半叶马尾藻多糖的提取和分析

采用热水浸提法提取半叶马尾藻多糖 [Sargassumhemiphyllum (Turner)C Ag polysaccharides ,SHP],并对其理化性质、提取率、含量、组成和性质进行了研究。SHP呈灰白色粉末状 ,溶于水 ,不溶于有机溶剂。碘 碘化钾反应呈阴性 ,说明提取物为非淀粉性多糖。提取率为 7 0 4 % ,总糖含量为 82 9%。紫外扫描结果表明多糖几乎不含核酸和蛋白质。红外光谱显示SHP主要为吡喃多糖 ,并显示多糖分子结构中存在 β 糖苷键。薄层层析结果提示该多糖可能为木聚糖。上述结果不仅说明该方法提取的物质是多糖 ,而且纯度好 ,提取效率高。     

The sorption heat pipe—a new device for thermal control and active cooling

The sorption heat pipe (SHP) is a new heat transfer device, which can be used as a sorption cooler or as a heat pipe. The SHP has a sorbent bed (adsorber/desorber and evaporator) at one end and a condenser+evaporator at the other end. This device is insensitive to some “g” acceleration and could be suggested for space and ground application. The most crucial feature of this device is that in different cases it can be used, for example, as a loop heat pipe, because they have the same evaporator and condenser, or as a SHP. The SHP can be used also as a cryogenic cooler. The SHP is convenient for cryogenic fluid storage, when the system does not work at low pressure and room temperature, and for use in the active cryogenic thermal control systems of spacecraft in orbit (cold plates for infrared observation of the Earth or space), or as an efficient electronic component cooling device.     

Lorentz Invariant Berry Phase for a Perturbed Relativistic Four Dimensional Harmonic Oscillator

We show the existence of Lorentz invariant Berry phases generated, in the Stueckelberg–Horwitz–Piron manifestly covariant quantum theory (SHP), by a perturbed four dimensional harmonic oscillator. These phases are associated with a fractional perturbation of the azimuthal symmetry of the oscillator. They are computed numerically by using time independent perturbation theory and the definition of the Berry phase generalized to the framework of SHP relativistic quantum theory.     

α-Al2O3单晶中Fe3+离子的电子顺磁共振

本文对α-Al₂O₃单晶体中Fe³⁺离子在室温下,X波段进行了电子顺磁共振研究,发现Fe³⁺离子实际上占据四种磁性不等价晶位。在同一氧离子层间的两种晶位上的Fe³⁺离子具有相同的自旋哈密顿参量,而不同氧离子层间的晶位上的Fe³⁺离子具有不同的自旋哈密顿参量,两种自旋哈密顿参量为:(1)g_‖=2.001,g_⊥=2.003,D=1679 关键词：     

Magnetic anisotropy and exchange interactions in Li-Al ferrites

The mechanism of exchange interactions in Li-Al ferrites is examined along with the nature of the magnetic crystallographic anisotropy. Calculation from a modified statistical model and another from Wolf's model may be used with observed curves for the temperature dependence of the magnetization and the first magnetic crystalline anisotropy constant to obtain values for the exchange integrals and the spin-Hamiltonian parameters SHP for Fe³⁺. It is shown that the SHP are substantially influenced by the exchange interactions, and the concentration relationships cannot be explained within the framework of the ionic crystalline-field theory.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 54–57, November, 1982.     

Electron Paramagnetic Resonance,Optical Spectra and DC Conductivity Studies of Vanadyl Doped Bi2O3 · BaO · B2O3 Glasses

Glasses with composition xBi₂O₃ ·(0.30 - x)BaO · 0.70B₂O₃ have been prepared in the range (0.00 ≤ x ≤ 0.15) containing 2.0 mol% of V₂O₅. Electron paramagnetic resonance (EPR), optical transmission and absorption spectra and DC conductivity of these glasses have been studied. The spin Hamiltonian parameters (SHP) of VO²⁺ ions, dipolar hyperfine coupling parameter P, Fermi contact interaction parameter K, and molecular orbital coefficients (α² and γ²) have been calculated. The SHP arc related with the theoretical optical basicity. A_th. The position of the absorption edge and the values of the optical band gap have also been reported. The effect of addition of Bi₂O₃ on the DC conductivity has also been studied.     

