Characterization of milk fatty acids based on genetic and herd parameters

The objective of this study was to characterize the fatty acids (FA) in milk based on genetic and herd parameters to investigate the origin of the different FA in milk. Milk samples of 1912 Dutch Holstein-Friesian cows were analysed for 39 different FA including odd and branched-chain fatty acids. The proportion of variation caused by genetic and herd effects was calculated. In addition, genetic and herd correlations among the fatty acids were estimated and a clustering technique was used to visualise these correlations. The results indicated that in Dutch milk C12:0 is not completely synthesised de novo but also partly blood derived. It was suggested that C20:0 in milk is formed from the action of elongase enzymes on C18:0 and that the odd-chain FA C5:0-C13:0 and a part of C15:0 and C17:0 are synthesised de novo while the other part of C15:0 and C17:0 is blood derived. Furthermore, this work gives an overview of the opportunities to change the concentration of individual FA both by breeding and feeding. It is clearly shown that the extent to which the individual FA can be changed varies greatly and is dependent on the origin of the different FA in milk

Fokken voor hogere kaasproductie : niet voer maar met name fokkerij beïnvloedt eiwitsamenstelling in melk

De hoeveelheid melkeiwit per lactatie per koe is meer dan verdubbeld: van 148 kilo in 1960 tot 330 kilo in 2009. Er is echter weinig kennis over de samenstelling van het melkeiwit en de mogelijkheden om deze met behulp van fokkerij te verbeteren. Fokken op het aandeel caseïnes in de melk blijkt haalbaar en dat is lucratief voor de kaasproductie

Structural Studies on Flavin Reductase PheA2 Reveal Binding of NAD in an Unusual Folded Conformation and Support Novel Mechanism of Action

The catabolism of toxic phenols in the thermophilic organism Bacillus thermoglucosidasius A7 is initiated by a two-component enzyme system. The smaller flavin reductase PheA2 component catalyzes the NADH-dependent reduction of free FAD according to a ping-pong bisubstrate-biproduct mechanism. The reduced FAD is then used by the larger oxygenase component PheA1 to hydroxylate phenols to the corresponding catechols. We have determined the x-ray structure of PheA2 containing a bound FAD cofactor (2.2 Angstrom), which is the first structure of a member of this flavin reductase family. We have also determined the x-ray structure of reduced holo-PheA2 in complex with oxidized NAD (2.1 Angstrom). PheA2 is a single domain homodimeric protein with each FAD-containing subunit being organized around a six-stranded beta-sheet and a capping alpha-helix. The tightly bound FAD prosthetic group (K-d=10 nM) binds near the dimer interface, and the re face of the FAD isoalloxazine ring is fully exposed to solvent. The addition of NADH to crystalline PheA2 reduced the flavin cofactor, and the NAD product was bound in a wide solvent-accessible groove adopting an unusual folded conformation with ring stacking. This is the first observation of an enzyme that is very likely to react with a folded compact pyridine nucleotide. The PheA2 crystallographic models strongly suggest that reactive exogenous FAD substrate binds in the NADH cleft after release of NAD product. Nanoflow electrospray mass spectrometry data indeed showed that PheA2 is able to bind one FAD cofactor and one FAD substrate. In conclusion, the structural data provide evidence that PheA2 contains a dual binding cleft for NADH and FAD substrate, which alternate during catalysis

Real-time monitoring of enzymatic DNA hydrolysis by electrospray ionization mass spectrometry

A fast and direct method for the monitoring of enzymatic DNA hydrolysis was developed using electrospray ionization mass spectrometry. We incorporated the use of a robotic chip-based electrospray ionization source for increased reproducibility and throughput. The mass spectrometry method allows the detection of DNA fragments and intact non-covalent protein–DNA complexes in a single experiment. We used the method to monitor in real-time single-stranded (ss) DNA hydrolysis by colicin E9 DNase and to characterize transient non-covalent E9 DNase–DNA complexes present during the hydrolysis reaction. The mass spectra showed that E9 DNase interacts with ssDNA in the absence of a divalent metal ion, but is strictly dependent on Ni(2+) or Co(2+) for ssDNA hydrolysis. We demonstrated that the sequence selectivity of E9 DNase is dependent on the ratio protein:ssDNA or the ssDNA concentration and that only 3′-hydroxy and 5′-phosphate termini are produced. It was also shown that the homologous E7 DNase is reactive with Zn(2+) as transition metal ion and that this DNase displays a different sequence selectivity. The method described is of general use to analyze the reactivity and specificity of nucleases

