Guanine-containing ssDNA and RNA induce dimeric and tetrameric structural forms of SAMHD1.

The dNTPase activity of tetrameric SAM and HD domain containing deoxynucleoside triphosphate triphosphohydrolase 1 (SAMHD1) plays a critical role in cellular dNTP regulation. SAMHD1 also associates with stalled DNA replication forks, DNA repair foci, ssRNA and telomeres. The above functions require nucleic acid binding by SAMHD1, which may be modulated by its oligomeric state. Here we establish in cryo-EM and biochemical studies that the guanine-specific A1 activator site of each SAMHD1 monomer is used to target the enzyme to guanine nucleotides within single-stranded (ss) DNA and RNA. Remarkably, nucleic acid strands containing a single guanine base induce dimeric SAMHD1, while two or more guanines with ∼20 nucleotide spacing induce a tetrameric form. A cryo-EM structure of ssRNA-bound tetrameric SAMHD1 shows how ssRNA strands bridge two SAMHD1 dimers and stabilize the structure. This ssRNA-bound tetramer is inactive with respect to dNTPase and RNase activity.

Evaluating impacts of bambusuril pocket size and sterics on anion binding trends using ChemFET sensors.

Chemically-sensitive Field Effect Transistors (ChemFETs) are a useful tool to evaluate aqueous anion affinity of hydrophobic supramolecular scaffolds. More specifically, ChemFETs can be used to probe impacts of receptor modification to aqueous anion affinity. In this study, ChemFETs are used to evaluate the anion affinity of both dodeca-n-butyl bambus[6]uril and dodecabenzyl bambus[6]uril to assess steric effects in the chemical selectivity of the sensor membrane. The ChemFETs were evaluated through a series of common anions in the Hofmeister series in order to ascertain the difference in detection limit imparted by the specific functionalization of the bambus[6]uril macrocycles, which are quite sensitive to modest steric effects. Significant improvements to perchlorate and nitrate detection limits were observed via n-butyl bambusuril-containing sensor membranes over detection limits recorded with benzyl bambusuril sensors.

Editorial Commentary: Routine Use of Suture Tape Augmentation for Primary Anterior Cruciate Ligament Reconstruction Surgery Is Not Justified.

High rates of graft failure after primary anterior cruciate ligament reconstruction (ACLR) and the need for revision ACLR continue to be a challenge. Multiple studies demonstrate graft failure rates and the need for revision ACLR in 10% to 15% of young patients participating in pivot sporting activities. Currently, a wide range of strategies to mitigate this is problem being investigated, including extra-articular augmentation (with modified lateral extra-articular tenodesis or anterolateral ligament reconstruction) and intra-articular fixation (that aim for primary anterior cruciate ligament healing or augmentation of an ACLR with suture tape). While the early data on suture tape augmentation of primary ACLR seem optimistic, it does not justify its routine use.

Azaphosphinines and their derivatives.

Six-membered heterocycles containing one phosphorus and one nitrogen atom, known as azaphosphinines, have existed in the shadows of their single heteroatom-containing analogues for almost 150 years. Despite this, recent chemistry has seen a rapid increase in publications concerning this uncommon scaffold. Azaphosphinines exist in one of six isomers-there are three possible orientations of the pnictogen atoms and in each of these, the phosphorus is in one of two valences (PIIIvs. PV). This review aims to outline and inform on the synthesis and applications of all six isomers. PV-oxo azaphosphinines are of particular interest to this review as many of the discussed heterocycles either form as the pentavalent species directly or oxidize to this over time. In very recent years the published applications of azaphosphinines have blossomed into subjects spanning several fields of chemistry such as asymmetric catalysis, supramolecular association, cellular imaging, and medicinal chemistry.

The Seated Trunk Control Test: Investigation of Reliability and Known-Groups Validity Using Individuals Post-Anterior Cruciate Ligament Reconstruction.

