High-frequency earth rotation variations deduced from altimetry-based ocean tides

A model of diurnal and semi-diurnal variations in Earth rotation parameters (ERP) is constructed based on altimetry-measured tidal heights from a multi-mission empirical ocean tide solution. Barotropic currents contributing to relative angular momentum changes are estimated for nine major tides in a global inversion algorithm that solves the two-dimensional momentum equations on a regular 0.5^\circ grid with a heavily weighted continuity constraint. The influence of 19 minor tides is accounted for by linear admittance interpolation of ocean tidal angular momentum, although the assumption of smooth admittance variations with frequency appears to be a doubtful concept for semi-diurnal mass terms in particular. A validation of the newly derived model based on post-fit corrections to polar motion and universal time (\Delta UT1) from the analysis of Very Long Baseline Interferometry (VLBI) observations shows a variance reduction for semi-diurnal \Delta UT1 residuals that is significant at the 0.05 level with respect to the conventional ERP model. Improvements are also evident for the explicitly modeled K_1, Q_1, and K_2 tides in individual ERP components, but large residuals of more than 15 \upmu as remain at the principal lunar frequencies of O_1 and M_2. We attribute these shortcomings to uncertainties in the inverted relative angular momentum changes and, to a minor extent, to violation of mass conservation in the empirical ocean tide solution. Further dedicated hydrodynamic modeling efforts of these anomalous constituents are required to meet the accuracy standards of modern space geodesy

Eccentric exercise slows in vivo microvascular reactivity during brief contractions in human skeletal muscle

Unaccustomed exercise involving eccentric contractions results in muscle soreness and an overall decline in muscle function, however, little is known about the effects of eccentric exercise on microvascular reactivity in human skeletal muscle. Fourteen healthy men and women performed eccentric contractions of the dorsiflexor muscles in one leg, while the contralateral leg served as a control. At baseline, and 24 and 48 h after eccentric exercise, the following were acquired bilaterally in the tibialis anterior muscle: 1) transverse relaxation time (T2)-weighted magnetic resonance images to determine muscle cross-sectional area (mCSA) and T2; 2) blood oxygen level-dependent (BOLD) images during and following brief, maximal voluntary contractions (MVC) to monitor the hyperemic responses with participants positioned supine in a 3T magnet; 3) muscle strength; and 4) pain pressure threshold. Compared with the control leg, eccentric exercise resulted in soreness, decline in strength (∼20%), increased mCSA (∼7%), and prolonged T2 (∼7%) at 24 and 48 h ( P &lt; 0.05). The BOLD response to a brief MVC was altered 24 and 48 h after eccentric exercise, such that time-to-peak (∼35%, P &lt; 0.05) and time-to-half-recovery (∼23%, P &lt; 0.05) were prolonged. The altered contraction-induced hyperemic response suggests slowed microvascular reactivity and altered matching of O2 delivery to O2 utilization within muscle tissue showing signs of muscle damage. These changes in microvascular regulation after eccentric exercise may impede rapid adjustments in muscle blood flow at exercise onset and during activities involving brief bursts of muscle activation, which may impair O2 delivery and contribute to reduced muscle function after eccentric exercise. </jats:p

Optimization of recombinant laccase production by Yarrowia lipolytica in a medium containing glucose as carbon source with Taguchi method

Introduction:Laccases (EC 1.10.3.2; benzenediol: oxygen oxidoreductase) are copper-containing oxidases that use molecular oxygen to oxidize various aromatic and non-aromatic compounds. Laccase is applied in delignification of lignocellulosic compounds for production of bioethanol, bioremediation of industrial wastewaters especially textile, food industries, and making biosensors. Materials and methods: The Taguchi experimental design method was used for optimization of laccase production in recombinant strain Yarrowia lipolytica YL4. A L-16 Taguchi orthogonal array was used to optimize the carbon and nitrogen sources along with vitamin in four levels. Results: The results showed that glucose, ammonium chloride, yeast extract and thiamine have significant effects on the production of laccase, respectively. The laccase activity reached to 1.52 U/mL after optimization of medium which is 7.6-fold higher than un-optimized medium. Discussion and conclusion: According to the analysis of results, the Taguchi experimental design method is a successful approach to increase laccase and recombinant proteins production in Y. lipolytica

Biological coloration of flax fabrics with flavonoids using laccase from trametes hirsuta

