bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensing and Acutuation of Composite Piezoelectric Materials for Smart Joint Applications
Authors: Konka Hari Prasad , Wahab M. A. , Lian Kun
Published: June 2010

Piezoelectric materials have the ability to provide desired transformation from mechanical to electrical energy and vice versa. When a mechanical force is applied to the piezoelectric material an electrical voltage is generated and when an electrical voltage is applied to the piezoelectric material it gets strained or mechanically deformed. Owing to these characteristics piezoelectric materials can be used as a sensor, an actuator, as well as a power generation unit. The high brittleness property of the original piezoelectric material is one of the major constraints in using them in engineering applications. In order to overcome this difficulty the composite piezoelectric materials were developed. The piezoelectric fiber material is flexible and can sustain large deformation without being damaged, and is compatible with the composite structures processing procedure; which makes it an ideal material to be used as an embedded sensor, power harvesting device, and a force actuator within the composite structures. The smart joint can be designed to have the piezoelectric materials embedded in them, wherein the piezoelectric materials can detect the various loads that act on the composite joint and could provide the required counter-balancing force to the externally applied input excitation forces acting on the joint; and thereby could reduce or even eliminate the effects of stress concentrations at the composite joint. High stress concentrations are one of the principal causes of structural failures as it may cause unexpected high stresses exceeding stress level caused by design loads. In this work our main objectives are to study the sensing and force generation capabilities of various commercially available composite piezoelectric configurations through series of experimentations; and to compare their performances in order to use them in the smart joint applications; and eventually, to reduce the detrimental effects of stress concentrations in the structures. Firstly, the sensing capabilities of these piezoelectric materials were investigated at various input frequencies and amplitudes of the vibration loads. Secondly, the tensile and bending force generation capabilities of these piezoelectric materials were inspected with respect to various input excitation voltages. The results of these experiments confirm that the voltage signals generated from these materials are proportional to the amplitudes of mechanical movement, with good response to high frequencies, even at micrometer deformation domain; but the force generation is relatively low under the input conditions investigated.
Evaluation and Refinement of the CRABI-6 Anthropomorphic Test Device Injury Criteria for Skull Fracture
Authors: Van Ee Chris , Moroski-Browne Barbara , Raymond David , Thibault Kirk , Hardy Warren , Plunkett John
Published: June 2010

Only sparse experimental pediatric tissue tolerance data are available for the development of pediatric surrogates and associated injury reference values. The objective of this study is to improve the efficacy of the CRABI series anthropometric test devices by increasing the foundational data used for head injury and skull fracture. To accomplish this, this study evaluated and refined the CRABI-6 injury assessment reference values (IARV) associated with skull fracture by correlating the test device response with the detailed fracture results of 50 infant cadaver drop studies reported by Weber in 1984 and 1985. Using the CRABI-6 test device, four 82-cm height free fall impacts were performed onto each of four different impact surfaces: concrete, carpet, 2-cm foam mat, and an 8-cm thick camel hair blanket. Average and standard deviation of peak head linear acceleration and HIC36 (Head Injury Criteria) were computed for each impact surface. The average CRABI impact response was mapped to the Weber fracture outcomes for corresponding impact surfaces and logistic regression was performed to define a skull fracture risk curve based on exposure. The 5%, 25%, 50%, 75%, and 95% risk for skull fracture correlated with a CRABI-6 peak linear head acceleration of 50, 70, 82, 94, and 114 g’s and a HIC36 of 87, 214, 290, 366 and 493, respectively. This study made use of the most extensive set of controlled infant cadaver head impact and fracture data currently available. Previous head IARVs for the CRABI-6 are given by Melvin (1995) and by Klinich et al. (2002). Based on a review of pediatric tissue experiments, scaling of adult and child dummy IARVs, and sled tests, Melvin suggested a HIC22 of 390 and a limit on peak head acceleration of 50 g’s. Klinich et al. reported the results of three reconstructions of airbag-related infant head injuries and three additional reconstructions not associated with head injury. They estimated the 50% risk of minor skull fracture to be 85 g’s and 220 HIC15. These previously reported estimates appear to be in agreement with the results reported from this study for CRABI-6 IARV of 50% risk of skull fracture at 82 g’s and 290 HIC36.
Even Flies Have Cravings
Authors: Gough Nancy R.
Published: June 2010

Mated fruit flies eat more protein in response to a peptide in male fly seminal fluid.
Toxic Clusters
Authors: Wong Wei
Published: June 2010

Forced clustering of metabotropic glutamate receptors by β-amyloid oligomers causes increased calcium influx.
Successful Treatment for Carriage of Methicillin-Resistant
Staphylococcus
aureus
and Importance of Follow-Up
Authors: Mollema F. P. N. , Severin J. A. , Nouwen J. L. , Ott A. , Verbrugh H. A. , Vos M. C.
Published: June 2010

With this prospective observational follow-up study of 165 methicillin-resistant
Staphylococcus aureus
(MRSA)-positive individuals (23 health care workers and 142 patients), we determined that our MRSA eradication therapy protocol results in a high success rate (81%). Five or more negative culture sets give a predictive value for MRSA eradication therapy success of >90%. Furthermore, MRSA colonization, at least in the throat, and the presence of wounds just before the start of MRSA eradication therapy are associated with MRSA eradication therapy failure.
Determining UV Inactivation of
Toxoplasma gondii
Oocysts by Using Cell Culture and a Mouse Bioassay
Authors: Ware Michael W. , Augustine Swinburne A. J. , Erisman David O. , See Mary Jean , Wymer Larry , Hayes Samuel L. , Dubey J. P. , Villegas Eric N.
Published: June 2010

