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Background: As clinicians strive to achieve consensus worldwide on how best to diagnose fetal alcohol spectrum disorders (FASD), the most recent FASD diagnosstic systems exhibit convergence and divergence. Applying these systems to a single clinical population illustrates contrasts between them, but validation studies are ultimately required to identify the best system. Currently, only the 4-Digit Code has published comprehensive validation studies. Methods: The 4-Digit Code and Hoyme 2016 FASD systems were applied to the records of 1,392 patients evaluated for FASD at the University of Washington to: 1) Compare the diagnostic criteria and tools used by each system, 2) Compare the prevalence and concordance of diagnostic outcomes and assess measures of validity. Results: Only 38% of patients received concordant diagnoses. The Hoyme criteria rendered half as many diagnoses under the umbrella of FASD (n=558) as the 4-Digit Code (n=1,092) and diagnosed a much higher proportion (53%) as fetal alcohol syndrome/partial fetal alcohol syndrome (FAS/PFAS) than the 4-Digit Code (7%). Key Hoyme factors contributing to discordance included relaxation of facial criteria (40% had the Hoyme FAS face, including patients with confirmed absence of alcohol exposure); setting alcohol exposure thresholds prevented 1/3 with confirmed exposure from receiving FAS/FASD diagnoses; and setting minimum age limits for Alcohol-Related Neurodevelopmental Disorder prevented 79% of alcohol-exposed infants with neurodevelopmental impairment a FASD diagnosis. The Hoyme Lip/Philtrum Guides differ substantively from the 4-Digit Lip-Philtrum Guides and thus are not valid for use with the 4-Digit Code. Conclusions: All FASD diagnostic systems need to publish comprehensive validation studies to identify which is the most accurate, reproducible, and medically valid.

This chapter briefly describes the history of fetal alcohol spectrum disorders (FASD), from references in antiquity to the modern understanding that prenatal alcohol exposure (PAE) can lead to birth defects including growth deficiency, a unique cluster of minor facial anomalies, and central nervous system (CNS) abnormalities. Diagnoses under the FASD umbrella include fetal alcohol syndrome (FAS), partial fetal alcohol syndrome (pFAS, in which “partial” refers to incomplete physical manifestations), and various diagnostic terms for individuals impacted by PAE who lack sentinel physical features but do have evidence of CNS damage. Areas of consensus and divergence in modern diagnostic criteria are explored, with attention to nomenclature, the problematic nature of alcohol thresholds, the importance of growth as a sentinel physical feature, the specificity of facial features of FAS, other congenital anomalies associated with PAE, structural criteria for CNS damage including imaging approaches, and differing definitions of CNS dysfunction. Recommendations are provided for guidelines to use in forensic practice. The extensive differential diagnosis of FASD is described, including genetic etiologies, other prenatal influences, perinatal risks, adverse childhood experiences, head injuries, substance use disorders, and mental health disorders. Practical suggestions for FASD evaluations in forensic practice are offered, from pre-detention screening through evaluations, reports, and testimony. The intended audience for this chapter includes legal and mental health professionals learning about medical diagnosis of FASDs, medical FASD experts new to forensic evaluations, and forensic-experienced physicians seeking training in FASD diagnosis.

Background: Risk of fetal alcohol spectrum disorder (FASD) is not based solely on the timing and level of prenatal alcohol exposure (PAE). The effects of teratogens can be modified by genetic differences in fetal susceptibility and resistance. This is best illustrated in twins. Objective: To compare the prevalence and magnitude of pairwise discordance in FASD diagnoses across monozygotic twins, dizygotic twins, full-siblings, and half-siblings sharing a common birth mother. Methods: Data from the Fetal Alcohol Syndrome Diagnostic & Prevention Network clinical database was used. Sibling pairs were matched on age and PAE, raised together, and diagnosed by the same University of Washington interdisciplinary team using the FASD 4-Digit Code. This design sought to assess and isolate the role of genetics on fetal vulnerability/resistance to the teratogenic effects of PAE by eliminating or minimizing pairwise discordance in PAE and other prenatal/postnatal risk factors. Results: As genetic relatedness between siblings decreased from 100% to 50% to 50% to 25% across the four groups (9 monozygotic, 39 dizygotic, 27 full-sibling and 9 half-sibling pairs, respectively), the prevalence of pairwise discordance in FASD diagnoses increased from 0% to 44% to 59% to 78%. Despite virtually identical PAE, 4 pairs of dizygotic twins had FASD diagnoses at opposite ends of the fetal alcohol spectrum—Partial Fetal Alcohol Syndrome versus Neurobehavioral Disorder/Alcohol-Exposed. Conclusion: Despite virtually identical PAE, fetuses can experience vastly different FASD outcomes. Thus, to protect all fetuses, especially the most genetically vulnerable, the only safe amount to drink is none at all.

