The Effects of Adding a Gel-Alike Curcuma longa L. Suspension as Color Agent on Some Quality and Sensory Properties of Yogurt

Color is an important characteristic of food products. This characteristic is related to consumer acceptability. To use the entire rhizome of Curcuma longa (CL) as a food colorant, a novel gel alike stable suspension (CLS) was previously developed using cellulose nanofibers (CNFs). Therefore, the present study was conducted to evaluate the CLS as a color additive on a stirred yogurt. Three concentrations of CLS were studied (0.1, 0.125, and 0.15 wt. %) and compared to yogurt without CLS. The obtained yogurts were characterized through the determination of pH, titratable acidity, syneresis, color and curcumin content after 1, 7, 14, and 21 days of storage. Additionally, rheological and sensory measurements were performed on the samples after one day of storage. Results show that the addition of CLS does not affect the pH and titratable acidity of the samples, but all the yogurts showed an increase in their syneresis during the storage time, showing a breakdown of the gel structure. Furthermore, the CLS suspension has the ability to impart a yellow color to yogurts, a characteristic that was stable during storage. Finally, the addition of 1 wt. % or 1.25 wt. % of CLS allows the development of a yogurt with adequate sensory perception.     

Results from the kaonic hydrogen X-ray measurement at DAFNE and outlook to future experiments

The $\overline{K}N$ system at rest plays a key role for the understanding of strong interaction of hadrons with strangeness involved. The experiment SIDDHARTA used X-ray spectroscopy of kaonic atoms to measure the strong interaction induced shift and width of the ground state. It was the first experiment on kaonic He3 and deuterium ever, kaonic hydrogen was measured with improved precision resulting in $\epsilon_{1s} = -283 \pm 36 \mbox{(stat)} \pm 6 \mbox{(syst)}$ eV and $\Gamma_{1s} = 541 \pm 89 \mbox{(stat)} \pm 22 \mbox{(syst)}$ eV. Additionally a scheme for an improved future experiment on kaonic deuterium is introduced in this contribution.     

Tuning the spin ground state in heterononanuclear nickel(II)-copper(II) cylinders with a triangular metallacyclophane core

Two new heterometallic Ni(II)(n)Cu(II)((9-n)) complexes [n = 1 (2) and 2 (3)] have been synthesized following a multicomponent self-assembly process from a n:(3 - n):2:6 stoichiometric mixture of Ni(2+), Cu(2+), L(6-), and [CuL'](2+), where L and L' are the bridging and blocking ligands 1,3,5-benzenetris(oxamate) and N,N,N',N',N'-pentamethyldiethylenetriamine, respectively. Complexes 2 and 3 possess a unique cyclindrical architecture formed by three oxamato-bridged trinuclear linear units connected through two 1,3,5-substituted benzenetris(amidate) bridges, giving a triangular metallacyclophane core. They behave as a ferromagnetically coupled trimer of two (2)/one (3) S = (1)/(2) Cu(II)(3) plus one (2)/two (3) S = 0 Ni(II)Cu(II)(2) linear units with overall S = 1 Ni(II)Cu(II)(8) (2) and S = (1)/(2) Ni(II)(2)Cu(II)(7) (3) ground states.     

Phosphine–Alkene Ligands as Mechanistic Probes in the Pauson–Khand Reaction

An alkyne tetracarbonyl dicobalt complex with a chelated phosphine–alkene ligand, in which the phosphorus atom and the alkene from the ligand are attached to the same cobalt atom has been prepared, isolated, and characterized by X‐ray crystallography. The complex serves as a mechanistic model for an intermediate of the Pauson–Khand (PK) reaction. Although the alkene fragment is located in an equatorial coordination site with an appropriate orientation, and, therefore, should undergo insertion, it failed to give the PK product upon either thermal or N‐methylmorpholine N‐oxide activation. However, a phosphine–alkene complex that contains a terminal alkene readily provided the corresponding PK product. We attribute this change in reactivity to the different ability of each olefin to undergo 1,2‐insertion. These results provide further insights into the factors that govern a crucial step in the PK reaction, the olefin insertion.     