The effect of UV exposure on
Toxoplasma gondii
oocysts has not been completely defined for use in water disinfection. This study evaluated UV-irradiated oocysts by three assays: a SCID mouse bioassay, an
in vitro T. gondii
oocyst plaque (TOP) assay, and a quantitative reverse transcriptase real-time PCR (RT-qPCR) assay. The results from the animal bioassay show that 1- and 3-log
10
inactivation is achieved with 4 mJ/cm
2
UV and 10 mJ/cm
2
low-pressure UV, respectively. TOP assay results, but not RT-qPCR results, correlate well with bioassay results. In conclusion, a 3-log
10
inactivation of
T. gondii
oocysts is achieved by 10-mJ/cm
2
low-pressure UV, and the
in vitro
TOP assay is a promising alternative to the mouse bioassay.
Novel Florfenicol and Chloramphenicol Resistance Gene Discovered in Alaskan Soil by Using Functional Metagenomics
Authors: Lang Kevin S. , Anderson Janet M. , Schwarz Stefan , Williamson Lynn , Handelsman Jo , Singer Randall S.
Published: June 2010

Functional metagenomics was used to search for florfenicol resistance genes in libraries of cloned DNA isolated from Alaskan soil. A gene that mediated reduced susceptibility to florfenicol was identified and designated
pexA
. The predicted PexA protein showed a structure similar to that of efflux pumps of the major facilitator superfamily.
A Second Soluble Hox-Type NiFe Enzyme Completes the Hydrogenase Set in
Thiocapsa roseopersicina
BBS
Authors: Maróti Judit , Farkas Attila , Nagy Ildikó K. , Maróti Gergely , Kondorosi Éva , Rákhely Gábor , Kovács Kornél L.
Published: June 2010

Three functional NiFe hydrogenases were previously characterized in
Thiocapsa roseopersicina
BBS: two of them are attached to the periplasmic membrane (HynSL and HupSL), and one is localized in the cytoplasm (HoxEFUYH). The ongoing genome sequencing project revealed the presence of genes coding for another soluble Hox-type hydrogenase enzyme (
hox2FUYH
). Hox2 is a heterotetrameric enzyme; no indication for an additional subunit was found. Detailed comparative
in vivo
and
in vitro
activity and expression analyses of HoxEFUYH (Hox1) and the newly discovered Hox2 enzyme were performed. Functional differences between the two soluble NiFe hydrogenases were disclosed. Hox1 seems to be connected to both sulfur metabolism and dark/photofermentative processes. The bidirectional Hox2 hydrogenase was shown to be metabolically active under specific conditions: it can evolve hydrogen in the presence of glucose at low sodium thiosulfate concentration. However, under nitrogen-fixing conditions, it can oxidize H
2
but less than the other hydrogenases in the cell.
Xer Site-Specific Recombination, an Efficient Tool To Introduce Unmarked Deletions into Mycobacteria
Authors: Cascioferro Alessandro , Boldrin Francesca , Serafini Agnese , Provvedi Roberta , Palù Giorgio , Manganelli Riccardo
Published: June 2010

Genetic manipulation of mycobacteria still represents a serious challenge due to the lack of tools and selection markers. In this report, we describe the development of an intrinsically unstable excisable cassette for introduction of unmarked mutations in both
Mycobacterium smegmatis
and
Mycobacterium tuberculosis
.
Validation of a Nylon-Flocked-Swab Protocol for Efficient Recovery of Bacterial Spores from Smooth and Rough Surfaces
Authors: Probst Alexander , Facius Rainer , Wirth Reinhard , Moissl-Eichinger Christine
Published: June 2010

In order to meet planetary-protection requirements, culturable bacterial spore loads are measured representatively for the total microbial contamination of spacecraft. However, the National Aeronautics and Space Administration's (NASA's) cotton swab protocols for spore load determination have not changed for decades. To determine whether a more efficient alternative was available, a novel swab was evaluated for recovery of different
Bacillus atrophaeus
spore concentrations on stainless steel and other surfaces. Two protocols for the nylon-flocked swab (NFS) were validated and compared to the present NASA standard protocol. The results indicate that the novel swab protocols recover 3- to 4-fold more (45.4% and 49.0% recovery efficiency)
B. atrophaeus
spores than the NASA standard method (13.2%). Moreover, the nylon-flocked-swab protocols were superior in recovery efficiency for spores of seven different
Bacillus
species, including
Bacillus anthracis
Sterne (recovery efficiency, 20%). The recovery efficiencies for
B. atrophaeus
spores from different surfaces showed a variation from 5.9 to 62.0%, depending on the roughness of the surface analyzed. Direct inoculation of the swab resulted in a recovery rate of about 80%, consistent with the results of scanning electron micrographs that allowed detailed comparisons of the two swab types. The results of this investigation will significantly contribute to the cleanliness control of future life detection missions and will provide significant improvement in detection of
B. anthracis
contamination for law enforcement and security efforts.
Requirement of the Type II Secretion System for Utilization of Cellulosic Substrates by
Cellvibrio japonicus
Authors: Gardner Jeffrey G. , Keating David H.
Published: June 2010

