Trimeric maltoporin (LamB protein) facilitates the diffusion of maltodextrins across the outer membrane of Gram-negative bacteria. The crystal structure of maltoporin from Escherichia coli, determined to a resolution of 3.1 angstroms, reveals an 18-stranded, antiparallel beta-barrel that forms the framework of the channel. Three inwardly folded loops contribute to a constriction about halfway through the channel. Six contingent aromatic residues line the channel and form a path from the vestibule to the periplasmic outlet. Soaking of a crystal with maltotriose revealed binding of the sugar to this hydrophobic track across the constriction, which suggests that maltose and linear oligosaccharides may be translocated across the membrane by guided diffusion along this path.

Objective-We explored the effect of hydrogen sulfide (H 2 S) on atherosclerotic progression, particularly on intracellular adhesion molecule-1 (ICAM-1) in apolipoprotein-E knockout (apoE Ϫ/Ϫ ) mice and human umbilical vein endothelial cells (HUVECs). Methods and Results-ApoEϪ/Ϫ mice were treated with sodium hydrosulfide (NaHS) or DL-propargylglycine (PPG); HUVECs were pretreated with NaHS. Compared with control mice, apoE Ϫ/Ϫ mice showed decreased plasma H 2 S level and aortic H 2 S production but increased plasma ICAM-1 and aortic ICAM-1 protein and mRNA. Compared with apoE Ϫ/Ϫ mice, apoE Ϫ/Ϫ ϩNaHS mice showed increased plasma H 2 S level, but decreased size of atherosclerotic plaque and plasma and aortic ICAM-1 levels, whereas apoE Ϫ/Ϫ ϩPPG mice showed decreased plasma H 2 S level but enlarged plaque size and increased plasma and aortic ICAM-1 levels. NaHS suppressed ICAM-1 expression in tumor necrosis factor (TNF)-␣-treated HUVECs. NaHS inhibited IB degradation and NF-B nuclear translocation in HUVECs treated with TNF-␣. Ⅲapolipoprotein E knockout mice Ⅲ human umbilical vein endothelial cells A therosclerosis is an important underlying pathology of cardiovascular diseases, the leading cause of morbidity and mortality in many countries. Over the past 50 years, numerous studies attempting to explain the complex events leading to atherosclerosis have been undertaken. Nitric oxide and carbon monoxide, which are small gaseous transmitters, freely permeable to membrane, endogenously and enzymatically generated, and have specific functions, are recommended as gasotransmitters. 1 They have been closely implicated in endothelial dysfunction and vascular remodeling in atherosclerotic arteries; researches into the two gasotransmitters have improved the understanding of atherogenesis. [2][3][4][5] However, the mechanisms of atherosclerosis have not been fully elucidated. Conclusions-The

The Smad family of proteins, which are frequently targeted by tumorigenic mutations in cancer, mediate TGF-beta signaling from cell membrane to nucleus. The crystal structure of a Smad3 MH1 domain bound to an optimal DNA sequence determined at 2.8 A resolution reveals a novel DNA-binding motif. In the crystals, base-specific DNA recognition is provided exclusively by a conserved 11-residue beta hairpin that is embedded in the major groove of DNA. A surface loop region, to which tumorigenic mutations map, has been identified as a functional surface important for Smad activity. This structure establishes a framework for understanding how Smad proteins may act in concert with other transcription factors in the regulation of TGF-beta-responsive genes.

No abstract

We have been able to observe the surface-enhanced Raman scattering (SERS) from 4-mercaptopyridine (4-Mpy) molecules adsorbed on ZnO nanocrystals, which display 10 3 enhancement factors (EFs). An excitation wavelength-dependent behavior is clearly observed. Another molecule BVPP is also observed to have surface-enhanced Raman signals. The chemical enhancement is most likely responsible for the observed enhancement, since plasmon resonances are ruled out. The research is important not only for a better understanding of the SERS mechanism, but also for extension of the application of Raman spectroscopy to a variety of adsorption problems on a semiconductor surface.

Direct dynamics classical trajectory simulations are used to study energy transfer and unimolecular dissociation in collisions of N-protonated glycine, (gly-H) + , with an argon atom and a hydrogenated diamond {111} surface. The (gly-H) + potential is represented by the AM1 semiempirical electronic structure theory and analytic potentials developed previously are used for the diamond surface and the (gly-H) + /Ar and (gly-H) + / diamond intermolecular potentials. The AM1 potential for (gly-H) + gives the same collisional energy transfer distributions as does the AMBER empirical force field. For (gly-H) + + diamond {111} at a collision energy and angle of 70 eV and 45°, the average percent energy transfer to (gly-H) + vibration/rotation, to the surface, and to final ion translation are 12, 38, and 50, respectively. A distribution of (gly-H) + dissociation products are observed in these collisions, with ∼55% of the dissociations occurring while (gly-H) + collides with the surface, i.e., shattering fragmentation. Shattering is initiated when the orientation of (gly-H) + and the "hardness" of the collision "drives" a H-atom from CH 2 to the carbonyl carbon or a H-atom from NH 3 to the carbonyl oxygen or ejects a H 2 molecule from NH 3 . Shattering is not important in (gly-H) + collisions with Ar at 13 eV and an impact parameter of zero, but as found for the surface collisions, the Ar collision may "force" H-atom transfer. The simulations suggest that nonstatistical fragmentation dynamics may be important in the collisional dissociation of protonated amino acids and peptides. The collision may directly "drive" the ion to a fragmentation transition state structure.

The objectives of this paper are to review the thermal degradation and stability of starch and starch‐based materials, including both fundamental sciences such as detecting techniques, the effect of amylose/amylopectin content in starches and starches modifications, as well as the effect of different processing environments, such as an open or sealed system, and shearless or shear stress conditions. The decomposition temperature of starches was increased with increasing amylopectin content in an open system. In the open system, the initial water content did not affect the decomposition temperature because all water had evaporated from samples prior to reaching the decomposition temperature. Two decomposition temperatures were observed in the sealed system: the first at lower temperature represents long chain scission; and the second at higher temperature involves decomposition of glucose ring. In the sealed system, the first degradation was increased with increasing amylopectin content. There is no observable difference of the second degradation for the samples containing different amylose/amylopectin ratios. The higher the moisture content is, the lower the second decomposition temperature is detected in the sealed system. Significant shear degradation was observed in amylopectin component of starch, while high amylose starch proved less sensitive to shear stress. The achievements in this area have increased the knowledge of polymer science, in particular to understand the degradation of natural polymers.

The adsorption of 4-mercaptopyridine (4-Mpy) molecules on ZnS nanocrystals was investigated by means of Raman spectroscopy. We compared the Raman signals of 4-Mpy molecules adsorbed on ZnS nanocrystals and Ag substrate. The differences in the adsorption of 4-Mpy molecules on the semiconductor and the metal substrate were noted. The results demonstrated that adsorbed species on the semiconductor ZnS nanocrystals can be detected by Raman spectroscopy.