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A symbolic Lie p-ring presentation defines a family of nilpotent Lie rings with p n elements for infinitely many primes p and a fixed positive integer n. Symbolic Lie p-ring presentations are used in the classification of isomorphism types of nilpotent Lie rings of order p n for all primes p and n ≤ 7 . We describe an algorithm to compute the Schur multipliers of all nilpotent Lie rings in the family defined by a symbolic Lie p-ring presentation. We apply this to determine the Schur multipliers of all nilpotent Lie rings of order dividing p 6 for all primes p ≥ 5 . Via the Lazard correspondence this yields the Schur multipliers of all groups of order dividing p 6 for all primes p ≥ 5 .

We prove that finite categorically equivalent p-rings have isomorphic additive groups (in particular, they have the same cardinality) and that the number of generators is a categorical invariant fo...

A new type of high-voltage termination, namely the “deep p-ring trench” termination design for high-voltage, high-power devices, is presented and extensively simulated. Termination of such devices consumes a large proportion of the chip size; the proposed design concept not only reduces the termination silicon area required but also removes the need for an additional mask as is the case of the traditional p+ ring-type termination. Furthermore, the presence of the p-ring under and around the bottom of the trench structure reduces the electric field peaks at the corners of the oxide, which results in reduced hot carrier injection and improved device reliability.

A novel Trench IGBT design, namely the p-ring Trench Schottky IGBT, with improved latch-up immunity and an enhanced safe-operating area is proposed. This design improves the performance of the FS+ IGBT by facilitating the collection of holes through a p-doped (p-ring) buried region connected through a Schottky contact to the source/cathode contact. This unique structure approach allows the improvement in the device reliability and it is shown under numerical studies to be highly effective in expanding the safe operating area (SOA), suppress dynamic avalanche, improve the latch up robustness and have the potential to improve the device switching operation.

Helicobacter pylori uses a cluster of polar, sheathed flagella for motility, which it requires for colonization of the gastric epithelium in humans. As part of a study to identify factors that contribute to localization of the flagella to the cell pole, we disrupted a gene encoding a cardiolipin synthase (clsC) in H. pylori strains G27 and B128. Flagellum biosynthesis was abolished in the H. pylori G27 clsC mutant but not in the B128 clsC mutant. Transcriptome sequencing analysis showed that flagellar genes encoding proteins needed early in flagellum assembly were expressed at wild-type levels in the G27 clsC mutant. Examination of the G27 clsC mutant by cryo-electron tomography indicated the mutant assembled nascent flagella that contained the MS ring, C ring, flagellar protein export apparatus, and proximal rod. Motile variants of the G27 clsC mutant were isolated after allelic exchange mutagenesis using genomic DNA from the B128 clsC mutant as the donor. Genome resequencing of seven motile G27 clsC recipients revealed that each isolate contained the flgI (encodes the P-ring protein) allele from B128. Replacing the flgI allele in the G27 clsC mutant with the B128 flgI allele rescued flagellum biosynthesis. We postulate that H. pylori G27 FlgI fails to form the P ring when cardiolipin levels in the cell envelope are low, which blocks flagellum assembly at this point. In contrast, H. pylori B128 FlgI can form the P ring when cardiolipin levels are low and allows for the biosynthesis of mature flagella. IMPORTANCEH. pylori colonizes the epithelial layer of the human stomach, where it can cause a variety of diseases, including chronic gastritis, peptic ulcer disease, and gastric cancer. To colonize the stomach, H. pylori must penetrate the viscous mucous layer lining the stomach, which it accomplishes using its flagella. The significance of our research is identifying factors that affect the biosynthesis and assembly of the H. pylori flagellum, which will contribute to our understanding of motility in H. pylori, as well as other bacterial pathogens that use their flagella for host colonization.

Many new results were obtained in this paper about P.P. ring. Semi-primitive ring R with (dcc) on principal-ideal P is always P.P.ring. Also, St-G-P.P. ring R is given to answer new question; is B-rings are P.P. ring. Also regular and Von Neumann regular rings are introduced to find a relationship between P.P. ring and these kind of the rings.

Structure–activity relationship studies of maitotoxin (MTX), a marine natural product produced by an epiphytic dinoflagellate, were conducted using chemically synthesized model compounds corresponding to the partial structures of MTX. Both enantiomers of the LMNO ring system were synthesized via aldol reaction of the LM ring aldehyde and the NO ring ketone. These fragments were derived from a common cis-fused pyranopyran intermediate prepared through a sequence involving Nozaki–Hiyama–Kishi reaction, intramolecular oxa-Michael addition, and Pummerer rearrangement. The NOPQR(S) ring system, in which the original seven-membered S ring was substituted with a six-membered ring, was also synthesized through the coupling of the QR(S) ring alkyne and the NO ring aldehyde and the construction of the P ring via 1,4-reduction, dehydration, and hydroboration. The inhibitory activities of the synthetic specimens against MTX-induced Ca2+ influx were evaluated. The LMNO ring system and its enantiomer induced 36 and 18%...

