Structural and functional studies of differentially O‐glycosylated analogs of a thrombin inhibitory peptide – variegin

Variegin is a 32‐amino acid long thrombin inhibitory peptide isolated from the salivary gland extract of tropical bont tick Amblyomma variegatum. It was identified to be O‐glycosylated on its Thr‐14 side chain, and this glycosylated form was 14‐fold more potent than that of its non‐glycosylated form. However, as the identity of this glycosylation remained elusive, the mechanistic details underlying its functional impact are not yet known. In this report, we synthesized four different O‐glycosylated analogs of variegin bearing physiologically relevant sugars on its Thr‐14. Functional characterization of these analogs by enzyme inhibitory kinetics and surface plasmon resonance methods showed that all the synthesized glycopeptides are strong thrombin inhibitors. Structural studies by macromolecular docking identified that the sugar moiety of these peptides can potentially mediate favorable interactions with amino acids at the base of thrombin's autolysis loop. This report, for the first time, describes the impact of differential glycosylation on the function of a thrombin inhibitory peptide and tries to provide structural insights into the relevance of peptide glycosylation in thrombin inhibition. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.     

Lactate modeling and its application to endurance training

1. 1. In this short review, previous studies regarding the modeling of lactate (La) response to exercise and its application to endurance training have been summarized.

2. 2. Additionally the result of a recent study by the present authors are shown.

3. 3. Several models for La response to step and ramp exercise are already proposed and deductions derived from them are used for practical purposes such as the prediction of race performance in middle-and long-distance runners as well as for construction of their training regimens.

4. 4. Only a limited number of models however have tried to quantify whole body La kinetics to exercise in humans concomitantly with describing physiological mechanisms underlying the observed phenomenon.

5. 5. In a recent study described further in this paper a 2 compartment model was used for the purpose of clarifying the current “La production vs degradation” controversy during La adaptation to training.

6. 6. It was determined from this investigation that the La metabolic clearance rate during recovery is enhanced by the endurance training.

7. 7. This is in accordance with another recent observation of an increased La metabolic clearance rate at high absolute work rates and all relative work rates during exercise.

Scavenging Rhodamine B dye using moringa oleifera seed pod

Moringa oliferia seed pod was modified using orthophosphoric acid (H₃PO₄) and used as adsorbent for sequestering Rhodamine B (Rh-B) dye from aqueous solution. The acid-modified adsorbent (MOSPAC) was characterized using Scanning Electron microscopy (SEM), Fourier Transform Infra Red (FTIR), Energy Dispersive X-ray (EDX), pH point of zero charge (pH_pzc) and Boehm Titration (BT) techniques, respectively. Operational parameters such as contact time, initial dye concentration, adsorbent dosage, pH and solution temperature were studied in batch process. Optimum dye adsorption was observed at pH 3.01. Equilibrium adsorption data was tested data using four different isotherm models: Langmuir, Freundlich, Temkin and Dubinin-Radushkevich. Langmuir isotherm model fitted most with maximum monolayer adsorption capacity of 1250 mg g^–1. Pseudo-second-order kinetic model provided the best correlation for the experimental data. Thermodynamic study showed that the process is endothermic, spontaneous and feasible. MOSPAC is an effective adsorbent for the removal of RhB dye from aqueous solutions.     

Mercury contamination and stable isotopes reveal variability in foraging ecology of generalist California gulls

Environmental contaminants are a concern for animal health, but contaminant exposure can also be used as a tracer of foraging ecology. In particular, mercury (Hg) concentrations are highly variable among aquatic and terrestrial food webs as a result of habitat- and site-specific biogeochemical processes that produce the bioaccumulative form, methylmercury (MeHg). We used stable isotopes and total Hg (THg) concentrations of a generalist consumer, the California gull (Larus californicus), to examine foraging ecology and illustrate the utility of using Hg contamination as an ecological tracer under certain conditions. We identified four main foraging clusters of gulls during pre-breeding and breeding, using a traditional approach based on light stable isotopes. The foraging cluster with the highest δ¹⁵N and δ³⁴S values in gulls (cluster 4) had mean blood THg concentrations 614% (pre-breeding) and 250% (breeding) higher than gulls with the lowest isotope values (cluster 1). Using a traditional approach of stable-isotope mixing models, we showed that breeding birds with a higher proportion of garbage in their diet (cluster 2: 63–82% garbage) corresponded to lower THg concentrations and lower δ¹⁵N and δ³⁴S values. In contrast, gull clusters with higher THg concentrations, which were more enriched in ¹⁵N and ³⁴S isotopes, consumed a higher proportion of more natural, estuarine prey. δ³⁴S values, which change markedly across the terrestrial to marine habitat gradient, were positively correlated with blood THg concentrations in gulls. The linkage we observed between stable isotopes and THg concentrations suggests that Hg contamination can be used as an additional tool for understanding animal foraging across coastal habitat gradients.     