Cellulosic biofuels represent a powerful alternative to petroleum but are currently limited by the inefficiencies of the conversion process. While Gram-positive and fungal organisms have been widely explored as sources of cellulases and hemicellulases for biomass degradation, Gram-negative organisms have received less experimental attention. We investigated the ability of
Cellvibrio japonicus
, a recently sequenced Gram-negative cellulolytic bacterium, to degrade bioenergy-related feedstocks. Using a newly developed biomass medium, we showed that
C. japonicus
is able to utilize corn stover and switchgrass as sole sources of carbon and energy for growth. We also developed tools for directed gene disruptions in
C. japonicus
and used this system to construct a mutant in the
gspD
gene, which is predicted to encode a component of the type II secretion system. The
gspD
::pJGG1 mutant displayed a greater-than-2-fold decrease in endoglucanase secretion compared to wild- type
C. japonicus
. In addition, the mutant strain showed a pronounced growth defect in medium with biomass as a carbon source, yielding 100-fold fewer viable cells than the wild type. To test the potential of
C. japonicus
to undergo metabolic engineering, we constructed a strain able to produce small amounts of ethanol from biomass. Collectively, these data suggest that
C. japonicus
is a useful platform for biomass conversion and biofuel production.
Facilitation of Direct Conditional Knockout of Essential Genes in
Bacillus licheniformis
DSM13 by Comparative Genetic Analysis and Manipulation of Genetic Competence
Authors: Hoffmann Kerstin , Wollherr Antje , Larsen Michael , Rachinger Michael , Liesegang Heiko , Ehrenreich Armin , Meinhardt Friedhelm
Published: June 2010

The genetic manageability of the biotechnologically important
Bacillus licheniformis
is hampered due to its poor transformability, whereas
Bacillus subtilis
efficiently takes up DNA during genetic competence, a quorum-sensing-dependent process. Since the sensor histidine kinase ComP, encoded by a gene of the quorum-sensing module
comQXPA
of
B. licheniformis
DSM13, was found to be inactive due to an insertion element within
comP
, the coding region was exchanged with a functional copy. Quorum sensing was restored, but the already-poor genetic competence dropped further. The inducible expression of the key regulator for the transcription of competence genes, ComK, in
trans
resulted in highly competent strains and facilitated the direct disruption of genes, as well as the conditional knockout of an essential operon. As ComK is inhibited at low cell densities by a proteolytic complex in which MecA binds ComK and such inhibition is antagonized by the interaction of MecA with ComS (the expression of the latter is controlled by cell density in
B. subtilis
), we performed an
in silico
analysis of MecA and the hitherto unidentified ComS, which revealed differences for competent and noncompetent strains, indicating that the reduced competence possibly is due to a nonfunctional coupling of the
comQXPA
-encoded quorum module and ComK. The obtained increased genetic tractability of this industrial workhorse should improve a wide array of scientific investigations.
Biosynthesis and Biodegradation of 3-Hydroxypropionate- Containing Polyesters
Authors: Andreeßen Björn , Steinbüchel Alexander
Published: June 2010

3-Hydroxypropionate (3HP) is an important compound in the chemical industry, and the polymerized 3HP can be used as a bioplastic. In this review, we focus on polyesters consisting of 3HP monomers, including the homopolyester poly(3-hydroxypropionate) and copolyesters poly(3-hydroxybutyrate-
co
-3-hydroxypropionate), poly(3-hydroxypropionate-
co
-3-hydroxybutyrate-
co
-3-hydroxyhexanoate-
co
-3-hydroxyoctanoate), poly(4-hydroxybutyrate-
co
-3-hydroxypropionate-
co
-lactate), and poly(3-hydroxybutyrate-
co
-3-hydroxypropionate-
co
-4-hydroxybutyrate-
co
-lactate). Homopolyesters like poly(3-hydroxybutyrate) are often highly crystalline and brittle, which limits some of their applications. The incorporation of 3HP monomers reduces the glass transition temperature, the crystallinity, and also, at up to 60 to 70 mol% 3HP, the melting point of the copolymer. This review provides a survey of the synthesis and physical properties of different polyesters containing 3HP.
Outer Membrane Proteins A (OmpA) and X (OmpX) Are Essential for Basolateral Invasion of
Cronobacter sakazakii
Authors: Kim Kyumson , Kim Kwang-Pyo , Choi Jeongjoon , Lim Jeong-A , Lee Junghyun , Hwang Sunyoung , Ryu Sangryeol
Published: June 2010

Cronobacter sakazakii
is an opportunistic pathogen that actively invades host eukaryotic cells. To identify invasion factors responsible for the intestinal translocation of
C. sakazakii
, we constructed for the first time outer membrane protein X (OmpX) and A (OmpA) deletion mutants using the lambda Red recombination system. The
ompX
and
ompA
deletion mutants showed significantly reduced invasion of human enterocyte-like epithelial Caco-2 and human intestinal epithelial INT-407 cells, and significantly fewer mutant cells were recovered from the livers and spleens of rat pups. Furthermore, compared with intact target cells, the invasion and initial association potentials of the mutants increased at a rate similar to that of the wild type in tight-junction-disrupted target cells, suggesting that OmpX and OmpA are involved in basolateral invasion by
C. sakazakii
. This is the first report of
C. sakazakii
virulence determinants that are essential for basolateral invasion and that may be critical for the virulence of
C. sakazakii
.
Improved
dsrA
-Based Terminal Restriction Fragment Length Polymorphism Analysis of Sulfate-Reducing Bacteria
Authors: Santillano Daniel , Boetius Antje , Ramette Alban
Published: June 2010

To better describe the community structure of sulfate-reducing bacteria in environmental systems, we compared several dissimilatory sulfite reductase (
dsr
) primer sets for terminal restriction fragment length polymorphism application. A new reverse primer that increased allelic diversity estimates up to 5-fold was applied to hydrocarbon seep samples to examine the relationship between guild activity and diversity.
Melanin Externalization in Candida albicans Depends on Cell Wall Chitin Structures
Authors: Walker Claire A. , Gómez Beatriz L. , Mora-Montes Héctor M. , Mackenzie Kevin S. , Munro Carol A. , Brown Alistair J. P. , Gow Neil A. R. , Kibbler Christopher C. , Odds Frank C.
Published: June 2010