Most bacteria can swim by rotating the flagellum. The basal body of the flagellum is an essential part for this motor function. Recent comprehensive analysis of the flagellar basal body structures across bacteria by cryo-electron tomography has revealed that they all share core structures, the rod, and rings: the C ring, M ring, S ring, L ring, and P ring. Furthermore, it also has uncovered that in some bacteria, there are extra ring structures in the periplasmic space and outer-membrane. Here, we describe a protocol to isolate the basal body of the flagellar basal body from a marine bacterium, Vibrio alginolyticus, for structural analysis of additional ring structures, the T ring and H ring.

A periplasmic flagellar chaperone protein, FlgA, is required for P-ring assembly in bacterial flagella of taxa such as Salmonella enterica or Escherichia coli. The mechanism of chaperone-mediated P-ring formation is poorly understood. Here we present the open and closed crystal structures of FlgA from Salmonella enterica serovar Typhimurium, grown under different crystallization conditions. An intramolecular disulfide cross-linked form of FlgA caused a dominant negative effect on motility of the wild-type strain. Pull-down experiments support a specific protein-protein interaction between FlgI, the P-ring component protein, and the C-terminal domain of FlgA. Surface plasmon resonance and limited-proteolysis indicate that flexibility of the domain is reduced in the covalently closed form. These results show that the structural flexibility of the C-terminal domain of FlgA, which is related to the structural difference between the two crystal forms, is intrinsically associated with its molecular chaperone function in P-ring assembly.

The structural parameters, energies, and spectroscopic characteristics of acetylene π-complexes of metalloporphyrins M(P)(π-C2H2), where M is a 3d-metal atom in different multiplicity states have been calculated by the density functional theory B3LYP method. It has been shown that the activation of the coordinated acetylene molecule is manifested in (i) a sharp weakening of its C-C bond, (ii) a 20°–40° decrease of the bond angles φ(HCC) and an elongation by 0.05–0.10 A of the R(CC) bond, (iii) a long-wavelength shift of the νstr(CC) stretching mode by 300–500 cm−1, (iv) considerable electron density transfer from the porphyrin ring (P ring) to the π-ligand, and (iv) a strong displacement (0.5–0.6 A) of the M atom from the P ring plane toward the π-ligand and the dome distortion of the P ring. There is a trend in the behavior of the activation effects along the 3d series and with a change in the electronic state multiplicity of the complexes.

The flagellar motor is composed of the stator and the rotor, and the interaction between the stator and the rotor at the cytoplasmic region is believed to produce mechanical force for the rotation of flagella. The periplasmic region of the stator has been proposed to play an important role in assembly around and incorporation into the motor. In this study, we provide evidence suggesting that the periplasmic region of the stator component MotB interacts with the P-ring component FlgI, which functions as a bearing for the rotor along with the L-ring protein FlgH, from a site-directed disulphide cross-linking approach. First, we prepared four FlgI and three MotB cysteine-substituted mutant proteins and co-expressed them in various combinations in Escherichia coli. We detected cross-linked combinations of FlgI G11C and MotB S248C when treated with the oxidant Cu-phenanthroline or bismaleimide cross-linkers. Furthermore, we performed Cys-scanning mutagenesis around these two residues and found additional combinations of cross-linked residues. Treatment with a protonophore CCCP significantly reduced the cross-linking efficiency between FlgI and MotB in flagellated cells, but not in non-flagellated cells. These results suggest a direct contact between MotB and FlgI upon assembly of the stator into a motor.

The bacterial flagellar motor is embedded in the cytoplasmic membrane, and penetrates the peptidoglycan layer and the outer membrane. A ring structure of the basal body called the P ring, which is located in the peptidoglycan layer, is thought to be required for smooth rotation and to function as a bushing. In this work, we characterized 32 cysteine-substituted Escherichia coli P-ring protein FlgI variants which were designed to substitute every 10th residue in the 346 aa mature form of FlgI. Immunoblot analysis against FlgI protein revealed that the cellular amounts of five FlgI variants were significantly decreased. Swarm assays showed that almost all of the variants had nearly wild-type function, but five variants significantly reduced the motility of the cells, and one of them in particular, FlgI G21C, completely disrupted FlgI function. The five residues that impaired motility of the cells were localized in the N terminus of FlgI. To demonstrate which residue(s) of FlgI is exposed to solvent on the surface of the protein, we examined cysteine modification by using the thiol-specific reagent methoxypolyethylene glycol 5000 maleimide, and classified the FlgI Cys variants into three groups: well-, moderately and less-labelled. Interestingly, the well- and moderately labelled residues of FlgI never overlapped with the residues known to be important for protein amount or motility. From these results and multiple alignments of amino acid sequences of various FlgI proteins, the highly conserved region in the N terminus, residues 1-120, of FlgI is speculated to play important roles in the stabilization of FlgI structure and the formation of the P ring by interacting with FlgI molecules and/or other flagellar components.

A new IGBT type structure, namely the p-ring FS+ Trench IGBT, with improved performance has been demonstrated. The improvement has been achieved through the utilization of p doped buried layers (p-rings) which allows for the simultaneous increase in the n enhancement layer doping concentration above the conventional levels without compromising the device breakdown rating. This unique lateral charge compensation approach is demonstrated to be highly effective in lowering the on-state losses. The experimental results show a 20% reduction in the on-state losses for a 1.7kV device.

