodate metal ions with different structural and ligand preferences with high affinity. As such, the HS peptide may be a scaffold offering binding of a variety of metal ions, and potentially serve for metal ion sequestration in biotechnological applications.
► We elucidate the molecular structure of large-scale extracted barley and oat β-glucans. ► Mutant barley β-glucan has a unique oligomer block structure compared to normal barley. ► We model the ...β-glucan oligomer profiles from NMR spectroscopic data. ► Low solubility of barley β-glucans is an effect of a high number of DP3 oligomer blocks. ► Complex relations of wide-ranging β-glucan data is elucidated by multivariate data analysis.
Health effects of β-glucan are typically related to dose, size and viscosity without taking the specific molecular structure into account. High β-glucan mutant barley, mother barley and oat β-glucans were large-scale extracted by comparable protocols using hot water, enzyme assisted hydrolysis and ethanol precipitation leading to similar molecular masses (200–300kDa). Multivariate data analysis on all compositional, structural and functional features demonstrated that the main variance among the samples was primarily explained by block structural differences as determined by HPSEC–PAD. In particular the barley high β-glucan mutant proved to exhibit a unique block structure with DP3 and DP4 contributions of: 78.9% and 16.7% as compared to the barley mother (72.1% and 21.4%) and oat (66.1% and 29.1%). This unique block structure was further confirmed by the 1H NMR determination of the β-1,4 to β-1,3 linkage ratio. Low solubility of the barley samples was potentially an effect of substructures consisting of longer repetitive cellotriosyl sequences. FT-Raman and NMR spectroscopy were useful in measuring sample impurities of α-glucans and prediction of β-linkage characteristics.
The aim of this study was to investigate if molecular interactions between the weak base cinnarizine and lipolysis products were affecting the morphology of precipitated drug formed during in vitro ...lipolysis. In vitro lipolysis studies of a self-nanoemulsifying drug delivery system with or without cinnarizine were conducted. The digestion phases (aqueous phase and pellet phase) were separated by ultracentrifugation, and the pellet was isolated and lyophilized. The lyophilized pellets were examined by X-ray powder diffraction, 13C solid-state nuclear magnetic resonance (13C NMR), 1H liquid-state NMR (1H NMR) spectroscopy and differential scanning calorimetry (DSC). The 13C NMR data indicated that the carbonyl groups and aliphatic part of the lipids undergo structural changes when the pellet contains cinnarizine. The 1H NMR data suggests interactions occurring around the nitrogens on cinnarizine and the carboxylic group of fatty acids. DSC thermograms showed cinnarizine to be homogeneously incorporated into the lipids of the pellet, and no free amorphous cinnarizine was present. The three techniques 13C NMR, 1H NMR, and DSC complement each other and suggest interactions to occur between fatty acids and cinnarizine, which in turn favors amorphous precipitation.
Display omitted
► A branching enzyme was used to modify thermally partially opened starch granules. ► Highly branched, molecularly uniform and cross-linked granular starch was generated. ► A new ...concept for enzyme-assisted modification of compact polysaccharides is provided.
In this study a branching enzyme (BE, α-1,4→α-1,6 glycosyltransferase) was used to modify starch granules of different structures at high temperature and at extreme starch dry matter content (30–40%, w/v) to restrict temperature-induced swelling. As opposed to diluted systems, such conditions led to stabilization of the granular structure for low-phosphate starch types at the highest BE activity. Bright field/polarized light and scanning electron microscopy confirmed maintenance of granular structure. The product compared to the control had significantly increased degree of branching as identified by shorter branch-length of the α-1,4 chains assessed by chromatography and larger proportion of α-1,6 links to α-1,4 links as assessed by 1H nuclear magnetic resonance spectroscopy. Size exclusion chromatography demonstrated the presence of uniform molecules with smaller size. Further the polysaccharide product was 40% more soluble at 25°C than the corresponding heat treated control. Both of these observations were supported by 13C solid-state MAS NMR. Hence, significant chain transfer took place in the semi-solid state starch permitting conservation of the main granular organization in the final product. A hypothetic model is presented to account for the observed phenomenon.
The strength of this study is the general population-based setup in various Danish geographic areas with a high attendance rate, thereby minimizing the risk of selection bias. ...the results are ...quite generalizable. ...we chose to use relative cutoff points at an observed 25% enlargement of the calculated normal diameters. ...this study found that the coexistence of multiple aortic dilations is high.
PDF