The fungal pathogen
Candida albicans
produces dark-pigmented melanin after 3 to 4 days of incubation in medium containing
l
-3,4-dihydroxyphenylalanine (
l
-DOPA) as a substrate. Expression profiling of
C. albicans
revealed very few genes significantly up- or downregulated by growth in
l
-DOPA. We were unable to determine a possible role for melanin in the virulence of
C. albicans
. However, we showed that melanin was externalized from the fungal cells in the form of electron-dense melanosomes that were free or often loosely bound to the cell wall exterior. Melanin production was boosted by the addition of
N
-acetylglucosamine to the medium, indicating a possible association between melanin production and chitin synthesis. Melanin externalization was blocked in a mutant specifically disrupted in the chitin synthase-encoding gene
CHS2
. Melanosomes remained within the outermost cell wall layers in
chs3
Δ and
chs2
Δ
chs3
Δ mutants but were fully externalized in
chs8
Δ and
chs2
Δ
chs8
Δ mutants. All the
CHS
mutants synthesized dark pigment at equivalent rates from mixed membrane fractions
in vitro
, suggesting it was the form of chitin structure produced by the enzymes, not the enzymes themselves, that was involved in the melanin externalization process. Mutants with single and double disruptions of the chitinase genes
CHT2
and
CHT3
and the chitin pathway regulator
ECM33
also showed impaired melanin externalization. We hypothesize that the chitin product of Chs3 forms a scaffold essential for normal externalization of melanosomes, while the Chs8 chitin product, probably produced in cell walls in greater quantity in the absence of
CHS2
, impedes externalization.
β(1-3)Glucanosyltransferase Gel4p Is Essential for Aspergillus fumigatus
Authors: Gastebois Amandine , Fontaine Thierry , Latgé Jean-Paul , Mouyna Isabelle
Published: June 2010

The β(1-3)glucanosyltransferase
GEL
family of
Aspergillus fumigatus
contains 7 genes, among which only 3 are expressed during mycelial growth. The role of the
GEL4
gene was investigated in this study. Like the other Gelps, it encodes a glycosylphosphatidylinositol (GPI)-anchored protein. In contrast to the other β(1-3)glucanosyltransferases analyzed to date, it is essential for this fungal species.
Genome Organization and Pathogenicity ofCorynebacterium diphtheriaeC7(−) and PW8 Strains
Authors: Iwaki Masaaki , Komiya Takako , Yamamoto Akihiko , Ishiwa Akiko , Nagata Noriyo , Arakawa Yoshichika , Takahashi Motohide
Published: June 2010

Corynebacterium diphtheriaeis the causative agent of diphtheria. In 2003, the complete genomic nucleotide sequence of an isolate (NCTC13129) from a large outbreak in the former Soviet Union was published, in which the presence of 13 putative pathogenicity islands (PAIs) was demonstrated. In contrast, earlier work on diphtheria mainly employed the C7(−) strain for genetic analysis; therefore, current knowledge of the molecular genetics of the bacterium is limited to that strain. However, genomic information on the NCTC13129 strain has scarcely been compared to strain C7(−). Another importantC. diphtheriaestrain is Park-Williams no. 8 (PW8), which has been the only major strain used in toxoid vaccine production and for which genomic information also is not available. Here, we show by comparative genomic hybridization that at least 37 regions from the reference genome, including 11 of the 13 PAIs, are considered to be absent in the C7(−) genome. Despite this, the C7(−) strain still retained signs of pathogenicity, showing a degree of adhesion to Detroit 562 cells, as well as the formation of and persistence in abscesses in animal skin comparable to that of the NCTC13129 strain. In contrast, the PW8 strain, suggested to lack 14 genomic regions, including 3 PAIs, exhibited more reduced signs of pathogenicity. These results, together with great diversity in the presence of the 37 genomic regions among variousC. diphtheriaestrains shown by PCR analyses, suggest great heterogeneity of this pathogen, not only in genome organization, but also in pathogenicity.
Frameshift Mutations in a Single Novel Virulence Factor Alter theIn VivoPathogenicity ofChlamydia trachomatisfor the Female Murine Genital Tract
Authors: Sturdevant Gail L. , Kari Laszlo , Gardner Donald J. , Olivares-Zavaleta Norma , Randall Linnell B. , Whitmire William M. , Carlson John H. , Goheen Morgan M. , Selleck Elizabeth M. , Martens Craig , Caldwell Harlan D.
Published: June 2010

Chlamydia trachomatisis a human pathogen of global importance. An obstacle to studying the pathophysiology of human chlamydial disease is the lack of a suitable murine model ofC. trachomatisinfection. Mice are less susceptible to infection with human isolates due in part to innate mouse-specific host defense mechanisms to which human strains are sensitive. Another possible factor that influences the susceptibility of mice to infection is that human isolates are commonly cultivatedin vitroprior to infection of mice; therefore, virulence genes could be lost as a consequence of negative selective pressure. We tested this hypothesis by infecting innate immunity-deficient C3H/HeJ female mice intravaginally with a human serovar D urogenital isolate that had undergone multiplein vitropassages. We observed early and late infection clearance phenotypes. Strains of each phenotype were isolated and then used to reinfect naïve mice. Following infection, the late-clearance strain was significantly more virulent. It caused unvarying infections of much longer durations with greater infectious burdens that naturally ascended to the upper genital tract, causing salpingitis. Despite contrastingin vivovirulence characteristics, the strains exhibited no differences in the results ofin vitroinfectivity assays or sensitivities to gamma interferon. Genome sequencing of the strains revealed mutations that localized to a single gene (CT135), implicating it as a critical virulence factor. Mutations in CT135 were not unique to serovar D but were also found in multiple oculogenital reference strains. Our findings provide new information about the pathogenomics of chlamydial infection and insights for improving murine models of infection using human strains.
Characterization of the Transposase Encoded by IS
256
, the Prototype of a Major Family of Bacterial Insertion Sequence Elements
Authors: Hennig Susanne , Ziebuhr Wilma
Published: June 2010