Background: Individuals with prenatal alcohol exposure (PAE) often present with a myriad of other prenatal (e.g. exposure to tobacco and other illicit drugs, poor prenatal care) and postnatal risk factors (e.g. multiple home placements, physical/sexual abuse, low socio-economic status)-all of which are likely contributing to their adverse outcomes. Methods: A comprehensive neuropsychological battery, coupled with magnetic resonance imaging, was administered to children with fetal alcohol spectrum disorders (FASD) in 2009. Study participants diagnosed with FASD by the University of Washington using the FASD 4-Digit Code were compared to typically-developing peers with no PAE. Data from this MRI study were used to explore the proportion of variance in brain structural and functional abnormalities explained by PAE and 14 other prenatal and postnatal risk factors. Results: PAE was the dominant risk factor explaining the largest proportion of variance in regional brain size (total brain, frontal lobe, caudate, hippocampus and corpus callosum) and brain function (intellect, achievement, memory, language, executive-function, motor, adaptation, behavior-attention and mental health symptoms). Other prenatal and postnatal risk factors were 3 to 7-fold more prevalent than in the general population. Individually, each risk factor explained a statistically significant, but smaller proportion of variance in brain outcome compared to PAE. In combination, the proportion of variance explained by the presence of multiple prenatal and postnatal risks rivaled that of PAE. Conclusion: A better understanding of the impact other prenatal and postnatal risk factors have on the neurodevelopmental outcomes of individuals with FASD can inform more effective prevention and intervention strategies.

Background: As clinicians strive to achieve consensus worldwide on how best to diagnose fetal alcohol spectrum disorders (FASD), the most recent FASD diagnostic systems show convergence and divergence. Applying these systems to a single clinical population illustrates the contrasts between them, but validation studies are ultimately required to identify the best system. Methods: The 4-Digit-Code, Hoyme 2016, Canadian 2015 and Australian 2016 FASD diagnostic systems were applied to 1,392 patient records evaluated for FASD at the University of Washington. The diagnostic criteria and tools, the prevalence and concordance of diagnostic outcomes, and validity measures were compared between the systems. Results: The proportion diagnosed with fetal alcohol syndrome (FAS) and FASD varied significantly (4-Digit-Code 2.1%

Dysbiosis is a key term in human microbiome research, especially when microbiome patterns are associated with disease states. Although some questions have been raised about how this term is applied, its use continues undiminished in the literature. We investigate the ways in which microbiome researchers discuss dysbiosis and then assess the impact of different concepts of dysbiosis on microbiome research. After an overview of the term’s historical roots, we conduct quantitative and qualitative analyses of a large selection of contemporary dysbiosis statements. We categorize both short definitions and longer conceptual statements about dysbiosis. Further analysis allows us to identify the problematic implications of how dysbiosis is used, particularly with regard to causal hypotheses and normal-abnormal distinctions. We suggest that researchers should reflect carefully on the ways in which they discuss dysbiosis, in order for the field to continue to develop greater predictive scope and explanatory depth.

The trimethoprim and sulfamethoxazole combination, co-trimoxazole, plays a vital role in the treatment of

It is generally assumed that the acquisition of antibiotic resistance is associated with a fitness cost. We have shown that overexpression of the MexEF-OprN efflux pump does not decrease the fitness of a resistant Pseudomonas aeruginosa strain compared to its wild-type counterpart. This lack of fitness cost was associated with a metabolic rewiring that includes increased expression of the anaerobic nitrate respiratory chain when cells are growing under fully aerobic conditions. It was not clear whether this metabolic compensation was exclusive to strains overexpressing MexEF-OprN or if it extended to other resistant strains that overexpress similar systems. To answer this question, we studied a set of P. aeruginosa mutants that independently overexpress the MexAB-OprM, MexCD-OprJ, or MexXY efflux pumps. We observed increased expression of the anaerobic nitrate respiratory chain in all cases, with a concomitant increase in NO 3 consumption and NO production. These efflux pumps are proton/substrate antiporters, and their overexpression may lead to intracellular H + accumulation, which may in turn offset the pH homeostasis. Indeed, all studied mutants showed a decrease in intracellular pH under anaerobic conditions. The fastest way to eliminate the excess of protons is by increasing oxygen consumption, a feature also displayed by all analyzed mutants. Taken together, our results support metabolic rewiring as a general mechanism to avoid the fitness costs derived from overexpression of P. aeruginosa multidrug efflux pumps. The development of drugs that block this metabolic “reaccommodation” might help in reducing the persistence and spread of antibiotic resistance elements among bacterial populations. IMPORTANCE It is widely accepted that the acquisition of resistance confers a fitness cost in such a way that in the absence of antibiotics, resistant populations will be outcompeted by susceptible ones. Based on this assumption, antibiotic cycling regimes have been proposed in the belief that they will reduce the persistence and spread of resistance among bacterial pathogens. Unfortunately, trials testing this possibility have frequently failed, indicating that resistant microorganisms are not always outcompeted by susceptible ones. Indeed, some mutations do not result in a fitness cost, and in case they do, the cost may be compensated for by a secondary mutation. Here we describe an alternative nonmutational mechanism for compensating for fitness costs, which consists of the metabolic rewiring of resistant mutants. Deciphering the mechanisms involved in the compensation of fitness costs of antibiotic-resistant mutants may help in the development of drugs that will reduce the persistence of resistance by increasing said costs.