超高静压协同中温对凝结芽孢杆菌芽孢灭活动力学规律的研究

研究了超高静压协同中温对凝结芽孢杆菌芽孢在磷酸缓冲液和牛奶(经超高温灭菌)中灭活的动力学规律, 并对超高静压的升压过程及相应的灭活效果进行了研究。结果表明, 升压过程对凝结芽孢杆菌芽孢灭活的影响不能忽略, 且随压力增加这种效果越强, 最高使其下降1.77个数量级; 凝结芽孢杆菌芽孢在牛奶中比在磷酸缓冲液中有更高的抗性; 在3种拟合模型(线性、Weibull和Log-logistic模型)中, 线性模型不适合模拟这些存活曲线, 而Log-logistic模型能更好地模拟这些存活曲线, 其次是Weibull模型。     

Thymidine kinase isoenzymes in human acute monocytic leukemia

Summary Two thymidine kinase isoenzymes, TK 3 and TK 4, from mononuclear leucocytes from a patient with acute monocytic leukemia, were purified and characterized in regard to the molecular weights and kinetic properties.The molecular weights of TK 3 and TK 4 were 60 000 and 45 000, respectively. In the presence of 2 mM ATP, the molecular weight of TK 3 increased to 200 000, whereas the molecular weight of TK 4 was unchanged.Studies of the kinetic properties showed clear differences between TK 3 and TK 4. With thymidine as substrate, TK 3 showed biphasic kinetics with a K_m of 22 µM, and TK 4 showed Michaelis-Menten kinetics with a K_m of 0.33 µM With ATP as substrate, TK 3 showed Michaelis-Menten kinetics with a K_m of 100 µM, and TK 4 showed biphasic kinetics with a Km of 3.5 µM. With dTTP as inhibitor, TK 3 showed cooperative inhibition kinetics, and TK 4 showed non-cooperative competitive inhibition kinetics. The dTTP concentration at 50% inhibition was 75 µM for TK 3 but 380 µM for TK 4.Comparison of the molecular weights and the kinetic properties of TK 3 and TK 4 with the corresponding data previously obtained for TK 1 and TK 2 from normal human lymphocytes indicate the existence of four thymidine kinase isoenzymes in human leucocytes.     

Metrics from nonlinear dynamics adapted for characterizing the behavior of nonequilibrium enzymatic rate functions

Several metrics from nonlinear dynamics and statistical mechanics have been characterized on computer-generated number series with various signal-to-noise ratios, demonstrating their individual reliability as a function of sample size and their relationships to each other. The root mean square (RMS) evaluates amplitude, and the power spectral density (PSD) provides a visual display of the frequency spectrum; both measures have very high reliability even for an N as low as 50. The Fractal Dimension (D) is shown to converge rapidly and also to be reliable when N is as low as 50. These three measures (RMS, PSD, and D) have been applied to the complex kinetics of tyrosine hydroxylase time courses (50-point curves) at various BH4 concentrations (near physiological, but far from equilibrium levels). Recently developed measures of spectral entropy and the Liapunov Exponent, -lambda are also characterized.     

Effects of detergents on catalytic activity of human endometase/matrilysin 2, a putative cancer biomarker

Matrix metalloproteinases (MMPs) are a family of hydrolytic enzymes that play significant roles in development, morphogenesis, inflammation, and cancer invasion. Endometase (matrilysin 2 or MMP-26) is a putative early biomarker for human carcinomas. The effects of the ionic and nonionic detergents on catalytic activity of endometase were investigated. The hydrolytic activity of endometase was detergent concentration dependent, exhibiting a bell-shaped curve with its maximum activity near the critical micelle concentration (CMC) of nonionic detergents tested. The effect of Brij-35 on human gelatinase B (MMP-9), matrilysin (MMP-7), and membrane-type 1 MMP (MT1-MMP) was further explored. Their maximum catalysis was observed near the CMC of Brij-35 (∼ 90 μM). Their IC₅₀ values were above the CMC. The inhibition mechanism of MMP-7, MMP-9, and MT1-MMP by Brij-35 was a mixed type as determined by Dixon’s plot; however, the inhibition mechanism of endometase was noncompetitive with a K_i value of 240 μM. The catalytic activities of MMPs are influenced by detergents. Monomer of detergents may activate and stabilize MMPs to enhance catalysis, but micelle of detergents may sequester enzyme and block the substrate binding site to impede catalysis. Under physiological conditions, a lipid or membrane microenvironment may regulate enzymatic activity.