Mechanistic roles of metal- and ligand-protonated species in hydrogen evolution with [Cp*Rh] complexes.

Protonation reactions involving organometallic complexes are ubiquitous in redox chemistry and often result in the generation of reactive metal hydrides. However, some organometallic species supported by η5-pentamethylcyclopentadienyl (Cp*) ligands have recently been shown to undergo ligand-centered protonation by direct proton transfer from acids or tautomerization of metal hydrides, resulting in the generation of complexes bearing the uncommon η4-pentamethylcyclopentadiene (Cp*H) ligand. Here, time-resolved pulse radiolysis (PR) and stopped-flow spectroscopic studies have been applied to examine the kinetics and atomistic details involved in the elementary electron- and proton-transfer steps leading to complexes ligated by Cp*H, using Cp*Rh(bpy) as a molecular model (where bpy is 2,2'-bipyridyl). Stopped-flow measurements coupled with infrared and UV-visible detection reveal that the sole product of initial protonation of Cp*Rh(bpy) is [Cp*Rh(H)(bpy)]+, an elusive hydride complex that has been spectroscopically and kinetically characterized here. Tautomerization of the hydride leads to the clean formation of [(Cp*H)Rh(bpy)]+. Variable-temperature and isotopic labeling experiments further confirm this assignment, providing experimental activation parameters and mechanistic insight into metal-mediated hydride-to-proton tautomerism. Spectroscopic monitoring of the second proton transfer event reveals that both the hydride and related Cp*H complex can be involved in further reactivity, showing that [(Cp*H)Rh] is not necessarily an off-cycle intermediate, but, instead, depending on the strength of the acid used to drive catalysis, an active participant in hydrogen evolution. Identification of the mechanistic roles of the protonated intermediates in the catalysis studied here could inform design of optimized catalytic systems supported by noninnocent cyclopentadienyl-type ligands.

Bacillus subtilis NrnB is expressed during sporulation and acts as a unique 3'-5' exonuclease.

All cells employ a combination of endo- and exoribonucleases to degrade long RNA polymers to fragments 2-5 nucleotides in length. These short RNA fragments are processed to monoribonucleotides by nanoRNases. Genetic depletion of nanoRNases has been shown to increase abundance of short RNAs. This deleteriously affects viability, virulence, and fitness, indicating that short RNAs are a metabolic burden. Previously, we provided evidence that NrnA is the housekeeping nanoRNase for Bacillus subtilis. Herein, we investigate the biological and biochemical functions of the evolutionarily related protein, B. subtilis NrnB (NrnBBs). These experiments show that NrnB is surprisingly different from NrnA. While NrnA acts at the 5' terminus of RNA substrates, NrnB acts at the 3' terminus. Additionally, NrnA is expressed constitutively under standard growth conditions, yet NrnB is selectively expressed during endospore formation. Furthermore, NrnA processes only short RNAs, while NrnB unexpectedly processes both short RNAs and longer RNAs. Indeed, inducible expression of NrnB can even complement the loss of the known global 3'-5' exoribonucleases, indicating that it acts as a general exonuclease. Together, these data demonstrate that NrnB proteins, which are widely found in Firmicutes, Epsilonproteobacteria and Archaea, are fundamentally different than NrnA proteins and may be used for specialized purposes.

The impact of musculoskeletal ill health on quality of life and function after critical care: a multicentre prospective cohort study.