We have engineered Saccharomyces cerevisiae to inducibly synthesize the prokaryotic signaling nucleotides cyclic di-GMP (cdiGMP), cdiAMP, and ppGpp in order to characterize the range of effects these nucleotides exert on eukaryotic cell function during bacterial pathogenesis. Synthetic genetic array (SGA) and transcriptome analyses indicated that, while these compounds elicit some common reactions in yeast, there are also complex and distinctive responses to each of the three nucleotides. All three are capable of inhibiting eukaryotic cell growth, with the guanine nucleotides exhibiting stronger effects than cdiAMP. Mutations compromising mitochondrial function and chromatin remodeling show negative epistatic interactions with all three nucleotides. In contrast, certain mutations that cause defects in chromatin modification and ribosomal protein function show positive epistasis, alleviating growth inhibition by at least two of the three nucleotides. Uniquely, cdiGMP is lethal both to cells growing by respiration on acetate and to obligately fermentative petite mutants. cdiGMP is also synthetically lethal with the ribonucleotide reductase (RNR) inhibitor hydroxyurea. Heterologous expression of the human ppGpp hydrolase Mesh1p prevented the accumulation of ppGpp in the engineered yeast and restored cell growth. Extensive in vivo interactions between bacterial signaling molecules and eukaryotic gene function occur, resulting in outcomes ranging from growth inhibition to death. cdiGMP functions through a mechanism that must be compensated by unhindered RNR activity or by functionally competent mitochondria. Mesh1p may be required for abrogating the damaging effects of ppGpp in human cells subjected to bacterial infection.

AcrAB-TolC is the paradigm resistance-nodulation-division (RND) multidrug resistance efflux system in Gram-negative bacteria, with AcrB being the pump protein in this complex. We constructed a nonfunctional AcrB mutant by replacing D408, a highly conserved residue essential for proton translocation. Western blotting confirmed that the AcrB D408A mutant had the same native level of expression of AcrB as the parental strain. The mutant had no growth deficiencies in rich or minimal medium. However, compared with wild-type SL1344, the mutant had increased accumulation of Hoechst 33342 dye and decreased efflux of ethidium bromide and was multidrug hypersusceptible. The D408A mutant was attenuated in vivo in mouse and Galleria mellonella models and showed significantly reduced invasion into intestinal epithelial cells and macrophages in vitro. A dose-dependent inhibition of invasion was also observed when two different efflux pump inhibitors were added to the wild-type strain during infection of epithelial cells. RNA sequencing (RNA-seq) revealed downregulation of bacterial factors necessary for infection, including those in the Salmonella pathogenicity islands 1, 2, and 4; quorum sensing genes; and phoPQ. Several general stress response genes were upregulated, probably due to retention of noxious molecules inside the bacterium. Unlike loss of AcrB protein, loss of efflux function did not induce overexpression of other RND efflux pumps. Our data suggest that gene deletion mutants are unsuitable for studying membrane transporters and, importantly, that inhibitors of AcrB efflux function will not induce expression of other RND pumps., IMPORTANCE Antibiotic resistance is a major public health concern. In Gram-negative bacteria, overexpression of the AcrAB-TolC multidrug efflux system confers resistance to clinically useful drugs. Here, we show that loss of AcrB efflux function causes loss of virulence in Salmonella enterica serovar Typhimurium. This is due to the reduction of bacterial factors necessary for infection, which is likely to be caused by the retention of noxious molecules inside the bacterium. We also show that, in contrast to loss of AcrB protein, loss of efflux does not induce overexpression of other efflux pumps from the same family. This indicates that there are differences between loss of efflux protein and loss of efflux that make gene deletion mutants unsuitable for studying the biological function of membrane transporters. Understanding the biological role of AcrB will help to assess the risks of targeting efflux pumps as a strategy to combat antibiotic resistance.

Antibiotic resistance is a prevalent problem in public health worldwide. In general, the carbapenem β-lactam antibiotics are considered a final resort against lethal infections by multidrug-resistant bacteria. Colistin is a cationic polypeptide antibiotic and acts as the last line of defense for treatment of carbapenem-resistant bacteria. Very recently, a new plasmid-borne colistin resistance gene, mcr-2, was revealed soon after the discovery of the paradigm gene mcr-1, which has disseminated globally. However, the molecular mechanisms for MCR-2 colistin resistance are poorly understood. Here we show a unique transposon unit that facilitates the acquisition and transfer of mcr-2. Evolutionary analyses suggested that both MCR-2 and MCR-1 might be traced to their cousin phosphoethanolamine (PEA) lipid A transferase from a known polymyxin producer, Paenibacillus. Transcriptional analyses showed that the level of mcr-2 transcripts is relatively higher than that of mcr-1. Genetic deletions revealed that the transmembrane regions (TM1 and TM2) of both MCR-1 and MCR-2 are critical for their location and function in bacterial periplasm, and domain swapping indicated that the TM2 is more efficient than TM1. Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) confirmed that all four MCR proteins (MCR-1, MCR-2, and two chimeric versions [TM1-MCR-2 and TM2-MCR-1]) can catalyze chemical modification of lipid A moiety anchored on lipopolysaccharide (LPS) with the addition of phosphoethanolamine to the phosphate group at the 4′ position of the sugar. Structure-guided site-directed mutagenesis defined an essential 6-residue-requiring zinc-binding/catalytic motif for MCR-2 colistin resistance. The results further our mechanistic understanding of transferable colistin resistance, providing clues to improve clinical therapeutics targeting severe infections by MCR-2-containing pathogens., IMPORTANCE Carbapenem and colistin are the last line of refuge in fighting multidrug-resistant Gram-negative pathogens. MCR-2 is a newly emerging variant of the mobilized colistin resistance protein MCR-1, posing a potential challenge to public health. Here we report transfer of the mcr-2 gene by a unique transposal event and its possible origin. Distribution of MCR-2 in bacterial periplasm is proposed to be a prerequisite for its role in the context of biochemistry and the colistin resistance. We also define the genetic requirement of a zinc-binding/catalytic motif for MCR-2 colistin resistance. This represents a glimpse of transferable colistin resistance by MCR-2.