Persistence infection is the keystone of the ruminant and human diseases called brucellosis and Malta fever, respectively, and is linked to the intracellular tropism of Brucella spp. While described as non-motile, Brucella spp. have all the genes except the chemotactic system, necessary to assemble a functional flagellum. We undertook to determine whether these genes are expressed and are playing a role in some step of the disease process. We demonstrated that in the early log phase of a growth curve in 2YT nutrient broth, Brucella melitensis expresses genes corresponding to the basal (MS ring) and the distal (hook and filament) parts of the flagellar apparatus. Under these conditions, a polar and sheathed flagellar structure is visible by transmission electron microscopy (TEM). We evaluated the effect of mutations in flagellar genes of B. melitensis encoding various parts of the structure, MS ring, P ring, motor protein, secretion apparatus, hook and filament. None of these mutants gave a discernible phenotype as compared with the wild-type strain in cellular models of infection. In contrast, all these mutants were unable to establish a chronic infection in mice infected via the intraperitoneal route, raising the question of the biological role(s) of this flagellar appendage.

The C-terminal half of the Salmonella flagellar protein FlgJ has peptidoglycan hydrolyzing activity and it has been suggested that it is a flagellum-specific muramidase which locally digests the peptidoglycan layer to permit assembly of the rod structure to proceed through the periplasmic space. It was also suggested that FlgJ might be involved in rod formation itself, although there was no direct evidence for this. We purified basal body structures from SJW1437(flgJ) transformed with plasmids encoding various mutant FlgJ proteins and found that these basal bodies possessed the periplasmic P ring but lacked the outer membrane L ring; they also lacked a hook at their distal end. All of these mutant FlgJ proteins had an altered or missing C-terminal domain but had at least the first 151 amino acid residues of the N-terminal domain. Immunoblotting analysis of fractionated cell extracts revealed that a rod/hook export class protein, FlgD, was exported to the periplasm but not to the culture supernatant in these mutants. FlgJ was shown to physically interact with several proteins, and especially FliE and FlgB, which are believed to reside at the cell-proximal end of the rod. On the basis of these results, we conclude that the N-terminal 151 amino acid residues of FlgJ are directly involved in rod formation and that the muramidase activity of FlgJ, though needed for formation of the L ring and subsequent events such as hook formation, is not essential for rod or P ring formation. In contrast, muramidase activity alone does not support rod assembly.

P ring is a periplasmic substructure of the flagellar basal body and is believed to connect with the peptidoglycan layer in Salmonella. Two flagellar genes, flgA and flgI, are known to be indispensable for P ring formation. The flgI gene encodes the component protein of the P ring. However, the role of the flgA gene product in P ring assembly remained unknown. Here, evidence is presented that FlgA is synthesized as a precursor form and exported via the Sec secretory pathway into the periplasmic space where P ring formation takes place. Overproduction of the FlgI protein led flgA mutants to form flagella with a P ring, suggesting that FlgA plays an auxiliary role in P ring assembly. Far-Western blot analysis revealed that FlgA binds in vitro to both FlgI and FlgA itself. Though a direct FlgI-FlgI interaction in the absence of FlgA could not be demonstrated, an indirect or direct interaction between the FlgI proteins was observed in the presence of FlgA. FlgA alone was very unstable in vivo, but co-expression with FlgI could stabilize FlgA. This suggests the presence of FlgA-FlgI interaction in vivo. On the basis of these results, a hypothesis is proposed that FlgA acts as a periplasmic chaperone, which assists a polymerization reaction of FlgI into the P ring through FlgA-FlgI interaction.