IS
256
is the founding member of the IS
256
family of insertion sequence (IS) elements. These elements encode a poorly characterized transposase, which features a conserved DDE catalytic motif and produces circular IS intermediates. Here, we characterized the IS
256
transposase as a DNA-binding protein and obtained insight into the subdomain organization and functional properties of this prototype enzyme of IS
256
family transposases. Recombinant forms of the transposase were shown to bind specifically to inverted repeats present in the IS
256
noncoding regions. A DNA-binding domain was identified in the N-terminal part of the transposase, and a mutagenesis study targeting conserved amino acid residues in this region revealed a putative helix-turn-helix structure as a key element involved in DNA binding. Furthermore, we obtained evidence to suggest that the terminal nucleotides of IS
256
are critically involved in IS circularization. Although small deletions at both ends reduced the formation of IS circles, changes at the left-hand IS
256
terminus proved to be significantly more detrimental to circle production. Taken together, the data lead us to suggest that the IS
256
transposase-mediated circularization reaction preferentially starts with a sequence-specific first-strand cleavage at the left-hand IS terminus.
Changes in the Min Oscillation Pattern before and after Cell Birth
Authors: Juarez Jennifer R. , Margolin William
Published: June 2010

The Min system regulates the positioning of the cell division site in many bacteria. In
Escherichia coli
, MinD migrates rapidly from one cell pole to the other. In conjunction with MinC, MinD helps to prevent unwanted FtsZ rings from assembling at the poles and to stabilize their positioning at midcell. Using time-lapse microscopy of growing and dividing cells expressing a
gfp-minD
fusion, we show that green fluorescent protein (GFP)-MinD often paused at midcell in addition to at the poles, and the frequency of midcell pausing increased as cells grew longer and cell division approached. At later stages of septum formation, GFP-MinD often paused specifically on only one side of the septum, followed by migration to the other side of the septum or to a cell pole. About the time of septum closure, this irregular pattern often switched to a transient double pole-to-pole oscillation in the daughter cells, which ultimately became a stable double oscillation. The splitting of a single MinD zone into two depends on the developing septum and is a potential mechanism to explain how MinD is distributed equitably to both daughter cells. Septal pausing of GFP-MinD did not require MinC, suggesting that MinC-FtsZ interactions do not drive MinD-septal interactions, and instead MinD recognizes a specific geometric, lipid, and/or protein target at the developing septum. Finally, we observed regular end-to-end oscillation over very short distances along the long axes of minicells, supporting the importance of geometry in MinD localization.
Catabolite Repression of the TodS/TodT Two-Component System and Effector-Dependent Transphosphorylation of TodT as the Basis for Toluene Dioxygenase Catabolic Pathway Control
Authors: Busch Andreas , Lacal Jesús , Silva-Jímenez Hortencia , Krell Tino , Ramos Juan L.
Published: June 2010

The TodS/TodT two-component system of
Pseudomonas putida
regulates the expression of the toluene dioxygenase (
tod
) operon for the metabolism of toluene, benzene, and ethylbenzene. The sensor kinase TodS has a complex domain arrangement containing two functional modules, each harboring a sensor and an autokinase domain separated by a receiver domain. The TodT protein is the cognate response regulator that activates transcription of the toluene dioxygenase (TOD) pathway genes at the P

todX

promoter. We report in this study that the
todST
operon is transcribed from a main promoter and that the +1 initiation point is located 31 nucleotides upstream from the A of the first ATG codon and is preceded by a −10/−35 canonical promoter. Expression from P

todS

is under catabolite control, and in cells growing with glucose, the level of expression from this promoter is reduced, which in turn translates to low levels of the TodS/TodT regulators and results in a decrease of transcription from the P

todX

promoter. Thus, the main underlying regulatory mechanisms of the
tod
structural genes are at the levels of catabolite repression control from P

todS

and transcription activation, mediated by the TodT response regulator through a regulatory cascade in which the effector enhances autophosphorylation of TodS by ATP, with subsequent transphosphorylation of TodT.
Phosphorylation and Dephosphorylation among Dif Chemosensory Proteins Essential for Exopolysaccharide Regulation inMyxococcus xanthus
Authors: Black Wesley P. , Schubot Florian D. , Li Zhuo , Yang Zhaomin
Published: June 2010

Myxococcus xanthussocial gliding motility, which is powered by type IV pili, requires the presence of exopolysaccharides (EPS) on the cell surface. The Dif chemosensory system is essential for the regulation of EPS production. It was demonstrated previously that DifA (methyl-accepting chemotaxis protein [MCP]-like), DifC (CheW-like), and DifE (CheA-like) stimulate whereas DifD (CheY-like) and DifG (CheC-like) inhibit EPS production. DifD was found not to function downstream of DifE in EPS regulation, as adifD difEdouble mutant phenocopied thedifEsingle mutant. It has been proposed that DifA, DifC, and DifE form a ternary signaling complex that positively regulates EPS production through the kinase activity of DifE. DifD was proposed as a phosphate sink of phosphorylated DifE (DifE∼P), while DifG would augment the function of DifD as a phosphatase of phosphorylated DifD (DifD∼P). Here we reportin vitrophosphorylation studies with all the Dif chemosensory proteins that were expressed and purified fromEscherichia coli. DifE was demonstrated to be an autokinase. Consistent with the formation of a DifA-DifC-DifE complex, DifA and DifC together, but not individually, were found to influence DifE autophosphorylation. DifD, which did not inhibit DifE autophosphorylation directly, was found to accept phosphate from autophosphorylated DifE. While DifD∼P has an unusually long half-life for dephosphorylationin vitro, DifG efficiently dephosphorylated DifD∼P as a phosphatase. These results support a model where DifE complexes with DifA and DifC to regulate EPS production through phosphorylation of a downstream target, while DifD and DifG function synergistically to divert phosphates away from DifE∼P.
Identification of the Biosynthetic Gene Cluster for thePseudomonas aeruginosaAntimetabolitel-2-Amino-4-Methoxy-trans-3-Butenoic Acid
Authors: Lee Xiaoyun , Fox Áine , Sufrin Janice , Henry Hugues , Majcherczyk Paul , Haas Dieter , Reimmann Cornelia
Published: June 2010