Streptolysin S (SLS)-like virulence factors from clinically relevant Gram-positive pathogens have been proposed to behave as potent cytotoxins, playing key roles in tissue infection. Listeriolysin S (LLS) is an SLS-like hemolysin/bacteriocin present among Listeria monocytogenes strains responsible for human listeriosis outbreaks. As LLS cytotoxic activity has been associated with virulence, we investigated the LLS-specific contribution to host tissue infection. Surprisingly, we first show that LLS causes only weak red blood cell (RBC) hemolysis in vitro and neither confers resistance to phagocytic killing nor favors survival of L. monocytogenes within the blood cells or in the extracellular space (in the plasma). We reveal that LLS does not elicit specific immune responses, is not cytotoxic for eukaryotic cells, and does not impact cell infection by L. monocytogenes. Using in vitro cell infection systems and a murine intravenous infection model, we actually demonstrate that LLS expression is undetectable during infection of cells and murine inner organs. Importantly, upon intravenous animal inoculation, L. monocytogenes is found in the gastrointestinal system, and only in this environment LLS expression is detected in vivo. Finally, we confirm that LLS production is associated with destruction of target bacteria. Our results demonstrate therefore that LLS does not contribute to L. monocytogenes tissue injury and virulence in inner host organs as previously reported. Moreover, we describe that LlsB, a putative posttranslational modification enzyme encoded in the LLS operon, is necessary for murine inner organ colonization. Overall, we demonstrate that LLS is the first SLS-like virulence factor targeting exclusively prokaryotic cells during in vivo infections.

Integrons ensure a rapid and “on demand” response to environmental stresses driving bacterial adaptation. They are able to capture, store, and reorder functional gene cassettes due to site-specific recombination catalyzed by their integrase. Integrons can be either sedentary and chromosomally located or mobile when they are associated with transposons and plasmids. They are respectively called sedentary chromosomal integrons (SCIs) and mobile integrons (MIs). MIs are key players in the dissemination of antibiotic resistance genes. Here, we used in silico and in vivo approaches to study cassette excision dynamics in MIs and SCIs. We show that the orientation of cassette arrays relative to replication influences attC site folding and cassette excision by placing the recombinogenic strands of attC sites on either the leading or lagging strand template. We also demonstrate that stability of attC sites and their propensity to form recombinogenic structures also regulate cassette excision. We observe that cassette excision dynamics driven by these factors differ between MIs and SCIs. Cassettes with high excision rates are more commonly found on MIs, which favors their dissemination relative to SCIs. This is especially true for SCIs carried in the Vibrio genus, where maintenance of large cassette arrays and vertical transmission are crucial to serve as a reservoir of adaptive functions. These results expand the repertoire of known processes regulating integron recombination that were previously established and demonstrate that, in terms of cassette dynamics, a subtle trade-off between evolvability and genetic capacitance has been established in bacteria.

An increasing number of human beings from developed countries are colonized by Escherichia coli strains producing colibactin, a genotoxin suspected to be associated with the development of colorectal cancers. Deoxynivalenol (DON) is the most prevalent mycotoxin that contaminates staple food—especially cereal products—in Europe and North America. This study investigates the effect of the food contaminant DON on the genotoxicity of the E. coli strains producing colibactin. In vitro, intestinal epithelial cells were coexposed to DON and E. coli producing colibactin. In vivo, newborn rats colonized at birth with E. coli producing colibactin were fed a DON-contaminated diet. Intestinal DNA damage was estimated by the phosphorylation of histone H2AX. DON exacerbates the genotoxicity of the E. coli producing colibactin in a time- and dose-dependent manner in vitro. Although DON had no effect on the composition of the gut microbiota, and especially on the number of E. coli, a significant increase in DNA damage was observed in intestinal epithelial cells of animals colonized by E. coli strains producing colibactin and coexposed to DON compared to animals colonized with E. coli strains unable to produce colibactin or animals exposed only to DON. In conclusion, our data demonstrate that the genotoxicity of E. coli strains producing colibactin, increasingly present in the microbiota of asymptomatic human beings, is modulated by the presence of DON in the diet. This raises questions about the synergism between food contaminants and gut microbiota with regard to intestinal carcinogenesis., IMPORTANCE An increasing number of human beings from developed countries are colonized by Escherichia coli strains producing colibactin, a genotoxin suspected to be associated with the development of colorectal cancers. Deoxynivalenol (DON) is the most prevalent mycotoxin that contaminates staple food—especially cereal products—in Europe and North America. Our in vitro and in vivo results demonstrate that the intestinal DNA damage induced by colibactin-producing E. coli strains was exacerbated by the presence of DON in the diet. This raises questions about the synergism between food contaminants and gut microbiota with regard to intestinal carcinogenesis.