With apologies to Charles Darwin (4), there is grandeur in the view of the flagellar motor provided by Liu et al. in an article published in this issue (9). They have used cryo-electron tomography (cryo-ET) to reconstruct, in a most elegant manner, the Borrelia burgdorferi version of one of nature's most exquisite nanomachines—the rotary flagellar motor. Their choice of this skinny spirochete, the causative agent of Lyme disease, for the study enabled them to use the full power of three-dimensional (3D) imaging afforded by tomography to probe the structure of this extraordinary rotary organelle. Tomography has been in increasing use lately to study intracellular components of bacteria, including the cytoskeleton (2) and chemoreceptor patch (3, 7) of the motile alphaproteobacterium Caulobacter crescentus and, in the article by Liu et al. (9), the flagellar motor of B. burgdorferi. Both bacteria are particularly well suited for cryo-ET studies because of their small diameters. In addition, both possess flagella that arise near the cell pole, making the basal bodies easier to locate. B. burgdorferi is further well suited for this study because it sports a small, linear cluster of adjacent flagellar motors that can be easily visualized. The principle underlying cryo-ET is that 3D volumes can be reconstructed from the integration of multiple two-dimensional views of thin electron microscopy sections taken at different angles relative to the electron beam. In a typical analysis, successive micrographs of a section are taken as the sample stage is tilted at 1-degree intervals, usually in the range of +70 to −70 degrees normal to the section. The basic idea is illustrated with a simple object in Fig. ​Fig.1.1. In this way, not only can a 3D representation be derived but the cross-sectional slice at each level of the structure can be obtained. FIG. 1. Principles behind electron tomography. A tissue section, or thin sample of frozen hydrated bacteria, is prepared for the electron microscope. The sample is inserted into the microscope so that electron micrographs of the section can be collected. In a ... Cryo-ET is a relatively recent technique, and its application to cells as tiny as bacteria is even newer. Together with light microscopic imaging of proteins tagged with fluorescent molecules, such as green fluorescent protein, cryo-ET is providing us with unprecedented insights into the in situ ultrastructures of large macromolecular assemblages in bacteria. Other electron microscopy approaches, such as single-particle analyses, have yielded excellent views of isolated flagellar basal-body structures (11, 12), but these results can be limited by the distortions that arise during the isolation of organelles. For an example, it is unlikely that the vertical displacement of the stators by the highly curved membrane of B. burgdorferi (discussed below) would be observed in in vitro preparations. Spirochetes have internalized flagella whose filaments rotate within the space between the cell wall and the outer membrane (1). The rotation of the small flagellar bundle in this cell compartment causes counter-rotation of the helical cell body so that the entire bacterium becomes the propeller that generates swimming (6). In B. burgdorferi, several flagellar motors are aligned in a row parallel to the long axis of the cell, as shown in Fig. 2 of the article by Liu et al. (9). Both the basal bodies and the hooks and filaments to which they give rise are clearly visible. One of the accomplishments of Liu et al. was to secure sufficient micrographs of different motors to obtain averaged images without imposing rotational symmetry. Therefore, confidence is high that the subunit stoichiometries of the different components of the motor are inherent properties of those objects rather than artifacts generated during construction of the 3D image. This is no small feat—several of the observations presented would not have been possible had such symmetry been imposed. The flagellar motor was reconstructed at a remarkable 3.5-nm resolution. The model includes the hook, rod, rotor, stator, C ring, and export apparatus. The hook is poorly resolved because it has a tilted orientation that presumably differs from one motor to the next. The rod shows much better resolution, and its hollow center, which represents the export channel, is clearly visible. The upper part of the motor shows a clear 16-fold symmetry at its periphery in the form of clockwise-tilted radial extensions, or spokes. At the level of the cell membrane, no clear symmetry is evident, but two concentric rings are seen, with the inner probably corresponding to the MS ring and the outer to the C ring. The diameter of the C ring is 57 nm, and the diameter of the MS ring is about half of that. This compares with a C-ring diameter of about 45 nm seen in the Salmonella flagellar motor (5). The rings show a faint periodicity that suggests that they contain a higher number of subunits. There is electron density between the two rings that may represent the FliG protein, which is predicted to join the two rings. Peripheral to the C ring, there is a blurry 16-fold symmetry that may correspond to stator units that have different positions in the membrane from one motor to the next. After treatment of cells with the nonionic detergent NP-40, only central elements of the motor remain at the level of the membrane. The presumptive stator elements disappear, as does the C ring. The remaining basal body attached to the cell envelope has a diameter of 45 nm, which may correspond to the MS ring with FliG attached. Even though the stator elements are gone, this ring shows a double 16-fold symmetry, with one set of spots on the outside and another located between, and more centrally than, the first. The side views of the reconstructed motor are even more striking. The extracellular portion of the basal body is quite complex, consisting of a hollow torus that fits closely around the distal rod, a “collar” outside of that, and then more-peripheral density that probably corresponds to the stator. The torus is the P ring, since it disappears in the basal bodies from flgI mutants, which nevertheless seem to have normal motility. The collar is a unique feature that may be present only in spirochetes, perhaps an adaptation to their internalized flagellar filaments. At the cytoplasmic face of the MS ring, there is significant, rather well resolved density that must represent the export apparatus, suggesting that it has a defined architecture as well. One of the most intriguing features of the side views is that the basal body at the membrane level shows a 180° rotational periodicity of about 6 nm in the vertical dimension. A similar periodicity of smaller amplitude exists in the next-higher and -lower levels of the basal body, whereas at the levels of the P ring and C ring, the vertical position of the basal body is not periodic. Since the greatest deviation in height is at the level of the stator proton-conducting transmembrane channels, the implication is that the position of the stators follows the curvature of the membrane, which is quite high in such a skinny bacterium. If all of the stators remain engaged with the rotor, it would seem that it must also exhibit some curvature at the level of the FliG motility domains. The flagellar motors of spirochetes may differ in some particulars from those of bacteria with external flagella, but certainly there are lessons to be learned from this elegant structure. The strong 16-fold symmetry at the level of the cell wall, if it represents the peptidoglycan-binding domains of stators, certainly suggests a highly ordered assembly. It is not known whether stator units join or leave rotors in B. burgdorferi on a short time scale, as in E. coli (8), but if they do, it becomes difficult to comprehend how this exchange of rotor elements can be so fast and accurate. It will be informative to determine the structure of a B. burgdorferi basal body equipped with subsaturating numbers of stators. The 16-fold symmetry seen at the level of FliG suggests a one-to-one match of accessible rotor motility domains and stator elements, something not typically incorporated into models for torque generation. For example, in E. coli there are thought to be on the order of 11 functional stator units per motor (10), whereas there are 24 to 26 FliG subunits per motor (13). Could it be that only half of the FliG proteins are engaged in rotation at any given moment or that one set is for clockwise direction and the other half for counterclockwise rotation? If that is generally true, new explanations must be developed to explain how flagella reverse their direction of rotation. The high probability that the position of the stator and rotor elements follows the curvature of the membrane also suggests that the link between the MS-ring-anchoring and motility domains of FliG must be very flexible. Seldom does one structure raise so many interesting questions. It will be fascinating to discover how generally applicable the B. burgdorferi flagellar motor is to other bacteria. It certainly gives all of us who work on motility a lot to think about.

