Genetic and clinical characterization of patients with an interstitial duplication 15q11-q13, emphasizing behavioral phenotype and response to treatment

The clinical significance of an interstitial duplication of (15)(q11-q13) remains unclear and controversial. The reported phenotypes vary widely and appear to be influenced by the parent of origin of the duplication. Aside from cases of dup(15) reported with autism, the behavioral phenotype of individuals with dup(15) has not been described. We present three families, two with intrachromosomal duplication (15)(q11-q13) ascertained because of developmental delay in a relative. Two families show clear evidence of multigenerational maternal inheritance. The individuals discussed in this paper have minor anomalies and developmental delays. In addition, we describe a behavioral phenotype which often includes attention deficit hyperactivity disorder (ADHD) and autistic spectrum disorder. Responses to medications used to manage these behaviors are also described, including a positive response to methylphenidate and a poor response to fluoxetine. The duplication in each presenting individual, and available family members, was investigated utilizing cytogenetic and molecular techniques including high resolution cytogenetics, fluorescence in situ hybridization (FISH), DNA methylation studies, and quantitative fluorescence PCR. High resolution cytogenetic techniques alone missed some cases, demonstrating the need to confirm results with other methods.

Seasonal variation in the niche, habitat availability and population fluctuations of a bivoltine thermophilous insect near its range margin

We investigated the niche requirements of the summer and autumn/spring generations of the bivoltine butterfly, Polyommatus bellargusRott., and their implications for population dynamics at sites occurring near its northern range margin. The larvae of this species are sedentary, and the turf height and shelter of Hippocrepis comosa foodplants selected for egg-laying accurately predict larval distributions within United Kingdom (UK) sites. We found a significant shift between the plants used for egg-laying in each generation, with the niche occupied by summer-feeding larvae being broader and different to the autumn one. Measurements of soil temperature confirmed that the short, sheltered foodplants selected by ovipositing females in autumn placed the autumn/spring-feeding generation of larvae in the warmest available microclimates within sites. In late spring, egg-laying females avoided the hottest spots but extended egg-laying into taller, less sheltered (relatively cool) turf where the microclimate was similar to that experienced by autumn/spring-feeding larvae. Using each generations' definition of niche requirement, we analysed surveys of foodplant populations available on 24 UK sites for P. bellargus, and estimated that nearly twice as many plants were available to the summer-feeding larvae compared to those feeding in the autumn. Annual adult population counts match these seasonal differences in site carrying capacity; first generation counts (from autumn-laid eggs) were generally half as abundant as in the second generation, and more variable. These results suggest that the seasonal cycle of niche switches represents an annual (autumn-spring) bottleneck for populations of this butterfly at its northern range margin. Under climate warming we predict that the inter-generational difference in niche availability, carrying capacity and population size will be reduced. We recommend revised management requirements for this threatened species under current and predicted climates in northern Europe.

Markedly elevated serum biotinidase activity may indicate glycogen storage disease type Ia

We report two children who presented with symptoms suggestive of biotinidase deficiency. Rather than deficiency, markedly elevated serum biotinidase activities were found. Based upon literature reports of elevated biotinidase activities in children with glycogen storage disease (GSD) type Ia, we considered the latter in our differential diagnosis and subsequently confirmed GSD type Ia in both patients by enzymatic testing. GSD type Ia should be considered in children with markedly elevated serum biotinidase activity.

A calibration approach to glandular tissue composition estimation in digital mammography