Cystic fibrosis (CF) lung microbiota composition has recently been redefined by the application of next-generation sequencing (NGS) tools, identifying, among others, previously undescribed anaerobic and uncultivable bacteria. In the present study, we monitored the fluctuations of this ecosystem in 15 CF patients during a 1-year follow-up period, describing for the first time, as far as we know, the presence of predator bacteria in the CF lung microbiome. In addition, a new computational model was developed to ascertain the hypothetical ecological repercussions of a prey-predator interaction in CF lung microbial communities. Fifteen adult CF patients, stratified according to their pulmonary function into mild (n = 5), moderate (n = 9), and severe (n = 1) disease, were recruited at the CF unit of the Ramón y Cajal University Hospital (Madrid, Spain). Each patient contributed three or four induced sputum samples during a 1-year follow-up period. Lung microbiota composition was determined by both cultivation and NGS techniques and was compared with the patients’ clinical variables. Results revealed a particular microbiota composition for each patient that was maintained during the study period, although some fluctuations were detected without any clinical correlation. For the first time, Bdellovibrio and Vampirovibrio predator bacteria were shown in CF lung microbiota and reduced-genome bacterial parasites of the phylum Parcubacteria were also consistently detected. The newly designed computational model allows us to hypothesize that inoculation of predators into the pulmonary microbiome might contribute to the control of chronic colonization by CF pathogens in early colonization stages., IMPORTANCE The application of NGS to sequential samples of CF patients demonstrated the complexity of the organisms present in the lung (156 species) and the constancy of basic individual colonization patterns, although some differences between samples from the same patient were observed, probably related to sampling bias. Bdellovibrio and Vampirovibrio predator bacteria were found for the first time by NGS as part of the CF lung microbiota, although their ecological significance needs to be clarified. The newly designed computational model allows us to hypothesize that inoculation of predators into the lung microbiome can eradicate CF pathogens in early stages of the process. Our data strongly suggest that lower respiratory microbiome fluctuations are not necessarily related to the patient’s clinical status.

Objective To understand the experience of families with children undergoing cleft surgery following adoption from a country outside the United States. To identify factors, including the timing of surgery, that influence family function throughout the surgical experience. Design Semistructured qualitative interviews were conducted with parents of internationally adopted children postrepair of cleft lip and/or cleft palate and coded by a multidisciplinary study team. Mixed methods were used to contextualize themes derived from the parent interviews. Results Twenty parent interviews were conducted, and four core themes were identified: (1) parental anxieties prior to surgery, (2) considerations for the timing of surgery, (3) impact of the surgical experience on the child and family, and (4) modifiable sociocontextual factors. Parents considered a strong child bond with at least one parent and the ability of the child to communicate basic needs to be important before undergoing surgery. In retrospect, parents generally felt that the surgical experience did not have a negative impact on their child or their families and that the surgical experience may have even facilitated bonding and attachment with their child. Acceleration of family bonding was expressed more often by parents of children who were adopted at older than 2 years. Conclusions In our study, parents reported that cleft surgery soon after international adoption did not appear to impair child bonding or adjustment. Specific family and provider factors that could optimize the experience for families were identified.

Two 3,5-disubstituted sulfonamide catechol ligands were synthesized. Tris(ligand) iron(III) complexes were prepared and investigated as MRI contrast agents. Longitudinal relaxivity (r1) values were determined for the complexes. The r1 values in water were substantially higher than those of typical six-coordinate iron(III) complexes. The r1 values in plasma under the same conditions increased. The iron(III) complexes were administered to rats, and the kidney and liver signal intensities were measured by T1-weighted MR imaging experiments.

▪ Abstract Green chemistry and engineering is the design of chemical manufacturing systems to minimize their adverse affects on the environment. Thus, a primary goal of green chemistry and engineering is to reduce the environmental impact of chemical processes and chemical manufacturing while simultaneously enhancing the overall process performance. Although it is beneficial to simply reduce the use of organic solvents in chemical processes, green chemistry and engineering goes further, in that it evaluates the entire manufacturing operation to identify techniques that can be applied to minimize the overall process hazard, while maintaining economic practicality. Evaluation of the environmental impacts of the manufacturing process requires a systems approach and appropriate metrics that permit quantitative assessment of environmental hazards. Thus, this chapter begins with a discussion of the drivers for green engineering and the metrics through which processes can be evaluated. Then, the hydroformylation process is used as a case study to illustrate the way in which green chemistry principles can be applied to real processes. Two elements are specifically highlighted: (a) the use of catalysts to facilitate active and selective chemistry and the immobilization of said catalysts within the reactor system, and (b) the development of processes based on benign reaction solvents, and the benefits that can accrue from simplified separations operations.

The hydroformylation of alkenes is a major commercial process used for the production of oxygenated organic compounds. When the hydroformylation reaction is performed using a homogeneous catalyst, an organic or aqueous solvent is employed, and a significant effort must be expended to recover the catalyst so it can be recycled. Development of a selective heterogeneous catalyst would allow simplification of the process design in an integrated system that minimizes waste generation. Recent studies have shown that supercritical carbon dioxide (scCO2) as a reaction solvent offers optimal environmental performance and presents advantages for ease of product separation. In particular, we have considered the conversion of 1-hexene to heptanal using rhodium- and platinum-phosphine catalysts tethered to supports insoluble in scCO2 to demonstrate the advantages and to understand the limitations of a solid-catalyzed process. One of the historical limitations of supported catalysts is the inability to control product regioselectivity. To address this concern, we have developed tethered catalysts with phosphinated silica and controlled pore size MCM-41 and MCM-20 supports that provide improved regioselectivity and conversion relative to their nonporous equivalents. Platinum catalysts supported on MCM-type supports were the most regioselective whereas the analogous rhodium catalysts were the most active for hydroformylation of 1-hexene in scCO2.

