Characterization of phosphotyrosine binding motifs in the cytoplasmic domain of platelet/endothelial cell adhesion molecule-1 (PECAM-1) that are required for the cellular association and activation of the protein-tyrosine phosphatase, SHP-2

Recent studies have shown that the Src homology-2 (SH2) domain-containing protein-tyrosine phosphatase, SHP-2, associates with the cytoplasmic domain of PECAM-1 as it becomes tyrosine-phosphorylated during platelet aggregation: a process that can be mimicked in part by small synthetic phosphopeptides corresponding to the cytoplasmic domain of PECAM-1 encompassing tyrosine residues Tyr-663 or Tyr-686. To further examine the molecular requirements for PECAM-1/SHP-2 interactions, we generated human embryonic kidney (HEK)-293 cell lines that stably expressed mutant forms of PECAM-1 harboring tyrosine to phenylalanine (Tyr --> Phe) mutations in the cytoplasmic domain. Y663F and Y686F forms of PECAM-1 were tyrosine-phosphorylated to a somewhat lesser extent than wild-type PECAM-1, and a doubly substituted Y663,686F form of PECAM-1 failed to become tyrosine-phosphorylated, suggesting that the PECAM-1 cytoplasmic domain tyrosine residues 596, 636 and 701 do not serve as substrates for cellular kinases. Interestingly, SHP-2 binding was lost when either Tyr-663 or Tyr-686 were changed to phenylalanine, indicating that both residues are required for SHP-2/PECAM-1 association. Although PECAM-1 phosphopeptides NSDVQpY663TEVQV and DTETVpY686SEVRK stimulated the catalytic activity of the phosphatase to a similar extent, surface plasmon resonance studies revealed that the Tyr-663-containing peptide had approximately 10-fold higher affinity for SHP-2 than did the Tyr-686 peptide. Finally, peptido-precipitation analysis showed that the NH2-terminal SH2 domain of SHP-2 reacted preferentially with the Tyr-663 PECAM-1 phosphopeptide, while the Tyr-686 phosphopeptide associated only with the COOH-terminal SH2 domain of the phosphatase. Together, these data provide a molecular model for PECAM-1/SHP-2 interactions that may shed light on the downstream events that follow PECAM-1-mediated interactions of vascular cells.     

Influence of the Electron Deficient Co‐Monomer on the Optoelectronic Properties and Photovoltaic Performance of Dithienogermole‐based Co‐Polymers

A series of donor–acceptor (D–A) conjugated polymers utilizing 4,4‐bis(2‐ethylhexyl)‐4H‐germolo[3,2‐b:4,5‐b′]dithiophene ( DTG ) as the electron rich unit and three electron withdrawing units of varying strength, namely 2‐octyl‐2H‐benzo[d][1,2,3]triazole ( BTz ), 5,6‐difluorobenzo[c][1,2,5]thiadiazole ( DFBT ) and [1,2,5]thiadiazolo[3,4‐c]pyridine ( PT ) are reported. It is demonstrated how the choice of the acceptor unit ( BTz , DFBT , PT ) influences the relative positions of the energy levels, the intramolecular transition energy (ICT), the optical band gap (E_g^opt), and the structural conformation of the DTG ‐based co‐polymers. Moreover, the photovoltaic performance of poly[(4,4‐bis(2‐ethylhexyl)‐4H‐germolo[3,2‐b:4,5‐b′]dithiophen‐2‐yl)‐([1,2,5]thiadiazolo[3,4‐c]pyridine)] ( PDTG‐PT ), poly[(4,4‐bis(2‐ethylhexyl)‐4H‐germolo[3,2‐b:4,5‐b′]dithiophen‐2‐yl)‐(2‐octyl‐2H‐benzo[d][1,2,3]triazole)] ( PDTG‐BTz ), and poly[(4,4‐bis(2‐ethylhexyl)‐4H‐germolo[3,2‐b:4,5‐b′]dithiophen‐2‐yl)‐(5,6‐difluorobenzo[c][1,2,5]thiadiazole)] ( PDTG‐DFBT ) is studied in blends with [6,6]‐phenyl‐C₇₀‐butyric acid methyl ester ( PC₇₀BM ). The highest power conversion efficiency (PCE) is obtained by PDTG‐PT (5.2%) in normal architecture. The PCE of PDTG‐PT is further improved to 6.6% when the device architecture is modified from normal to inverted. Therefore, PDTG‐PT is an ideal candidate for application in tandem solar cells configuration due to its high efficiency at very low band gaps (E_g^opt = 1.32 eV). Finally, the 6.6% PCE is the highest reported for all the co‐polymers containing bridged bithiophenes with 5‐member fused rings in the central core and possessing an E_g^opt below 1.4 eV.     