Physical disability is a common component of post-intensive care syndrome, but the importance of musculoskeletal health in this population is currently unknown. We aimed to determine the musculoskeletal health state of intensive care unit survivors and assess its relationship with health-related quality of life; employment; and psychological and physical function. We conducted a multicentre prospective cohort study of adults admitted to intensive care for > 48 h without musculoskeletal trauma or neurological insult. Patients were followed up 6 months after admission where musculoskeletal health state was measured using the validated Musculoskeletal Health Questionnaire score. Of the 254 participants, 150 (59%) had a musculoskeletal problem and only 60 (24%) had received physiotherapy after discharge. Functional Comorbidity Index, Clinical Frailty Scale, duration of intensive care unit stay and prone positioning were all independently associated with worse musculoskeletal health. Musculoskeletal health state moderately correlated with quality of life, rs = 0.499 (95%CI 0.392-0.589); anxiety, rs = -0.433 (95%CI -0.538 to -0.315); and depression, rs = -0.537 (95%CI -0.631 to -0.434) (all p < 0.001). Patients with a musculoskeletal problem were less physically active than those without a problem (median (IQR [range]) number of 30 min physical activity sessions per week 1 (0-3.25 [0-7]) vs. 4 (1-7 [0-7]), p < 0.001, respectively). This study found that musculoskeletal health problems were common after intensive care unit stay. However, we observed that < 25% of patients received physical rehabilitation after discharge home. Our work has identified potential high-risk groups to target in future interventional studies.

NrnA is a 5'-3' exonuclease that processes short RNA substrates in vivo and in vitro.

Bacterial RNases process RNAs until only short oligomers (2-5 nucleotides) remain, which are then processed by one or more specialized enzymes until only nucleoside monophosphates remain. Oligoribonuclease (Orn) is an essential enzyme that acts in this capacity. However, many bacteria do not encode for Orn and instead encode for NanoRNase A (NrnA). Yet, the catalytic mechanism, cellular roles and physiologically relevant substrates have not been fully resolved for NrnA proteins. We herein utilized a common set of reaction assays to directly compare substrate preferences exhibited by NrnA-like proteins from Bacillus subtilis, Enterococcus faecalis, Streptococcus pyogenes and Mycobacterium tuberculosis. While the M. tuberculosis protein specifically cleaved cyclic di-adenosine monophosphate, the B. subtilis, E. faecalis and S. pyogenes NrnA-like proteins uniformly exhibited striking preference for short RNAs between 2-4 nucleotides in length, all of which were processed from their 5' terminus. Correspondingly, deletion of B. subtilis nrnA led to accumulation of RNAs between 2 and 4 nucleotides in length in cellular extracts. Together, these data suggest that many Firmicutes NrnA-like proteins are likely to resemble B. subtilis NrnA to act as a housekeeping enzyme for processing of RNAs between 2 and 4 nucleotides in length.

Bacterial riboswitches cooperatively bind Ni(2+) or Co(2+) ions and control expression of heavy metal transporters.

Bacteria regularly encounter widely varying metal concentrations in their surrounding environment. As metals become depleted or, conversely, accrue to toxicity, microbes will activate cellular responses that act to maintain metal homeostasis. A suite of metal-sensing regulatory ("metalloregulatory") proteins orchestrate these responses by allosterically coupling the selective binding of target metals to the activity of DNA-binding domains. However, we report here the discovery, validation, and structural details of a widespread class of riboswitch RNAs, whose members selectively and tightly bind the low-abundance transition metals, Ni(2+) and Co(2+). These riboswitches bind metal cooperatively, and with affinities in the low micromolar range. The structure of a Co(2+)-bound RNA reveals a network of molecular contacts that explains how it achieves cooperative binding between adjacent sites. These findings reveal that bacteria have evolved to utilize highly selective metalloregulatory riboswitches, in addition to metalloregulatory proteins, for detecting and responding to toxic levels of heavy metals.

Serial sexual murder by juveniles and the role of sexual sadism: An international study.

This is a descriptive study of 21 cases of serial sexual murder by children and adolescents spanning nearly the past century and a half. No earlier cases worldwide were identified. Each of these youth committed two or more sexual homicides prior to age 18. Their psychopathological, psychosocial, crime scene behaviors, and offender-victim relationship characteristics are presented. Additionally, the role of sexual sadism and its measurement using the SADSEX-SH rating scale is addressed. Nearly all of the sample had conduct disorder, a paraphilic disorder, and sadistic fantasies, and two-thirds had sexual sadism disorder. Family dysfunction, serious school problems, and average or above IQ levels were typical. Their modus operandi generally reflected predatory behavior and direct contact methods of killing were most common. Two case reports are provided to illustrate the breadth and complexity of these offenders. Juvenile Serial Sexual Homicide is an extremely rare but persistent phenomenon. Prognostic implications and future research directions are discussed.