CONTEXT: Decreased trunk neuromuscular control is a risk factor for both upper- and lower-extremity injuries, yet there are few reliable and valid clinical tests to identify deficits. OBJECTIVE: The purpose of this study was to determine the reliability and known-groups validity of a novel clinical test, the seated trunk control test (STCT). DESIGN: Cross-sectional reliability and known-groups validity study. SETTING: Laboratory. PARTICIPANTS: 89 unique participants: 34 were 3 months postoperative anterior cruciate ligament reconstruction (ACLR) and 55 healthy controls. METHODS: For the STCT, participants sat on a balance board with their eyes closed for three 30-second trials while investigators counted balance errors. Intraclass correlations (ICCs) were used to assess interrater reliability (N = 20) and test-retest reliability (N = 40). To assess known-groups validity, independent t tests were used to compare STCT errors at 3 months post-ACLR with healthy matched controls (N = 34/group). Area under a receiver operating characteristic curve identified an optimal cutoff for distinguishing between groups. RESULTS: The STCT had perfect interrater reliability (ICC2,3 = 1.00) and good test-retest reliability (ICC3,3 = .79; 95% confidence interval = .61-.89). The ACLR group made significantly more errors on the STCT (mean [SD] = 15.5 [5.4]) than controls (mean [SD] = 8.2 [4.1]; P < .001, Cohen d = 1.52). The STCT's ability to distinguish between groups was excellent (area under a ROC curve = 0.86). A cutoff of 12 errors maximized sensitivity (76%) and specificity (85%). CONCLUSIONS: The STCT is reliable between raters and across days. It also has excellent ability to distinguish between individuals with a recent ACLR and healthy matched controls, which provides initial evidence to suggest that the STCT may be clinically useful for identifying deficits in trunk neuromuscular control.

Impact of Internal Charge Transfer on the Photophysical Properties of Pyridine-Fused Phosphorus-Nitrogen Heterocycles.

The phosphaquinolinone scaffold has been previously studied as a modular core for a variety of fluorescent species where use of substituent effects has focused on increasing or decreasing electron density in the core rings. We now report the synthesis and analysis of several pyridine-containing phosphaquinolinone species exhibiting notable linear conjugation from the aryl-substituent to electron-withdrawing pyridyl nitrogen. Varying the nature of the aryl substituent from electron-withdrawing to electron-donating leads to the generation of an internal charge-transfer (ICT) band in the absorbance spectrum, which becomes the dominant absorbance in terms of intensity in the most electron-rich -NMe2 example. This heterocycle exhibits improved photophysical properties compared to others in the set including high quantum yield and considerably red-shifted emission. The enhanced ICT can be observed in the X-ray data where a rare example of molecule co-planarity is observed. Computational data show increased localization of negative charge on the pyridyl nitrogen as the electron-donating character of the aryl-substituent increases.

2-λ5-Phosphaquinolin-2-ones as Non-cytotoxic, Targetable, and pH-Stable Fluorophores.

Several phosphaquinolinone derivatives have been synthesized and characterized to explore their usefulness in the realm of cell imaging. Solution-state photophysical properties in both aqueous and organic solutions were collected for these derivatives. Additionally, CCK-8 cell viability assays and fluorescent imaging in HeLa cells incubated with the new heterocyclic derivatives show evidence of favorable cell permeability, cell viability, and moderate intracellular localization when appended with the well-known morpholine targeting motif.

C-H⋯S hydrogen bonding interactions.

The short C-H⋯S contacts found in available structural data for both small molecules and larger biomolecular systems suggest that such contacts are an often overlooked yet important stabilizing interaction. Moreover, many of these short C-H⋯S contacts meet the definition of a hydrogen bonding interaction. Using available structural data from the Cambridge Structural Database (CSD), as well as selected examples from the literature in which important C-H⋯S contacts may have been overlooked, we highlight the generality of C-H⋯S hydrogen bonding as an important stabilizing interaction. To uncover and establish the generality of these interactions, we compare C-H⋯S contacts with other traditional hydrogen bond donors and acceptors as well as investigate how coordination number and metal bonding affect the preferred geometry of interactions in the solid state. This work establishes that the C-H⋯S bond meets the definition of a hydrogen bond and serves as a guide to identify C-H⋯S hydrogen bonds in diverse systems.

Controlling Tautomerization in Pyridine-Fused Phosphorus-Nitrogen Heterocycles.

Inclusion of a second nitrogen atom in the aromatic core of phosphorus-nitrogen (PN) heterocycles results in unexpected tautomerization to a nonaromatic form. This tautomerization, initially observed in the solid state through X-ray crystallography, is also explained by computational analysis. We prepared an electron deficient analogue (2 e) with a fluorine on the pyridine ring and showed that the weakly basic pyridine resisted tautomerization, providing key insights to why the transformation occurs. To study the difference in solution vs. solid-state heterocycles, alkylated analogues that lock in the quinoidal tautomer were synthesized and their different 1 H NMR and UV/Vis spectra studied. Ultimately, we determined that all heterocycles are the aromatic tautomer in solution and all but 2 e switch to the quinoidal tautomer in the solid state. Better understanding of this transformation and under what circumstances it occurs suggest future use in a switchable on/off hydrogen-bond-directed receptor that can be tuned for complementary hydrogen bonding.