Modeling of mode-locking in a laser with spatially separate gain media

We present a novel laser mode-locking scheme and discuss its unusual properties and feasibility using a theoretical model. A large set of single-frequency continuous-wave lasers oscillate by amplification in spatially separated gain media. They are mutually phase-locked by nonlinear feedback from a common saturable absorber. As a result, ultra short pulses are generated. The new scheme offers three significant benefits: the light that is amplified in each medium is continuous wave, thereby avoiding issues related to group velocity dispersion and nonlinear effects that can perturb the pulse shape. The set of frequencies on which the laser oscillates, and therefore the pulse repetition rate, is controlled by the geometry of resonator-internal optical elements, not by the cavity length. Finally, the bandwidth of the laser can be controlled by switching gain modules on and off. This scheme offers a route to mode-locked lasers with high average output power, repetition rates that can be scaled into the THz range, and a bandwidth that can be dynamically controlled. The approach is particularly suited for implementation using semiconductor diode laser arrays.Comment: 13 pages, 5 figures, submitted to Optics Expres

Primary Proton Spectrum of Cosmic Rays measured with Single Hadrons

The flux of cosmic-ray induced single hadrons near sea level has been measured with the large hadron calorimeter of the KASCADE experiment. The measurement corroborates former results obtained with detectors of smaller size if the enlarged veto of the 304 m^2 calorimeter surface is encounted for. The program CORSIKA/QGSJET is used to compute the cosmic-ray flux above the atmosphere. Between E_0=300 GeV and 1 PeV the primary proton spectrum can be described with a power law parametrized as dJ/dE_0=(0.15+-0.03)*E_0^{-2.78+-0.03} m^-2 s^-1 sr^-1 TeV^-1. In the TeV region the proton flux compares well with the results from recent measurements of direct experiments.Comment: 13 pages, accepted by Astrophysical Journa

Melkvet met meerwaarde

Fokken op melkvet richt zich vooralsnog alleen op de hoeveelheid vet. Onderzoekers van Wageningen Universiteit tonen aan dat niet alleen de hoeveelheid melkvet, maar ook de melkvetsamenstelling met behulp van fokkerij verbeterd kan worde

Large scale cosmic-ray anisotropy with KASCADE

The results of an analysis of the large scale anisotropy of cosmic rays in the PeV range are presented. The Rayleigh formalism is applied to the right ascension distribution of extensive air showers measured by the KASCADE experiment.The data set contains about 10^8 extensive air showers in the energy range from 0.7 to 6 PeV. No hints for anisotropy are visible in the right ascension distributions in this energy range. This accounts for all showers as well as for subsets containing showers induced by predominantly light respectively heavy primary particles. Upper flux limits for Rayleigh amplitudes are determined to be between 10^-3 at 0.7 PeV and 10^-2 at 6 PeV primary energy.Comment: accepted by The Astrophysical Journa

Coulomb-assisted braiding of Majorana fermions in a Josephson junction array

We show how to exchange (braid) Majorana fermions in a network of superconducting nanowires by control over Coulomb interactions rather than tunneling. Even though Majorana fermions are charge-neutral quasiparticles (equal to their own antiparticle), they have an effective long-range interaction through the even-odd electron number dependence of the superconducting ground state. The flux through a split Josephson junction controls this interaction via the ratio of Josephson and charging energies, with exponential sensitivity. By switching the interaction on and off in neighboring segments of a Josephson junction array, the non-Abelian braiding statistics can be realized without the need to control tunnel couplings by gate electrodes. This is a solution to the problem how to operate on topological qubits when gate voltages are screened by the superconductor