l-2-Amino-4-methoxy-trans-3-butenoic acid (AMB) is a potent antibiotic and toxin produced byPseudomonas aeruginosa.Using a novel biochemical assay combined with site-directed mutagenesis in strain PAO1, we have identified a five-gene cluster specifying AMB biosynthesis, probably involving a thiotemplate mechanism. Overexpression of this cluster in strain PA7, a natural AMB-negative isolate, led to AMB overproduction.
Genome Sequence of a Cellulose-Producing Bacterium,
Gluconacetobacter hansenii
ATCC 23769
Authors: Iyer Prashanti R. , Geib Scott M. , Catchmark Jeff , Kao Teh-hui , Tien Ming
Published: June 2010

The Gram-negative bacterium
Gluconacetobacter hansenii
is considered a model organism for studying cellulose synthesis. We have determined the genome sequence of strain ATCC 23769.
Transcriptional Activation of the Aldehyde Reductase YqhD by YqhC and Its Implication in Glyoxal Metabolism of
Escherichia coli
K-12
Authors: Lee Changhan , Kim Insook , Lee Junghoon , Lee Kang-Lok , Min Bumchan , Park Chankyu
Published: June 2010

The reactive α-oxoaldehydes such as glyoxal (GO) and methylglyoxal (MG) are generated
in vivo
from sugars through oxidative stress. GO and MG are believed to be removed from cells by glutathione-dependent glyoxalases and other aldehyde reductases. We isolated a number of GO-resistant (GO
r
) mutants from
Escherichia coli
strain MG1655 on LB plates containing 10 mM GO. By tagging the mutations with the transposon Tn
phoA
-132 and determining their cotransductional linkages, we were able to identify a locus to which most of the GO
r
mutations were mapped. DNA sequencing of the locus revealed that it contains the
yqhC
gene, which is predicted to encode an AraC-type transcriptional regulator of unknown function. The GO
r
mutations we identified result in missense changes in
yqhC
and were concentrated in the predicted regulatory domain of the protein, thereby constitutively activating the product of the adjacent gene
yqhD
. The transcriptional activation of
yqhD
by wild-type YqhC and its mutant forms was established by an assay with a β-galactosidase reporter fusion, as well as with real-time quantitative reverse transcription-PCR. We demonstrated that YqhC binds to the promoter region of
yqhD
and that this binding is abolished by a mutation in the potential target site, which is similar to the consensus sequence of its homolog SoxS. YqhD facilitates the removal of GO through its NADPH-dependent enzymatic reduction activity by converting it to ethadiol via glycolaldehyde, as detected by nuclear magnetic resonance, as well as by spectroscopic measurements. Therefore, we propose that YqhC is a transcriptional activator of YqhD, which acts as an aldehyde reductase with specificity for certain aldehydes, including GO.
Escherichia coli SRP, Its Protein Subunit Ffh, and the Ffh M Domain Are Able To Selectively Limit Membrane Protein Expression When Overexpressed
Authors: Yosef Ido , Bochkareva Elena S. , Bibi Eitan
Published: June 2010

The
Escherichia coli
signal recognition particle (SRP) system plays an important role in membrane protein biogenesis. Previous studies have suggested indirectly that in addition to its role during the targeting of ribosomes translating membrane proteins to translocons, the SRP might also have a quality control role in preventing premature synthesis of membrane proteins in the cytoplasm. This proposal was studied here using cells simultaneously overexpressing various membrane proteins and either SRP, the SRP protein Ffh, its 4.5S RNA, or the Ffh M domain. The results show that SRP, Ffh, and the M domain are all able to selectively inhibit the expression of membrane proteins. We observed no apparent changes in the steady-state mRNA levels or membrane protein stability, suggesting that inhibition may occur at the level of translation, possibly through the interaction between Ffh and ribosome-hydrophobic nascent chain complexes. Since
E. coli
SRP does not have a eukaryote-like translation arrest domain, we discuss other possible mechanisms by which this SRP might regulate membrane protein translation when overexpressed.