The healthy breast is almost entirely composed of a mixture of fatty, epithelial, and stromal tissues which can be grouped into two distinctly attenuating tissue types: fatty and glandular. Further, the amount of glandular tissue is linked to breast cancer risk, so an objective quantitative analysis of glandular tissue can aid in risk estimation. Highnam and Brady have measured glandular tissue composition objectively. However, they argue that their work should only be used for "relative" tissue measurements unless a careful calibration has been performed. In this work, we perform such a "careful calibration" on a digital mammography system and use it to estimate breast tissue composition of patient breasts. We imaged 0%, 50%, and 100% glandular-equivalent phantoms of varying thicknesses for a number of clinically relevant x-ray techniques on a digital mammography system. From these images, we extracted mean signal and noise levels and computed calibration curves that can be used for quantitative tissue composition estimation. In this way, we calculate the percent glandular composition of a patient breast on a pixelwise basis. This tissue composition estimation method was applied to 23 digital mammograms. We estimated the quantitative impact of different error sources on the estimates of tissue composition. These error sources include compressed breast height estimation error, residual scattered radiation, quantum noise, and beam hardening. Errors in the compressed breast height estimate contribute the most error in tissue composition--on the order of +/-7% for a 4 cm compressed breast height: The spatially varying scattered radiation will contribute quantitatively less error overall, but may be significant in regions near the skinline. It is calculated that for a 4 cm compressed breast height, a residual scatter signal error is mitigated by approximately sixfold in the composition estimate. The error in composition due to the quantum noise, which is the limiting noise source in the system, is shown to be less than 1% glandular for most breasts.

Parasitoid secretions provoke ant warfare

Insect social parasites are extreme specialists that typically use mimicry or stealth to enter ant colonies to exploit the rich, but fiercely protected, resources within their nests. Here we show how a parasitic wasp (parasitoid) contrives to reach its host, itself an endangered species of social parasite that lives inside the brood chambers of ant nests, by releasing semiochemicals to induce in-fighting between worker ants, locking the colony in combat and leaving it underprotected. Four of these chemicals are new to biology and have the potential to control pest species by inducing different agonistic behaviours in ants.

Fighting foam with phages?

Seventeen (17) phages infective for the mycolata were isolated from six samples of activated sludge using 21 prospective hosts from the genera Dietzia, Gordonia, Nocardia, Rhodococcus, Tsukamurella and Mycobacterium. Their morphology indicated that they were all members of the viral family Siphoviridae, but they varied in the size of the icosahedral head and length of non-contractile tail, suggesting they were different. This was confirmed by host-range studies with 47 strains of mycolata, which showed that each phage had a unique host-range, and this was polyvalent in the majority (15/17) of cases, with 12 phages infective for hosts representing two or three of the genera Gordonia, Nocardia and Rhodococcus. The potential for use of these phages in the control of foaming and other applications is discussed.

Rapid responses of British butterflies to opposing forces of climate and habitat change

Habitat degradation and climate change are thought to be altering the distributions and abundances of animals and plants throughout the world, but their combined impacts have not been assessed for any species assemblage. Here we evaluated changes in the distribution sizes and abundances of 46 species of butterflies that approach their northern climatic range margins in Britain-where changes in climate and habitat are opposing forces. These insects might be expected to have responded positively to climate warming over the past 30 years, yet three-quarters of them declined: negative responses to habitat loss have outweighed positive responses to climate warming. Half of the species that were mobile and habitat generalists increased their distribution sites over this period (consistent with a climate explanation), whereas the other generalists and 89% of the habitat specialists declined in distribution size (consistent with habitat limitation). Changes in population abundances closely matched changes in distributions. The dual forces of habitat modification and climate change are likely to cause specialists to decline, leaving biological communities with reduced numbers of species and dominated by mobile and widespread habitat generalists.

Emergency physician practice and steroid use in the management of acute exacerbations of asthma

This study seeks to determine patterns of emergency physician (EP) practice regarding steroid use in the management of acute asthma attacks in the emergency department (ED), and to compare practices of academic and private practice EPs. Two hundred eight questionnaires were mailed to academic and private practice EPs. The survey requested information regarding the preferred initial route (oral or intravenous) for steroid administration; the initial dose of steroid; the preferred steroid regimen for outpatient management; and whether or not inhaled steroids were routinely prescribed at the time of discharge. The overall response rate was 74%; 91% for the academic EPs and 56% for private practice EPs. Sixty-five percent (99/143) of all EPs used the intravenous route for their initial dose of steroids. A significantly greater percentage of private practice EPs (45/58 or 78%) used intravenous steroids compared with academic EPs (54/95 or 57%; P = .009). A total of 41% (63/153) of EPs used a tapering steroid regime for outpatient therapy; a significantly greater percentage (34/58 or 59%; P = .0006) of private practice EPs used a tapering regimen of steroids compared with academic EPs (29/95 or 31%). A total of 32%(31) academic and 34% (20) private practice EPs prescribed inhaled steroids as part of their routine discharge instructions. Emergency physician practice patterns regarding initial steroid route of administration and dose, and outpatient-dosing regimens are variable. Only a minority of EPs prescribe steroid metered dose inhalers as part of their outpatient management of asthma.

