Sex-linked differentiation between incipient species of Anopheles gambiae

Emerging species within the primary malaria vector Anopheles gambiae show different ecological preferences and significant prezygotic reproductive isolation. They are defined by fixed sequence differences in X-linked rDNA, but most previous studies have failed to detect large and significant differentiation between these taxa elsewhere in the genome, except at two other loci on the X chromosome near the rDNA locus. Hypothesizing that this pericentromeric region of the X chromosome may be accumulating differences faster than other regions of the genome, we explored the pattern and extent of differentiation between A. gambiae incipient species and a sibling species, A. arabiensis, from Burkina Faso, West Africa, at 17 microsatellite loci spanning the X chromosome. Interspecific differentiation was large and significant across the entire X chromosome. Among A. gambiae incipient species, we found some of the highest levels of differentiation recorded in a large region including eight independent loci near the centromere of the X chromosome. Outside of this region, no significant differentiation was detected. This pattern suggests that selection is playing a role in the emergence of A. gambiae incipient species. This process, associated with efficient exploitation of anthropogenic modifications to the environment, has public health implications as it fosters the spread of malaria transmission both spatially and temporally.     

Mathematical modelling of interwound DNA supercoils

Small loops of DNA are affected by a variety of enzymes which remove turns of twist relative to the underlying double-helical structure. The molecule adopts a complex three-dimensional shape known as a supercoil in order to relieve the resulting internal stresses. This article describes an approach to modelling the overall shape of the supercoiled structure using elastic rod theory, which leads to simple expressions for predicting the shape of the structure. Predictions on the number of crossings in the balanced ply and the length of the end loops are compared to data in the literature and show reasonable agreement. The effect of the charged phosphate groups along the backbone of the DNA on the resulting supercoiled shape are also examined, and it is shown that this shape is very sensitive to the ionic concentration of the solution.     

Oleic acid uptake and binding by rat adipocytes define dual pathways for cellular fatty acid uptake

Oleic acid (OA) uptake by rat adipocytes and the proportions of intracellular unesterified [3H]OA and its 3H-labeled esters were determined over 300 s. Uptake was linear for 20;-30 s, with rapid esterification indicating entry into normal metabolic pathways. Initial rates of OA uptake and its binding to plasma membranes were studied over a spectrum of oleic acid:bovine serum albumin (BSA) ratios, and expressed as functions of unbound OA concentrations calculated with both the 1971 OA:BSA association constants of Spector, Fletcher, and Ashbrook and more recent constants (e.g., the 1993 constants of Richieri, Anel, and Kleinfeld), which generate concentrations 10- to 100-fold lower. In either case, uptake was the sum of saturable and linear processes, with > or =90% occurring via the saturable pathway when the OA:BSA molar ratio was within the physiologic range (0.5;-3.0). Within this range, rate constants for saturable transmembrane influx (k(s)), calculated from both sets of constants, were similar (2.9 s(-1)) and were 10- to 30-fold faster than those for nonsaturable uptake (k(ns) = 0.26;-0.10 s(-1), t1/2 = 2.7;-6.6 s, based on the constants of Spector et al. and Richieri et al., respectively). The rate of oleic acid flip-flop into rat adipocytes (k(ff) = 0.16 +/- 0.02 s(-1), t1/2 = 4.3 +/- 0.5 s), computed from published data, was similar to k(ns). Thus, OA uptake occurs by both a saturable mechanism and passive flip-flop. This conclusion is independent of the OA:BSA association constants used to analyze the experimental measurements.     

Crystal Structure of Cytomegalovirus IE1 Protein Reveals Targeting of TRIM Family Member PML via Coiled-Coil Interactions