IMPORTANCE
The eukaryotic SRP slows down translation of SRP substrates by cytoplasmic ribosomes. This activity is important for preventing premature synthesis of secretory and membrane proteins in the cytoplasm. It is likely that an analogous quality control step would be required in all living cells. However, on the basis of its composition and domain structure and limited
in vitro
studies, it is believed that the
E. coli
SRP is unable to regulate ribosomes translating membrane proteins. Nevertheless, several
in vivo
studies have suggested otherwise. To address this issue further
in vivo
, we utilized unbalanced conditions under which
E. coli
simultaneously overexpresses SRP and each of several membrane or cytosolic proteins. Surprisingly, our results clearly show that the
E. coli
SRP is capable of regulating membrane protein synthesis and demonstrate that the M domain of Ffh mediates this activity. These results thus open the way for mechanistic characterization of this quality control process in bacteria.
Oxidation of cyclic N-(arylamino)imides. An EPR study of hydrazoxyl radicals
Authors: Omelka Ladislav , Reinhardt Michael , Kluge Ralph , Schulz Manfred
Published: June 2010

New types of hydrazoxyl radicals were identified by ESR spectroscopic method during oxidation of N-(arylamino)imides. The ESR parameters of radicals generated were obtained by a spectral simulation. The effect of substituents on the values of splitting constants of nitrogen atoms N1 and N2 is discussed. The splitting constants a(N1) well correlate with the σ-Hammett constants of substituents of the 1-phenyl group.
Vilsmeier-Haack reaction of 2-amino-X-benzothiazoles with N-phenylformamide in the presence of benzenesulfonyl chloride
Authors: Lácová Margita , Nga Nguyen Thi , Halgaš Ján
Published: June 2010

2-Amino-X-benzothiazoles (X = H, 4-Cl, 6-Cl, 6-NO2, 6-CH3, 6-OCH3, 6-Br) react with N-phenylformamide and two equivalents of benzenesulfonyl chloride in pyridine, affording different products in dependence on the substituent X: N-(X-2-benzothiazolyl)formamidines, N-phenyl-N’-(X-2-benzothiazolyl)formamidines, N-phenyl-N’,N’’-bis(X-2-benzothiazolyl)triaminomethanes, N-(X-2-benzothiazolyl)benzenesulfonamides and N-2-((X-3-phenyliminomethyl)-benzothiazolylidene)benzenesulfonamides. In the presence of one equivalent of benzenesulfonyl chloride, benzothiazoles I either do not react or are partially benzenesulfonated.
1-Methyl-, 1-phenyl-, and 1-(2-(2-dimethylaminoethoxy)-phenyl)-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole and their 2-substituted derivatives: Synthesis and pharmacological screening
Authors: Hulinská Hana , Taufmann Petr , Frycová Hana , Protiva Miroslav
Published: June 2010

1-Methyl- and 1-phenyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole (I and IV) were transformed via the chloroacetyl derivatives II and V to the 4-methylpiperazinoacetyl compounds III and VI; compound VI inhibits effectively the formation of the indomethacin-induced gastric ulcers in rats but is devoid of anticholinergic activity and does not inhibit the gastric secretion in rats. Reaction of tryptamine with 2-(2-dimethylaminoethoxy)benzaldehyde afforded compound IX which proved inactive in tests for antidepressant activity. Compounds IV and IX were treated with ethyl chloroformate and gave carbamates VI and X; compound VII does not show anticonvulsant activity.
X-ray photoelectron spectroscopic (XPS) studies of iodine oxocompounds
Authors: Bastl Zdeněk , Gehlmann Heidrun
Published: June 2010

The core electron binding energies of eighteen compounds containing iodine in different oxidation states ranging from (-I) to (VII) have been measured. The observed chemical shifts differ from the literature data. The anticipated existence of hexavalent iodine in certain compounds has not been demonstrated. The relative subshell photoemission intensities of iodine have been determined. Empirically derived atomic sensitivity factors and theoretical photoionization cross-sections have been used to calculate the surface stoichiometry. The concentration ratios obtained via the two methods are compared. In agreement with generally accepted view the results of this comparison imply that, for quantitative surface analysis, empirical values should be used rather than theoretical data.
The methanolysis kinetics and dissociation constants of 1-(subst. benzoyl)-3-phenylthioureas
Authors: Kaválek Jaromír , Jirman Josef , Macháček Vladimír , Štěrba Vojeslav
Published: June 2010

A series of seven 1-(subst. benzoyl)-3-phenylthioureas have been prepared and their dissociation constants and solvolysis rate constants have been measured in methanol at 25 °C. The reaction constants found show that the solvolysis rate is limited by the attack of methoxide ion on the benzoyl carbonyl group of the non-dissociated substrate. The polar effect of substituents in benzoyl group is extensively transferred also by the intramolecular hydrogen bond.
Reactivity of hydroxyl groups of 1,6 : 2,3- and 1,6 : 3,4-dianhydrido-β-D-hexapyranoses in methylation with iodomethane
Authors: Sámek Stanislav , Trnka Tomáš , Černý Miloslav
Published: June 2010

Relative rate constants for reaction of 1,6 : 2,3- and 1,6 : 3,4-dianhydro-β-D-hexapyranoses with iodomethane in acetonitrile in the presence of silver oxide were measured. Their values, ranging from 1 to 8.6 were interpreted on the basis of polar and steric effects and intramolecular hydrogen bonds.
Synthesis of ethyl ortho-substituted benzoylacetates and investigation of the influence of ortho-substituents on keto-enol tautomerism and MS fragmentation behaviour
Authors: Sicker Dieter , Mann Gerhard
Published: June 2010

A series of seven ethyl 2-acetyl-(2-substituted benzoyl)acetates II-VIII was synthesized, together with their parent compound I, from the corresponding acid chlorides. The tautomerism of these β-tricarbonyl compounds in tetrachloromethane was studied by 1H NMR spectroscopy and former results concerning this problem were critically evaluated. A further series of seven ortho-substituted ethyl benzoylacetates X-XV and XVII was obtained from the corresponding precursors II-VIII. The keto-enol tautomerism of these β-keto esters was studied by 1H NMR in different solvents and compared with ethyl benzoylacetate IX as standard. Differences caused by the ortho-substituents are discussed. Investigation of the mass spectrometric fragmentation of the β-keto esters IX-XV and XVII showed both common fragmentation pathways due to the same substance class and typical differences in relative intensities according to the nature of the ortho-substituent.
Formation of N-methyl-2-nitroso-4,6-dinitroaniline from methyl ester of N-methyl-N-(2,4,6-trinitrophenyl)glycine
Authors: Kaválek Jaromír , Macháček Vladimír , Štěrba Vojeslav , Lyčka Antonín
Published: June 2010