The quality and isolation of habitat patches both determine where butterflies persist in fragmented landscapes

Habitat quality and metapopulation effects are the main hypotheses that currently explain the disproportionate decline of insects in cultivated Holarctic landscapes. The former assumes a degradation in habitat quality for insects within surviving ecosystems, the latter that too few, small or isolated islands of ecosystem remain in landscapes for populations to persist. These hypotheses are often treated as alternatives, and this can lead to serious conflict in the interpretations of conservationists. We present the first empirical demonstration that habitat quality and site isolation are both important determinants of where populations persist in modern landscapes. We described the precise habitat requirements of Melitaea cinxia, Polyommatus bellargus and Thymelicus acteon, and quantified the variation in carrying capacity within each butterfly's niche. We then made detailed surveys to compare the distribution and density of every population of each species with the size, distance apart and quality of their specific habitats in all their potential habitat patches in three UK landscapes. In each case, within-site variation in habitat quality explained which patches supported a species' population two to three times better than site isolation. Site area and occupancy were not correlated in any species. Instead of representing alternative paradigms, habitat quality and spatial effects operate at different hierarchical levels within the same process: habitat quality is the missing third parameter in metapopulation dynamics, contributing more to species persistence, on the basis of these results, than site area or isolation. A reorientation in conservation priorities is recommended.

Aging and oxidation of reactive protein sulfhydryls

Protein sulfhydryls are potential sites of reversible oxidative modification by S-glutathiolation, and S-nitrosylation, but they are also susceptible to irreversible damage by oxidative conditions. In the absence of adequate antioxidant protection, these reactive sites may become useless because of this irreversible damage. It has recently become possible to directly access the nature and amount of irreversibly oxidized protein sulfhydryls by both gel-based methods and direct amino acid analysis. Results are in keeping with the concept that irreversible oxidation of protein sulfhydryls is more extensive in aged tissue samples. It is proposed that an adequate pool of glutathione is essential to prevent this increase in sulfhdryl oxidation. The increased amount of protein sulfhydryl damage may be critically important to the function of signal-transduction and transcription events that utilize proteins containing these reactive sites.

Training in communication skills for informal carers of people suffering from dementia: a cluster randomized clinical trial comparing a therapist led workshop and a booklet

The objective of the study was to evaluate whether a short training workshop in communication techniques is more effective than an information booklet for improving communication skills in informal carers of people suffering from dementia. 30 informal carers were allocated to the workshop sessions and 15 to the booklet. Outcome measures included awareness of communication strategies; perceived frequency of communication breakdown at home, and the associated level of distress; general stress; and consumer satisfaction. At six week follow-up, the workshop group demonstrated a significantly greater awareness of communication strategies than the booklet-only group. Both groups reported some reduction in the frequency of communication problems at home, and a reduction in the associated level of distress. The frequency of other problem behaviours remained stable. Satisfaction with the workshop indicated that training was helpful but depended on the stage of illness of the partner.

Regulation of dendritic cell recruitment into resting and inflamed airway epithelium: use of alternative chemokine receptors as a function of inducing stimulus

Dendritic cells (DC) were purified by flow cytometry from rat tracheal mucosa; they exhibited the phenotypic characteristics of immature DC including high endocytic activity, low CD80/86 expression, and in vitro responsiveness to a broad range of CC chemokines. Daily treatment of adult rats with the selective CCR1 and CCR5 antagonist Met-RANTES reduced baseline numbers of tracheal intraepithelial DC by 50-60%, and pretreatment of animals with Met-RANTES before inhalation of aerosol containing heat-killed bacteria abolished the rapid DC influx into the epithelium that occurred in untreated controls, implicating CCR1 and CCR5 and their ligands in recruitment of immature DC precursors into resting airway tissues and during acute bacterial-induced inflammation. Comparable levels of DC recruitment were observed during airway mucosal Sendai virus infection and after aerosol challenge of sensitized animals with the soluble recall Ag OVA. However, Met-RANTES did not affect these latter responses, indicating the use of alternative chemokine receptors/ligands for DC recruitment, or possibly attraction of different DC subsets, depending on the nature of the eliciting stimulus.