Salmonella FlgA, a periplasmic protein essential for flagellar P-ring assembly, has been crystallized in two forms. The native protein crystallized in space group C222, with unit-cell parameters a = 107.5, b = 131.8, c = 49.4 Å, and diffracted to about 2.0 Å resolution (crystal form I). In this crystal, the asymmetric unit is likely to contain one molecule, with a solvent content of 66.8%. Selenomethionine-labelled FlgA protein crystallized in space group C222(1), with unit-cell parameters a = 53.2, b = 162.5, c = 103.5 Å, and diffracted to 2.7 Å resolution (crystal form II). In crystal form II, the asymmetric unit contained two molecules with a solvent content of 48.0%. The multiple-wavelength and single-wavelength anomalous dispersion methods allowed the visualization of the electron-density distributions of the form I and II crystals, respectively. The two maps suggested that FlgA is in two different conformations in the two crystals.

The process of flagellar assembly was investigated in Salmonella typhimurium. Seven types of flagellar precursors produced by various flagellar mutants were purified by CsCl density gradient protocol. They were characterized morphologically by electron microscopy, and biochemically by two-dimensional gel electrophoresis. The MS ring is formed in the absence of any other flagellar components, including the switch complex and the putative export apparatus. Four proteins previously identified as rod components, FlgB, FlgC, FlgF, FlgG, and another protein, FliE, assemble co-operatively into a stable structure. The hook is formed in two distinct steps; formation of its proximal part and elongation. Proximal part formation occurs, but elongation does not occur, in the absence of the LP ring. FlgD is necessary for hook formation, but not for LP-ring formation. A revised pathway of flagellar assembly is proposed based on these and other results.

The Salmonella typhimurium basal body, a part of the flagellar rotary motor, consists of four rings (denoted M, S, P and L) and a coaxial rod. Using low-dose electron microscopy and image averaging methods on negatively stained and frozen-hydrated preparations, we examined whole basal body complexes and subcomplexes obtained by dissociation in acid. Dissociation occurs in steps, allowing us to obtain images of substructures lacking the M ring, lacking the M and S rings, and lacking the M and S rings and the proximal portion of the rod. We obtained images of the L and P ring subcomplex. The existence of a subcomplex missing only the M ring suggests either that the S and M rings derive from two different proteins, or that the M ring is a labile domain of a single protein, which makes up both rings. At the 25 to 30 A resolution of our averaged images, the L, P and S rings appear cylindrically symmetric. Images of the M ring show variability that may be due to differences in angular orientation of the grid, but equally could be due to structural variations. Three-dimensional reconstructions of these structures from the averaged images reveal the internal structure and spatial organization of these components.

The basal body of Wolinella succinogenes consists of a central rod, a set of two rings (L and P rings), a basal disk from 70 to 200 nm in diameter, and a terminal knob. In negatively stained preparations of flagellar hook-basal body complexes, some disks remain fixed perpendicularly to the grid and show that such a disk is located on the distal side of the P ring. The basal disks have been isolated with and without the P ring; in both cases there is a hole in the center of the disk. The diameter of the disk is smaller in the presence of the P ring. The L-P ring complex is therefore assumed to be a bushing for the rod. Thin sections of whole bacteria and spheroplasts reveal that the disk is attached to the inner surface of the outer membrane. At the insertions of the flagellar hook-basal body-basal disk complexes, depressions are visible in negatively stained preparations of whole bacteria and spheroplasts. A new ringlike structure is connected to an elongation of the basal body into the cytoplasm in both preparations. Its diameter (60 nm) is larger than that of the M ring. A heavily stained compartment can be seen in between the new ringlike structure and the basal disk, which may be formed by the energy transducing units.

The bacterial flagellar motor is a remarkable nanomachine that provides motility through flagellar rotation. Prior structural studies have revealed the stunning complexity of the purified rotor and C-ring assemblies from flagellar motors. In this study, we used high-throughput cryo-electron tomography and image analysis of intact Borrelia burgdorferi to produce a three-dimensional (3-D) model of the in situ flagellar motor without imposing rotational symmetry. Structural details of B. burgdorferi , including a layer of outer surface proteins, were clearly visible in the resulting 3-D reconstructions. By averaging the 3-D images of ∼1,280 flagellar motors, a ∼3.5-nm-resolution model of the stator and rotor structures was obtained. flgI transposon mutants lacked a torus-shaped structure attached to the flagellar rod, establishing the structural location of the spirochetal P ring. Treatment of intact organisms with the nonionic detergent NP-40 resulted in dissolution of the outermost portion of the motor structure and the C ring, providing insight into the in situ arrangement of the stator and rotor structures. Structural elements associated with the stator followed the curvature of the cytoplasmic membrane. The rotor and the C ring also exhibited angular flexion, resulting in a slight narrowing of both structures in the direction perpendicular to the cell axis. These results indicate an inherent flexibility in the rotor-stator interaction. The FliG switching and energizing component likely provides much of the flexibility needed to maintain the interaction between the curved stator and the relatively symmetrical rotor/C-ring assembly during flagellar rotation.