铬离子与酪氨酸作用的光谱研究

在pH 5.6的0.1mol/LN-2-羟乙基哌嗪-N1-2-乙磺酸(Hepes)及室温条件下,用荧光光度计进行了Cr3+对酪氨酸(Tyr)的滴定.结果表明Cr(Ⅲ)与Tyr形成1∶1的配合物.再用不同比例的[EDTA]/[Cr3+]系列溶液分别滴定Tyr,由EDTA与Tyr的竞争结合,间接求得Cr(Ⅲ)与Tyr的结合...     

Type II c-Met inhibitors: molecular insight into crucial interactions for effective inhibition

The c-Met tyrosine kinase plays an important role in human cancers. Preclinical studies demonstrated that c-Met is over-expressed, mutated and amplified in a variety of human tumor types and design of more potent c-Met inhibitors is a priority. In this study, 14 molecular dynamics simulations of potent type II c-Met inhibitors were run to resolve the critical interactions responsible for high affinity of ligands towards c-Met considering the essential flexibility of protein–ligand interactions. Residues Phe1223 and Tyr1159, involved in pi-pi interactions were recognized as the most effective residues in the ligand binding in terms of binding free energies. Hydrogen bond interaction with Met1160 was also found necessary for effective type II ligand binding to c-Met.

Graphic abstract

     

REDAN: relative entropy-based dynamical allosteric network model

ABSTRACT

Protein allostery is ubiquitous phenomena that are important for cellular signalling processes. Despite extensive methodology development, a quantitative model is still needed to accurately measure protein allosteric response upon external perturbation. Here, we introduced the relative entropy concept from information theory as a quantitative metric to develop a method for measurement of the population shift with regard to protein structure during allosteric transition. This method is referred to as relative entropy-based dynamical allosteric network (REDAN) model. Using this method, protein allostery could be evaluated at three mutually dependent structural levels: allosteric residues, allosteric pathways, and allosteric communities. All three levels are carried out using rigorous searching algorithms based on relative entropy. Application of the REDAN model on the second PDZ domain (PDZ2) in the human PTP1E protein provided metric-based insight into its allostery upon peptide binding.     

Identification of tyrosine in the presence of tryptophan using Cd-enriched colloidal CdS nanoparticles: A fluorescence spectroscopic study

A simpler identification method of tyrosine in the presence of tryptophan using CdS nanoparticles by conventional spectroscopic technique is proposed. Effect of both sulfide-enriched CdS as well as Cd²⁺-enriched CdS on tryptophan is investigated through absorption and emission spectroscopy. Quenching of tryptophan emission obeyed Stern-Volmer relation and was found to be independent of temperature, indicating a possible static quenching. The time-resolved fluorescence decay of tryptophan was minimally affected by sulfide-enriched CdS as well as Cd²⁺-enriched CdS nanoparticles, suggesting quenching to be static. In the presence of Cd²⁺-enriched CdS nanoparticles, the emission of tryptophan in phosphate buffer shows a typical spectral broadening along with a long wavelength increase in fluorescence emission. Additionally, spectra followed a typical isoemissive point at 440 nm when tryptophan alone was there. Similarly, isoemissive point at 340 nm was observed in the case of tyrosine. However, a further red shift of isoemissive point (470 nm) in the mixture of both tyrosine and tryptophan was observed. This observation might make Cd²⁺-enriched CdS nanoparticles useful for using as marker for tyrosine in the presence of tyrptophan.     

