Active Transport of Membrane Components by Self-Organization of the Min Proteins

Heterogeneous distribution of components in the biological membrane is critical in the process of cell polarization. However, little is known about the mechanisms that can generate and maintain the heterogeneous distribution of the membrane components. Here, we report that the propagating wave patterns of the bacterial Min proteins can impose steric pressure on the membrane, resulting in transport and directional accumulation of the component in the membrane. Therefore, the membrane component waves represent transport of the component in the membrane that is caused by the steric pressure gradient induced by the differential levels of binding and dissociation of the Min proteins in the propagating waves on the membrane surface. The diffusivity, majorly influenced by the membrane anchor of the component, and the repulsed ability, majorly influenced by the steric property of the membrane component, determine the differential spatial distribution of the membrane component. Thus, transportation of the membrane component by the Min proteins follows a simple physical principle, which resembles a linear peristaltic pumping process, to selectively segregate and maintain heterogeneous distribution of materials in the membrane.

Chemically modified porcine hemoglobins and their biological properties

Hemoglobin cross-linked with small molecular modifiers turns out to be more stable. Modifications of proteins with polyethylene glycol (PEG) have been proven to enlarge the molecular size of proteins, to prolong their retention time in the circulation as well as blunt immune reactions. In the present study, the optimal conditions for porcine hemoglobin (pHb) modification with bis (3, 5-dibromosalicyl) fumarate (DBBF) and PEG were evaluated. The derivative of DBBF cross-linked pHb (DBBF-pHb) showed improved oxygen affinity and the ability to resist the dissociation of the alpha2beta2 tetramer compared with the natural protein. DBBF-pHb was then bound to the activated PEG. The results indicated that the pHb modified with DBBF and PEG had more stable tetrameric conformation with a molecular weight of 107000. Their oxygen half-saturation pressure (P50) is around 3.33 kPa, which approximates the physiological P50 of human red blood cells. Both routine and reinforced immunizing methods were adopted to study the immunogenicity of modified products and the results showed that the products had very low immunogenicity evaluated by enzyme-linked immunoadsordent assay (ELISA). Somewhat beneficial effects were shown in the treatment of hemorrhagic shock where modified hemoglobin solutions were used as resuscitation fluids in the hemorrhagic shock Sprague-Dawley (SD) rats model.     

Enzymatic activity of glucose oxidase covalently wired via viologen to electrically conductive polypyrrole films

The surface functionalization of an electrically conductive polypyrrole film (PPY) with a viologen, (N-(2-carboxyl-ethyl)-N'-(4-vinyl-benzyl)-4,4'-bipyridinium dichloride, or CVV) for the covalent immobilization of glucose oxidase (GOD) has been carried out. The viologen was first synthesized and graft polymerized on PPY film. It then served as an anchor via its carboxyl groups for the covalent immobilization of GOD. The surface composition of the as-functionalized substrates was characterized by X-ray photoelectron spectroscopy (XPS). The effects of the CVV monomer concentration on the CVV-graft polymer concentration and the amount of GOD immobilized on the surface were investigated. The activity of the immobilized GOD was compared with that of free GOD and the kinetic effects were also obtained. The cyclic voltammetric (CV) response of the GOD-functionalized PPY substrates was studied in a phosphate buffer solution under an argon atmosphere. The CV results support the mechanism in which CVV acts as a mediator to transfer electron between the electrode and enzyme, and hence regenerating the enzyme in the enzymatic reaction with glucose. High sensitivity and linear response of the enzyme electrode was observed with glucose concentration ranging from 0 to 20 mM.     

Tetrahydroisoquinoline derivatives as melatonin MT2 receptor antagonists

A series of tetrahydroisoquinolines has yielded potent MT(2) receptor antagonists, which are selective versus the MT(1) receptor.     

蹲跳、反向跳和下落跳的膝关节屈伸肌群肌电信号分析

目的：通过观察肌电图（EMG）的变化,了解运动员与普通中学生在纵跳过程中,膝关节屈伸肌群工作特点,为运动员科学选材提供依据。方法：30名男女青少年运动员和30名男女普通中学生进行各种形式纵跳（蹲跳、反向跳、下落跳）,测试膝关节屈伸肌群的EMG变化情况。结果：主动肌（股外肌）EMG的变化存在性别差异,随着下肢工作强度的增加,男运动员积分肌电图（iEMG)和平均功率频率（Fmean)均没有显著变化,女运动员iEMG增加,Fmean没有显著变化,对抗肌（股二头肌）,随着下肢工作强度的增加。青少年运动员EMG活动变化较小,而普通中学生的EMG活动明显增加。结论：在增加工作负荷的过程中,男运动员膝关节伸肌群以提高效率为主,女运动员以提高肌肉的募集数量为主;运动员的对抗肌协调水平高于普通中学生。     

Rapid localization of Gag/GagPol complexes to detergent-resistant membrane during the assembly of human immunodeficiency virus type 1

During human immunodeficiency virus type 1 (HIV-1) assembly in HIV-1-transfected COS7 cells, almost all steady-state Gag/Gag and Gag/GagPol complexes are membrane bound. However, exposure to 1% Triton X-100 gives results indicating that while all Gag/GagPol complexes remain associated with the detergent-resistant membrane (DRM), only 30% of Gag/Gag complexes are associated with the DRM. Analysis of the localization of newly synthesized Gag/Gag and Gag/GagPol to the membrane indicates that after a 10-min pulse with radioactive [(35)S]Cys-[(35)S]Met, all newly synthesized Gag/GagPol is found at the DRM. Only 30% of newly synthesized Gag/Gag moves to the membrane, and at 0 min of chase, only 38% of this membrane-bound Gag/Gag is associated with the DRM. During the first 30 min of chase, most membrane-bound Gag/Gag moves to the DRM, while between 30 and 60 min of chase, there is a significant decrease in membrane-bound Gag/Gag and Gag/GagPol. Since the localization of newly synthesized Gag/Gag to the DRM and the interaction of GagPol with Gag both depend upon Gag multimerization, the rapid localization of GagPol to the DRM probably reflects the interaction of all newly synthesized GagPol with the first newly synthesized polymeric Gag to associate with the DRM.     

Self-stabilized CpG DNAs optimally activate human B cells and plasmacytoid dendritic cells

We recently showed that 5'-terminal secondary structures in CpG DNA affect activity significantly more than those at the 3'-end [Biochem. Biophys. Res. Commun. 306 (2003) 948]. The need for an accessible 5'-end of CpG DNA for activity suggested that the receptor reads the DNA sequence from this end. In continuation of these studies, we have designed immunomodulatory oligonucleotides (IMOs), consisting of a nine-mer stimulatory domain, containing a CpG motif and a hairpin-loop structure at the 3'-end, referred to as self-stabilized CpG DNAs. We studied the ability of self-stabilized CpG DNAs to stimulate human B-cell proliferation and interferon-alpha (IFN-alpha) secretion in plasmacytoid dendritic cell (pDC) culture assays. Self-stabilized CpG DNAs activated human B cells and induced plasmacytoid dendritic cells to secrete high levels of IFN-alpha. While both stimulatory and secondary structures in CpG DNAs were required for pDC activation, CpG motifs were sufficient to activate B cells. Interestingly, CpG motifs were not required for activity in the hairpin duplex region. Further modifications of the hairpin duplex region with a mixture of oligodeoxynucleotides and oligo-2'-O-methylribonucleotides in a heteroduplex formation permitted activation of both human B cells and pDCs.