The stoichiometries of components within the flagellar hook-(basal-body) complex of Salmonella typhimurium have been determined. The hook protein (FlgE), the most abundant protein in the complex, is present at approximately 130 subunits. Hook-associated protein 1 (FlgK) is present at approximately 12 subunits. The distal rod protein (FlgG) is present at approximately 26 subunits, while the proximal rod proteins (FlgB, FlgC and FlgF) are present at only approximately six subunits each. The stoichiometries of the proximal rod proteins and hook-associated protein 1 are, within experimental error, consistent with values of 5 or 6, and 11, respectively. Such values would correspond to either one or two turns of a helical structure with a basic helix of approximately 5.5 subunits per turn, which is the geometry of both the hook and the filament and, one supposes, the rod and hook-associated proteins. These stoichiometries may derive from rules for the heterologous interactions that occur when a helical structure consists of successive segments constructed from different proteins; the stoichiometries within the hook and the distal portion of the rod must, however, be set by different mechanisms. The stoichiometries for the ring proteins are approximately 26 subunits each for the M-ring protein (FliF), the P-ring protein (FlgI), and the L-ring protein (FlgH); the protein responsible for the S-ring feature is not known. The rings presumably have rotational rather than helical symmetry, in which case the stoichiometries would be directly constrained by the intersubunit bonding angle. The ring stoichiometries are discussed in light of other information concerning flagellar structure and function.

Peer-to-peer systems have emerged as a robust, scalable and decentralized way to share and publish data. In this paper, we propose P-Ring, a new P2P index structure that supports both equality and range queries. P-Ring is fault-tolerant, provides logarithmic search performance even for highly skewed data distributions and efficiently supports large sets of data items per peer. We experimentally evaluate P-Ring using both simulations and a real distributed deployment on PlanetLab, and we compare its performance with Skip Graphs, Online Balancing and Chord.

Cationic cluster Ti 2 P 6 + has been studied within density functional theory. The structure of this cluster is predicted to be a slightly distorted tetragonal prism. The dissociation energy of this cationic cluster is higher than that of the known sandwich compound, [(P 5 ) 2 Ti] 2 - , because of the different bonding in these two compounds. In Ti 2 P 6 + , the hybridization of P atoms of the ring is sp 3 . The bonding between the metal atoms and the P ring is mainly σ-π. While in [(P 5 ) 2 Ti] 2 - , the P atoms take sp 2 hybridization, the bonding between the metal atom and the rings is the typical π-π interaction. The electronic delocalization is another stabilizing factor for Ti 2 P 6 + . The nuclear independent chemical shift indicates that Ti 2 P 6 + is a three-dimensional aromatic molecule. The predicted infrared and NMR help to identify the Ti 2 P 6 + conformations in experiment.

The P ring of the bacterial flagellar motor consists of multiple copies of FlgI, a periplasmic protein. The intramolecular disulfide bond in FlgI has previously been reported to be essential for P-ring assembly in Escherichia coli , because the P ring was not assembled in a dsbB strain that was defective for disulfide bond formation in periplasmic proteins. We, however, found that the two Cys residues of FlgI are not conserved in other bacterial species. We then assessed the role of this intramolecular disulfide bond in FlgI. A Cys-eliminated FlgI derivative formed a P ring that complemented the flagellation defect of our Δ flgI strain when it was overproduced, suggesting that disulfide bond formation in FlgI is not absolutely required for P-ring assembly. The levels of the mature forms of the FlgI derivatives were significantly lower than that of wild-type FlgI, although the precursor protein levels were unchanged. Moreover, the FlgI derivatives were more susceptible to degradation than wild-type FlgI. Overproduction of FlgI suppressed the motility defect of Δ dsbB cells. Additionally, the low level of FlgI observed in the Δ dsbB strain increased in the presence of l -cystine, an oxidative agent. We propose that intramolecular disulfide bond formation facilitates the rapid folding of the FlgI monomer to protect against degradation in the periplasmic space, thereby allowing its efficient self-assembly into the P ring.

We have designed and fabricated a highly sensitive magnetotransistor which ernploys the ernitter region as a Hall plate for inducing Hall voltage across the emitter. The Hall voltage modulates the emitter-base junction bias on both sides of the ernitter so that a large collector current difference is resulted. The specially designed p ring around the emitter enhances accumulation of the drifted electrons in the emitter and thus increases the Hall voltage. A relative sensitivity of 240/tesla is measured by operating the device in the saturation mode.