Biological environmentally friendly concepts are emerging to replace chemical treatments of fabrics. In this work, a new process for the coloration of flax fabrics via enzymatic oxidation of natural flavonoids (morin, quercetin) has been developed. Laccase from Trametes hirsuta is able to react with flavonoids and polymerize them, resulting in a strongly colored polymeric solution which can be applied to the coloration of flax fabrics. Two methods were investigated: (i) the simultaneous enzymatic polymerization and coloration of fabrics and (ii) the polymerization of flavonoids with laccase, followed by a further coloration of the flax fabrics. Factors such as temperature, reaction time, presence of NaCl or the use of bleached or unbleached fabrics were evaluated in order to increase the color of the fabrics and the color fastness. The increase of temperature, the presence of salt and the use of unbleached fabrics allowed the final color to be improved. Colorized flax fabrics with oxidized quercetin solution showed a color fixation two times higher than the fabrics colorized with oxidized morin. Finally, the polymerization of flavonoids and their binding to fibers were verified using Fourier transform infrared spectroscopy (FT-IR). The results confirmed this environmentally friendly process as useful for the coloration of flax fabrics. A similar technique could also be extended to the treatment of other types of fabrics in textile processes

Engineering Yarrowia lipolytica to Produce Glycoproteins Homogeneously Modified with the Universal Man3GlcNAc2 N-Glycan Core

Yarrowia lipolytica is a dimorphic yeast that efficiently secretes various heterologous proteins and is classified as “generally recognized as safe.” Therefore, it is an attractive protein production host. However, yeasts modify glycoproteins with non-human high mannose-type N-glycans. These structures reduce the protein half-life in vivo and can be immunogenic in man. Here, we describe how we genetically engineered N-glycan biosynthesis in Yarrowia lipolytica so that it produces Man3GlcNAc2 structures on its glycoproteins. We obtained unprecedented levels of homogeneity of this glycanstructure. This is the ideal starting point for building human-like sugars. Disruption of the ALG3 gene resulted in modification of proteins mainly with Man5GlcNAc2 and GlcMan5GlcNAc2 glycans, and to a lesser extent with Glc2Man5GlcNAc2 glycans. To avoid underoccupancy of glycosylation sites, we concomitantly overexpressed ALG6. We also explored several approaches to remove the terminal glucose residues, which hamper further humanization of N-glycosylation; overexpression of the heterodimeric Apergillus niger glucosidase II proved to be the most effective approach. Finally, we overexpressed an α-1,2-mannosidase to obtain Man3GlcNAc2 structures, which are substrates for the synthesis of complex-type glycans. The final Yarrowia lipolytica strain produces proteins glycosylated with the trimannosyl core N-glycan (Man3GlcNAc2), which is the common core of all complex-type N-glycans. All these glycans can be constructed on the obtained trimannosyl N-glycan using either in vivo or in vitro modification with the appropriate glycosyltransferases. The results demonstrate the high potential of Yarrowia lipolytica to be developed as an efficient expression system for the production of glycoproteins with humanized glycans

Characterization of an Alkali- and Halide-Resistant Laccase Expressed in E. coli: CotA from <i>Bacillus clausii</i>

The limitations of fungal laccases at higher pH and salt concentrations have intensified the search for new extremophilic bacterial laccases. We report the cloning, expression, and characterization of the bacterial cotA from Bacillus clausii, a supposed alkalophilic ortholog of cotA from B. subtilis. Both laccases were expressed in E. coli strain BL21(DE3) and characterized fully in parallel for strict benchmarking. We report activity on ABTS, SGZ, DMP, caffeic acid, promazine, phenyl hydrazine, tannic acid, and bilirubin at variable pH. Whereas ABTS, promazine, and phenyl hydrazine activities vs. pH were similar, the activity of B. clausii cotA was shifted upwards by ~0.5-2 pH units for the simple phenolic substrates DMP, SGZ, and caffeic acid. This shift is not due to substrate affinity (K(M)) but to pH dependence of catalytic turnover: The k(cat) of B. clausii cotA was 1 s⁻¹ at pH 6 and 5 s⁻¹ at pH 8 in contrast to 6 s⁻¹ at pH 6 and 2 s⁻¹ at pH 8 for of B. subtilis cotA. Overall, k(cat)/K(M) was 10-fold higher for B. subtilis cotA at pH(opt). While both proteins were heat activated, activation increased with pH and was larger in cotA from B. clausii. NaCl inhibited activity at acidic pH, but not up to 500-700 mM NaCl in alkaline pH, a further advantage of the alkali regime in laccase applications. The B. clausii cotA had ~20 minutes half-life at 80°C, less than the ~50 minutes at 80°C for cotA from B. subtilis. While cotA from B. subtilis had optimal stability at pH~8, the cotA from B. clausii displayed higher combined salt- and alkali-resistance. This resistance is possibly caused by two substitutions (S427Q and V110E) that could repel anions to reduce anion-copper interactions at the expense of catalytic proficiency, a trade-off of potential relevance to laccase optimization