Evidence for Charge Delocalization in Diazafluorene Ligands Supporting Low-Valent [Cp*Rh] Complexes.

Ligands based upon the 4,5-diazafluorene core are an important class of emerging ligands in organometallic chemistry, but the structure and electronic properties of these ligands have received less attention than they deserve. Here, we show that 9,9'-dimethyl-4,5-diazafluorene (Me2 daf) can stabilize low-valent complexes through charge delocalization into its conjugated π-system. Using a new platform of [Cp*Rh] complexes with three accessible formal oxidation states (+III, +II, and +I), we show that the methylation in Me2 daf is protective, blocking Brønsted acid-base chemistry commonly encountered with other daf-based ligands. Electronic absorption spectroscopy and single-crystal X-ray diffraction analysis of a family of eleven new compounds, including the unusual Cp*Rh(Me2 daf), reveal features consistent with charge delocalization driven by π-backbonding into the LUMO of Me2 daf, reminiscent of behavior displayed by the workhorse 2,2'-bipyridyl ligand. Taken together with spectrochemical data demonstrating clean conversion between oxidation states, our findings show that 9,9'-dialkylated daf-type ligands are promising building blocks for applications in reductive chemistry and catalysis.

Remote Oxidative Activation of a [Cp*Rh] Monohydride.

Half-sandwich rhodium monohydrides are often proposed as intermediates in catalysis, but little is known regarding the redox-induced reactivity accessible to these species. Herein, the bis(diphenylphosphino)ferrocene (dppf) ligand has been used to explore the reactivity that can be induced when a [Cp*Rh] monohydride undergoes remote (dppf-centered) oxidation by 1e- . Chemical and electrochemical studies show that one-electron redox chemistry is accessible to Cp*Rh(dppf), including a unique quasi-reversible RhII/I process at -0.96 V vs. ferrocenium/ferrocene (Fc+/0 ). This redox manifold was confirmed by isolation of an uncommon RhII species, [Cp*Rh(dppf)]+ , that was characterized by electron paramagnetic resonance (EPR) spectroscopy. Protonation of Cp*Rh(dppf) with anilinium triflate yielded an isolable and inert monohydride, [Cp*Rh(dppf)H]+ , and this species was found to undergo a quasireversible electrochemical oxidation at +0.41 V vs. Fc+/0 that corresponds to iron-centered oxidation in the dppf backbone. Thermochemical analysis predicts that this dppf-centered oxidation drives a dramatic increase in acidity of the Rh-H moiety by 23 pKa units, a reactivity pattern confirmed by in situ 1 H NMR studies. Taken together, these results show that remote oxidation can effectively induce M-H activation and suggest that ligand-centered redox activity could be an attractive feature for the design of new systems relying on hydride intermediates.

Canine coat pigmentation genetics: a review.

Our understanding of canine coat colour genetics and the associated health implications is developing rapidly. To date, there are 15 genes with known roles in canine coat colour phenotypes. Many coat phenotypes result from complex and/or epistatic genetic interactions among variants within and between loci, some of which remain unidentified. Some genes involved in canine pigmentation have been linked to aural, visual and neurological impairments. Consequently, coat pigmentation in the domestic dog retains considerable ethical and economic interest. In this paper we discuss coat colour phenotypes in the domestic dog, the genes and variants responsible for these phenotypes and any proven coat colour-associated health effects.

Arrested Friendships? Justice Involvement and Interpersonal Exclusion among Rural Youth.