The reaction of methyl ester of N-methyl-N-(2,4,6-trinitrophenyl)glycine with methoxide in methanol produces N-methyl-2-nitroso-4,6-dinitroaniline. The kinetics of formation of the nitroso compound have been studied, and a mechanism of its formation has been suggested consisting in the intramolecular attack of CH2 group of aziridinone intermediate by oxygen atom of nitro group and in subsequent E2 elimination reaction. The aziridinone intermediate is formed by the attack of carbon atom of carboxylic group of 1,3-adduct of the starting ester with methoxide by the formally electroneutral tertiary nitrogen. In methoxide solution, N-methyl-2-nitroso-4,6-dinitroaniline undergoes another reduction-oxidation reaction giving 2-amino-2'-methylamino-3,3',5,5'-tetranitroazoxybenzene.
Preparation and spectral properties of imidazo- and triazoloquinolines with angular ring fusion
Authors: Milata Viktor , Ilavský Dušan , Leško Ján
Published: June 2010

The imidazo- and triazolo[4,5-f]quinolines (Va, Vb) and imidazo- and triazolo[4,5-h]quinolines (Xa, Xb) have been synthetized by the Gould-Jacobs reaction starting from the quinolinecarboxylic acids II and VII prepared by base-catalyzed hydrolysis of the esters I and VI, resp. The decarboxylation of the acids II and VII gives the quinolones III and VIII, resp., which are aromatized to the corresponding chloroquinolines IV and IX. The latter compounds give the azoloquinolines V and X on catalytic reduction. The structure of the condensed heterocyclic compounds with angular ring fusion has been proved by 1H and 13C NMR, IR, UV, and mass spectra.
Ab initio MO study of protonation of carbamic acid, methyl carbamate and methyl N-methylcarbamate
Authors: Remko Milan
Published: June 2010

The ab initio SCF method was applied to the protonation of the carbonyl group in carbamic acid and its methyl derivatives, viz. methyl carbamate and methyl N-methylcarbamate. Complete geometry optimization was accomplished for these compounds and their protonated species using the MINI-1, 3-21 G, and 6-31 G* bases and the proton affinities were calculated at the MINI-1, 3-21 G, 6-31 G*, and 6-31 G** levels. 2nd and 3rd order Moller-Plesset perturbation calculations were also performed for examining the effect of the correlation energy on the calculated protonation energies. The carbonyl protonation energies were found to increase in order carbamic acid < methyl carbamate < methyl N-methylcarbamate. The absolute values of calculated gas phase proton affinities depend on the basis used and way of evaluating the correlation energy. The results are discussed with respect to the theoretical proton affinities of structurally related amides and to related available theoretical gas phase proton affinities.
Conformations of molecules bearing two carbonyl groups on adjacent atoms
Authors: Exner Otto , Jehlička Václav , Tinant Bernard
Published: June 2010

Conformation of α-acyloxyketones IIIa-IIIc was determined from their dipole moments in benzene solution. Around the C-O bond the ap conformation prevails over sc, around the C-C bond several conformations are present and those with a larger distance between the two carbonyl oxygens are preferred. The conformation in thus quite different than in crystal. Similarities of the crystal conformations of III to I or II are due mainly to crystal packing forces, while the interaction of the two carbonyl oxygen atoms is of little importance.
A general method of preparation of N-diformylmethylazoles and cycloimonium diformyl methylides
Authors: Král Vladimír , Semenov Viktor Vladimirovich , Kanishchev Mikhail Ivanovich , Arnold Zdeněk , Shevelev Svyatoslav Arkadievich , Fainzilberg Albert Aleksandrovich
Published: June 2010

Formylation of easily accessible heteroarylacetic acids (R-CH2COOH, R = imidazole, pyrazole, tetrazole, pyridine) afforded in high yields the corresponding trimethinium salts R-C(=CH-N(CH3)2)CH=N(CH3)2)n+ nX- which on alkaline hydrolysis were converted into N-diformylmethylazoles R-C(CHO)=CH-OH. Their quaternization gave cycloimonium diformyl methylides.
An intermediate of reaction of 2-naphthol with activated sludge
Authors: Komers Karel , Lyčka Antonín , Jirman Josef , Kolb Ivan
Published: June 2010

A redbrown intermediate has been isolated from a reaction mixture of 2-naphthol and the activated sludge, and its structure has been determined on the basis of its IR, MS, and especially 2D 1H and 13C NMR spectra. It corresponds to 4-(2-hydroxy-1-naphthyl)-6-hydroxy-1,2-naphthoquinone (I). In aqueous media I behaves as an acid-base indicator with the colour transition from yellow to redbrown. The concentration dissociation constants of I have been determined spectrophotometrically: K1 = 3·47 . 10-7, K2 = 3·80 . 10-10 for the standard state c0 = 1 mol dm-3, 298 K, 105 Pa.
Lateral edge effect in electrodiffusion measurements of wall shear stress
Authors: Wein Ondřej
Published: June 2010

The influence of three-dimensional diffusion at lateral edges of an electrodiffusion sensor of friction is analysed by the method of singular perturbations for PeL ≫ 1. It is shown that lateral diffusion at PeL ≫ 1 has a more pronounced effect than longitudinal diffusion at the back edge of the sensor, which has hitherto been exclusively considered.