Maxillofacial implications and surgical treatment of arthrogryposis multiplex congenita

A case of arthrogryposis multiplex congenita that affected a patient's temporomandibular joint is described. Preoperatively, the patient's interincisal opening was limited to 9 mm. Elective surgery was performed, which consisted of bilateral coronoidotomies, right and left meninscectomies, capsular release, and lateral pterygoid myotomies. Physical therapy was initiated postoperatively. Eighteen weeks after the surgery, the patient was able to open 18 mm and force open to 20 mm. The patient also noted significant improvement in speech and jaw function in the postoperative period.

Involvement of cyclic AMP response element binding protein (CREB) and estrogen receptor phosphorylation in the synergistic activation of the estrogen receptor by estradiol and protein kinase activators

Estrogen receptor (ER) and cAMP signaling pathways interact in a number of estrogen target tissues including mammary and uterine tissues. One aspect of this interaction is that estradiol and protein kinase A (PKA) activators can cooperate synergistically to activate ER-mediated transcription of both endogenous genes and reporter genes containing only estrogen response elements. The purpose of this study was to investigate the molecular mechanism of this interaction between signaling pathways. Site-directed mutagenesis of the potential PKA phosphorylation sites in the ER indicated that phosphorylation of these sites was not necessary for the observed transcriptional synergy. In transient transfection assays in two different cell lines using reporter constructs containing either cAMP response elements, estrogen response elements or both types of elements, with the addition or absence of cAMP response element binding protein (CREB) expression plasmid, we observed that only one of these cell lines exhibited estrogen/PKA transcriptional synergy. Experiments demonstrated that CREB itself was involved in the transcriptional synergy, and that transfection of CREB restored transcriptional synergy in the cell line in which it was lacking. A functional interaction between ER and CREB was also demonstrated using a mammalian cell protein interaction assay; a dominant negative mutant of CREB did not exhibit this interaction. Therefore, these data indicate that CREB protein is required for the transcriptional synergy between cAMP and estrogen signaling pathways. Furthermore, CREB cooperated with the ER on genes that did not contain cAMP response elements, but contained only estrogen response elements. We propose that activated CREB is recruited to estrogen responsive genes by an ER--coactivator complex containing proteins such as CREB binding protein (CBP) and that the interaction of CREB with ER may assist in stabilizing its interaction with CBP and in promoting estrogen-ER and PKA transcriptional synergy.

Oxidative modification of H-ras: S-thiolation and S-nitrosylation of reactive cysteines

The reactive cysteines in H-ras are subject to oxidative modifications that potentially alter the cellular function of this protein. In this study, purified H-ras was modified by thiol oxidants such as hydrogen peroxide (H(2)O(2)), S-nitrosoglutathione, diamide, glutathione disulphide (GSSG) and cystamine, producing as many as four charge-isomeric forms of the protein. These results suggest that all four reactive cysteines of H-ras are potential sites of regulatory modification reactions. S-nitrosylated and S-glutathiolated forms of H-ras were identified by protocols that depend on separation of alkylated proteins on electrofocusing gels. S-nitrosoglutathione could S-nitrosylate H-ras on four cysteine residues, while reduced glutathione (GSH) and H(2)O(2) mediate S-glutathiolation on at least one cysteine of H-ras. Either GSSG or diamide S-glutathiolated at least two cysteine residues of purified H-ras. Iodoacetic acid reacts with three cysteine residues. In intact NIH-3T3 cells, wild-type H-ras was S-glutathiolated by diamide. Similarly, cells expressing a C118S mutant or a C181S/C184S double mutant of H-ras were S-glutathiolated by diamide. These results suggest that H-ras can be S-glutathiolated on multiple thiols in vivo and that at least one of these thiols is normally lipid-modified. In cells treated with S-nitrosocysteine, evidence for both S-nitrosylated and S-glutathiolated H-ras was obtained and S-nitrosylation was the predominant modification. These results show that oxidative modification of H-ras can be extensive in vivo, that both S-nitrosylated and S-glutathiolated forms may be important, and that oxidation may occur on reactive cysteines that are normally targeted for lipid-modification reactions.