Objectives: We examine the impacts of adolescent arrest on friendship networks. In particular, we extend labeling theory by testing hypotheses for three potential mechanisms of interpersonal exclusion related to the stigma of arrest: rejection, withdrawal, and homophily. Method: We use longitudinal data on 48 peer networks from PROSPER, a study of rural youth followed through middle and high school. We test our hypotheses using stochastic actor-based models. Results: Our findings suggest that arrested youth are less likely to receive friendship ties from school peers, and are also less likely to extend them. Moreover, these negative associations are attenuated by higher levels of risky behaviors among peers, suggesting that results are driven by exclusion from normative rather than non-normative friendships. We find evidence of homophily on arrest but it appears to be driven by other selection mechanisms rather than a direct preference for similarity on arrest. Conclusions: Overall, our findings speak to how arrest may foster social exclusion in rural schools, thereby limiting social capital for already disadvantaged youth.

Does Early Adolescent Arrest Alter the Developmental Course of Offending into Young Adulthood?

Adolescent involvement in risky behavior is ubiquitous and normative. Equally pervasive is the rapid decline in risky behavior during the transition to adulthood. Yet, for many, risky behavior results in arrest. Whereas prior research finds that arrest is associated with an increased risk of experiencing a host of detrimental outcomes, less understood is the impact of an arrest on the developmental course of offending compared to what it would have looked like if no arrest had occurred-the counterfactual. This study examines the developmental implications of an arrest early in the life course. The sample (N = 1293) was 37% female, 42% non-white, with a mean age of 13.00 years (SD = 0.82, range = 12-14) at baseline and followed annually for 15 years. Analyses combine propensity score matching and multilevel modeling techniques to estimate the impact of early arrest (i.e., 14 or younger) on the development of offending from adolescence into adulthood. The results indicate that early arrest alters the developmental course of offending in two primary ways. First, early arrest heightens involvement, frequency, and severity of offending throughout adolescence and into early young adulthood even after controlling for subsequent arrests. The detrimental influence of early arrest on the developmental course of offending is found regardless of gender or race/ethnicity. Second, even among youth with an early arrest, offending wanes over time with self-reported offending among all youth nearly absent by the mid- to late-twenties. The findings advance understanding of the developmental implications of early arrest beyond typical and expected offending.

Nematodes and trematodes associated with terrestrial gastropods in Nottingham, England.

A parasitological survey of terrestrial slugs and snails was conducted at popular dog walking locations across the city of Nottingham, with the intensions of finding gastropods infected with parasites of medical (or veterinary) importance such as lungworm (metastrongyloid nematodes) and trematodes. A total of 800 gastropods were collected from 16 sites over a 225 km2 area. The extracted nematodes and trematodes were identified by molecular barcoding. Of the 800 gastropods collected, 227 were infected (172 had nematode infections, 37 had trematode infections and 18 had both nematode and trematode infections). Of the nematode infected gastropods genotyped, seven species were identified, Agfa flexilis, Angiostoma gandavense, Angiostoma margaretae, Cosmocerca longicauda, Phasmarhabditis hermaphrodita, Phasmarhabditis neopapillosa and an unknown Cosmocercidae species. Of the trematode infected gastropods genotyped, four species were identified, Brachylaima arcuate, Brachylaima fuscata, Brachylaima mesostoma and an unknown Plagiorchioidea species. No lungworm species were found within the city of Nottingham. To our knowledge, this study represents the first survey of gastropod-associated nematodes and trematodes in the East midlands of the United Kingdom.

An autoinhibitory mechanism controls RNA-binding activity of the nitrate-sensing protein NasR.