Platinum–phosphine complexes anchored on silica and on mesoporous MCM-41 supports were synthesized. Hydroformylation of 1-hexene was performed at 100 °C in supercritical carbon dioxide (pressure=2700 psi) using these supported platinum catalysts with SnCl2 · 2H2O (Sn:Pt=3.5:1) as co-catalyst. No hydrogenation was observed and high regioselectivity to heptanal was obtained.

The hydroformylation of 1-hexene in supercritical carbon dioxide is catalyzed with a heterogeneous rhodium catalyst that is active, selective, and stable for the formation of heptanal. The aldehyde yield and regioselectivity can be affected through changes in catalyst support structure, CO2 solvent pressure, and reaction temperature. A complex reaction pathway model is described that allows determination of rate constants, which are in turn, evaluated as a function of temperature and pressure. Analysis reveals an activation volume of −474 cm3/mol and activation energy of 31.9 kJ/mol for the hydroformylation pathways.

The heterogeneously catalyzed hydroformylation of 1-hexene in supercritical carbon dioxide is demonstrated as an alternative to homogeneous catalysis through the use of a rhodium–phosphine catalyst tethered to a silica support. Reaction over the heterogeneous catalyst in supercritical CO2 is compared with the use of this catalyst in liquid-phase toluene, and toluene expanded with CO2. Likewise, the performance of the tethered catalyst is compared with a homogeneous rhodium–phosphine catalyst, and shown to be equally effective under identical reaction conditions. Comparable reaction rates were obtained using the heterogeneous rhodium catalyst in supercritical CO2 and CO2-expanded toluene, both of which were superior to the reaction rate with the heterogeneous catalyst in liquid-phase toluene. Initial aldehyde selectivity obtained with the heterogeneous species was also comparable to that obtained with the homogeneous catalyst, but decreased over the course of the reaction. These results demonstrate the value of using phase behavior, and the importance of understanding this behavior in the development and analysis of greener solvent/catalyst systems.

Environmental needs associated with green chemistry require a reduction in the use of reaction solvents and separation materials. Heterogenization of homogeneous catalysts can be used to simplify the recovery steps in a reaction process. The use of a supercritical fluid for reaction and separation can further reduce the need for organic solvents throughout the process. The current paper describes the development of a tethered homogeneous catalyst for the hydroformylation of 1-hexene in supercritical carbon dioxide that is shown to be active, stable, and selective for the reaction. A reaction rate model that shows similarities to both the homogeneous and heterogeneous models is developed based on the assumption of a tethered catalyst and provides rate constants that are consistent with previous estimates.

Controlled potential bulk reductive electrolysis of trans -[PtI 2 (PEt 3 ) 2 ] in 5:2 C 6 H 5 CN:C 6 H 6 (saturated with NaClO 4 ) at a Hg pool electrode at −1.5 V (vs. Ag/AgCl) and at approximately 0°C, yielded two compounds detectable by 31 P{ 1 H} NMR spectroscopy. One compound was the starting material, trans -[PtI 2 (PEt 3 ) 2 ], while the other displayed a complex spectrum. Analysis of the 1 H, 31 P{ 1 H} and 195 Pt{ 1 H} NMR spectra suggested that the compound contained an unaccounted for spin one-half nucleus. Scanning electron microscopy–energy dispersive spectroscopy and inductively coupled plasma atomic emission spectroscopy indicated that the compound contained mercury and the spectra could be satisfactorily interpreted in terms of a mercury–platinum–hydride structure.

The platina-β-diketones [Pt2{(COR)2H}2(μ-Cl)2] (1, R = Me a, Et b) react with phosphines L in a molar ratio of 1 : 4 through cleavage of acetaldehyde to give acylplatinum(II) complexes trans-[Pt(COR)Cl(L)2] (2) (R/L = Me/P(p-FC6H4)3a, Me/P(p-CH2=CHC6H4)Ph2b, Me/P(n-Bu)3c, Et/P(p-MeOC6H4)3d). 1 a reacts with Ph2As(CH2)2PPh2 (dadpe) in a molar ratio of 1 : 2 through cleavage of acetaldehyde yielding [Pt(COMe)Cl(dadpe)] (3 a) (configuration index: SP-4-4) and [Pt(COMe)Cl(dadpe)] (configuration index: SP-4-2) (3 b) in a ratio of about 9 : 1. All acyl complexes were characterized by 1H, 13C and 31P NMR spectroscopy. The molecular structures of 2 a and 3 a were determined by single-crystal X-ray diffraction. The geometries at the platinum centers are close to square planar. In both complexes the plane of the acyl ligand is nearly perpendicular to the plane of the complex (88(2)° 2 a, 81.2(5)° 3 a). Zur Reaktivitat von Platina-β-diketonen – Synthese und Reaktvitat von Acylplatin(II)-Komplexen Die Platina-β-diketone [Pt2{(COR)2H}2 · (μ-Cl)2] (1, R = Me a, Et b) reagieren mit Phosphinen L im molaren Verhaltnis 1 : 4 unter Abspaltung von Acetaldehyd zu Acylplatin(II)-Komplexen trans-[Pt(COR)Cl(L)2] (2) (R/L = Me/P(p-FC6H4)3a, Me/P(p-CH2=CHC6H4)Ph2b, Me/P(n-Bu)3c, Et/P(p-MeOC6H4)3d). 1 a setzt sich im Molverhaltnis 1 : 2 mit Ph2As(CH2)2PPh2 (dadpe) unter Abspaltung von Acetaldehyd zu [Pt(COMe)Cl(dadpe)] (3 a) (Konfigurationsindex: SP-4-4) und [Pt(COMe)Cl(dadpe)] (Konfigurationsindex: SP-4-2) (3 b) im Verhaltnis von ungefahr 9 : 1 um. Alle Acylkomplexe sind durch 1H-, 13C- and 31P-NMR-Spektroskopie charakterisiert worden. Die Molekulstrukturen von 2 a und 3 a sind durch Rontgeneinkristallstruturanalyse ermittelt worden. Sie weisen eine ungefahr quadratisch-planare Anordnung der zentralen Platinatome auf. In beiden Komplexen steht die Ebene des Acylliganden nahezu senkrecht auf der Komplexebene (88(2)° 2 a, 81.2(5)° 3 a).