Physical limits on computation by assemblies of allosteric proteins

Assemblies of allosteric proteins are the principle information processing devices in biology. Using the Ca2+-sensitive cardiac regulatory assembly as a paradigm for Brownian computation, I examine how system complexity and system resetting impose physical limits on computation. Nearest-neighbor-limited interactions among assembly components constrain the topology of the system's macrostate free energy landscape and produce degenerate transition probabilities. As a result, signaling fidelity and deactivation kinetics cannot be simultaneously optimized. This imposes an upper limit on the rate of information processing by assemblies of allosteric proteins that couple to a single ligand type.     

二阶导数荧光分光光度法同时测定色氨酸和酷氨酸

本文描述了用二阶导数荧光光度法同时测定色氨酸和酪氨酸。在 p H 7.4的条件下 ,用 2 2 1nm作为激发波长 ,记录色氨酸和酪氨酸的发射光谱 ,并进行二阶导数处理。色氨酸在 318nm处 ,酪氨酸在 2 83nm处 ,二阶导数峰高与浓度成线性关系。色氨酸工作曲线的线性回归方程为 c =0 .0 0 0 7H - 0 .0 0 4,r =0 .996 4,线性范围为 0 .0 0 4到 0 .2 0 0μg . m L- 1 。酪氨酸工作曲线的线性回归方程为 c =0 .0 0 12 H -0 .0 0 40 ,r=0 .9971。线性范围为 0 .0 0 2到 0 .2 5 0 μg· m L- 1 。实验了 p H、温度和干扰离子对测定的影响 ,测定了苹果中的色氨酸和酪氨酸的含量 ,回收率分别为 (92 .0～ 10 4.0 ) %和 (98.70～ 10 2 .0 ) % ,相对标准偏差分别为 3.5 %和 2 .8%。     

Nonequilibrium dynamic mechanism for allosteric effect

Allosteric regulation is often viewed as thermodynamic in nature. However, protein internal motions during an enzymatic reaction cycle can slow the hoping processes over numerous potential barriers. We propose that regulating molecules may function by modifying the nonequilibrium protein dynamics. The theory predicts that an enzyme under the new mechanism has a different temperature dependence, waiting time distribution of the turnover cycle, and dynamic fluctuation patterns with and without an effector. Experimental tests of the theory are proposed.     

Insulin signaling inhibits the 5-HT2C receptor in choroid plexus via MAP kinase

Background

G protein-coupled receptors (GPCRs) interact with heterotrimeric GTP-binding proteins (G proteins) to modulate acute changes in intracellular messenger levels and ion channel activity. In contrast, long-term changes in cellular growth, proliferation and differentiation are often mediated by tyrosine kinase receptors and certain GPCRs by activation of mitogen-activated protein (MAP) kinases. Complex interactions occur between these signaling pathways, but the specific mechanisms of such regulatory events are not well-understood. In particular it is not clear whether GPCRs are modulated by tyrosine kinase receptor-MAP kinase pathways.

Results

Here we describe tyrosine kinase receptor regulation of a GPCR via MAP kinase. Insulin reduced the activity of the 5-HT_2C receptor in choroid plexus cells which was blocked by the MAP kinase kinase (MEK) inhibitor, PD 098059. We demonstrate that the inhibitory effect of insulin and insulin-like growth factor type 1 (IGF-1) on the 5-HT_2C receptor is dependent on tyrosine kinase, RAS and MAP kinase. The effect may be receptor-specific: insulin had no effect on another GPCR that shares the same G protein signaling pathway as the 5-HT_2C receptor. This effect is also direct: activated MAP kinase mimicked the effect of insulin, and removing a putative MAP kinase site from the 5-HT_2C receptor abolished the effect of insulin.

Conclusion

These results show that insulin signaling can inhibit 5-HT_2C receptor activity and suggest that MAP kinase may play a direct role in regulating the function of a specific GPCR.     