PML nuclear bodies (PML-NBs) are enigmatic structures of the cell nucleus that act as key mediators of intrinsic immunity against viral pathogens. PML itself is a member of the E3-ligase TRIM family of proteins that regulates a variety of innate immune signaling pathways. Consequently, viruses have evolved effector proteins to modify PML-NBs; however, little is known concerning structure-function relationships of viral antagonists. The herpesvirus human cytomegalovirus (HCMV) expresses the abundant immediate-early protein IE1 that colocalizes with PML-NBs and induces their dispersal, which correlates with the antagonization of NB-mediated intrinsic immunity. Here, we delineate the molecular basis for this antagonization by presenting the first crystal structure for the evolutionary conserved primate cytomegalovirus IE1 proteins. We show that IE1 consists of a globular core (IE1_CORE) flanked by intrinsically disordered regions. The 2.3 Å crystal structure of IE1_CORE displays an all α-helical, femur-shaped fold, which lacks overall fold similarity with known protein structures, but shares secondary structure features recently observed in the coiled-coil domain of TRIM proteins. Yeast two-hybrid and coimmunoprecipitation experiments demonstrate that IE1_CORE binds efficiently to the TRIM family member PML, and is able to induce PML deSUMOylation. Intriguingly, this results in the release of NB-associated proteins into the nucleoplasm, but not of PML itself. Importantly, we show that PML deSUMOylation by IE1_CORE is sufficient to antagonize PML-NB-instituted intrinsic immunity. Moreover, co-immunoprecipitation experiments demonstrate that IE1_CORE binds via the coiled-coil domain to PML and also interacts with TRIM5α We propose that IE1_CORE sequesters PML and possibly other TRIM family members via structural mimicry using an extended binding surface formed by the coiled-coil region. This mode of interaction might render the antagonizing activity less susceptible to mutational escape.     

尿毒症皮肤瘙痒患者采取腹膜透析与血液透析治疗的效果探究

目的：探究尿毒症皮肤瘙瘁患者采取腹膜透析与血液透析治疗的临床效果,并为该病的临床治疗提供经验积累。方法：选取我院肾内科于2005年1月-2012年12月收治的52例尿毒症皮肤瘙痒患者,利用随机数字表法进行分组,分别设为研究组和对照组。其中对照组实施血液透析治疗,而研究组开展腹膜透析治疗。记录两组在治疗前和治疗后第8周末血生化客观指标及皮肤瘙痒程度,并做好对比。结果：两组在治疗前的皮肤瘙痒评分、β2-MG、PTH、p3,BUN、SCr值差异无统计学意义（P〉0．05）;治疗后,研究组皮肤瘙瘁评分为（3．4±0．8）分,对照组为（5．8±0．9）分,差异有统计学意义（P〈0．05）。治疗后,研究组β2-MG、PTH及Ps．均低于对照组,差异有统计学意义（P〈0．05）。结论：尿毒症皮肤瘙痒患者的主要致敏因子为大中分子,采取腹膜透析能够有效清除大分子物质,进而达到瘙痒程度的有效改善。     

Computational Tool for Ensemble Averaging of Single-Molecule Data

Molecular motors couple chemical transitions to conformational changes that perform mechanical work in a wide variety of biological processes. Disruption of this coupling can lead to diseases, and therefore there is a need to accurately measure mechanochemical coupling in motors in both health and disease. Optical tweezers with nanometer spatial and millisecond temporal resolution have provided valuable insights into these processes. However, fluctuations due to Brownian motion can make it difficult to precisely resolve these conformational changes. One powerful analysis technique that has improved our ability to accurately measure mechanochemical coupling in motor proteins is ensemble averaging of individual trajectories. Here, we present a user-friendly computational tool, Software for Precise Analysis of Single Molecules (SPASM), for generating ensemble averages of single-molecule data. This tool utilizes several conceptual advances, including optimized procedures for identifying single-molecule interactions and the implementation of a change-point algorithm, to more precisely resolve molecular transitions. Using both simulated and experimental data, we demonstrate that these advances allow for accurate determination of the mechanics and kinetics of the myosin working stroke with a smaller set of data. Importantly, we provide our open-source MATLAB-based program with a graphical user interface that enables others to readily apply these advances to the analysis of their own data.     

重组人MASP2蛋白在大肠杆菌中的表达和纯化

目的:获得酶原形式的重组人甘露聚糖结合凝集素相关丝氨酸蛋白酶2(MASP2)。方法:在大肠杆菌中诱导表达重组人MASP2全长蛋白,包涵体裂解后,经复性、透析、浓缩、考马斯亮蓝染色、SDS-PAGE及Western印迹,鉴定纯化结果及酶活性。结果:复性后的MASP2蛋白经考马斯亮蓝染色未见杂带。自激活实验表明,当MASP2浓度在1μmool/L以下时,无论在4℃还是37℃,都能较稳定地保持酶原形式;蛋白浓度为3.5μmool/L时只能在4℃保持稳定,37℃发生自激活;蛋白浓度达到12μmool/L后,在4℃时已不能稳定存在。结论:获得了较纯的重组人MASP2蛋白,且具有自激活活性。