Reactions of the cyclobutadiene platinum complexes [PtCl 2 (C 4 R 4 )] (R=Me 1a , R=Et 1b ) with diphosphines Ph 2 P ⋂ PPh 2 ( ⋂ =–C C– (dppa), –CH 2 – (dppm), –(CH 2 ) 2 – (dppe), –(CH 2 ) 3 – (dppp), –(CH 2 ) 4 – (dppb)) in a 2:1 molar ratio result in formation of novel binuclear cyclobutadiene platinum complexes [{PtCl 2 (C 4 R 4 )} 2 ( μ -Ph 2 P ⋂ PPh 2 )] (R=Me 2 , Et 3 ). In contrast, reactions in equimolar ratio lead to formation of cationic complexes with dppe, dppp and dppb [PtCl(C 4 R 4 ){Ph 2 P(CH 2 ) n PPh 2 }]Cl ( n =2–4, R=Me 5 , Et 6 ). Complexes 2 , 3 and 5 , 6 were fully characterized by microanalysis and by NMR and IR spectroscopies. Structural characterization of [{PtCl 2 (C 4 Me 4 )} 2 ( μ -Ph 2 PCH 2 PPh 2 )] ( 2b ) reveals a piano-stool coordination at each platinum center defined by the η 4 -C 4 Me 4 ligand, two Cl atoms and one P atom. The P–C–P angle of 131.0(4)° is larger than that expected for tetrahedral geometry. The X-ray structure of [PtCl(C 4 Me 4 ){Ph 2 P(CH 2 ) 3 PPh 2 }]Cl·CH 2 Cl 2 ( 5b· CH 2 Cl 2 ) reveals a Pt atom coordinated by the η 4 -C 4 Me 4 ligand, chloride and the two phosphorus donors in a piano-stool conformation. In the solid state, these cations are arranged to form channels with a diameter of 13.8 A in which solvent molecules (CH 2 Cl 2 ) are embedded.

Rh2(O2CCH3)4·2C⋮NC6H4R (R = (CH3)2N−(1), −H (2), −CF3 (3)) were synthesized and characterized by X-ray crystallography. The structures exhibited several common features: (i) a relatively short Rh−...

The platina-β-diketone [Pt2{(COMe)2H}2(μ-Cl)2] (1) reacts with 2,2‘-bipyridine (bpy), 4,4‘-dimethyl-2,2‘-bipyridine (me2bpy), or 4,4‘-di(tert-butyl)-2,2‘-bipyridine (t-bu2bpy) to give novel acyl(hydrido)platinum(IV) complexes [PtCl(H)(COMe)2(NN)] (NN = bpy (2a), me2bpy (2b), t-bu2bpy (2c)). The complexes 2 show an astonishing thermal stability in the solid state up to 180 °C. They decompose with cleavage of acetaldehyde to form the acylplatinum(II) complexes [PtCl(COMe)(NN)] (3). The identities of 2 and 3 were determined by microanalysis and NMR (1H, 13C) and IR spectroscopies. The crystal structure of [PtCl(H)(COMe)2(t-bu2bpy)] (2c) has been determined. The Pt−H bond distance was found to be 1.72(5) A.

The binuciear palladium(I) complex, [Pd2Cl2(μ-dppm)2] (dppm = bis(diphenylphosphino)methane), has been shown to react with bis(diethylamino)acetylene, Et2NC≡CNEt2, in methylene chloride solution to yield two isolable products, the known methylene-bridged complex, [Pd2Cl2(μ-CH2)(μ-dppm)2], and hexakis(diethylamino)benzene, C6(NEt2)6, both of which have been characterized crystallographically. The source of the bridging methylene group in [Pd2Cl2(μ-CH2)(μ-dppm)2] has been shown to be the methylene chloride solvent. A mechanism that accounts for the formation of the two isolable products is proposed. The complex, [Pd2Cl2(μdmpm)2] (dmpm = bis(dimethylphosphino)methane), was similarly found to react with Et2NC≡NEt2 in methylene chloride solution to yield [Pd2Cl2(μ-CH2)(μ-dmpm)2], which was identified spectroscopically. Key words: acetylene, palladium, cyclooligomerization, aminoacetylene, hexakis(diethylamino)benzene.