Evidence-based rationale for treatment of meniscal lesions in athletes.

Meniscal injuries in elite athletes are a common cause of missed game time and even have the potential to be career shortening. In this patient group, care must be paid not only to the pathology, but also to a player's contract status, time in the season, specific demands of his/her sport and position on the field, and future consequences. Successful treatment requires the clinician to understand the player's goals and needs, communicate effectively between all stakeholders, and a have knowledge of the challenges posed by the different types of meniscal tear seen in this population. Paramount is the distinction between injuries to the medial and lateral meniscus. Deficiency of the lateral meniscus, as a result of a tear or a meniscectomy, leads to frequent early problems and inexorably to chondral degeneration thereby affecting an athlete's ability to perform. Therefore, it is strongly recommended to repair the majority of lateral meniscal tears. Medial meniscal tears pose a more challenging treatment dilemma, as the success of partial meniscectomy in achieving reproducible, early return to play must be balanced against the long-term degenerative consequences. Many meniscal tears are correctly treated non-operatively.Level of evidence V.

Multilevel Selection on Offspring Size and the Maintenance of Variation.

AbstractMultilevel selection on offspring size occurs when offspring fitness depends on both absolute size (hard selection) and size relative to neighbors (soft selection). We examined multilevel selection on egg size at two biological scales-within clutches and among clutches from different females-using an external fertilizing tube worm. We exposed clutches of eggs to two sperm environments (limiting and saturating) and measured their fertilization success. We then modeled environmental (sperm-dependent) differences in hard and soft selection on individual eggs as well as selection on clutch-level traits (means and variances). Hard and soft selection differed in strength and form depending on sperm availability-hard selection was consistently stabilizing; soft selection was directional and favored eggs relatively larger (sperm limitation) or smaller (sperm saturation) than the clutch mean. At the clutch level, selection on mean egg size was largely concave, while selection on within-clutch variance was weak but generally negative-although some correlational selection occurred between these two traits. Importantly, we found that the optimal clutch mean egg size differed for mothers and offspring, suggesting some antagonism between the levels of selection. We thus identify several pathways that may maintain offspring size variation: environmentally (sperm-) dependent soft selection, antagonistic multilevel selection, and correlational selection on clutch means and variances. Multilevel approaches are powerful but seldom-used tools for studies of offspring size, and we encourage their future use.

Correlations of Single-Leg Performance Tests to Patient-Reported Outcomes After Primary Anterior Cruciate Ligament Reconstruction.

OBJECTIVE: To determine the relationship between patient-reported outcomes (PROs) to the single-leg step-down test (SLSD) and the Y-balance anterior reach (YB-A) 6 months after primary anterior cruciate ligament reconstruction (ACLR). DESIGN: Cross-sectional. SETTING: Laboratory. PARTICIPANTS: Sixty-six patients 6 months after ACLR participated. INTERVENTIONS: Patients performed the SLSD, YB-A, and completed PROs after ACLR. MAIN OUTCOME MEASURES: Patients completed the International Knee Documentation Committee Score (IKDC), the Lysholm Activity Scale, the Tampa Scale of Kinesiophobia (TSK-11), and the Knee Injury and Osteoarthritis Outcome Score (KOOS)-Symptom, -Sport, and -Quality of Life (QOL) subscales. The SLSD requires subjects to complete as many single-leg step-downs as possible in 60 seconds, and the YB-A involves reaching anteriorly on a single limb. Pearson product moment correlations were used to assess relationships between the YB-A and SLSD performance to each PRO. RESULTS: Single-leg step-down test symmetry was significantly correlated with the TSK-11 (r = -0.70), KOOS-Sport (r = 0.40), -Symptom (r = 0.46), and -QOL (r = 0.42). The YB-A symmetry was significantly correlated with the KOOS-Symptom (r = 0.30) and KOOS-Sport (r = 0.30). CONCLUSIONS: Single-leg step-down test performance demonstrated stronger relationships to patient-reported knee function than the YB-A. Furthermore, the SLSD symmetry was strongly correlated with fear of movement. The SLSD provides a robust method for clinicians to assess dynamic knee function and may aid in identifying patients who could benefit from intervention to reduce fear of movement or reinjury.

Juvenile African Clawed Frogs (Xenopus laevis) Express Growth, Metamorphosis, Mortality, Gene Expression, and Metabolic Changes When Exposed to Thiamethoxam and Clothianidin.