The bacterial flagellum is a supramolecular structure which originates from the cell envelope and extends into the extracellular space. The individual flagellum consists of at least three substructures: a basal body, a hook, and a filament (1, 5). The basal body is embedded in the cell membrane and consists of a rod with an inner ring (MS ring) and two outer rings (L and P rings). The rod crosses the inner membrane, the periplasmic space, and the outer membrane. The MS ring is associated with the inner membrane, whereas the L ring connects with the outer membrane. The P ring resides in the periplasmic space and is believed to interact with the peptidoglycan layer (6). The MS ring is composed of a single species of protein, FliF, and is believed to be built first during the assembly of the basal body (1, 20, 36). Four proteins, FlgB, FlgC, FlgF, and FlgG, comprise the rod and are postulated to be transported from the cytoplasm into the periplasmic space via a flagellum-specific protein export pathway (12). These proteins assemble onto the MS ring to form the MS ring-rod structure. Subsequently, the FlgI and FlgH proteins, which are transported via the conventional signal sequence-dependent export pathway, assemble around the rod to form the P and L rings, respectively (16). Therefore, the rod is the earliest structure which should penetrate and assemble through the peptidoglycan layer. Because the peptidoglycan is a mechanically rigid structure (11, 31), it has been postulated that breakdown of peptidoglycan should be a prerequisite for rod formation (7, 9). Peptidoglycan hydrolases such as muramidase and amidase (10, 33) are presumed to be responsible for this process. In addition to the structural genes for the rod subunit proteins, more than 10 genes are known to be required for rod formation (19, 35). Most of them are believed to encode the component proteins of the flagellum-specific export apparatus. They include flhA, fliI, and fliH (37). Mutants defective in any one of these genes produce the MS ring lacking the rod and other flagellar substructures (19). Because flgJ mutants also produce the MS ring lacking the rod (19), FlgJ must be essential for the rod assembly. Through the comparative study of the primary structures of proteins, Joris et al. (17) demonstrated that the C-terminal half of FlgJ has homology to the catalytic domain of two species of muramidase, autolysin from Streptococcus faecalis and muramidase 2 from Enterococcus hirae. Recently, the same region of FlgJ was also shown to be homologous to the Lactococcus lactis AcmA protein, which acts as a muramidase essential for cell separation (4). Especially, two amino acids, aspartic acid and glutamic acid, which are conserved in the active center of the enzymes of the muramidase family, are also present in the corresponding positions of FlgJ (Glu-223 and Asp-248) (Fig. ​(Fig.1A).1A). According to these observations, Dijkstra and Keck (7) proposed a hypothesis that FlgJ may be responsible for the penetration of the peptidoglycan by the rod structure. However, this remained to be proven experimentally. This work was carried out to address this issue. FIG. 1 Structures of the wild-type (A), His-tagged (B), and mutant (C) FlgJ proteins. Asterisks indicate the amino acids which are conserved in the putative active center of the enzymes of the muramidase family. Numbers above the bars indicate amino acid residues ... We showed that the purified FlgJ protein has a peptidoglycan-hydrolyzing activity in its C-terminal half. The flgJ mutants with amino acid substitutions in the putative active center of muramidase produced FlgJ proteins with reduced enzymatic activity and showed poor motility. We showed further that FlgJ is exported into the periplasmic space. These results suggest that FlgJ may be the flagellum-specific muramidase which hydrolyzes the peptidoglycan layer to construct the rod structure in the periplasmic space. On the basis of this and other available information, we propose a model of rod assembly in the periplasmic space.

This contribution is the summary of a letter of intend submitted to the CERN SPSL Committee by about sixty physicists. The SuperLEAR project consists of a dedicated high current p ring at CERN. In the internal gas jet operating mode SuperLEAR has the following properties : o 1. (i) a variable p energy between 2 and 10 GeV/c. 2. (ii) a narrow beam resolution corresponding to a ∼ 300 KeV in the p p center of mass system. 3. (iii) a luminosity of 10 32 cm −2 sec −1 . It is proposed to search for the missing c c charmonium states and for exotic charmonium states containing a valence gluon ( c c g hybrids ) by measuring their excitation as a function of p momentum, specifically p p → c c g → mesons , in exclusive final states which contain either J ψ (→ e + e − ) or ν c (→γγ) associated with one or several mesons (π 0 , ν, ν', ω), and leading to several detected photons. It is also proposed to search for new varieties of exotic light mesons (glueballs, hybrids and multiquark states) in the rather unexplored 2–3 GeV mass range by studying p p annihilation at a fixed p momentum into exiusive final states involving neutral mesons (ν, ν', ω) and leading also to several detected photons. The apparatus is specialized in the detection of e + e − pairs and multiphoton events with large angular coverage and good angular and energy resolutions. In the heavy c c domain the cross section sensitivity limit is of one pb.

The basal body, a part of the rotary motor of the bacterial flagellum, is a multiprotein assembly that consists of four rings (denoted M, S, P, and L) and an axial rod (denoted R). From analysis of scanning transmission electron microscopy images of hook-basal body preparations isolated from Salmonella typhimurium, we have determined the masses of the basal body and three of its subcomplexes. The mass of the basal body (i.e., the four rings and rod) is 4400 +/- 490 kDa (mean +/- SD; n = 54). The mass of the LPR subcomplex (i.e., L and P rings and the whole rod) is 2600 +/- 380 kDa (n = 55), that of the L and P rings and the distal part of the rod is 2100 +/- 320 kDa (n = 25), and the mass of the L and P ring subcomplex is 1700 +/- 260 kDa (n = 514). These results, together with the masses of the component proteins, indicate that the rings contain approximately 26 subunits each and that the mass of the rod is consistent with a composition of approximately 6 copies each of three of the rod proteins FlgB, FlgC, and FlgF and approximately 26 copies of FlgG as determined by Jones et al. [Jones, C. J., Macnab, R. M., Okino, H. & Aizawa, S.-I. (1990) J. Mol. Biol. 212, 377-387] using quantitative gel electrophoresis. The results of Jones et al., together with ours, account for all proteins in the basal body to within approximately 5% (or 200 kDa).