谱分解技术在营尔凹陷长沙岭地区薄储层预测中的应用

谱分解技术就是通过对地震道进行特定的数学变换,形成相应的地震数据体(调谐体和共频体),通过调谐体和共频体的处理解释实现对特定地质目标的地质解释。本文针对营尔凹陷长沙岭构造带下沟组上段砂岩储层特点,采用谱分解薄层识别技术进行储层预测。实际应用时,利用沿层调谐体,确定了薄砂层调谐频率范围;利用共频体对薄层进行检测,预测了砂泥岩互层发育的三角洲、扇三角洲前缘砂体分布范围,预测结果与实际钻探情况较为吻合。     

多方法联合识别河道技术在南八仙地区的应用

本文以柴达木盆地北缘南八仙构造北斜坡为研究对象,在充分了解目标区地质和地球物理特征的基础上,采用地震属性、谱分解、Sobel相干、能量比相干和普通相干及可视化等系列技术,对该区N21层河道砂体分布规律进行研究,同时对各种方法的特点和效果进行了分析和对比。研究结果表明,仙北斜波河道砂体发育,并沿东南向西北方向展布,是该区的岩性圈闭远景区。     

Photofabrication of biofiber‐based polymer matrix composites

The novel development of a photofabrication process of biofiber composites, based on oil palm empty fruit bunch fibers, is reported. The process consists of the following steps: (1) the preparation by a wet process of nonwoven mat of biofiber, either alone or in combination with glass and nylon; (2) drying the mat; (3) preparation of photocurable resin matrix, consisting of vinyl ester and photoinitiator; (4) impregnation of the mat by photocurable resin; and (5) irradiation of the impregnated mat by UV radiation to effect the cure of the composite. The nonwoven mat was formed in a “headbox” into which was poured a slurry of fibers. A wet mat was formed by after dewatering of the slurry. Biofiber, glass, and nylon fibers were mixed in different proportions. A “mixture experimental design” was used to generate experimental compositions of the reinforcing fibers and to model dependency of the response variables on the components through mathematical relationships. These relationships were meant to (1) determine the effect of composition of the reinforcing fibers on the physical and mechanical properties, (2) predict the response for any unknown composition of fibers, and (3) determine the optimum values of any identified properties. Because the product was characterized by multiple responses, simultaneous maximization of all properties was not feasible. The product must be considered in the definition of the trade‐off or compromise of properties to obtain overall satisfactory performance. Such an optimization was carried out and the results are reported. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1493–1499, 2005     

Dough aeration and rheology: Part 3. Effect of the presence of gas bubbles in bread dough on measured bulk rheology and work input rate

The effects of dough aeration on measured bulk rheology of dough were investigated by preparing doughs with various gas contents and assessing their rheology under large deformation biaxial extension using the SMS Dough Inflation System. Doughs were mixed to various gas contents using a laboratory‐scale mixer, the Tweedy 1, at various mixer headspace pressures. In order to consider the effect of oxidation processes, doughs were mixed in air, in nitrogen and in a controlled oxygen‐nitrogen atmosphere in which the partial pressure of oxygen was kept constant. In the latter two cases a flow rate of gas through the mixer was maintained, while the doughs mixed in air had a static headspace. Dough aeration was quantified using density measurements. The dough rheology tests were performed under two different modes: constant volumetric air flow rate; and constant strain rate at two levels, 0.1 and 0.05 s⁻¹. Analysis of the stress–strain data of an inflating dough bubble using an exponential model enabled the strain hardening index, failure strain and failure stress to be determined. The strain hardening index, failure strain and failure stress decreased with gas content, indicating that gas bubbles in dough disrupt the integrity of dough structure. The faster strain rate tended to give higher values of all parameters and to be more discriminating, while testing at a constant volumetric air flow rate gave lower values. Doughs mixed under a constant partial pressure of oxygen resulted in the strain hardening index being minimally affected by the gas content, although failure strain and failure stress decreased with increasing gas content in the dough. The flow of gas through the mixer appeared to affect dough aeration and rheology, and the rate of work input was found to increase with increasing mixer headspace pressures. These suggest that dough aeration not only affects the rheology of static dough through the physical presence of gas bubbles following mixing, it also affects the development of its rheological properties within the mixer, through the physical presence of the bubbles affecting the rate of work input that develops the doughs, and also through the turnover of air that supplies oxygen to facilitate this development. Copyright © 2005 Society of Chemical Industry     

Thermal degradation and flammability of P/Si polysilsesquioxane epoxy nanocomposites

A thermal stable epoxy nanocomposite prepared from the 4,4′‐diglycidylether bisphenol A (DGEBA) and the P/Si ladder‐like polysilsesquioxane (PSSQ). The activation energies of thermal degradation were calculated by Kissinger's and Ozawa's methods. The higher ladder‐like PSSQ content not only increase the oligomer content but also generate the steric hindrance. Which steric hindrance influence the epoxy/amine curing reaction of the modified epoxy system was more than the pristine DGEBA epoxy system. The P‐Si synergistic effect on the thermal stability of the nanocomposites was discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Separation of squalene from palm fatty acid distillate using adsorption chromatography

A method to separate squalene from palm fatty acid distillate (PFAD) using neutralization‐hydrolysis‐neutralization before employing adsorption column chromatography was developed. Extraneous matters, especially free fatty acids (83.8%) and acylglycerols (12.7%), were first neutralized and removed before being subjected to hydrolysis by using commercially available, immobilized Candida antartica lipase, at 65 °C for 8 h. Neutralization followed by hydrolysis and repeated neutralization successfully concentrated squalene from an initial amount of 3.76% to 27.5%. Oil extracted from neutralized‐hydrolyzed‐neutralized PFAD was then passed through a Diaion HP‐20 column using reverse‐phase adsorption chromatography. Squalene was desorbed by hexane, with a recovery of 93%.