酪氨酸的太赫兹频谱研究

利用太赫兹时域光谱技术探测了室温条件下的酪氨酸样品的频谱响应, 获得了酪氨酸的太赫兹频谱。实验结果表明,酪氨酸在太赫兹波段存在特征频谱响应,可以用来探测分子的结构和振动情况。在获得的太赫兹频谱中,首次观察到0.23和2.46 THz附近存在的吸收峰。用HF方法和DFT计算了酪氨酸单分子和酪氨酸二聚体的太赫兹频谱,对理论计算和实验测量的偏离进行了详细的分析。在0.23 THz处的吸收峰,初步标定为氢键连接的2个酪氨酸分子的面外摇摆振动。     

Exact classical and quantum solutions for a covariant oscillator near the black hole horizon in Stueckelberg-Horwitz-Piron theory

We found exact solutions for canonical classical and quantum dynamics for general relativity in Horwitz general covariance theory. These solutions can be obtained by solving the generalized geodesic equation and Schrödinger-Stueckelberg-Horwitz-Piron (SHP) wave equation for a simple harmonic oscillator in the background of a two dimensional dilaton black hole spacetime metric. We proved the existence of an orthonormal basis of eigenfunctions for generalized wave equation. This basis functions form an orthogonal and normalized (orthonormal) basis for an appropriate Hilbert space. The energy spectrum has a mixed spectrum with one conserved momentum p according to a quantum number n. To find the ground state energy we used a variational method with appropriate boundary conditions. A set of mode decomposed wave functions and calculated for the Stueckelberg-Schrodinger equation on a general five dimensional blackhole spacetime in Hamilton gauge.     

荧光光谱法研究羟基自由基诱导的酪氨酸氧化

二酪氨酸是酪氨酸氧化的标志性产物.为研究影响羟基自由基诱导酪氨酸氧化的因素,采用同步荧光光谱结合二维相关技术研究羟基自由基诱导酪氨酸氧化的反应过程.结果表明:pH变化时,二酪氨酸的荧光峰位、峰强发生变化.在羟基自由基诱导酪氨酸氧化体系中,随着酪氨酸浓度的增加,二酪氨酸产量升高;随着过氧化氧浓度的增加,二酪氨酸产量降低;...     

Artificial allosteric control of maltose binding protein

We demonstrate the allosteric control of a protein based on mechanical tension. When substrate binding is accompanied by a significant change of conformation of the protein, a mechanical tension favoring one or the other conformation will alter the binding affinity for the substrate. We have constructed a chimera where the two lobes of the maltose-binding protein are covalently coupled to the ends of a DNA oligomer. The mechanical tension on the protein is controlled externally by exploiting the difference in stiffness between single stranded and double stranded DNA. We report that the binding affinity of the protein for its substrates is significantly altered by the tension.     

Regulatory role of kinases and phosphatases on the internalisation of caveolae in HepG2 cells

The caveolar cycle is thought to be regulated by synchronised function of kinases and phosphatases. Using ocadaic acid--a serine/threonine protein phosphatase inhibitor--and an inhibitor of tyrosine phosphatase (sodium orthovanadate) we have followed the internalisation of caveolae. Since albumin binding to its receptor (gp60) can induce pinching off of caveolae from the plasma membrane, we also used this physiological ligand to induce the internalisation. Our confocal microscopic results show that both ocadaic acid and vanadate treatments have significantly decreased caveolin (caveolin-1 and -2) labelling on the cell surface, while the cytoplasmic labelling became much stronger. Quite often large, strongly labelled "granules" appear at the perinuclear region. Very strong caveolin labelling was detected along the actin-cytoskeleton suggesting that caveolae might move along these filaments. Our electron microscopic results also show an intensive caveolae pinching off from the plasma membrane. After ocadaic acid and vanadate treatments the number of surface connected vesicles (caveolae) decreases. At the same time, large multivesicular bodies (termed caveosomes) appear in the perinuclear area of the cytoplasm. By immunoprecipitation and Western blot analysis we detect an increased tyrosine phosphorylation of a approximately 29kDa protein in ocadaic acid and vanadate treated samples. This protein was identified as caveolin-2. No significant change in the tyrosine phosphorylation of caveolin-1 was found. From these data we can conclude that caveolae internalisation is regulated by phosphorylation of caveolin-2.