The ANTAR domain harnesses RNA-binding activity to promote transcription attenuation. Although several ANTAR proteins have been analyzed by high-resolution structural analyses, the residues involved in RNA-recognition and transcription attenuation have not been identified. Nor is it clear how signal-responsive domains are allosterically coupled with ANTAR domains for control of gene expression. Herein, we examined the sequence conservation of ANTAR domains to find residues that may associate with RNA. We subjected the corresponding positions of Klebsiella oxytoca NasR to site-directed alanine substitutions and measured RNA-binding activity. This revealed a functionally important patch of residues that forms amino acid pairing interactions with residues from NasR's nitrate-sensing NIT domain. We hypothesize these amino acid pairing interactions are part of an autoinhibitory mechanism that holds the structure in an "off" state in the absence of nitrate signal. Indeed, mutational disruption of these interactions resulted in constitutively active proteins, freed from autoinhibition and no longer influenced by nitrate. Moreover, sequence analyses suggested the autoinhibitory mechanism has been evolutionarily maintained by NasR proteins. These data reveal a molecular mechanism for how NasR couples its nitrate signal to RNA-binding activity, and generally show how signal-responsive domains of one-component regulatory proteins have evolved to exert control over RNA-binding ANTAR domains.

Comparing Xe+ pFIB and Ga+ FIB for TEM sample preparation of Al alloys: Minimising FIB-induced artefacts.

Recently, the dual beam Xe+ plasma focused ion beam (Xe+ pFIB) instrument has attracted increasing interest for site-specific transmission electron microscopy (TEM) sample preparation for a local region of interest as it shows several potential benefits compared to conventional Ga+ FIB milling. Nevertheless, challenges and questions remain especially in terms of FIB-induced artefacts, which hinder reliable S/TEM microstructural and compositional analysis. Here we examine the efficacy of using Xe+ pFIB as compared with conventional Ga+ FIB for TEM sample preparation of Al alloys. Three potential source of specimen preparation artefacts were examined, namely: (1) implantation-induced defects such as amophisation, dislocations, or 'bubble' formation in the near-surface region resulting from ion bombardment of the sample by the incident beam; (2) compositional artefacts due to implantation of the source ions and (3) material redeposition due to the milling process. It is shown that Xe+ pFIB milling is able to produce improved STEM/TEM samples compared to those produced by Ga+ milling, and is therefore the preferred specimen preparation route. Strategies for minimising the artefacts induced by Xe+ pFIB and Ga+ FIB are also proposed. LAY DESCRIPTION: FIB (focused ion beam) instruments have become one of the most important systems in the preparation of site-specific TEM specimens, which are typically 50-100 nm in thickness. TEM specimen preparation of Al alloys is particularly challenging, as convention Ga-ion FIB produces artefacts in these materials that make microstructural analysis difficult or impossible. Recently, the use of noble gas ion sources, such as Xe, has markedly improved milling speeds and is being used for the preparation of various materials. Hence, it is necessary to investigate the structural defects formed during FIB milling and assess the ion-induced chemical contamination in these TEM samples. Here we explore the feasibility and efficiency of using Xe+ PFIB as a TEM sample preparation route for Al alloys in comparison with the conventional Ga+FIB.

Genetics of canine myxomatous mitral valve disease.

Myxomatous mitral valve disease (MMVD) is the most common heart disease and cause of cardiac death in domestic dogs. MMVD is characterised by slow progressive myxomatous degeneration from the tips of the mitral valves onwards with subsequent mitral valve regurgitation, and left atrial and ventricular dilatation. Although the disease usually has a long asymptomatic period, in dogs with severe disease, mortality is typically secondary to left-sided congestive heart failure. Although it is not uncommon for dogs to survive long enough in the asymptomatic period to die from unrelated causes; a proportion of dogs rapidly advance into congestive heart failure. Heightened prevalence in certain breeds, such as the Cavalier King Charles Spaniel, has indicated that MMVD is under a genetic influence. The genetic characterisation of the factors that underlie the difference in progression of disease is of strong interest to those concerned with dog longevity and welfare. Advanced genomic technologies have the potential to provide information that may impact treatment, prevalence, or severity of MMVD through the elucidation of pathogenic mechanisms and the detection of predisposing genetic loci of major effect. Here we describe briefly the clinical nature of the disorder and consider the physiological mechanisms that might impact its occurrence in the domestic dog. Using results from comparative genomics we suggest possible genetic approaches for identifying genetic risk factors within breeds. The Cavalier King Charles Spaniel breed represents a robust resource for uncovering the genetic basis of MMVD.