Neonicotinoids (NEO) represent the main class of insecticides currently in use, with thiamethoxam (THX) and clothianidin (CLO) primarily applied agriculturally. With few comprehensive studies having been performed with non-target amphibians, the aim was to investigate potential biomarker responses along an adverse outcome pathway of NEO exposure, whereby data were collected on multiple biological hierarchies. Juvenile African clawed frogs, Xenopus laevis, were exposed to commercial formulations of THX and CLO at high (100 ppm) and low (20 ppm) concentrations of the active ingredient. Mortality, growth, development, liver metabolic enzyme activity, and gene expression endpoints were quantified. Tadpoles (n > 1000) from NF 47 through tail resorption stage (NF 66) were exposed to NEO or to NEO-free media treatments. Liver cell reductase activity and cytotoxicity were quantified by flow cytometry. Compared to control reference gene expressions, levels of expression for NEO receptor subunits, cell structure, function, and decontamination processes were measured by RT-qPCR by using liver and brain. Mortality in THX high was 21.5% compared to the control (9.1%); the metabolic conversion of THX to CLO may explain these results. The NF 57 control tadpoles were heavier, longer, and more developed than the others. The progression of development from NF 57-66 was reduced by THX low, and weight gain was impaired. Liver reductases were highest in the control (84.1%), with low NEO exhibiting the greatest reductions; the greatest cytotoxicity was seen with THX high. More transcriptional activity was noted in brains than in livers. Results affirm the utility of a study approach that considers multiple complexities in ecotoxicological studies with non-target amphibians, underscoring the need for simultaneously considering NEO concentration-response relationships with both whole-organism and biomarker endpoints.

Tuning Supramolecular Selectivity for Hydrosulfide: Linear Free Energy Relationships Reveal Preferential C-H Hydrogen Bond Interactions.

Supramolecular anion receptors can be used to study the molecular recognition properties of the reactive yet biologically critical hydrochalcogenide anions (HCh-). Achieving selectivity for HCh- over the halides is challenging but necessary for not only developing future supramolecular probes for HCh- binding and detection, but also for understanding the fundamental properties that govern these binding and recognition events. Here we demonstrate that linear free energy relationships (LFERs)-including Hammett and Swain-Lupton plots-reveal a clear difference in sensitivity to the polarity of an aryl C-H hydrogen bond (HB) donor for HS- over other HCh- and halides. Analysis using electrostatic potential maps highlights that this difference in sensitivity results from a preference of the aryl C-H HB donor for HS- in this host scaffold. From this study, we demonstrate that LFERs are a powerful tool to gain interpretative insight into motif design for future anion-selective supramolecular receptors and highlight the importance of C-H HB donors for HS- recognition. From our results, we suggest that aryl C-H HB donors should be investigated in the next generation of HS- selective receptors based on the enhanced HS- selectivity over other competing anions in this system.

Solvent-Dependent Linear Free-Energy Relationship in a Flexible Host-Guest System.

Supramolecular chemistry provides an effective strategy for the molecular recognition of diverse molecules. Significant efforts to design synthetic hosts have enabled the successful binding of many types of guests; however, less is known about how host-guest environments influence binding. Herein, we present a comprehensive study in which we measure the host-guest binding of a bis(arylethynyl phenylurea) host with a chloride guest in eight solvents spanning ET(30) values ranging from nonpolar (40.7 kcal mol-1) to polar (47.4 kcal mol-1). Polar solvents show significantly weaker binding in comparison to nonpolar solvents, and the bulk solvent polarity parameter, ET(30), shows a linear free-energy relationship with respect to the free energy of binding in the host-guest complex. These studies provide a better understanding of how host-guest binding in flexible receptors is governed by their environments and highlight the importance of host reorganization contributions in the free energy of binding. In addition, these studies highlight that preorganization may not be as important as previously thought for weak binding in which enthalpic contributions are smaller versus in polar solvents where solvent effects are magnified.

Amplification of the Quantum Yields of 2-λ5-Phosphaquinolin-2-ones through Phosphorus Center Modification.

We report the synthesis and characterization of P-phenyl modified phosphorus- and nitrogen-containing phosphaquinolinone heterocycles. The change from -OPh to -Ph results in a marked increase in the quantum yield of the scaffold as well as a moderate red-shifting of the emission. While calculations suggest that π to π* transitions are dominant, intramolecular charge transfer (ICT) also contributes in the excited state. Solution- and solid-state studies of the dimerization of this new congener to the P-phenoxy variant are also reported, showing retention of the dimerization behavior in this scaffold.