Food-plant niche selection rather than the presence of ant nests explains oviposition patterns in the myrmecophilous butterfly genus Maculinea

It has been suggested that the socially parasitic butterfly Maculinea alcon detects ant odours before ovipositing on initial larval food plants near colonies of its obligate ant host Myrmica ruginodis. It has also been suggested that overcrowding on food plants near M. ruginodis is avoided by an ability to detect high egg loads, resulting in a switch to selecting plants near less suitable ant species. If confirmed, this hypothesis (H1) would have serious implications for the application of current population models aimed at the conservation of endangered Maculinea species, which are based on the null hypothesis (H0) that females randomly select food plants whose flower buds are at a precise phenological stage, making oviposition independent of ants. If H1 were wrong, practical management based upon its assumptions could lead to the extinction of protected populations. We present data for the five European species of Maculinea which show that (i) each oviposits on a phenologically restricted flower-bud stage, which accounts for the apparent host-ant-mediated niche separation in sympatric populations of Maculinea nausithous and Maculinea teleius, (ii) there is no temporal shift in oviposition by Maculinea arion in relation to host ant distribution or egg density, and (iii) oviposition patterns in 13 populations of M. alcon's closest relative, Macaulinea rebeli, conform to H0 not H1 predictions. It is concluded that conservation measures should continue to be based on H0.

The estrogen receptor: a structure-based approach to the design of new specific hormone-receptor combinations

BACKGROUND

The specificity of hormone action arises from complementary steric and electronic interactions between a hormonal ligand and its cognate receptor. An analysis of such key ligand-receptor contact sites, often delineated by mutational mapping and X-ray crystallographic studies, can suggest ways in which hormone-receptor specificity might be altered.

RESULTS

We have altered the hormonal specificity of the estrogen receptor alpha (ER) by making 'coordinated' changes in the A-ring of the ligand estradiol and in the A-ring binding subpocket of ER. These changes were designed to maintain a favorable interaction when both E and ER are changed, but to disfavor interaction when only E or ER is changed. We have evaluated several of these altered ligand and receptor pairs in quantitative ligand binding and reporter gene assays.

CONCLUSIONS

In best cases, the new interaction is sufficiently favorable and orthogonal so as to represent the creation of a new hormone specificity, which might be useful in the regulation of transgene activity.

Improving pharmacy supply-chain management in the operating room

Anesthesia services can account for a significant portion of a healthcare organization's costs. Deaconess Hospital of Evansville, Indiana, used a collaborative, multidisciplinary effort to implement process improvements that yielded significant cost savings while improving patient care. Shifting responsibility for drug distribution from the operating room (OR) nurses to a pharmacist, the hospital established a satellite pharmacy service for the OR. As a result, the hospital was able to improve control of drug distribution and record-keeping, reduce turnaround time for medication preparation, lower its medication charge error rate, and increase the percentage of surgeries that start on time. The success of the OR satellite pharmacy led the hospital to expand satellite pharmacy services to labor and delivery, the cardiac cath laboratory, and the intensive care units.

Epidermoid cysts of the testis: the case for conservative surgery

The series comprises 6 patients (mean age, 21 years) who presented with an epidermoid cyst of the testis between 1991 and 1998. Pre-operative ultrasonography suggested the presence of a testicular cancer in 3 patients who underwent a radical orchidectomy. The ultrasound successfully predicted the true diagnosis in 3 patients who had a wedge excision of the cyst together with a cuff of normal surrounding tissue. All patients are free of disease with a mean follow-up of 3 years. With increasing awareness of the condition coupled with accurate pre-operative radiological imaging, local excision of an epidermoid cyst with preservation of the remainder of the testis is now a feasible and rational alternative to more radical surgery.