Roan, ticked and clear coat patterns in the canine are associated with three haplotypes near usherin on CFA38.

White coat patterning is a feature of many dog breeds and is known to be coded primarily by the gene micropthalmia-associated transcription factor (MITF). This patterning in the coat can be modified by other factors to produce the attractive phenotypes termed 'ticked' and 'roan' that describe the presence of flecks of color that vary in distribution and intensity within otherwise 'clear' white markings. The appearance of the pigment in the white patterning caused by ticking and roaning intensifies in the weeks after birth. We applied genome-wide association to compare English Cocker Spaniels of roan phenotype (N = 34) with parti-color (non-roan) English Cocker Spaniels (N = 9) and identified an associated locus on CFA 38, CFA38:11 057 040 (Praw  = 8.9 × 10-10 , Pgenome  = 2.7 × 10-5 ). A local case-control association in English Springer Spaniels comparing 11 ticked and six clear dogs identified indicative association with a different haplotype, CFA38:11 122 467G>T (Praw  = 1.7 × 10-5 ) and CFA38:11 124 294A>C (Praw  = 1.7 × 10-5 ). We characterize three haplotypes in Spaniels according to their putative functional variant profiles at CFA38:11 111 286C>T (missense), CFA38:11 131 841-11 143 239DUP.insTTAA (using strongly linked marker CFA38:11 143 243C>T) and CFA38:11 156 425T>C (splice site). In Spaniels, the haplotypes work as an allelic series including alleles (t, recessive clear; T, dominant ticked/parti-color; and TR , incomplete dominant roan) to control the appearance of pigmented spots or flecks in otherwise white areas of the canine coat. In Spaniels the associated haplotypes are t (CCT), T (TCC) and TR (TTT) for SNP markers on CFA38 at 11 111 286C>T, 11 143 243C>T and 11 156 425T>C respectively. It is likely that other alleles exist in this series and together the haplotypes result in a complex range of patterning that is only visible when dogs have white patterning resulting from the epistatic gene Micropthalmia-associated transcription factor (the S-locus).

Revenge filicide: An international perspective through 62 cases.

Filicide is the purposeful killing of one or more children by a parent, step-parent, or other parental figure. Revenge filicide is a poorly understood, rare form of filicide in which a parent murders their child to cause emotional harm to the child's other parent. This descriptive study presents an international case series consisting of 62 revenge filicide cases from nine countries. Perpetrators were about equally likely to be male or female. Over half of the sample had an active mental disorder of any type, most often a personality disorder. A history of domestic violence was common. The mean victim age was 6 years. They were typically killed by asphyxiation, firearms, or knives, and preschool age children were targeted most frequently. In half of the cases, more than one child was murdered. Post-crime suicidal behavior was commonplace, and one-third of the sample died by suicide. Four revenge filicide subtypes were identified: rejection, custody/visitation dispute, infidelity/jealousy, and argument/conflict. These categories may prove useful in future research and for helping to identify children at high risk of becoming filicide victims. All surviving offenders were criminally convicted, and in only one case was a mental health defense successful in lessening culpability. Notable similarities and differences between the US and international cases are discussed.

Ultrafast Spectroscopy of [Mn(CO)3] Complexes: Tuning the Kinetics of Light-Driven CO Release and Solvent Binding.

