Xenon Induces Its Own Preferred Heterochiral Host from Exclusive Homochiral Assembly.

Xenon binding represents a formidable challenge, and efficient hosts remain rare. Here we report our findings that while enantiomeric bis(urea)-bis(thiourea) macrocycles form exclusive homochiral dimeric assemblies, xenon is able to overcome the narcissism and induces an otherwise-nonobservable heterochiral assembly as its preferred host. An experimental approach and fitting model were developed to obtain binding constants associated with the invisible assembly species. The determined xenon binding affinity with the heterochiral capsule reaches 1600 M-1, which is 15 times higher than that with the homochiral capsule and represents the highest record for an assembled host. The origin of the large difference in xenon affinity between the two subtle diastereotopic assemblies was revealed by single-crystal analysis. In the heterochiral capsule with S4 symmetry, the xenon atom is more tightly enclosed by van der Waals surroundings of the four thiourea groups arranged in a spherical cross-array, superior to the antiparallel array in the homochiral capsule with D2 symmetry.

Tibial Spine Height Measured by Radiograph Is a Risk Factor for Non-Contact Anterior Cruciate Ligament Injury in Males: A Retrospective Case-Control Study.

Various anatomic abnormalities are implicated in non-contact anterior cruciate ligament (ACL) injury, but researchers rarely deal with the relation between tibial spine height and ACL injury. We conducted a retrospective case-control study to include 96 patients with and without non-contact ACL injuries. Tibial plateau width (TPW), medial and lateral tibial spine height (MTSH and LTSH), and tibial spine width (TSW) were measured by radiographs. The parameters were compared among subgroups. Binary regression mode, receiver operating characteristic curves, and the area under the curve (AUC) were used to evaluate the specific correlation of the parameters with ACL injury. As a result, we found that the ratio of LTSH/TPW was larger in ACL-injured patients than in ACL-intact controls (p = 0.015). In the study group, LTSH/TPW (p = 0.007) and MTSH/TPW (p = 0.002) were larger in males than in females. The ratio of LTSH/TPW had an AUC of 0.60 and a significant OR of 1.3 for ACL injury in males, but not in females. In conclusion, LTSH was larger in patients with ACL injury and is a risk factor for ACL injury in males. The impact of increased LTSH on the impingement between the grafts and lateral tibial spine during ACL reconstruction warrants further investigation.

Femoral fixation methods for hamstring graft in anterior cruciate ligament reconstruction: A network meta-analysis of controlled clinical trials.

OBJECTIVE: To compare the clinical effectiveness of cortical button (CB), cross-pin (CP) and compression with interference screws (IS) fixation techniques in anterior cruciate ligament (ACL) reconstruction using hamstring graft. METHODS: Studies were systematically retrieved from PubMed, Embase, Cochrane Library and Web of Science up to May 20, 2021. Primary outcomes were KT-1000 assessment, International Knee Documentation Committee (IKDC) score A or B, Lachman's test, pivot-shift test, visual analogue scale (VAS) score, Lysholm score, Tegner score, and Cincinnati Knee Score. Secondary outcomes included reconstruction failures and synovitis. League tables, rank probabilities and forest plots were drawn for efficacy comparison. RESULTS: Twenty-six controlled clinical trials (CCTs) with 1,824 patients undergoing ACL reconstruction with hamstring graft were included. No significant differences were found among CB, CP and IS fixation methods regarding the 10 outcomes. For KT-1000 assessment, IKDC score A or B, Lachman's test, VAS score and pivot-shift test, CP had the greatest probability of becoming the best method, and IS may be the suboptimal method in 4 out of these 5 outcomes except pivot-shift test. CONCLUSIONS: CP, CB and IS fixations have comparable clinical performance, while CP fixation is most likely to be the optimum fixation technique for hamstring graft in ACL reconstruction. Future larger-sample studies of high quality comparing these techniques in more clinical outcomes are required.

Xenon binding by a tight yet adaptive chiral soft capsule.

Xenon binding has attracted interest due to the potential for xenon separation and emerging applications in magnetic resonance imaging. Compared to their covalent counterparts, assembled hosts that are able to effectively bind xenon are rare. Here, we report a tight yet soft chiral macrocycle dimeric capsule for efficient and adaptive xenon binding in both crystal form and solution. The chiral bisurea-bisthiourea macrocycle can be easily synthesized in multi-gram scale. Through assembly, the flexible macrocycles are locked in a bowl-shaped conformation and buckled to each other, wrapping up a tight, completely sealed yet adjustable cavity suitable for xenon, with a very high affinity for an assembled host. A slow-exchange process and drastic spectral changes are observed in both 1H and 129Xe NMR. With the easy synthesis, modification and reversible characteristics, we believe the robust yet adaptive assembly system may find applications in xenon sequestration and magnetic resonance imaging-based biosensing.

Chiral Macrocycle-Enabled Counteranion Trapping for Boosting Highly Efficient and Enantioselective Catalysis.

The tight binding enabled by tailor-made macrocycles can be manipulated for tuning the catalysis process. In parallel to well-developed crown ether-based cation-binding catalysis, a macrocycle-enabled counteranion trapping strategy is presented for boosting highly efficient and enantioselective catalysis. A set of bis-diarylthiourea macrocycles containing two BINOL moieties were designed and synthesized. They possess a well-confined chiral cavity and strong binding affinities towards disulfonate anions. Caused by the tight binding, just 1 mol % macrocycle in combination with 1 mol % ethanedisulfonic acid can promote excellent conversion and up to 99 % ee in the Friedel-Crafts reaction of indoles with imines. The acid or the macrocycle alone do not afford any reactivity. The high catalytic efficiency and excellent stereocontrol was ascribed to large, complexation-induced acidity enhancement and tight ion-pairing facilitated by cave-like macrocyclic cavity.

Facile and Sensitive Near-Infrared Fluorescence Probe for the Detection of Endogenous Alkaline Phosphatase Activity In Vivo.

Alkaline phosphatase (ALP) is an essential enzyme and widely distributes in a variety of tissues. To date, various nanomaterial and small-molecule fluorescent probes for ALP have been constructed successfully, but the emission wavelengths of these probes are in the ultraviolet or visible range, which is not beneficial for bioimaging. Herein, a hemicyanine-based near-infrared (NIR) fluorescent probe named CyP is first synthesized and used to detect ALP activity. The characteristics of probe CyP are as follows: (1) The probe possesses a facile structure, which can be obtained by easy synthetic steps. (2) The fluorescence emission of the sensing system is at 738 nm belonging to NIR region, which is suitable for bioimaging in vivo. (3) The probe exhibits high sensitivity to ALP with 10-fold fluorescence enhancement and low detection limit (0.003 U/mL) can match the level of ALP in vivo. (4) The fluorescent change of the probe is attributed to the fact that ALP-catalyzed cleavage of the phosphate group in CyP induces the transformation of CyP (fluorescence off) into CyOH (fluorescence on), which is proved by HPLC, 31P NMR, MS, and DFT calculation. (5) The NIR fluorescent probe is applied for the detection of endogenous ALP activity in various biological samples such as cell, tissue, and living animal with satisfactory results.