Effect of S-nitrosothiols on cellular glutathione and reactive protein sulfhydryls

S-Nitrosothiols may cause many of the biological effects of NO and cellular effects have been attributed to S-nitrosylation of reactive protein sulfhydryls. This report examines the effect of S-nitrosothiols on the low-molecular-weight thiols and protein thiols in NIH/3T3 cells. A low concentration of S-nitrosocysteine increased the cysteine content of the cells, with no evidence of either low-molecular-weight thiol or protein S-nitrosylation. Millimolar amounts of S-nitrosocysteine produced S-nitrosoglutathione (GSNO), cysteinyl glutathione, cysteine, and glutathione disulfide. Large amounts of protein S-nitrosylation and lesser amounts of protein S-glutathiolation and S-cysteylation were also observed. GSNO and S-nitroso-N-acetylpenicillamine (SNAP) were much less effective than S-nitrosocysteine, but a combination of cysteine and GSNO produced S-nitrosocysteine-like effects. In cultured hepatocytes, millimolar S-nitrosocysteine was significantly less effective since the cells contained three times more glutathione than NIH/3T3 cells. Results suggest that S-nitrosocysteine enters cells intact, and low concentrations do not significantly increase cellular pools of S-nitrosothiol or S-nitrosylated protein. Millimolar concentrations of S-nitrosocysteine generate S-nitrosylated, S-glutathiolated, and S-cysteylated proteins, as well as a variety of low-molecular-weight disulfides and S-nitrosothiols.

Crystal structure of S-glutathiolated carbonic anhydrase III

S-Glutathiolation of carbonic anhydrase III (CAIII) occurs rapidly in hepatocytes under oxidative stress. The crystal structure of the S-glutathiolated CAIII from rat liver reveals covalent adducts on cysteines 183 and 188. Electrostatic charge and steric contacts at each modification site inversely correlate with the relative rates of reactivity of these cysteines toward glutathione (GSH). Diffuse electron density associated with the GSH adducts suggests a lack of preferred bonding interactions between CAIII and the glutathionyl moieties. Hence, the GSH adducts are available for binding by a protein capable of reducing this mixed disulfide. These properties are consistent with the participation of CAIII in the protection/recovery from the damaging effects of oxidative agents.

p53 protein oxidation in cultured cells in response to pyrrolidine dithiocarbamate: a novel method for relating the amount of p53 oxidation in vivo to the regulation of p53-responsive genes

A novel method was developed to determine the oxidation status of proteins in cultured cells. Methoxy-polyethylene glycol-maleimide MW 2000 (MAL-PEG) was used to covalently tag p53 protein that was oxidized at cysteine residues in cultured cells. Treatment of MCF7 breast cancer cells with pyrrolidine dithiocarbamate (PDTC), a metal chelator, resulted in a minimum of 25% oxidation of p53. The oxidized p53 had an average of one cysteine residue oxidized per p53 protein molecule. The effect of PDTC treatment on downstream components of the p53 signal-transduction pathway was tested. PDTC treatment prevented actinomycin D-mediated up-regulation of two p53 effector gene products, murine double minute clone 2 oncoprotein and p21(WAF1/CIP1) (where WAF1 corresponds to wild-type p53-activated fragment 1 and CIP1 corresponds to cyclin-dependent kinase-interacting protein 1). Actinomycin D treatment led to accumulation of p53 protein in the nucleus. However, when cells were simultaneously treated with PDTC and actinomycin D, p53 accumulated in both the nucleus and the cytoplasm. The data indicate that an average of one cysteine residue per p53 protein molecule is highly sensitive to oxidation and that p53 can be efficiently oxidized by PDTC in cultured cells. PDTC-mediated oxidation of p53 correlates with altered p53 subcellular localization and reduced activation of p53 downstream effector genes. The novel method for detecting protein oxidation detailed in the present study may be used to determine the oxidation status of specific proteins in cells.