The reported heterogenous photocatalytic sythesis of NH 3 from N 2 and H 2 O in the presence of iron-doped TiO 2 or other semiconducting metal oxides has been investigated. Skepticism about this thermodynamically and mechanistically daunting process is appropriate, and the results reported here support a skeptical position. To assess the reproducibility of the results obtained by previous workers, we performed a large number of experiments under various conditions similar to those employed with apparent success by others. We also carried out 15 N isotope labelling experiments in which the lower limit of detection was around 0.2–1 nmol of added 15 NH 3 in 10 μmol of natural ammonia, i.e. two to three orders of magnitude below the levels reported in successful syntheses by others. All the catalysts tested promoted the photo-oxidation of ammonia under the conditions said to give ammonia photosynthesis. Photocatalytic nitrogen fixation was not found in any of the experiments, although in some cases results were obtained that could have been mistaken for nitrogen fixation. Our results suggest that the reported putative reaction does not occur. We recommend that any further research in this area should be based on standards of demonstration as rigorous as those applied in experiments on the biological fixation of nitrogen.

The photoassisted oxidation of dilute aqueous ammonia (0–100 μM) to NO2− and NO3− was investigated over heterogeneous catalysts of TiO2 doped with iron oxide in quartz vessels and with radiation from mercury lamps. Effects on the reaction rate of varying concentration, radiation intensity, amount of catalyst, and pH were studied. The rate of ammonia consumption increased with radiation intensity and was independent of the amount of catalyst over the range of 0.1–1.0 g suspended in 50 ml of solution. In acidic solutions (pH 1–6), the simultaneous action of catalyst and radiation was needed, while in strongly basic solutions (pH 12) only illumination was required. Moreover, the nature and yields of products were dependent on pH: in acidic solutions NO3− was the main product and in basic solutions NO2− was the primary one. Control experiments showed that the reaction rate increased with pH in the absence of catalyst, and the catalyst was active only when irradiated. The reaction was first-order in NH3. The chemical reaction and the mechanism of the photooxidation of NH3 are discussed.

This work is an investigation of the putative photocatalytic reduction of N 2 to NH 3 in dilute aqueous ferrofluid, a recently reported reaction. We tested four different types of commercially available ferrofluid. Diluted ferrofluids were irradiated under nitrogen or argon, and the concentrations of ammonia , nitrate and nitrite in the reactor were measured at regular intervals. The substitution of argon for nitrogen produced no discernible difference in the experimental results. The possibility of the photocatalytic degradation of ammonia in aqueous solutions of ferrofluid was also investigated. In all of our experiments, variations in the measured concentrations of ammonia, nitrite and nitrate were small and random with respect to the irradiation time. There was no evidence that ammonia was either produced or degraded. Isotope-labeling experiments were performed, in which 15 N 2 was irradiated in the presence of dilute ferrofluid. Small amounts of excess 15 NH 3 (0.5–1.5 nmol) were measured in experimental samples and in control samples in which no nitrogen could have been fixed. The levels of 15 NH 3 were too low to establish that any photocatalytic nitrogen reduction had occured, and were consistent with the hypothesis that no ammonia was produced.

An investigation of bis(diphenylphosphino)methane dioxide (dppm dioxide), cis-[PtCl2(PPh3)2] cis-[PtCl2{P(p-C6H4Cl)3}2] and cis-[PtBr2(PPh3)2] by solid-state CP/MAS 31P NMR spectroscopy, x-ray powder diffraction and 1H, 13C{1H} and 31P{1H} solution NMR methods illustrates the sensitivity of the appearance of solid-state NMR spectra to solvation effects in crystalline solids. The presence or absence of solvent of crystallization and the slow loss of solvent of crystallization from a sample over time are clearly manifested in the solid-state NMR spectra as the local site symmetry in the solid is changed. These effects have led workers to report different data for a given compound when, in fact, different types of solvates were investigated.

The 31P CP/MAS NMR spectrum of cis-[PtCl2(PPh2nPr)(BzS{O}Bz)] was found to exhibit two central resonances with appropriate couplings to 195Pt, despite the fact that a single-crystal x-ray diffraction study indicated that the complex crystallized in the monoclinic space group P21/n with Z = 4, i.e. that there is only a single crystallographically unique phosphorus atom. The possibility that the 21 screw axis was absent (i.e. that the space group was actually Pn) was examined by a reinvestigation of the original x-ray data, but no definitive evidence for the alternative space group could be obtained. An examination of a bulk sample of cis- [PtCl2(PPh2nPr)(BzS{O}Bz)] by x-ray powder diffraction and comparison of the results with data from the single-crystal x-ray diffraction experiment revealed that the crystal selected for diffraction studies was a different polymorph from the bulk of the sample which was used for the 31P CP/MAS NMR measurements. X-ray powder diffraction is thus shown to provide a valuable bridge between solid-state CP/MAS NMR measurements and single-crystal x-ray diffraction data.

A. Introductio B. Properties of metal nuclei . . 204 C. Solid state NMR . . . 204 D. Studies of metal nuclei 209 (i) The d-block metals . 209 (a) Group 3 (SC, Y, La) . 209 (b) Group 4 (Ti, Zr, Hf) . . . . 211 (c) Group 5 (V, Nb, Ta) . 213 (d) Group 6 (Cr, MO, W) . . 214 (e) Group 7 (Mn, Tc, Re) . . 217 (f) Group 8 (Fe, Ru, OS) . 219 (g) Group 9 (Co, Rh, Ir) . . . 220 (h) Group 10 (Ni, Pd, Pt) 220 (i) Group 11 (Cu, Ag, Au) 222 (j) Group 12 (Zn, Cd, Hg) 223 (ii) The p-block metals . . 229 (a) Group 13 (Al, Ga, In, Tl) 229 (b) Group 14 (Ge, Sn, Pb) 230 (c) Group 15 (Sb, Bi) 238 E. Concluding remarks 238 References . . . . . . 239