Manganese tricarbonyl complexes are promising catalysts for CO2 reduction, but complexes in this family are often photosensitive and decompose rapidly upon exposure to visible light. In this report, synthetic and photochemical studies probe the initial steps of light-driven speciation for Mn(CO)3(Rbpy)Br complexes bearing a range of 4,4'-disubstituted 2,2'-bipyridyl ligands (Rbpy, where R = tBu, H, CF3, NO2). Transient absorption spectroscopy measurements for Mn(CO)3(Rbpy)Br coordination compounds with R = tBu, H, and CF3 in acetonitrile reveal ultrafast loss of a CO ligand on the femtosecond time scale, followed by solvent coordination on the picosecond time scale. The Mn(CO)3(NO2bpy)Br complex is unique among the four compounds in having a longer-lived excited state that does not undergo CO release or subsequent solvent coordination. The kinetics of photolysis and solvent coordination for light-sensitive complexes depend on the electronic properties of the disubstituted bipyridyl ligand. The results indicate that both metal-to-ligand charge-transfer (MLCT) and dissociative ligand-field (d-d) excited states play a role in the ultrafast photochemistry. Taken together, the findings suggest that more robust catalysts could be prepared with appropriately designed complexes that avoid crossing between the excited states that drive photochemical CO loss.

Association of missense variants in GDF9 with litter size in Entlebucher Mountain dogs.

In the past two decades, average litter size (ALS) in Entlebucher Mountain dogs decreased by approximately 0.8 puppies. We conducted a GWAS for ALS using the single-step methodology to take advantage of 1632 pedigree records, 892 phenotypes and 372 genotypes (173 662 markers) for which only 12% of the dogs had both phenotypes and genotypes available. Our analysis revealed associations towards the growth differentiation factor 9 gene (GDF9), which is known to regulate oocyte maturation. The trait heritability was estimated at 43.1%, from which approximately 15% was accountable by the GDF9 locus alone. Therefore, markers flanking GDF9 explained approximately 6.5% of the variance in ALS. Analysis of WGSs revealed two missense substitutions in GDF9, one of which (g.11:21147009G>A) affected a highly conserved nucleotide in vertebrates. The derived allele A was validated in 111 dogs and shown to be associated with decreased ALS (-0.75 ± 0.22 puppies per litter). The variant was further predicted to cause a proline to serine substitution. The affected residue was immediately followed by a six-residue deletion that is fixed in the canine species but absent in non-canids. We further confirmed that the deletion is prevalent in the Canidae family by sequencing three species of wild canids. Since canids uniquely ovulate oocytes at the prophase stage of the first meiotic division, requiring maturation in the oviduct, we conjecture that the amino acid substitution and the six-residue deletion of GDF9 may serve as a model for insights into the dynamics of oocyte maturation in canids.

4,5-Diazafluorene and 9,9'-Dimethyl-4,5-Diazafluorene as Ligands Supporting Redox-Active Mn and Ru Complexes.

4,5-diazafluorene (daf) and 9,9'-dimethyl-4,5-diazafluorene (Me2daf) are structurally similar to the important ligand 2,2'-bipyridine (bpy), but significantly less is known about the redox and spectroscopic properties of metal complexes containing Me2daf as a ligand than those containing bpy. New complexes Mn(CO)3Br(daf) (2), Mn(CO)3Br(Me2daf) (3), and [Ru(Me2daf)3](PF6)2 (5) have been prepared and fully characterized to understand the influence of the Me2daf framework on their chemical and electrochemical properties. Structural data for 2, 3, and 5 from single-crystal X-ray diffraction analysis reveal a distinctive widening of the daf and Me2daf chelate angles in comparison to the analogous Mn(CO)3(bpy)Br (1) and [Ru(bpy)3]2+ (4) complexes. Electronic absorption data for these complexes confirm the electronic similarity of daf, Me2daf, and bpy, as spectra are dominated in each case by metal-to-ligand charge transfer bands in the visible region. However, the electrochemical properties of 2, 3, and 5 reveal that the redox-active Me2daf framework in 3 and 5 undergoes reduction at a slightly more negative potential than that of bpy in 1 and 4. Taken together, the results indicate that Me2daf could be useful for preparation of a variety of new redox-active compounds, as it retains the useful redox-active nature of bpy but lacks the acidic, benzylic C-H bonds that can induce secondary reactivity in complexes bearing daf.