A novel magnetotransistor using a separated drift field with a p+ ring around an emitter has been designed and fabricated. The operating principle of the proposed magnetic field sensor is based on the emitter injection modulation. The p+ ring around the n-type emitter confines drifted electrons in the emitter and hence, the induced Hall voltage in the emitter is increased. The measured relative sensitivity of the separated drift field magnetotransistor with the p+ ring is about 140 times larger than that of the device without the ring.

The basal body is thought to be a part of the rotary motor of the bacterial flagellum. It consists of a central rod coaxial with a set of four rings, which are associated with the cell envelope. We used single-particle averaging methods to analyze images of negatively stained basal bodies of Salmonella typhimurium. Several averages were computed, so that the reliability of features could be assessed. We carried out the same analysis on electron micrographs of isolated, negatively stained LP rings. In order to interpret the averages in terms of a three-dimensional structure, we carried out image reconstruction on them. The resulting three-dimensional map corresponds to the cylindrically averaged structure of the basal body. To show that the reconstruction procedure is legitimate, we demonstrate it on model data. The results of the modelling show that features very near to the axis of the reconstruction are not reliable but that broader, off-axis features are represented faithfully. The L ring is L-shaped, with the long arm of the L parallel to the axis of the rod, and the short arm pointing away from the rod. The P ring, on the other hand, appears to be a ring or disk. The position of the LP ring complex on the rod seems to vary somewhat, consistent with its putative role as a bushing. The cross-sectional shape of the S ring is that of a frustum rather than a disk. The M ring, which is oval in cross section, sits atop the S ring, making contact with it at an outer radius. The S ring appears to make contact with the rod, whereas the M ring does not. This situation, if true, is difficult to reconcile with the common notion that the S ring is stationary and the M ring rotates. It seems more likely that the S ring and rod rotate as a unit.

The electrical circuit of the HERA (Hadron Electron Ring Accelerator) proton ring (p-ring) is divided in octants so that in the case of a quench, the current has to be commutated to dumping resistors. The authors describe the application of superconducting switches which would enable the main circuit to remain at 4 K during a quench while the current is forced to flow through instantaneously loaded leads and dumping resistors. The main specifications of the required switches are: current of 6.5 kA, minimum off-resistance 12 Omega , energy absorbed 1 MJ, and self protecting. The various design and feasibility aspects of superconducting switches for this application are discussed. The requirement of being passively protected against a self-quench is considered the most critical design problem. It is still uncertain whether it remains necessary to apply an active protection scheme to enable safe operation of the switch. >

The magnitudes and relative signs of the long-range 1 H 31 P spin coupling constants between the side-chain protons and the 31 P nucleus in tri-(5-methyl-2-furyl)-phosphine, its sulfide and methyl phosphonium salt have been obtained. The relative signs were deduced from homonuclear spin tickling and selective decoupling experiments. Upon tetracoordination of phosphorus a change in the sign for this long-range (five- and/or six-bond) coupling is observed. For the phosphine | J PCH 3 | = 0.19 Hz and has the same sign as the 1 H 31 P ring coupling constants ( 3 J PH(3) and 4 J PH(4) ), i.e., positive, whereas for the phosphine sulfide and methyl phosphonium salt | J PCH 3 | equals 0.46 and 0.38 Hz, respectively, and are both of opposite sign to the 1 H 31 P ring couplings, i.e., negative.

Are the low ring structures on the Moon older than the craters ? A study of the Flamsteed P ring structure revealed by photographs taken by the U.S. lunar probes Orbiter I and Surveyor I throws new light on this question.

The hook-basal body complex of Salmonella typhimurium, a major component of its flagellar apparatus, was subjected to detailed analysis by electron microscopy and gel electrophoresis. The study was facilitated by the development of an improved protocol for isolation of the complexes in high yield and purity. Nine proteins were identified with the structure. These proteins had apparent molecular weights of 65,000 (65K), 60K, 42K, 38K, 32K, 30K, 27K, 16K, and 14K. Small but reproducible shifts in the apparent molecular weights of specific proteins from conditionally nonflagellate mutants indicated the following gene-polypeptide correspondences: flaFV, 42K; flaFVI, 32K; flaFVII, 30K; flaFIX, 38K; flaAII.1, 65K. Several new morphological features of hook-basal body complexes were recognized, including a clawlike structure on the cytoplasm-proximal M ring and additional material at the cytoplasmic face of the M ring. Based on this study and the work of others, we suggest that the morphological features of the hook-basal body complex correspond to the following proteins: hook-filament junction, 60K; hook, 42K; rod, 30K and 32K; L ring and outer cylinder wall, 27K; P ring, 38K; S ring, unknown; M ring 65K.

The compound forms by (2 + 2) cycloaddition of (CH3)3SiN(t-C4H9)P(S)=NC4H9-t with SOCl2 in pentane at -78°C and warming up to room temperature. It is purified by sublimation. The structure was not investigated. The existence of the four-membered SN2P ring in a ca. 50:50 mixture of the isomeric cis and trans forms is assumed. M.p. 42 to 51°C, b.p. 84 to 86°C/0.01 Torr.