Surface expression of O-specific lipopolysaccharide in Escherichia coli requires the function of the TolA protein

We investigated the involvement of Tol proteins in the surface expression of lipopolysaccharide (LPS). tolQ, -R, -A and -B mutants of Escherichia coli K-12, which do not form a complete LPS-containing O antigen, were transformed with the O7+ cosmid pJHCV32. The tolA and tolQ mutants showed reduced O7 LPS expression compared with the respective isogenic parent strains. No changes in O7 LPS expression were found in the other tol mutants. The O7-deficient phenotype in the tolQ and tolA mutants was complemented with a plasmid encoding the tolQRA operon, but not with a similar plasmid containing a frameshift mutation inactivating tolA. Therefore, the reduction in O7 LPS was attributed to the lack of a functional tolA gene, caused either by a direct mutation of this gene or by a polar effect on tolA gene expression exerted by the tolQ mutation. Reduced surface expression of O7 LPS was not caused by changes in lipid A-core structure or downregulation of the O7 LPS promoter. However, an abnormal accumulation of radiolabelled mannose was detected in the plasma membrane. As mannose is a sugar unique to the O7 subunit, this result suggested the presence of accumulated O7 LPS biosynthesis intermediates. Attempts to construct a tolA mutant in the E. coli O7 wild-type strain VW187 were unsuccessful, suggesting that this mutation is lethal. In contrast, a polar tolQ mutation affecting tolA expression in VW187 caused slow growth rate and serum sensitivity in addition to reduced O7 LPS production. VW187 tolQ cells showed an elongated morphology and became permeable to the membrane-impermeable dye propidium iodide. All these phenotypes were corrected upon complementation with cloned tol genes but were not restored by complementation with the tolQRA operon containing the frameshift mutation in tolA. Our results demonstrate that the TolA protein plays a critical role in the surface expression of O antigen subunits by an as yet uncharacterized involvement in the processing of O antigen.

Controlling substitution chemistry in ruthenium(II) systems. Synthesis of heteroleptic complexes incorporating the [Ru([9]aneS3)]2+ metal center

The complex [Ru(py)3([9]aneS3)][PF6]2, 1 (py = pyridine), has proved to be a suitable starting material for the synthesis of heteroleptic Ru(II) complexes. By exploiting unfavorable steric interactions between 2-H and 6-H hydrogens of coordinated pyridyl ligands, we have synthesized half-sandwich complexes incorporating the thiocrown [9]aneS3 and a variety of facially coordinated N-donor ligands. Such complexes are easily prepared: Stirring 1 at room temperature in the presence of a suitable nitrile ligand leads to the exclusive substitution of one py ligand to produce complexes such as [([9]aneS3)Ru(py)2(NCMe)][PF6]2, 2. However, if the same reaction is carried out at higher temperatures, two py ligands are substituted, leading to complexes such as [([9]aneS3)Ru(py)(NCMe)2][PF6]2, 3. An alternative approach to such heteroleptic species has also been developed which exploits the restricted ability of thioethers to neutralize positive charges through sigma-donation. This phenomenon allows the synthesis of heteroleptic complexes in a two-step procedure via monocationic species. By variation of the donor/acceptor properties of ligands incorporated into the [Ru([9]aneS3)]2+ metal center, it is possible to tune the Ru(III)/Ru(II) redox couple over a range of > 700 mV. The solid-state structures of 1-3 were confirmed by X-ray crystallography studies. Crystal data: C22H30F12N4O2P2RuS3 (1.CH3NO2), monoclinic, Cc, a = 23.267(5) A, b = 11.5457(18) A, c = 26.192(5) A, alpha = 90 degrees, beta = 114.836(10) degrees, gamma = 90 degrees, Z = 8; C18H25F12N3P2RuS3 (2), triclinic, P1, a = 11.3958(19) A, b = 11.4280(19) A, c = 11.930(2) A, alpha = 100.518(3) degrees, beta = 100.542(3) degrees, gamma = 112,493(3) degrees, Z = 2; C15H23F12N3P2RuS3 (3), orthorhombic, Pna2(1)), a = 14.748(5) A, b = 18.037(18) A, c = 10.341(5) A, alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees, Z = 4.