Hydrosulfide Oxidation at a Molybdenum Tetrasulfido Complex.

Hydrogen sulfide (H2S) is an important biological signaling molecule and one of three established gasotransmitters. Upon oxidation, H2S can form reactive sulfur species (RSS) that play a central role in protein persulfidation. Here we report that a molybdenum tetrasulfide can react directly with hydrosulfide to form polysulfides and oxidize the Mo center. Specifically, [NBu4][TpMoS(S4)] reacts with 2 equiv of [NBu4][SH] to form [NBu4][TpMoS3]. Trapping experiments with BnBr confirm the formation of polysulfides, as evidenced by the direct trapping of Bn2S2. This work demonstrates new reaction pathways for H2S oxidation and RSS generation from metal-bound polysulfides that will increase our understanding of the potential roles that metals play in signaling processes.

Local adaptation of antipredator behaviors in populations of a temperate reef fish.

The temperament of animals can vary among individuals and among populations, but it is often unclear whether spatial variation in temperament is the result of acclimation to local environmental conditions or genetic adaptation to spatial differences in natural selection. This study tested whether populations of a marine fish that experience different levels of mortality and fishing exhibited local adaptation in behaviors related to predator avoidance and evasion. First, we measured variation in reactivity to perceived risk in wild populations of black surfperch (Embiotoca jacksoni). We compared flight initiation distances (FID) between populations with significantly different mortality rates. After finding that FID values were substantially lower in the low-risk locations, we tested for local adaptation by rearing lab-born offspring from both high- and low-risk populations in a common environment before measuring their behavior. Lab-reared offspring from high- and low-risk populations exhibited significant differences in several behaviors related to reactivity. Between 23 and 43% of the total variation in behaviors we measured could be attributed to source population. These results thus suggest that a substantial amount of spatial variation in behaviors related to predator evasion may represent local adaptation. In addition, behaviors we measured had an average, broad-sense heritability of 0.24, suggesting that the behavioral tendencies of these populations have some capacity to evolve further in response to any changes in selection.

Distal chromosome 16p11.2 duplications containing SH2B1 in patients with scoliosis.

INTRODUCTION: Adolescent idiopathic scoliosis (AIS) is a common musculoskeletal disorder with strong evidence for a genetic contribution. CNVs play an important role in congenital scoliosis, but their role in idiopathic scoliosis has been largely unexplored. METHODS: Exome sequence data from 1197 AIS cases and 1664 in-house controls was analysed using coverage data to identify rare CNVs. CNV calls were filtered to include only highly confident CNVs with >10 average reads per region and mean log-ratio of coverage consistent with single-copy duplication or deletion. The frequency of 55 common recurrent CNVs was determined and correlated with clinical characteristics. RESULTS: Distal chromosome 16p11.2 microduplications containing the gene SH2B1 were found in 0.7% of AIS cases (8/1197). We replicated this finding in two additional AIS cohorts (8/1097 and 2/433), resulting in 0.7% (18/2727) of all AIS cases harbouring a chromosome 16p11.2 microduplication, compared with 0.06% of local controls (1/1664) and 0.04% of published controls (8/19584) (p=2.28×10-11, OR=16.15). Furthermore, examination of electronic health records of 92 455 patients from the Geisinger health system showed scoliosis in 30% (20/66) patients with chromosome 16p11.2 microduplications containing SH2B1 compared with 7.6% (10/132) of controls (p=5.6×10-4, OR=3.9). CONCLUSIONS: Recurrent distal chromosome 16p11.2 duplications explain nearly 1% of AIS. Distal chromosome 16p11.2 duplications may contribute to scoliosis pathogenesis by directly impairing growth or by altering expression of nearby genes, such as TBX6. Individuals with distal chromosome 16p11.2 microduplications should be screened for scoliosis to facilitate early treatment.

"Design of Experiments" as a Method to Optimize Dynamic Disulfide Assemblies: Cages and Functionalizable Macrocycles.

Cyclophanes are a venerable class of macrocyclic and cage compounds that often contain unusual conformations, high strain, and unusual properties. However, synthesis of complex, functional derivatives remains difficult due to low functional group tolerance, high dilution, extreme reaction conditions, and sometimes low yields using traditional stepwise synthetic methods. "Design of experiments" (DOE) is a method employed for the optimization of reaction conditions, and we showcase this approach to generate a dramatic increase in the yield of specific targets from two different self-assembling systems. These examples demonstrate that DOE provides an additional tool in tuning self-assembling, dynamic covalent systems.