Transformation of variables and the condition number in ridge estimation

Ridge estimation (RE) is an alternative method to ordinary least squares (OLS) estimation when collinearity is detected in a linear regression model. After applying RE, it is sensible to determine whether such collinearity has been mitigated. The condition number (CN) is a commonly applied measure to detect the presence of collinearity in econometric models, but to the best of our knowledge, it has not been extended to be applied after RE. In OLS estimation, Belsley et al. (Regression diagnostics: identifying influential data and sources of collinearity, Wiley, New York, 1980) established that the regressors must be of unit length and not centered to correctly calculate the CN. This paper reviews this requirement in the context of RE and presents an expression to calculate the CN in RE.     

Binding of a Diphosphorylated-ITAM peptide to spleen tyrosine kinase (Syk) induces distal conformational changes: A hydrogen exchange mass spectrometry study

Structural flexibility plays a crucial role in protein function. To assess whether specific structural changes are associated with the binding of an immunoreceptor tyrosine-based activation motif (ITAM) to the tandem Src homology-2 domains (tSH2) of the spleen tyrosine kinase [EC 2.7.7.112] (Syk), we used an approach based on protein hydrogen/deuterium exchange in the presence and absence of the diphosphorylated ITAM peptide. The protein deuterium uptake by the intact Syk protein was monitored in time by electrospray mass spectrometry, which revealed a dramatic relative decrease in deuterium uptake when the protein was bound to the ITAM peptide, suggesting an overall change in protein dynamics. Subsequently, the deuterium incorporation of individual segments of the protein was investigated using proteolysis and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) peptide mass-analysis, which revealed that several regions of Syk tSH2 are significantly more protected from exchange in the presence of the ITAM peptide. Four protected regions encompass the phosphotyrosine and hydrophobic binding sites on the SH2 domains, whereas two other protected regions are located in the inter-SH2 linker motif and do not make any direct contacts with the peptide. Interestingly, our data suggest that binding of the ITAM peptide to Syk tSH2 induces distal structural effects on the protein that stabilize the inter-SH2 linker region, possibly by raising the degree of helical structure upon binding.     

The influence of electron donor and electron acceptor groups on the electronic structure of the anti‐inflammatory tripeptide Cys‐Asn‐Ser

It has been discussed in the literature that electron delocalization along the peptide backbone and side chain modulates the physical and chemical features of peptides and proteins. The structure and properties of peptides are determined by their charge‐density distribution, such that the modification of its side chain plays an important role on its electronic structure and physicochemical properties. Research on Entamoeba histolytica soluble factors led to the identification of the pentapeptide Met‐Gln‐Cys‐Asn‐Ser, with anti‐inflammatory in vivo and in vitro effects. A synthetic pentapeptide, Met‐Pro‐Cys‐Asn‐Ser, maintained the same anti‐inflammatory actions in experimental assays. A previous theoretical study allowed proposing the Cys‐Asn‐Ser tripeptide (CNS tripeptide) as the pharmacophore group of both molecules. This theoretical hypothesis was recently confirmed experimentally. The objective of this work was to study the influence of the electron donor and electron withdrawing substituent groups on the electronic structure and physicochemical properties of the CNS tripeptide derivatives through a theoretical study at the density functional theory level of theory. Our results in deprotonation energies showed that the relative acidity of hydrogen atom (H2) of the serine‐amide group increases with the electron withdrawing groups. This result was confirmed by means of a study of bond order. The proton affinities illustrated that the electron donor groups favored the basicity of the amino group of the cysteine amino acid. Atomic charges, Frontier molecular orbitals (HOMO–LUMO), and electrostatic potential isosurface and its geometric parameters permitted to analyze the effect that provoked the electron donor and electron attractor groups on its electronic structure and physicochemical features and to identify some reactive sites that could be associated with the anti‐inflammatory activity of tripeptide CNS derivatives. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2398–2410, 2010